html/edit/005-sandbox.mu.html


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<title>Mu - 515parse-float.mu</title>
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<a href='https://github.com/akkartik/mu/blob/main/515parse-float.mu'>https://github.com/akkartik/mu/blob/main/515parse-float.mu</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr">  1 </span><span class="muComment"># no support for scientific notation yet</span>
<span id="L2" class="LineNr">  2 </span><span class="PreProc">fn</span> <span class="muFunction"><a href='515parse-float.mu.html#L2'>parse-float-decimal</a></span> in: (addr stream byte)<span class="PreProc"> -&gt; </span>_/<span class="Constant">xmm1</span>: float <span class="Delimiter">{</span>
<span id="L3" class="LineNr">  3 </span>  <span class="PreProc">var</span> zero: float
<span id="L4" class="LineNr">  4 </span>  <span class="PreProc">var</span> result/<span class="Constant">xmm1</span>: float <span class="Special">&lt;-</span> copy zero
<span id="L5" class="LineNr">  5 </span>  <span class="PreProc">var</span> first-iter?/<span class="muRegEcx">ecx</span>: int <span class="Special">&lt;-</span> copy <span class="Constant">1</span>/true
<span id="L6" class="LineNr">  6 </span>  <a href='106stream.subx.html#L59'>rewind-stream</a> in
<span id="L7" class="LineNr">  7 </span>  <span class="PreProc">var</span> negative?/<span class="muRegEdx">edx</span>: int <span class="Special">&lt;-</span> copy <span class="Constant">0</span>/false
<span id="L8" class="LineNr">  8 </span>  <span class="muComment"># first loop: integer part</span>
<span id="L9" class="LineNr">  9 </span>  <span class="PreProc">var</span> ten/eax: int <span class="Special">&lt;-</span> copy <span class="Constant">0xa</span>
<span id="L10" class="LineNr"> 10 </span>  <span class="PreProc">var</span> ten-f/<span class="Constant">xmm2</span>: float <span class="Special">&lt;-</span> convert ten
<span id="L11" class="LineNr"> 11 </span>  <span class="Delimiter">{</span>
<span id="L12" class="LineNr"> 12 </span>    <span class="PreProc">var</span> done?/eax: boolean <span class="Special">&lt;-</span> <a href='309stream.subx.html#L6'>stream-empty?</a> in
<span id="L13" class="LineNr"> 13 </span>    compare done?, <span class="Constant">0</span>/false
<span id="L14" class="LineNr"> 14 </span>    <span class="PreProc">break-if-!=</span>
<span id="L15" class="LineNr"> 15 </span>    <span class="PreProc">var</span> key/eax: byte <span class="Special">&lt;-</span> <a href='112read-byte.subx.html#L13'>read-byte</a> in
<span id="L16" class="LineNr"> 16 </span>    compare key, <span class="Constant">0x2e</span>/decimal-point
<span id="L17" class="LineNr"> 17 </span>    <span class="PreProc">break-if-=pre { line-height: 125%; }
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<pre id='vimCodeElement'>
<span class="SalientComment">## running code from the editor and creating sandboxes</span>
<span class="Comment">#</span>
<span class="Comment"># Running code in the sandbox editor prepends its contents to a list of</span>
<span class="Comment"># (non-editable) sandboxes below the editor, showing the result and a maybe</span>
<span class="Comment"># few other things.</span>
<span class="Comment">#</span>
<span class="Comment"># This layer draws the menubar buttons non-editable sandboxes but they don't</span>
<span class="Comment"># do anything yet. Later layers implement each button.</span>

<span class="muRecipe">def!</span> main [
  <span class="Constant">local-scope</span>
  open-console
  initial-recipe:text<span class="Special"> &lt;- </span>restore <span class="Constant">[recipes.mu]</span>
  initial-sandbox:text<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
  hide-screen <span class="Constant">0/screen</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment <span class="Constant">0/screen</span>, initial-recipe, initial-sandbox
  env<span class="Special"> &lt;- </span>restore-sandboxes env
  render-all <span class="Constant">0/screen</span>, env, render
  event-loop <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>, env
  <span class="Comment"># never gets here</span>
]

<span class="muData">container</span> environment [
  sandbox:&amp;:sandbox  <span class="Comment"># list of sandboxes, from top to bottom</span>
  render-from:num
  number-of-sandboxes:num
]

<span class="muRecipe">after</span> <span class="Constant">&lt;programming-environment-initialization&gt;</span> [
  *result<span class="Special"> &lt;- </span>put *result, <span class="Constant">render-from:offset</span>, <span class="Constant">-1</span>
]

<span class="muData">container</span> sandbox [
  data:text
  response:text
  <span class="Comment"># coordinates to track clicks</span>
  <span class="Comment"># constraint: will be 0 for sandboxes at positions before env.render-from</span>
  starting-row-on-screen:num
  code-ending-row-on-screen:num  <span class="Comment"># past end of code</span>
  screen:&amp;:screen  <span class="Comment"># prints in the sandbox go here</span>
  next-sandbox:&amp;:sandbox
]

<span class="muScenario">scenario</span> run-and-show-results [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
  <span class="Comment"># recipe editor is empty</span>
  <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, <span class="Constant">[]</span>, <span class="Constant">[divide-with-remainder 11, 3]</span>
  <span class="Comment"># run the code in the editors</span>
  assume-console [
    press F4
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># check that screen prints the results</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎divide-with-remainder 11, 3                      .</span>
   <span class="Constant"> .                                                  ╎3                                                .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
  screen-should-contain-in-color <span class="Constant">7/white</span>, [
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                   divide-with-remainder 11, 3                      .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
  ]
  screen-should-contain-in-color <span class="Constant">245/grey</span>, [
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
   <span class="Constant"> .                                                  ╎3                                                .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
  <span class="Comment"># sandbox menu in reverse video</span>
  screen-should-contain-in-color <span class="Constant">232/black</span>, [
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                                                                    .</span>
   <span class="Constant"> .                                                   0   edit          copy            delete         .</span>
  ]
  <span class="Comment"># run another command</span>
  assume-console [
    left-click <span class="Constant">1</span>, <span class="Constant">80</span>
    type <span class="Constant">[add 2, 2]</span>
    press F4
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># check that screen prints both sandboxes</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
   <span class="Constant"> .                                                  ╎4                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎divide-with-remainder 11, 3                      .</span>
   <span class="Constant"> .                                                  ╎3                                                .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
]

<span class="muRecipe">after</span> <span class="Constant">&lt;global-keypress&gt;</span> [
  <span class="Comment"># F4? load all code and run all sandboxes.</span>
  <span class="Delimiter">{</span>
    do-run?:bool<span class="Special"> &lt;- </span>equal k, <span class="Constant">65532/F4</span>
    <span class="muControl">break-unless</span> do-run?
    screen<span class="Special"> &lt;- </span>update-status screen, <span class="Constant">[running...       ]</span>, <span class="Constant">245/grey</span>
    error?:bool, env, screen<span class="Special"> &lt;- </span>run-sandboxes env, screen
    <span class="Comment"># F4 might update warnings and results on both sides</span>
    screen<span class="Special"> &lt;- </span>render-all screen, env, render
    <span class="Delimiter">{</span>
      <span class="muControl">break-if</span> error?
      screen<span class="Special"> &lt;- </span>update-status screen, <span class="Constant">[                 ]</span>, <span class="Constant">245/grey</span>
    <span class="Delimiter">}</span>
    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, sandbox-in-focus?, env
    <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
  <span class="Delimiter">}</span>
]

<span class="muRecipe">def</span> run-sandboxes env:&amp;:environment, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>errors-found?:bool, env:&amp;:environment, screen:&amp;:screen [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  errors-found?:bool, env, screen<span class="Special"> &lt;- </span>update-recipes env, screen
  <span class="muControl">return-if</span> errors-found?
  <span class="Comment"># check contents of right editor (sandbox)</span>
<span class="Constant">  &lt;run-sandboxes-begin&gt;</span>
  current-sandbox:&amp;:editor<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
  <span class="Delimiter">{</span>
    sandbox-contents:text<span class="Special"> &lt;- </span>editor-contents current-sandbox
    <span class="muControl">break-unless</span> sandbox-contents
    <span class="Comment"># if contents exist, first save them</span>
    <span class="Comment"># run them and turn them into a new sandbox</span>
    new-sandbox:&amp;:sandbox<span class="Special"> &lt;- </span>new <span class="Constant">sandbox:type</span>
    *new-sandbox<span class="Special"> &lt;- </span>put *new-sandbox, <span class="Constant">data:offset</span>, sandbox-contents
    <span class="Comment"># push to head of sandbox list</span>
    dest:&amp;:sandbox<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
    *new-sandbox<span class="Special"> &lt;- </span>put *new-sandbox, <span class="Constant">next-sandbox:offset</span>, dest
    *env<span class="Special"> &lt;- </span>put *env, <span class="Constant">sandbox:offset</span>, new-sandbox
    <span class="Comment"># update sandbox count</span>
    sandbox-count:num<span class="Special"> &lt;- </span>get *env, <span class="Constant">number-of-sandboxes:offset</span>
    sandbox-count<span class="Special"> &lt;- </span>add sandbox-count, <span class="Constant">1</span>
    *env<span class="Special"> &lt;- </span>put *env, <span class="Constant">number-of-sandboxes:offset</span>, sandbox-count
    <span class="Comment"># clear sandbox editor</span>
    init:&amp;:duplex-list:char<span class="Special"> &lt;- </span>push <span class="Constant">167/§</span>, <span class="Constant">0/tail</span>
    *current-sandbox<span class="Special"> &lt;- </span>put *current-sandbox, <span class="Constant">data:offset</span>, init
    *current-sandbox<span class="Special"> &lt;- </span>put *current-sandbox, <span class="Constant">top-of-screen:offset</span>, init
  <span class="Delimiter">}</span>
  <span class="Comment"># save all sandboxes before running, just in case we die when running</span>
  save-sandboxes env
  <span class="Comment"># run all sandboxes</span>
  curr:&amp;:sandbox<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
  idx:num<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> curr
    curr<span class="Special"> &lt;- </span>update-sandbox curr, env, idx
    curr<span class="Special"> &lt;- </span>get *curr, <span class="Constant">next-sandbox:offset</span>
    idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
<span class="Constant">  &lt;run-sandboxes-end&gt;</span>
]

<span class="Comment"># copy code from recipe editor, persist, load into mu</span>
<span class="Comment"># replaced in a later layer (whereupon errors-found? will actually be set)</span>
<span class="muRecipe">def</span> update-recipes env:&amp;:environment, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>errors-found?:bool, env:&amp;:environment, screen:&amp;:screen [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  recipes:&amp;:editor<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
  in:text<span class="Special"> &lt;- </span>editor-contents recipes
  save <span class="Constant">[recipes.mu]</span>, in  <span class="Comment"># newlayer: persistence</span>
  reload in
  errors-found?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
]

<span class="Comment"># replaced in a later layer</span>
<span class="muRecipe">def!</span> update-sandbox sandbox:&amp;:sandbox, env:&amp;:environment, idx:num<span class="muRecipe"> -&gt; </span>sandbox:&amp;:sandbox, env:&amp;:environment [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  data:text<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
  response:text, _, fake-screen:&amp;:screen<span class="Special"> &lt;- </span>run-sandboxed data
  *sandbox<span class="Special"> &lt;- </span>put *sandbox, <span class="Constant">response:offset</span>, response
  *sandbox<span class="Special"> &lt;- </span>put *sandbox, <span class="Constant">screen:offset</span>, fake-screen
]

<span class="muRecipe">def</span> update-status screen:&amp;:screen, msg:text, color:num<span class="muRecipe"> -&gt; </span>screen:&amp;:screen [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  screen<span class="Special"> &lt;- </span>move-cursor screen, <span class="Constant">0</span>, <span class="Constant">2</span>
  screen<span class="Special"> &lt;- </span>print screen, msg, color, <span class="Constant">238/grey/background</span>
]

<span class="muRecipe">def</span> save-sandboxes env:&amp;:environment [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  current-sandbox:&amp;:editor<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
  <span class="Comment"># first clear previous versions, in case we deleted some sandbox</span>
  $system <span class="Constant">[rm lesson/[0-9]</span>* &gt;/dev/null <span class="Constant">2</span>&gt;/dev/null]  <span class="Comment"># some shells can't handle '&gt;&amp;'</span>
  curr:&amp;:sandbox<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
  idx:num<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> curr
    data:text<span class="Special"> &lt;- </span>get *curr, <span class="Constant">data:offset</span>
    filename:text<span class="Special"> &lt;- </span>to-text idx
    save filename, data
<span class="Constant">    &lt;end-save-sandbox&gt;</span>
    idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
    curr<span class="Special"> &lt;- </span>get *curr, <span class="Constant">next-sandbox:offset</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
]

<span class="muRecipe">def!</span> render-sandbox-side screen:&amp;:screen, env:&amp;:environment, <span class="Delimiter">{</span>render-editor: (recipe (address screen) (address editor)<span class="muRecipe"> -&gt; </span>number number (address screen) (address editor))<span class="Delimiter">}</span><span class="muRecipe"> -&gt; </span>screen:&amp;:screen, env:&amp;:environment [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  trace <span class="Constant">11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render sandbox side]</span>
  current-sandbox:&amp;:editor<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
  row:num, column:num<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>, <span class="Constant">0</span>
  left:num<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">left:offset</span>
  right:num<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">right:offset</span>
  <span class="Comment"># render sandbox editor</span>
  render-from:num<span class="Special"> &lt;- </span>get *env, <span class="Constant">render-from:offset</span>
  <span class="Delimiter">{</span>
    render-current-sandbox?:bool<span class="Special"> &lt;- </span>equal render-from, <span class="Constant">-1</span>
    <span class="muControl">break-unless</span> render-current-sandbox?
    row, column, screen, current-sandbox<span class="Special"> &lt;- </span>call render-editor, screen, current-sandbox
    clear-screen-from screen, row, column, left, right
    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># render sandboxes</span>
  draw-horizontal screen, row, left, right
  sandbox:&amp;:sandbox<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
  row, screen<span class="Special"> &lt;- </span>render-sandboxes screen, sandbox, left, right, row, render-from
  clear-rest-of-screen screen, row, left, right
]

<span class="muRecipe">def</span> render-sandboxes screen:&amp;:screen, sandbox:&amp;:sandbox, left:num, right:num, row:num, render-from:num, idx:num<span class="muRecipe"> -&gt; </span>row:num, screen:&amp;:screen, sandbox:&amp;:sandbox [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="muControl">return-unless</span> sandbox
  screen-height:num<span class="Special"> &lt;- </span>screen-height screen
  at-bottom?:bool<span class="Special"> &lt;- </span>greater-or-equal row, screen-height
  <span class="muControl">return-if</span> at-bottom?:bool
  hidden?:bool<span class="Special"> &lt;- </span>lesser-than idx, render-from
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> hidden?
    <span class="Comment"># render sandbox menu</span>
    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
    screen<span class="Special"> &lt;- </span>move-cursor screen, row, left
    screen<span class="Special"> &lt;- </span>render-sandbox-menu screen, idx, left, right
    <span class="Comment"># save menu row so we can detect clicks to it later</span>
    *sandbox<span class="Special"> &lt;- </span>put *sandbox, <span class="Constant">starting-row-on-screen:offset</span>, row
    <span class="Comment"># render sandbox contents</span>
    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
    screen<span class="Special"> &lt;- </span>move-cursor screen, row, left
    sandbox-data:text<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
    row, screen<span class="Special"> &lt;- </span>render-code screen, sandbox-data, left, right, row
    *sandbox<span class="Special"> &lt;- </span>put *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>, row
    <span class="Comment"># render sandbox warnings, screen or response, in that order</span>
    sandbox-response:text<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">response:offset</span>
<span class="Constant">    &lt;render-sandbox-results&gt;</span>
    <span class="Delimiter">{</span>
      sandbox-screen:&amp;:screen<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">screen:offset</span>
      empty-screen?:bool<span class="Special"> &lt;- </span>fake-screen-is-empty? sandbox-screen
      <span class="muControl">break-if</span> empty-screen?
      row, screen<span class="Special"> &lt;- </span>render-screen screen, sandbox-screen, left, right, row
    <span class="Delimiter">}</span>
    <span class="Delimiter">{</span>
      <span class="muControl">break-unless</span> empty-screen?
<span class="Constant">      &lt;render-sandbox-response&gt;</span>
      row, screen<span class="Special"> &lt;- </span>render-text screen, sandbox-response, left, right, <span class="Constant">245/grey</span>, row
    <span class="Delimiter">}</span>
<span class="Constant">    +render-sandbox-end</span>
    at-bottom?:bool<span class="Special"> &lt;- </span>greater-or-equal row, screen-height
    <span class="muControl">return-if</span> at-bottom?
    <span class="Comment"># draw solid line after sandbox</span>
    draw-horizontal screen, row, left, right
  <span class="Delimiter">}</span>
  <span class="Comment"># if hidden, reset row attributes</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> hidden?
    *sandbox<span class="Special"> &lt;- </span>put *sandbox, <span class="Constant">starting-row-on-screen:offset</span>, <span class="Constant">0</span>
    *sandbox<span class="Special"> &lt;- </span>put *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>, <span class="Constant">0</span>
<span class="Constant">    &lt;end-render-sandbox-reset-hidden&gt;</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># draw next sandbox</span>
  next-sandbox:&amp;:sandbox<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">next-sandbox:offset</span>
  next-idx:num<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
  row, screen<span class="Special"> &lt;- </span>render-sandboxes screen, next-sandbox, left, right, row, render-from, next-idx
]

<span class="muRecipe">def</span> render-sandbox-menu screen:&amp;:screen, sandbox-index:num, left:num, right:num<span class="muRecipe"> -&gt; </span>screen:&amp;:screen [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  move-cursor-to-column screen, left
  edit-button-left:num, edit-button-right:num, copy-button-left:num, copy-button-right:num, delete-button-left:num<span class="Special"> &lt;- </span>sandbox-menu-columns left, right
  print screen, sandbox-index, <span class="Constant">232/dark-grey</span>, <span class="Constant">245/grey</span>
  start-buttons:num<span class="Special"> &lt;- </span>subtract edit-button-left, <span class="Constant">1</span>
  clear-line-until screen, start-buttons, <span class="Constant">245/grey</span>
  print screen, <span class="Constant">[edit]</span>, <span class="Constant">232/black</span>, <span class="Constant">94/background-orange</span>
  clear-line-until screen, edit-button-right, <span class="Constant">94/background-orange</span>
  _, col:num<span class="Special"> &lt;- </span>cursor-position screen
  at-start-of-copy-button?:bool<span class="Special"> &lt;- </span>equal col, copy-button-left
  assert at-start-of-copy-button?, <span class="Constant">[aaa]</span>
  print screen, <span class="Constant">[copy]</span>, <span class="Constant">232/black</span>, <span class="Constant">58/background-green</span>
  clear-line-until screen, copy-button-right, <span class="Constant">58/background-green</span>
  _, col:num<span class="Special"> &lt;- </span>cursor-position screen
  at-start-of-delete-button?:bool<span class="Special"> &lt;- </span>equal col, delete-button-left
  assert at-start-of-delete-button?, <span class="Constant">[bbb]</span>
  print screen, <span class="Constant">[delete]</span>, <span class="Constant">232/black</span>, <span class="Constant">52/background-red</span>
  clear-line-until screen, right, <span class="Constant">52/background-red</span>
]

<span class="Comment"># divide up the menu bar for a sandbox into 3 segments, for edit/copy/delete buttons</span>
<span class="Comment"># delete-button-right == right</span>
<span class="Comment"># all left/right pairs are inclusive</span>
<span class="muRecipe">def</span> sandbox-menu-columns left:num, right:num<span class="muRecipe"> -&gt; </span>edit-button-left:num, edit-button-right:num, copy-button-left:num, copy-button-right:num, delete-button-left:num [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  start-buttons:num<span class="Special"> &lt;- </span>add left, <span class="Constant">4/space-for-sandbox-index</span>
  buttons-space:num<span class="Special"> &lt;- </span>subtract right, start-buttons
  button-width:num<span class="Special"> &lt;- </span>divide-with-remainder buttons-space, <span class="Constant">3</span>  <span class="Comment"># integer division</span>
  buttons-wide-enough?:bool<span class="Special"> &lt;- </span>greater-or-equal button-width, <span class="Constant">8</span>
  assert buttons-wide-enough?, <span class="Constant">[sandbox must be at least 30 or so characters wide]</span>
  edit-button-left:num<span class="Special"> &lt;- </span>copy start-buttons
  copy-button-left:num<span class="Special"> &lt;- </span>add start-buttons, button-width
  edit-button-right:num<span class="Special"> &lt;- </span>subtract copy-button-left, <span class="Constant">1</span>
  delete-button-left:num<span class="Special"> &lt;- </span>subtract right, button-width
  copy-button-right:num<span class="Special"> &lt;- </span>subtract delete-button-left, <span class="Constant">1</span>
]

<span class="Comment"># print a text 's' to 'editor' in 'color' starting at 'row'</span>
<span class="Comment"># clear rest of last line, move cursor to next line</span>
<span class="muRecipe">def</span> render-text screen:&amp;:screen, s:text, left:num, right:num, color:num, row:num<span class="muRecipe"> -&gt; </span>row:num, screen:&amp;:screen [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="muControl">return-unless</span> s
  column:num<span class="Special"> &lt;- </span>copy left
  screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
  screen-height:num<span class="Special"> &lt;- </span>screen-height screen
  i:num<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  len:num<span class="Special"> &lt;- </span>length *s
  <span class="Delimiter">{</span>
<span class="Constant">    +next-character</span>
    done?:bool<span class="Special"> &lt;- </span>greater-or-equal i, len
    <span class="muControl">break-if</span> done?
    done?<span class="Special"> &lt;- </span>greater-or-equal row, screen-height
    <span class="muControl">break-if</span> done?
    c:char<span class="Special"> &lt;- </span>index *s, i
    <span class="Delimiter">{</span>
      <span class="Comment"># at right? wrap.</span>
      at-right?:bool<span class="Special"> &lt;- </span>equal column, right
      <span class="muControl">break-unless</span> at-right?
      <span class="Comment"># print wrap icon</span>
      wrap-icon:char<span class="Special"> &lt;- </span>copy <span class="Constant">8617/loop-back-to-left</span>
      print screen, wrap-icon, <span class="Constant">245/grey</span>
      column<span class="Special"> &lt;- </span>copy left
      row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
      screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
      <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>  <span class="Comment"># retry i</span>
    <span class="Delimiter">}</span>
    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
    <span class="Delimiter">{</span>
      <span class="Comment"># newline? move to left rather than 0</span>
      newline?:bool<span class="Special"> &lt;- </span>equal c, <span class="Constant">10/newline</span>
      <span class="muControl">break-unless</span> newline?
      <span class="Comment"># clear rest of line in this window</span>
      <span class="Delimiter">{</span>
        done?:bool<span class="Special"> &lt;- </span>greater-than column, right
        <span class="muControl">break-if</span> done?
        space:char<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
        print screen, space
        column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
        <span class="muControl">loop</span>
      <span class="Delimiter">}</span>
      row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
      column<span class="Special"> &lt;- </span>copy left
      screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
      <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>
    <span class="Delimiter">}</span>
    print screen, c, color
    column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  was-at-left?:bool<span class="Special"> &lt;- </span>equal column, left
  clear-line-until screen, right
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> was-at-left?
    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
  <span class="Delimiter">}</span>
  move-cursor screen, row, left
]

<span class="Comment"># assumes programming environment has no sandboxes; restores them from previous session</span>
<span class="muRecipe">def</span> restore-sandboxes env:&amp;:environment<span class="muRecipe"> -&gt; </span>env:&amp;:environment [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="Comment"># read all scenarios, pushing them to end of a list of scenarios</span>
  idx:num<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  curr:&amp;:sandbox<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  prev:&amp;:sandbox<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  <span class="Delimiter">{</span>
    filename:text<span class="Special"> &lt;- </span>to-text idx
    contents:text<span class="Special"> &lt;- </span>restore filename
    <span class="muControl">break-unless</span> contents  <span class="Comment"># stop at first error; assuming file didn't exist</span>
                           <span class="Comment"># todo: handle empty sandbox</span>
    <span class="Comment"># create new sandbox for file</span>
    curr<span class="Special"> &lt;- </span>new <span class="Constant">sandbox:type</span>
    *curr<span class="Special"> &lt;- </span>put *curr, <span class="Constant">data:offset</span>, contents
<span class="Constant">    &lt;end-restore-sandbox&gt;</span>
    <span class="Delimiter">{</span>
      <span class="muControl">break-if</span> idx
      *env<span class="Special"> &lt;- </span>put *env, <span class="Constant">sandbox:offset</span>, curr
    <span class="Delimiter">}</span>
    <span class="Delimiter">{</span>
      <span class="muControl">break-unless</span> idx
      *prev<span class="Special"> &lt;- </span>put *prev, <span class="Constant">next-sandbox:offset</span>, curr
    <span class="Delimiter">}</span>
    idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
    prev<span class="Special"> &lt;- </span>copy curr
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># update sandbox count</span>
  *env<span class="Special"> &lt;- </span>put *env, <span class="Constant">number-of-sandboxes:offset</span>, idx
]

<span class="Comment"># print the fake sandbox screen to 'screen' with appropriate delimiters</span>
<span class="Comment"># leave cursor at start of next line</span>
<span class="muRecipe">def</span> render-screen screen:&amp;:screen, sandbox-screen:&amp;:screen, left:num, right:num, row:num<span class="muRecipe"> -&gt; </span>row:num, screen:&amp;:screen [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="muControl">return-unless</span> sandbox-screen
  <span class="Comment"># print 'screen:'</span>
  row<span class="Special"> &lt;- </span>render-text screen, <span class="Constant">[screen:]</span>, left, right, <span class="Constant">245/grey</span>, row
  screen<span class="Special"> &lt;- </span>move-cursor screen, row, left
  <span class="Comment"># start printing sandbox-screen</span>
  column:num<span class="Special"> &lt;- </span>copy left
  s-width:num<span class="Special"> &lt;- </span>screen-width sandbox-screen
  s-height:num<span class="Special"> &lt;- </span>screen-height sandbox-screen
  buf:&amp;:@:screen-cell<span class="Special"> &lt;- </span>get *sandbox-screen, <span class="Constant">data:offset</span>
  stop-printing:num<span class="Special"> &lt;- </span>add left, s-width, <span class="Constant">3</span>
  max-column:num<span class="Special"> &lt;- </span>min stop-printing, right
  i:num<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  len:num<span class="Special"> &lt;- </span>length *buf
  screen-height:num<span class="Special"> &lt;- </span>screen-height screen
  <span class="Delimiter">{</span>
    done?:bool<span class="Special"> &lt;- </span>greater-or-equal i, len
    <span class="muControl">break-if</span> done?
    done?<span class="Special"> &lt;- </span>greater-or-equal row, screen-height
    <span class="muControl">break-if</span> done?
    column<span class="Special"> &lt;- </span>copy left
    screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
    <span class="Comment"># initial leader for each row: two spaces and a '.'</span>
    space:char<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
    print screen, space, <span class="Constant">245/grey</span>
    print screen, space, <span class="Constant">245/grey</span>
    full-stop:char<span class="Special"> &lt;- </span>copy <span class="Constant">46/period</span>
    print screen, full-stop, <span class="Constant">245/grey</span>
    column<span class="Special"> &lt;- </span>add left, <span class="Constant">3</span>
    <span class="Delimiter">{</span>
      <span class="Comment"># print row</span>
      row-done?:bool<span class="Special"> &lt;- </span>greater-or-equal column, max-column
      <span class="muControl">break-if</span> row-done?
      curr:screen-cell<span class="Special"> &lt;- </span>index *buf, i
      c:char<span class="Special"> &lt;- </span>get curr, <span class="Constant">contents:offset</span>
      color:num<span class="Special"> &lt;- </span>get curr, <span class="Constant">color:offset</span>
      <span class="Delimiter">{</span>
        <span class="Comment"># damp whites down to grey</span>
        white?:bool<span class="Special"> &lt;- </span>equal color, <span class="Constant">7/white</span>
        <span class="muControl">break-unless</span> white?
        color<span class="Special"> &lt;- </span>copy <span class="Constant">245/grey</span>
      <span class="Delimiter">}</span>
      print screen, c, color
      column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
      i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
      <span class="muControl">loop</span>
    <span class="Delimiter">}</span>
    <span class="Comment"># print final '.'</span>
    print screen, full-stop, <span class="Constant">245/grey</span>
    column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
    <span class="Delimiter">{</span>
      <span class="Comment"># clear rest of current line</span>
      line-done?:bool<span class="Special"> &lt;- </span>greater-than column, right
      <span class="muControl">break-if</span> line-done?
      print screen, space
      column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
      <span class="muControl">loop</span>
    <span class="Delimiter">}</span>
    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
]

<span class="muScenario">scenario</span> run-updates-results [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">12/height</span>
  <span class="Comment"># define a recipe (no indent for the 'add' line below so column numbers are more obvious)</span>
  recipes:text<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
<span class="Constant">recipe foo [</span>
<span class="Constant">local-scope</span>
<span class="Constant">z:num &lt;- add 2, 2</span>
<span class="Constant">reply z</span>
<span class="Constant">]</span>]
  <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, recipes, <span class="Constant">[foo]</span>
  <span class="Comment"># run the code in the editors</span>
  assume-console [
    press F4
  ]
  event-loop screen, console, env
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
   <span class="Constant"> .recipe foo [                                      ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .local-scope                                       ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .z:num &lt;- add 2, 2                                 ╎foo                                              .</span>
   <span class="Constant"> .reply z                                           ╎4                                                .</span>
   <span class="Constant"> .]                                                 ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
  <span class="Comment"># make a change (incrementing one of the args to 'add'), then rerun</span>
  assume-console [
    left-click <span class="Constant">4</span>, <span class="Constant">28</span>  <span class="Comment"># one past the value of the second arg</span>
    press backspace
    type <span class="Constant">[3]</span>
    press F4
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># check that screen updates the result on the right</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
   <span class="Constant"> .recipe foo [                                      ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .local-scope                                       ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .z:num &lt;- add 2, 3                                 ╎foo                                              .</span>
   <span class="Constant"> .reply z                                           ╎5                                                .</span>
   <span class="Constant"> .]                                                 ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
]

<span class="muScenario">scenario</span> run-instruction-manages-screen-per-sandbox [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">20/height</span>
  <span class="Comment"># left editor is empty</span>
  <span class="Comment"># right editor contains an instruction</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, <span class="Constant">[]</span>, <span class="Constant">[print-integer screen, 4]</span>
  <span class="Comment"># run the code in the editor</span>
  assume-console [
    press F4
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># check that it prints a little toy screen</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎print-integer screen, 4                          .</span>
   <span class="Constant"> .                                                  ╎screen:                                          .</span>
   <span class="Constant"> .                                                  ╎  .4                             .               .</span>
   <span class="Constant"> .                                                  ╎  .                              .               .</span>
   <span class="Constant"> .                                                  ╎  .                              .               .</span>
   <span class="Constant"> .                                                  ╎  .                              .               .</span>
   <span class="Constant"> .                                                  ╎  .                              .               .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
]

<span class="muRecipe">def</span> editor-contents editor:&amp;:editor<span class="muRecipe"> -&gt; </span>result:text [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  buf:&amp;:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80</span>
  curr:&amp;:duplex-list:char<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
  <span class="Comment"># skip § sentinel</span>
  assert curr, <span class="Constant">[editor without data is illegal; must have at least a sentinel]</span>
  curr<span class="Special"> &lt;- </span>next curr
  <span class="muControl">return-unless</span> curr, <span class="Constant">0</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> curr
    c:char<span class="Special"> &lt;- </span>get *curr, <span class="Constant">value:offset</span>
    buf<span class="Special"> &lt;- </span>append buf, c
    curr<span class="Special"> &lt;- </span>next curr
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  result<span class="Special"> &lt;- </span>buffer-to-array buf
]

<span class="muScenario">scenario</span> editor-provides-edited-contents [
  <span class="Constant">local-scope</span>
  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
  e:&amp;:editor<span class="Special"> &lt;- </span>new-editor <span class="Constant">[abc]</span>, screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
  assume-console [
    left-click <span class="Constant">1</span>, <span class="Constant">2</span>
    type <span class="Constant">[def]</span>
  ]
  run [
    editor-event-loop screen, console, e
    s:text<span class="Special"> &lt;- </span>editor-contents e
    <span class="Constant">1</span>:@:char/<span class="Special">raw &lt;- </span>copy *s
  ]
  memory-should-contain [
    <span class="Constant">1</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abdefc]</span>
  ]
]

<span class="Comment"># keep the bottom of recipes from scrolling off the screen</span>

<span class="muScenario">scenario</span> scrolling-down-past-bottom-of-recipe-editor [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, <span class="Constant">[]</span>, <span class="Constant">[]</span>
  render-all screen, env, render
  assume-console [
    press enter
    press down-arrow
  ]
  event-loop screen, console, env
  <span class="Comment"># no scroll</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
]

<span class="muScenario">scenario</span> cursor-down-in-recipe-editor [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, <span class="Constant">[]</span>, <span class="Constant">[]</span>
  render-all screen, env, render
  assume-console [
    press enter
    press up-arrow
    press down-arrow  <span class="Comment"># while cursor isn't at bottom</span>
  ]
  event-loop screen, console, env
  cursor:char<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
  print screen, cursor
  <span class="Comment"># cursor moves back to bottom</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
   <span class="Constant"> .␣                                                 ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
]

<span class="Comment"># we'll not use the recipe-editor's 'bottom' element directly, because later</span>
<span class="Comment"># layers will add other stuff to the left side below the editor (error messages)</span>

<span class="muData">container</span> environment [
  recipe-bottom:num
]

<span class="muRecipe">after</span> <span class="Constant">&lt;render-recipe-components-end&gt;</span> [
  *env<span class="Special"> &lt;- </span>put *env, <span class="Constant">recipe-bottom:offset</span>, row
]

<span class="muRecipe">after</span> <span class="Constant">&lt;global-keypress&gt;</span> [
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> sandbox-in-focus?
    down-arrow?:bool<span class="Special"> &lt;- </span>equal k, <span class="Constant">65516/down-arrow</span>
    <span class="muControl">break-unless</span> down-arrow?
    recipe-editor:&amp;:editor<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
    recipe-cursor-row:num<span class="Special"> &lt;- </span>get *recipe-editor, <span class="Constant">cursor-row:offset</span>
    recipe-editor-bottom:num<span class="Special"> &lt;- </span>get *recipe-editor, <span class="Constant">bottom:offset</span>
    at-bottom-of-editor?:bool<span class="Special"> &lt;- </span>greater-or-equal recipe-cursor-row, recipe-editor-bottom
    <span class="muControl">break-unless</span> at-bottom-of-editor?
    more-to-scroll?:bool<span class="Special"> &lt;- </span>more-to-scroll? env, screen
    <span class="muControl">break-if</span> more-to-scroll?
    <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> sandbox-in-focus?
    page-down?:bool<span class="Special"> &lt;- </span>equal k, <span class="Constant">65518/page-down</span>
    <span class="muControl">break-unless</span> page-down?
    more-to-scroll?:bool<span class="Special"> &lt;- </span>more-to-scroll? env, screen
    <span class="muControl">break-if</span> more-to-scroll?
    <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
  <span class="Delimiter">}</span>
]

<span class="muRecipe">after</span> <span class="Constant">&lt;global-type&gt;</span> [
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> sandbox-in-focus?
    page-down?:bool<span class="Special"> &lt;- </span>equal k, <span class="Constant">6/ctrl-f</span>
    <span class="muControl">break-unless</span> page-down?
    more-to-scroll?:bool<span class="Special"> &lt;- </span>more-to-scroll? env, screen
    <span class="muControl">break-if</span> more-to-scroll?
    <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
  <span class="Delimiter">}</span>
]

<span class="muRecipe">def</span> more-to-scroll? env:&amp;:environment, screen:&amp;:screen<span class="muRecipe"> -&gt; </span>result:bool [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  recipe-bottom:num<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipe-bottom:offset</span>
  height:num<span class="Special"> &lt;- </span>screen-height screen
  result<span class="Special"> &lt;- </span>greater-or-equal recipe-bottom, height
]

<span class="muScenario">scenario</span> scrolling-down-past-bottom-of-recipe-editor-2 [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, <span class="Constant">[]</span>, <span class="Constant">[]</span>
  render-all screen, env, render
  assume-console [
    <span class="Comment"># add a line</span>
    press enter
    <span class="Comment"># cursor back to top line</span>
    press up-arrow
    <span class="Comment"># try to scroll</span>
    press page-down  <span class="Comment"># or ctrl-f</span>
  ]
  event-loop screen, console, env
  <span class="Comment"># no scroll, and cursor remains at top line</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
]

<span class="muScenario">scenario</span> scrolling-down-past-bottom-of-recipe-editor-3 [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, <span class="Constant">[]</span>, <span class="Constant">[ab</span>
<span class="Constant">cd]</span>
  render-all screen, env, render
  assume-console [
    <span class="Comment"># add a line</span>
    press enter
    <span class="Comment"># switch to sandbox</span>
    press ctrl-n
    <span class="Comment"># move cursor</span>
    press down-arrow
  ]
  event-loop screen, console, env
  cursor:char<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
  print screen, cursor
  <span class="Comment"># no scroll on recipe side, cursor moves on sandbox side</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎ab                                               .</span>
   <span class="Constant"> .                                                  ╎␣d                                               .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
]

<span class="Comment"># scrolling through sandboxes</span>

<span class="muScenario">scenario</span> scrolling-down-past-bottom-of-sandbox-editor [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
  <span class="Comment"># initialize sandbox side</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, <span class="Constant">[]</span>, <span class="Constant">[add 2, 2]</span>
  render-all screen, env, render
  assume-console [
    <span class="Comment"># create a sandbox</span>
    press F4
  ]
  event-loop screen, console, env
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
  ]
  <span class="Comment"># switch to sandbox window and hit 'page-down'</span>
  assume-console [
    press ctrl-n
    press page-down
  ]
  run [
    event-loop screen, console, env
    cursor:char<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
    print screen, cursor
  ]
  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
  <span class="Comment"># cursor moves to first sandbox</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎␣   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
   <span class="Constant"> .                                                  ╎4                                                .</span>
  ]
  <span class="Comment"># hit 'page-up'</span>
  assume-console [
    press page-up
  ]
  run [
    event-loop screen, console, env
    cursor:char<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
    print screen, cursor
  ]
  <span class="Comment"># sandbox editor displays again, cursor is in editor</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎␣                                                .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
  ]
]

<span class="Comment"># page-down on sandbox side updates render-from to scroll sandboxes</span>
<span class="muRecipe">after</span> <span class="Constant">&lt;global-keypress&gt;</span> [
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> sandbox-in-focus?
    page-down?:bool<span class="Special"> &lt;- </span>equal k, <span class="Constant">65518/page-down</span>
    <span class="muControl">break-unless</span> page-down?
    sandbox:&amp;:sandbox<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
    <span class="muControl">break-unless</span> sandbox
    <span class="Comment"># slide down if possible</span>
    <span class="Delimiter">{</span>
      render-from:num<span class="Special"> &lt;- </span>get *env, <span class="Constant">render-from:offset</span>
      number-of-sandboxes:num<span class="Special"> &lt;- </span>get *env, <span class="Constant">number-of-sandboxes:offset</span>
      max:num<span class="Special"> &lt;- </span>subtract number-of-sandboxes, <span class="Constant">1</span>
      at-end?:bool<span class="Special"> &lt;- </span>greater-or-equal render-from, max
      <span class="muControl">jump-if</span> at-end?, <span class="Constant">+finish-event:label</span>  <span class="Comment"># render nothing</span>
      render-from<span class="Special"> &lt;- </span>add render-from, <span class="Constant">1</span>
      *env<span class="Special"> &lt;- </span>put *env, <span class="Constant">render-from:offset</span>, render-from
    <span class="Delimiter">}</span>
    hide-screen screen
    screen<span class="Special"> &lt;- </span>render-sandbox-side screen, env, render
    show-screen screen
    <span class="muControl">jump</span> <span class="Constant">+finish-event:label</span>
  <span class="Delimiter">}</span>
]

<span class="Comment"># update-cursor takes render-from into account</span>
<span class="muRecipe">after</span> <span class="Constant">&lt;update-cursor-special-cases&gt;</span> [
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> sandbox-in-focus?
    render-from:num<span class="Special"> &lt;- </span>get *env, <span class="Constant">render-from:offset</span>
    scrolling?:bool<span class="Special"> &lt;- </span>greater-or-equal render-from, <span class="Constant">0</span>
    <span class="muControl">break-unless</span> scrolling?
    cursor-column:num<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">left:offset</span>
    screen<span class="Special"> &lt;- </span>move-cursor screen, <span class="Constant">2/row</span>, cursor-column  <span class="Comment"># highlighted sandbox will always start at row 2</span>
    <span class="muControl">return</span>
  <span class="Delimiter">}</span>
]

<span class="Comment"># 'page-up' on sandbox side is like 'page-down': updates render-from when necessary</span>
<span class="muRecipe">after</span> <span class="Constant">&lt;global-keypress&gt;</span> [
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> sandbox-in-focus?
    page-up?:bool<span class="Special"> &lt;- </span>equal k, <span class="Constant">65519/page-up</span>
    <span class="muControl">break-unless</span> page-up?
    render-from:num<span class="Special"> &lt;- </span>get *env, <span class="Constant">render-from:offset</span>
    at-beginning?:bool<span class="Special"> &lt;- </span>equal render-from, <span class="Constant">-1</span>
    <span class="muControl">break-if</span> at-beginning?
    render-from<span class="Special"> &lt;- </span>subtract render-from, <span class="Constant">1</span>
    *env<span class="Special"> &lt;- </span>put *env, <span class="Constant">render-from:offset</span>, render-from
    hide-screen screen
    screen<span class="Special"> &lt;- </span>render-sandbox-side screen, env, render
    show-screen screen
    <span class="muControl">jump</span> <span class="Constant">+finish-event:label</span>
  <span class="Delimiter">}</span>
]

<span class="Comment"># sandbox belonging to 'env' whose next-sandbox is 'in'</span>
<span class="Comment"># return 0 if there's no such sandbox, either because 'in' doesn't exist in 'env', or because it's the first sandbox</span>
<span class="muRecipe">def</span> previous-sandbox env:&amp;:environment, in:&amp;:sandbox<span class="muRecipe"> -&gt; </span>out:&amp;:sandbox [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  curr:&amp;:sandbox<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
  <span class="muControl">return-unless</span> curr, <span class="Constant">0/nil</span>
  next:&amp;:sandbox<span class="Special"> &lt;- </span>get *curr, <span class="Constant">next-sandbox:offset</span>
  <span class="Delimiter">{</span>
    <span class="muControl">return-unless</span> next, <span class="Constant">0/nil</span>
    found?:bool<span class="Special"> &lt;- </span>equal next, in
    <span class="muControl">break-if</span> found?
    curr<span class="Special"> &lt;- </span>copy next
    next<span class="Special"> &lt;- </span>get *curr, <span class="Constant">next-sandbox:offset</span>
    <span class="muControl">loop</span>
  <span class="Delimiter">}</span>
  <span class="muControl">return</span> curr
]

<span class="muScenario">scenario</span> scrolling-down-on-recipe-side [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
  <span class="Comment"># initialize sandbox side and create a sandbox</span>
  recipes:text<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
<span class="Constant">]</span>
  <span class="Comment"># create a sandbox</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, recipes:text, <span class="Constant">[add 2, 2]</span>
  render-all screen, env, render
  assume-console [
    press F4
  ]
  event-loop screen, console, env
  <span class="Comment"># hit 'down' in recipe editor</span>
  assume-console [
    press page-down
  ]
  run [
    event-loop screen, console, env
    cursor:char<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
    print screen, cursor
  ]
  <span class="Comment"># cursor moves down on recipe side</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .␣                                                 ╎                                                 .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
  ]
]

<span class="muScenario">scenario</span> scrolling-through-multiple-sandboxes [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
  <span class="Comment"># initialize environment</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, <span class="Constant">[]</span>, <span class="Constant">[]</span>
  render-all screen, env, render
  <span class="Comment"># create 2 sandboxes</span>
  assume-console [
    press ctrl-n
    type <span class="Constant">[add 2, 2]</span>
    press F4
    type <span class="Constant">[add 1, 1]</span>
    press F4
  ]
  event-loop screen, console, env
  cursor:char<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
  print screen, cursor
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎␣                                                .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
   <span class="Constant"> .                                                  ╎4                                                .</span>
  ]
  <span class="Comment"># hit 'page-down'</span>
  assume-console [
    press page-down
  ]
  run [
    event-loop screen, console, env
    cursor:char<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
    print screen, cursor
  ]
  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
  <span class="Comment"># cursor moves to first sandbox</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎␣   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
   <span class="Constant"> .                                                  ╎4                                                .</span>
  ]
  <span class="Comment"># hit 'page-down' again</span>
  assume-console [
    press page-down
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># just second sandbox displayed</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
   <span class="Constant"> .                                                  ╎4                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
  <span class="Comment"># hit 'page-down' again</span>
  assume-console [
    press page-down
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># no change</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
   <span class="Constant"> .                                                  ╎4                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
  <span class="Comment"># hit 'page-up'</span>
  assume-console [
    press page-up
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># back to displaying both sandboxes without editor</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
   <span class="Constant"> .                                                  ╎4                                                .</span>
  ]
  <span class="Comment"># hit 'page-up' again</span>
  assume-console [
    press page-up
  ]
  run [
    event-loop screen, console, env
    cursor:char<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
    print screen, cursor
  ]
  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎␣                                                .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
   <span class="Constant"> .                                                  ╎4                                                .</span>
  ]
  <span class="Comment"># hit 'page-up' again</span>
  assume-console [
    press page-up
  ]
  run [
    event-loop screen, console, env
    cursor:char<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
    print screen, cursor
  ]
  <span class="Comment"># no change</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎␣                                                .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
   <span class="Constant"> .                                                  ╎4                                                .</span>
  ]
]

<span class="muScenario">scenario</span> scrolling-manages-sandbox-index-correctly [
  <span class="Constant">local-scope</span>
  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
  <span class="Comment"># initialize environment</span>
  env:&amp;:environment<span class="Special"> &lt;- </span>new-programming-environment screen, <span class="Constant">[]</span>, <span class="Constant">[]</span>
  render-all screen, env, render
  <span class="Comment"># create a sandbox</span>
  assume-console [
    press ctrl-n
    type <span class="Constant">[add 1, 1]</span>
    press F4
  ]
  event-loop screen, console, env
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
  <span class="Comment"># hit 'page-down' and 'page-up' a couple of times. sandbox index should be stable</span>
  assume-console [
    press page-down
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
  <span class="Comment"># cursor moves to first sandbox</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
  <span class="Comment"># hit 'page-up' again</span>
  assume-console [
    press page-up
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
<span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
  <span class="Comment"># hit 'page-down'</span>
  assume-console [
    press page-down
  ]
  run [
    event-loop screen, console, env
  ]
  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
  <span class="Comment"># cursor moves to first sandbox</span>
  screen-should-contain [
   <span class="Constant"> .                                                                                 run (F4)           .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
   <span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
   <span class="Constant"> .                                                  ╎2                                                .</span>
   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
   <span class="Constant"> .                                                  ╎                                                 .</span>
  ]
]
</pre>
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