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* 6206Kartik Agaram2020-04-176-115/+66
* 6155Kartik Agaram2020-03-201-1/+3
* 6066 - Vim syntax highlighting for Mu filesKartik Agaram2020-02-281-1/+1
* 5960Kartik Agaram2020-01-301-0/+1
* 5959Kartik Agaram2020-01-301-1/+1
* 5853Kartik Agaram2020-01-013-135/+0
* 5852Kartik Agaram2020-01-01232-3/+3
* 5787Kartik Agaram2019-12-026-18/+262
* 5494Kartik Agaram2019-07-271-0/+11
* 5485 - promote SubX to top-levelKartik Agaram2019-07-27229-0/+80488
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<a href='https://github.com/akkartik/mu/blob/main/101screen.subx'>https://github.com/akkartik/mu/blob/main/101screen.subx</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="subxComment"># Primitives for screen control.</span>
<span id="L2" class="LineNr"> 2 </span><span class="subxComment">#</span>
<span id="L3" class="LineNr"> 3 </span><span class="subxComment"># We need to do this in machine code because Mu doesn't have global variables</span>
<span id="L4" class="LineNr"> 4 </span><span class="subxComment"># yet (for the start of video memory).</span>
<span id="L5" class="LineNr"> 5 </span>
<span id="L6" class="LineNr"> 6 </span>== code
<span id="L7" class="LineNr"> 7 </span>
<span id="L8" class="LineNr"> 8 </span><span class="subxFunction">pixel-on-real-screen</span>:  <span class="subxComment"># x: int, y: int, color: int</span>
<span id="L9" class="LineNr"> 9 </span>    <span class="subxS1Comment"># . prologue</span>
<span id="L10" class="LineNr">10 </span>    55/push-ebp
<span id="L11" class="LineNr">11 </span>    89/&lt;- %ebp 4/r32/esp
<span id="L12" class="LineNr">12 </span>    <span class="subxComment">#</span>
<span id="L13" class="LineNr">13 </span>    (<a href='101screen.subx.html#L21'>pixel-on-screen-buffer</a> *<span class="SpecialChar"><a href='boot.subx.html#L650'>Video-memory-addr</a></span> *(ebp+8) *(ebp+0xc) *(ebp+0x10) 0x400 0x300)
<span id="L14" class="LineNr">14 </span><span class="Constant">$pixel-on-real-screen:end</span>:
<span id="L15" class="LineNr">15 </span>    <span class="subxS1Comment"># . epilogue</span>
<span id="L16" class="LineNr">16 </span>    89/&lt;- %esp 5/r32/ebp
<span id="L17" class="LineNr">17 </span>    5d/pop-to-ebp
<span id="L18" class="LineNr">18 </span>    c3/return
<span id="L19" class="LineNr">19 </span>
<span id="L20" class="LineNr">20 </span><span class="subxComment"># 'buffer' here is not a valid Mu type: a naked address without a length.</span>
<span id="L21" class="LineNr">21 </span><span class="subxFunction">pixel-on-screen-buffer</span>:  <span class="subxComment"># buffer: (addr byte), x: int, y: int, color: int, width: int, height: int</span>
<span id="L22" class="LineNr">22 </span>    <span class="subxS1Comment"># . prologue</span>
<span id="L23" class="LineNr">23 </span>    55/push-ebp
<span id="L24" class="LineNr">24 </span>    89/&lt;- %ebp 4/r32/esp
<span id="L25" class="LineNr">25 </span>    <span class="subxS1Comment"># . save registers</span>
<span id="L26" class="LineNr">26 </span>    50/push-eax
<span id="L27" class="LineNr">27 </span>    51/push-ecx
<span id="L28" class="LineNr">28 </span>    <span class="subxComment"># bounds checks</span>
<span id="L29" class="LineNr">29 </span>    8b/-&gt; *(ebp+0xc) 0/r32/eax  <span class="subxComment"># foo</span>
<span id="L30" class="LineNr">30 </span>    3d/compare-eax-and 0/imm32
<span id="L31" class="LineNr">31 </span>    7c/jump-if-&lt; $pixel-on-screen-buffer:end/disp8
<span id="L32" class="LineNr">32 </span>    3b/compare 0/r32/eax *(ebp+0x18)
<span id="L33" class="LineNr">33 </span>    7d/jump-if-&gt;= $pixel-on-screen-buffer:end/disp8
<span id="L34" class="LineNr">34 </span>    8b/-&gt; *(ebp+0x10) 0/r32/eax
<span id="L35" class="LineNr">35 </span>    3d/compare-eax-and 0/imm32
<span id="L36" class="LineNr">36 </span>    7c/jump-if-&lt; $pixel-on-screen-buffer:end/disp8
<span id="L37" class="LineNr">37 </span>    3b/compare 0/r32/eax *(ebp+0x1c)
<span id="L38" class="LineNr">38 </span>    7d/jump-if-&gt;= $pixel-on-screen-buffer:end/disp8
<span id="L39" class="LineNr">39 </span>    <span class="subxComment"># eax = y*width + x</span>
<span id="L40" class="LineNr">40 </span>    8b/-&gt; *(ebp+0x10) 0/r32/eax
<span id="L41" class="LineNr">41 </span>    0f af/multiply-&gt; *(ebp+0x18) 0/r32/eax
<span id="L42" class="LineNr">42 </span>    03/add-&gt; *(ebp+0xc) 0/r32/eax
<span id="L43" class="LineNr">43 </span>    <span class="subxComment"># eax += location of frame buffer</span>
<span id="L44" class="LineNr">44 </span>    03/add-&gt; *(ebp+8) 0/r32/eax
<span id="L45" class="LineNr">45 </span>    <span class="subxComment"># *eax = color</span>
<span id="L46" class="LineNr">46 </span>    8b/-&gt; *(ebp+0x14) 1/r32/ecx
<span id="L47" class="LineNr">47 </span>    88/byte&lt;- *eax 1/r32/CL
<span id="L48" class="LineNr">48 </span><span class="Constant">$pixel-on-screen-buffer:end</span>:
<span id="L49" class="LineNr">49 </span>    <span class="subxS1Comment"># . restore registers</span>
<span id="L50" class="LineNr">50 </span>    59/pop-to-ecx
<span id="L51" class="LineNr">51 </span>    58/pop-to-eax
<span id="L52" class="LineNr">52 </span>    <span class="subxS1Comment"># . epilogue</span>
<span id="L53" class="LineNr">53 </span>    89/&lt;- %esp 5/r32/ebp
<span id="L54" class="LineNr">54 </span>    5d/pop-to-ebp
<span id="L55" class="LineNr">55 </span>    c3/return
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