7538 - baremetal: screen coords in graphemes

4 files changed, 54 insertions, 42 deletions

diff --git a/baremetal/103grapheme.subx b/baremetal/103grapheme.subx
index f854e03d..5b160bfe 100644
--- a/baremetal/103grapheme.subx
+++ b/baremetal/103grapheme.subx
@@ -2,9 +2,16 @@
 #
 # We need to do this in machine code because Mu doesn't have global variables
 # yet (for the start of video memory).
+#
+# There are uncomfortable assumptions baked in here about english/latin
+# script. We convert the grid of pixels into a fixed-width grid of graphemes,
+# which may not work well with other language families.
 
 == code
 
+# The Mu computer's screen is 1024px wide and 768px tall.
+# The Mu computer's font is 8px wide and 16px tall.
+# Therefore 'x' here is in [0, 128), and 'y' is in [0, 48)
 draw-grapheme-on-real-screen:  # g: grapheme, x: int, y: int, color: int, background-color: int
     # . prologue
     55/push-ebp
@@ -22,25 +29,29 @@ draw-grapheme-on-real-screen:  # g: grapheme, x: int, y: int, color: int, backgr
     # if (letter-bitmap >= 0x9000) return  # characters beyond ASCII currently not supported
     81 7/subop/compare %esi 0x9000/imm32
     7d/jump-if->= $draw-grapheme-on-real-screen:end/disp8
-    # edx = y
+    # var ycurr/edx: int = y*16
     8b/-> *(ebp+0x10) 2/r32/edx
-    # var ymax/ebx: int = y + 16
+    c1 4/subop/shift-left %edx 4/imm8
+    # var ymax/ebx: int = ycurr + 16
     8b/-> *(ebp+0x10) 3/r32/ebx
+    c1 4/subop/shift-left %ebx 4/imm8
     81 0/subop/add %ebx 0x10/imm32
     {
-      # if (y >= ymax) break
+      # if (ycurr >= ymax) break
       39/compare %edx 3/r32/ebx
       7d/jump-if->= break/disp8
-      # eax = x + 7
+      # var xcurr/eax: int = x*8 + 7
       8b/-> *(ebp+0xc) 0/r32/eax  # font-width - 1
+      c1 4/subop/shift-left %eax 3/imm8
       81 0/subop/add %eax 7/imm32
-      # var xmin/ecx: int = x
+      # var xmin/ecx: int = x*8
       8b/-> *(ebp+0xc) 1/r32/ecx
+      c1 4/subop/shift-left %ecx 3/imm8
       # var row-bitmap/ebx: int = *letter-bitmap
       53/push-ebx
       8b/-> *esi 3/r32/ebx
       {
-        # if (x < xmin) break
+        # if (xcurr < xmin) break
         39/compare %eax 1/r32/ecx
         7c/jump-if-< break/disp8
         # shift LSB from row-bitmap into carry flag (CF)
diff --git a/baremetal/500text-screen.mu b/baremetal/500text-screen.mu
index 96c6644f..b387496f 100644
--- a/baremetal/500text-screen.mu
+++ b/baremetal/500text-screen.mu
@@ -45,13 +45,14 @@ fn initialize-screen screen: (addr screen), width: int, height: int {
   copy-to *dest, 0
 }
 
+# in graphemes
 fn screen-size screen: (addr screen) -> _/eax: int, _/ecx: int {
   var width/eax: int <- copy 0
   var height/ecx: int <- copy 0
   compare screen, 0
   {
     break-if-!=
-    return 0x400, 0x300  # 1024x768
+    return 0x80, 0x30  # 128x48
   }
   # fake screen
   var screen-addr/esi: (addr screen) <- copy screen
diff --git a/baremetal/501draw-text.mu b/baremetal/501draw-text.mu
index ca100831..0bb95dee 100644
--- a/baremetal/501draw-text.mu
+++ b/baremetal/501draw-text.mu
@@ -9,7 +9,7 @@ fn cursor-left screen: (addr screen) {
     break-if->
     return
   }
-  cursor-x <- subtract 8  # font-width
+  cursor-x <- decrement
   set-cursor-position screen, cursor-x, cursor-y
 }
 
@@ -26,7 +26,7 @@ fn cursor-right screen: (addr screen) {
     break-if-<
     return
   }
-  cursor-x <- add 8  # font-width
+  cursor-x <- increment
   set-cursor-position screen, cursor-x, cursor-y
 }
 
@@ -39,7 +39,7 @@ fn cursor-up screen: (addr screen) {
     break-if->
     return
   }
-  cursor-y <- subtract 0x10  # screen-height
+  cursor-y <- decrement
   set-cursor-position screen, cursor-x, cursor-y
 }
 
@@ -56,7 +56,7 @@ fn cursor-down screen: (addr screen) {
     break-if-<
     return
   }
-  cursor-y <- add 0x10  # screen-height
+  cursor-y <- increment
   set-cursor-position screen, cursor-x, cursor-y
 }
 
@@ -82,7 +82,7 @@ fn draw-text-rightward screen: (addr screen), text: (addr array byte), x: int, x
     var g/eax: grapheme <- read-grapheme stream
     compare g, 0xffffffff  # end-of-file
     break-if-=
-    xcurr <- add 8  # font-width
+    xcurr <- increment
     loop
   }
   compare xcurr, xmax
@@ -98,7 +98,7 @@ fn draw-text-rightward screen: (addr screen), text: (addr array byte), x: int, x
     compare g, 0xffffffff  # end-of-file
     break-if-=
     draw-grapheme screen, g, xcurr, y, color
-    xcurr <- add 8  # font-width
+    xcurr <- increment
     loop
   }
   set-cursor-position screen, xcurr, y
@@ -130,12 +130,12 @@ fn draw-text-wrapping-right-then-down screen: (addr screen), text: (addr array b
     var g/eax: grapheme <- read-grapheme stream
     compare g, 0xffffffff  # end-of-file
     break-if-=
-    xcurr <- add 8  # font-width
+    xcurr <- increment
     compare xcurr, xmax
     {
       break-if-<
       xcurr <- copy xmin
-      ycurr <- add 0x10  # font-height
+      ycurr <- increment
     }
     loop
   }
@@ -153,12 +153,12 @@ fn draw-text-wrapping-right-then-down screen: (addr screen), text: (addr array b
     compare g, 0xffffffff  # end-of-file
     break-if-=
     draw-grapheme screen, g, xcurr, ycurr, color
-    xcurr <- add 8  # font-width
+    xcurr <- increment
     compare xcurr, xmax
     {
       break-if-<
       xcurr <- copy xmin
-      ycurr <- add 0x10  # font-height
+      ycurr <- increment
     }
     loop
   }
@@ -170,12 +170,12 @@ fn move-cursor-rightward-and-downward screen: (addr screen), xmin: int, xmax: in
   var cursor-x/eax: int <- copy 0
   var cursor-y/ecx: int <- copy 0
   cursor-x, cursor-y <- cursor-position screen
-  cursor-x <- add 8  # font-width
+  cursor-x <- increment
   compare cursor-x, xmax
   {
     break-if-<
     cursor-x <- copy xmin
-    cursor-y <- add 0x10  # font-height
+    cursor-y <- increment
   }
   set-cursor-position screen, cursor-x, cursor-y
 }
@@ -193,12 +193,12 @@ fn draw-text-wrapping-right-then-down-from-cursor screen: (addr screen), text: (
   var cursor-y/ecx: int <- copy 0
   cursor-x, cursor-y <- cursor-position screen
   var end-x/edx: int <- copy cursor-x
-  end-x <- add 8  # font-width
+  end-x <- increment
   compare end-x, xmax
   {
     break-if-<
     cursor-x <- copy xmin
-    cursor-y <- add 0x10  # font-height
+    cursor-y <- increment
   }
   cursor-x, cursor-y <- draw-text-wrapping-right-then-down screen, text, xmin, ymin, xmax, ymax, cursor-x, cursor-y, color
 }
@@ -223,12 +223,12 @@ fn draw-int32-hex-wrapping-right-then-down screen: (addr screen), n: int, xmin:
     var g/eax: grapheme <- read-grapheme stream
     compare g, 0xffffffff  # end-of-file
     break-if-=
-    xcurr <- add 8  # font-width
+    xcurr <- increment
     compare xcurr, xmax
     {
       break-if-<
       xcurr <- copy xmin
-      ycurr <- add 0x10  # font-height
+      ycurr <- increment
     }
     loop
   }
@@ -246,12 +246,12 @@ fn draw-int32-hex-wrapping-right-then-down screen: (addr screen), n: int, xmin:
     compare g, 0xffffffff  # end-of-file
     break-if-=
     draw-grapheme screen, g, xcurr, ycurr, color
-    xcurr <- add 8  # font-width
+    xcurr <- increment
     compare xcurr, xmax
     {
       break-if-<
       xcurr <- copy xmin
-      ycurr <- add 0x10  # font-height
+      ycurr <- increment
     }
     loop
   }
@@ -272,12 +272,12 @@ fn draw-int32-hex-wrapping-right-then-down-from-cursor screen: (addr screen), n:
   var cursor-y/ecx: int <- copy 0
   cursor-x, cursor-y <- cursor-position screen
   var end-x/edx: int <- copy cursor-x
-  end-x <- add 8  # font-width
+  end-x <- increment
   compare end-x, xmax
   {
     break-if-<
     cursor-x <- copy xmin
-    cursor-y <- add 0x10  # font-height
+    cursor-y <- increment
   }
   cursor-x, cursor-y <- draw-int32-hex-wrapping-right-then-down screen, n, xmin, ymin, xmax, ymax, cursor-x, cursor-y, color
 }
@@ -302,12 +302,12 @@ fn draw-int32-decimal-wrapping-right-then-down screen: (addr screen), n: int, xm
     var g/eax: grapheme <- read-grapheme stream
     compare g, 0xffffffff  # end-of-file
     break-if-=
-    xcurr <- add 8  # font-width
+    xcurr <- increment
     compare xcurr, xmax
     {
       break-if-<
       xcurr <- copy xmin
-      ycurr <- add 0x10  # font-height
+      ycurr <- increment
     }
     loop
   }
@@ -325,12 +325,12 @@ fn draw-int32-decimal-wrapping-right-then-down screen: (addr screen), n: int, xm
     compare g, 0xffffffff  # end-of-file
     break-if-=
     draw-grapheme screen, g, xcurr, ycurr, color
-    xcurr <- add 8  # font-width
+    xcurr <- increment
     compare xcurr, xmax
     {
       break-if-<
       xcurr <- copy xmin
-      ycurr <- add 0x10  # font-height
+      ycurr <- increment
     }
     loop
   }
@@ -351,12 +351,12 @@ fn draw-int32-decimal-wrapping-right-then-down-from-cursor screen: (addr screen)
   var cursor-y/ecx: int <- copy 0
   cursor-x, cursor-y <- cursor-position screen
   var end-x/edx: int <- copy cursor-x
-  end-x <- add 8  # font-width
+  end-x <- increment
   compare end-x, xmax
   {
     break-if-<
     cursor-x <- copy xmin
-    cursor-y <- add 0x10  # font-height
+    cursor-y <- increment
   }
   cursor-x, cursor-y <- draw-int32-decimal-wrapping-right-then-down screen, n, xmin, ymin, xmax, ymax, cursor-x, cursor-y, color
 }
@@ -385,7 +385,7 @@ fn draw-text-downward screen: (addr screen), text: (addr array byte), x: int, y:
     var g/eax: grapheme <- read-grapheme stream
     compare g, 0xffffffff  # end-of-file
     break-if-=
-    ycurr <- add 0x10  # font-height
+    ycurr <- increment
     loop
   }
   compare ycurr, ymax
@@ -401,7 +401,7 @@ fn draw-text-downward screen: (addr screen), text: (addr array byte), x: int, y:
     compare g, 0xffffffff  # end-of-file
     break-if-=
     draw-grapheme screen, g, x, ycurr, color
-    ycurr <- add 0x10  # font-height
+    ycurr <- increment
     loop
   }
   set-cursor-position screen, x, ycurr
@@ -432,11 +432,11 @@ fn draw-text-wrapping-down-then-right screen: (addr screen), text: (addr array b
     var g/eax: grapheme <- read-grapheme stream
     compare g, 0xffffffff  # end-of-file
     break-if-=
-    ycurr <- add 0x10  # font-height
+    ycurr <- increment
     compare ycurr, ymax
     {
       break-if-<
-      xcurr <- add 8  # font-width
+      xcurr <- increment
       ycurr <- copy ymin
     }
     loop
@@ -455,11 +455,11 @@ fn draw-text-wrapping-down-then-right screen: (addr screen), text: (addr array b
     compare g, 0xffffffff  # end-of-file
     break-if-=
     draw-grapheme screen, g, xcurr, ycurr, color
-    ycurr <- add 0x10  # font-height
+    ycurr <- increment
     compare ycurr, ymax
     {
       break-if-<
-      xcurr <- add 8  # font-width
+      xcurr <- increment
       ycurr <- copy ymin
     }
     loop
@@ -481,11 +481,11 @@ fn draw-text-wrapping-down-then-right-from-cursor screen: (addr screen), text: (
   var cursor-y/ecx: int <- copy 0
   cursor-x, cursor-y <- cursor-position screen
   var end-y/edx: int <- copy cursor-y
-  end-y <- add 0x10  # font-height
+  end-y <- increment
   compare end-y, ymax
   {
     break-if-<
-    cursor-x <- add 8  # font-width
+    cursor-x <- increment
     cursor-y <- copy ymin
   }
   cursor-x, cursor-y <- draw-text-wrapping-down-then-right screen, text, xmin, ymin, xmax, ymax, cursor-x, cursor-y, color
diff --git a/baremetal/ex4.mu b/baremetal/ex4.mu
index 52b681bc..8a3e285e 100644
--- a/baremetal/ex4.mu
+++ b/baremetal/ex4.mu
@@ -11,5 +11,5 @@
 
 fn main {
   var g/eax: grapheme <- copy 0x41  # 'A'
-  draw-grapheme 0, g, 0x10, 0x10, 0xa
+  draw-grapheme 0, g, 2, 1, 0xa  # x of 2 graphemes = 16px from top-left; y of 1 grapheme = 16px down from top-left
 }