reimplement Bresenham circle in Mu

508circle.mu

@@ -0,0 +1,90 @@
+fn draw-circle screen: (addr screen), cx: int, cy: int, radius: int, color: int {
+  var x: int
+  var y: int
+  var err: int
+  # x = -r
+  var tmp/eax: int <- copy radius
+  tmp <- negate
+  copy-to x, tmp
+  # err = 2 - 2*r
+  tmp <- copy radius
+  tmp <- shift-left 1
+  tmp <- negate
+  tmp <- add 2
+  copy-to err, tmp
+  #
+  var tmpx/ecx: int <- copy 0
+  var tmpy/edx: int <- copy 0
+  {
+    # pixel(cx-x, cy+y)
+    tmpx <- copy cx
+    tmpx <- subtract x
+    tmpy <- copy cy
+    tmpy <- add y
+    pixel screen, tmpx, tmpy, color
+    # pixel(cx-y, cy-x)
+    tmpx <- copy cx
+    tmpx <- subtract y
+    tmpy <- copy cy
+    tmpy <- subtract x
+    pixel screen, tmpx, tmpy, color
+    # pixel(cx+x, cy-y)
+    tmpx <- copy cx
+    tmpx <- add x
+    tmpy <- copy cy
+    tmpy <- subtract y
+    pixel screen, tmpx, tmpy, color
+    # pixel(cx+y, cy+x)
+    tmpx <- copy cx
+    tmpx <- add y
+    tmpy <- copy cy
+    tmpy <- add x
+    pixel screen, tmpx, tmpy, color
+    # r = err
+    tmp <- copy err
+    copy-to radius, tmp
+    # if (r <= y) { ++y; err += (y*2 + 1); }
+    {
+      tmpy <- copy y
+      compare radius, tmpy
+      break-if->
+      increment y
+      tmpy <- copy y
+      tmpy <- shift-left 1
+      tmpy <- increment
+      add-to err, tmpy
+    }
+    # if (r > x || err > y) { ++x; err += (x*2 + 1); }
+    $draw-circle:second-check: {
+      {
+        tmpx <- copy x
+        compare radius, tmpx
+        break-if->
+        tmpy <- copy y
+        compare err, tmpy
+        break-if->
+        break $draw-circle:second-check
+      }
+      increment x
+      tmpx <- copy x
+      tmpx <- shift-left 1
+      tmpx <- increment
+      add-to err, tmpx
+    }
+    # loop termination condition
+    compare x, 0
+    loop-if-<
+  }
+}
+
+fn draw-disc screen: (addr screen), cx: int, cy: int, radius: int, color: int, border-color: int {
+  var r/eax: int <- copy 0
+  {
+    compare r, radius
+    break-if->=
+    draw-circle screen, cx cy, r, color
+    r <- increment
+    loop
+  }
+  draw-circle screen, cx cy, r, border-color
+}