Reverse gradients to make them easier/faster.

Make update rectangles more square for performance.

src/bar_code.toit

@@ -74,14 +74,11 @@ class BarCodeEanElement extends CustomElement:
 
   // Make a white background behind the bar code and draw the digits along the bottom.
   draw_background_ canvas/Canvas:
-    if not (x and y): return
-    Background.draw background_ canvas x_ y_ w h
-
     // Bar code coordinates.
-    text_x := x + EAN_13_QUIET_ZONE_WIDTH + EAN_13_START_WIDTH
-    text_y := y + EAN_13_HEIGHT + number_height_ - EAN_13_BOTTOM_SPACE + 1
+    text_x := EAN_13_QUIET_ZONE_WIDTH + EAN_13_START_WIDTH
+    text_y := EAN_13_HEIGHT + number_height_ - EAN_13_BOTTOM_SPACE + 1
 
-    canvas.text (x + 1) text_y --text=code_[..1] --color=color_ --font=sans10_
+    canvas.text 1 text_y --text=code_[..1] --color=color_ --font=sans10_
 
     code_[1..7].split "":
       if it != "":
@@ -97,18 +94,15 @@ class BarCodeEanElement extends CustomElement:
     canvas.text text_x text_y --text=">" --color=color_ --font=sans10_
 
   // Redraw routine.
-  draw canvas/Canvas:
-    if not (x and y): return
-    if (canvas.bounds_analysis x y w h) == Canvas.ALL_OUTSIDE: return
+  custom_draw canvas/Canvas:
     draw_background_ canvas
 
-    x := x_ + EAN_13_QUIET_ZONE_WIDTH
-    top := y_
+    x := EAN_13_QUIET_ZONE_WIDTH
     long_height := EAN_13_HEIGHT
     short_height := EAN_13_HEIGHT - EAN_13_BOTTOM_SPACE
     // Start bars: 101.
-    canvas.rectangle x     top --w=1 --h=long_height --color=color_
-    canvas.rectangle x + 2 top --w=1 --h=long_height --color=color_
+    canvas.rectangle x     0 --w=1 --h=long_height --color=color_
+    canvas.rectangle x + 2 0 --w=1 --h=long_height --color=color_
     x += 3
     first_code := EAN_13_FIRST_CODES_[code_[0] & 0xf]
     // Left digits using the L or G mapping.
@@ -117,20 +111,20 @@ class BarCodeEanElement extends CustomElement:
       code := ((first_code >> (6 - i)) & 1) == 0 ? (l_ digit) : (g_ digit)
       for b := 6; b >= 0; b--:
         if ((1 << b) & code) != 0:
-          canvas.rectangle x top --w=1 --h=short_height --color=color_
+          canvas.rectangle x 0 --w=1 --h=short_height --color=color_
         x++
     // Middle bars: 01010
-    canvas.rectangle x + 1 top --w=1 --h=long_height --color=color_
-    canvas.rectangle x + 3 top --w=1 --h=long_height --color=color_
+    canvas.rectangle x + 1 0 --w=1 --h=long_height --color=color_
+    canvas.rectangle x + 3 0 --w=1 --h=long_height --color=color_
     x += 5
     // Left digits using the R mapping.
     for i := 7; i < 13; i++:
       digit := code_[i]
       code := r_ digit
       for b := 6; b >= 0; b--:
         if ((1 << b) & code) != 0:
-          canvas.rectangle x top --w=1 --h=short_height --color=color_
+          canvas.rectangle x 0 --w=1 --h=short_height --color=color_
         x++
     // End bars: 101.
-    canvas.rectangle x     top --w=1 --h=long_height --color=color_
-    canvas.rectangle x + 2 top --w=1 --h=long_height --color=color_
+    canvas.rectangle x     0 --w=1 --h=long_height --color=color_
+    canvas.rectangle x + 2 0 --w=1 --h=long_height --color=color_

src/common.toit

@@ -64,18 +64,30 @@ abstract class Canvas:
   abstract make_alpha_map -> Canvas
   abstract make_alpha_map --padding/int -> Canvas
 
-  static ALL_OUTSIDE ::= 0
-  static ALL_INSIDE ::= 1
-  static MIXED_BOUNDS ::= 2
+  /*
+  A, C disjoint or one of them is empty 0
+  A subset of C, A not empty            1
+  C subset of A, C not empty            2
+  A identical to C and non-empty        3
+  */
+
+  static DISJOINT           ::= 0  // The area and the canvas are disjoint.
+  static AREA_IN_CANVAS     ::= 1  // The area is a subset of the canvas.
+  static CANVAS_IN_AREA     ::= 2  // The canvas is a subset of the area.
+  static COINCIDENT         ::= 3  // The area and the canvas are identical.
+  static OVERLAP            ::= 4  // The areas overlap, but neither is a subset of the other.
 
   bounds_analysis x/int y/int w/int h/int -> int:
-    if h == 0 or w == 0: return ALL_OUTSIDE
+    if h == 0 or w == 0 or width_ == 0 or height_ == 0: return DISJOINT
     transform.xywh x y w h: | x2 y2 w2 h2 |
       right := x2 + w2
       bottom := y2 + h2
-      if right < 0 or bottom < 0 or x2 >= width_ or y2 >= height_: return ALL_OUTSIDE
-      if x2 >= 0 and y2 >= 0 and right <= width_ and bottom <= height_: return ALL_INSIDE
-    return MIXED_BOUNDS
+      if right < 0 or bottom < 0 or x2 >= width_ or y2 >= height_: return DISJOINT
+      if x2 >= 0 and y2 >= 0 and right <= width_ and bottom <= height_:
+        if x2 == 0 and y2 == 0 and right == width_ and bottom == height_: return COINCIDENT
+        return AREA_IN_CANVAS
+      if x2 <= 0 and y2 <= 0 and right >= width_ and bottom >= height_: return CANVAS_IN_AREA
+    return OVERLAP
 
   abstract composit frame_opacity frame_canvas/Canvas painting_opacity painting_canvas/Canvas
 

src/element.toit

@@ -228,7 +228,7 @@ class Div extends Element:
   draw canvas/Canvas -> none:
     old_transform := canvas.transform
     canvas.transform = old_transform.translate x_ y_
-    Background.draw background_ canvas 0 0 w h
+    Background.draw background_ canvas 0 0 w h --no-autocropped
     custom_draw canvas
     if border_: border_.draw canvas 0 0 w h
     canvas.transform = old_transform
@@ -423,10 +423,12 @@ abstract class CustomElement extends ClippingDiv:
 
   draw canvas/Canvas -> none:
     if not (x and y): return
-    if (canvas.bounds_analysis x y w h) == Canvas.ALL_OUTSIDE: return
+    analysis := canvas.bounds_analysis x y w h
+    if analysis == Canvas.DISJOINT: return
+    autocropped := analysis == Canvas.CANVAS_IN_AREA or analysis == Canvas.COINCIDENT
     old_transform := canvas.transform
     canvas.transform = old_transform.translate x_ y_
-    Background.draw background_ canvas 0 0 w h
+    Background.draw background_ canvas 0 0 w h --autocropped=autocropped
     custom_draw canvas
     if border_: border_.draw canvas 0 0 w h
     canvas.transform = old_transform
@@ -494,7 +496,7 @@ class ClippingDiv extends Div:
   draw canvas/Canvas -> none:
     // If we are outside the window and the decorations, there is nothing to do.
     extent: | x2 y2 w2 h2 |
-      if (canvas.bounds_analysis x2 y2 w2 h2) == Canvas.ALL_OUTSIDE: return
+      if (canvas.bounds_analysis x2 y2 w2 h2) == Canvas.DISJOINT: return
 
     old_transform := canvas.transform
     canvas.transform = old_transform.translate x_ y_
@@ -521,7 +523,7 @@ class ClippingDiv extends Div:
       if border_: border_.draw border_canvas 0 0 w h
 
     painting_canvas := canvas.create_similar
-    Background.draw background_ painting_canvas 0 0 w h
+    Background.draw background_ painting_canvas 0 0 w h --autocropped
     custom_draw painting_canvas
 
     canvas.composit frame_opacity border_canvas content_opacity painting_canvas
@@ -584,7 +586,7 @@ class PngElement extends CustomElement:
   // Redraw routine.
   custom_draw canvas/Canvas:
     y2 := 0
-    while y2 < h and (canvas.bounds_analysis 0 y2 w (h - y2)) != Canvas.ALL_OUTSIDE:
+    while y2 < h and (canvas.bounds_analysis 0 y2 w (h - y2)) != Canvas.DISJOINT:
       png_.get_indexed_image_data y2 h
           --accept_8_bit=canvas.supports_8_bit
           --need_gray_palette=canvas.gray_scale: | y_from/int y_to/int bits_per_pixel/int pixels/ByteArray line_stride/int palette/ByteArray alpha_palette/ByteArray |
@@ -689,9 +691,9 @@ class Slider extends CustomElement:
         analysis = canvas.bounds_analysis 0 0 (w - boundary_) h
       else:
         analysis = canvas.bounds_analysis 0 0 w (h - boundary_)
-      if analysis != Canvas.ALL_OUTSIDE:
-        if analysis == Canvas.ALL_INSIDE:
-          background_lo_.draw canvas 0 0 w h
+      if analysis != Canvas.DISJOINT:
+        if analysis == Canvas.CANVAS_IN_AREA or analysis == Canvas.COINCIDENT:
+          background_lo_.draw canvas 0 0 w h --autocropped
         else:
           blend = true
     if background_hi_ and boundary_ < thumb_max:
@@ -700,9 +702,9 @@ class Slider extends CustomElement:
         analysis = canvas.bounds_analysis (w - boundary_) 0 w h
       else:
         analysis = canvas.bounds_analysis 0 (h - boundary_) w h
-      if analysis != Canvas.ALL_OUTSIDE:
-        if analysis == Canvas.ALL_INSIDE:
-          background_hi_.draw canvas 0 0 w h
+      if analysis != Canvas.DISJOINT:
+        if analysis == Canvas.CANVAS_IN_AREA or analysis == Canvas.COINCIDENT:
+          background_hi_.draw canvas 0 0 w h --autocropped
         else:
           blend = true
     if not blend: return
@@ -717,13 +719,13 @@ class Slider extends CustomElement:
         lo_alpha.rectangle 0 0 --w=(w - boundary_) --h=h --color=0xff
       else:
         lo_alpha.rectangle 0 0 --w=w --h=(h - boundary_) --color=0xff
-      background_lo_.draw lo 0 0 w h
+      Background.draw background_lo_ lo 0 0 w h --autocropped
     if background_hi_:
       if horizontal_:
         hi_alpha.rectangle (w - boundary_) 0 --w=boundary_ --h=h --color=0xff
       else:
         hi_alpha.rectangle 0 (h - boundary_) --w=w --h=boundary_ --color=0xff
-      background_hi_.draw hi 0 0 w h
+      Background.draw background_hi_ hi 0 0 w h --autocropped
 
     canvas.composit hi_alpha hi lo_alpha lo