Proposal: Add support for even-odd fill and clip to Canvas

https://bugs.webkit.org/show_bug.cgi?id=106188

Patch by Rik Cabanier <cabanier@adobe.com> on 2013-01-21
Reviewed by Dirk Schulze.

Source/WebCore:

This patch adds support for an optional winding rule to fill, clip
and isPointInPath in canvas 2d. By default, the fill is non-zero but
you can now pass in an optional winding rule string ("nonzero" or "evenodd")
to make an explicit choice.

Tests: fast/canvas/canvas-clip-rule.html
       fast/canvas/canvas-fill-rule.html
       fast/canvas/canvas-isPointInPath-winding.html

* html/canvas/CanvasRenderingContext2D.cpp: Change implementation so it sets the windig rule in the context.
(WebCore::parseWinding):
(WebCore):
(WebCore::CanvasRenderingContext2D::fill):
(WebCore::CanvasRenderingContext2D::clip):
(WebCore::CanvasRenderingContext2D::isPointInPath):
* html/canvas/CanvasRenderingContext2D.h:
(CanvasRenderingContext2D):
* html/canvas/CanvasRenderingContext2D.idl: Change the idl so the new API is exposed to JavaScript.
* platform/graphics/cg/GraphicsContextCG.cpp: Fixes a bug where the wrong winding rule was set for clipping in Core Graphics.
(WebCore::GraphicsContext::clip):

LayoutTests:

Add tests to verify that the winding rule work as expected with clip, fill and isPointInPath

* fast/canvas/canvas-clip-rule-expected.txt: Added.
* fast/canvas/canvas-clip-rule.html: Added.
* fast/canvas/canvas-fill-rule-expected.txt: Added.
* fast/canvas/canvas-fill-rule.html: Added.
* fast/canvas/canvas-isPointInPath-winding-expected.txt: Added.
* fast/canvas/canvas-isPointInPath-winding.html: Added.
* fast/canvas/script-tests/canvas-clip-rule.js: Added.
(pixelDataAtPoint):
(checkResult):
(prepareTestScenario):
* fast/canvas/script-tests/canvas-fill-rule.js: Added.
(pixelDataAtPoint):
(checkResult):
(prepareTestScenario):
* fast/canvas/script-tests/canvas-isPointInPath-winding.js: Added.
(prepareTestScenario):

git-svn-id: svn://svn.chromium.org/blink/trunk@140352 bbb929c8-8fbe-4397-9dbb-9b2b20218538

3 files changed, 175 insertions, 0 deletions

diff --git a/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-clip-rule.js b/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-clip-rule.js
new file mode 100644
index 0000000..e6a45ed
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-clip-rule.js
@@ -0,0 +1,69 @@
+description("Series of tests to ensure correct results of the winding rule.");
+
+
+var tmpimg = document.createElement('canvas');
+tmpimg.width = 200;
+tmpimg.height = 200;
+ctx = tmpimg.getContext('2d');
+
+// Create the image for blending test with images.
+var img = document.createElement('canvas');
+img.width = 100;
+img.height = 100;
+var imgCtx = img.getContext('2d');
+
+function pixelDataAtPoint()
+{
+  return ctx.getImageData(50, 50, 1, 1).data;
+}
+
+function checkResult(expectedColors, sigma) {
+    for (var i = 0; i < 4; i++)
+	    shouldBeCloseTo("pixelDataAtPoint()[" + i + "]", expectedColors[i], sigma);
+}
+
+// Execute test.
+function prepareTestScenario() {
+    debug('Testing default clip');
+    ctx.fillStyle = 'rgb(255,0,0)';
+    ctx.fillRect(0, 0, 100, 100);
+    ctx.fillStyle = 'rgb(0,255,0)';
+    ctx.beginPath();
+    ctx.rect(0, 0, 100, 100);
+    ctx.rect(25, 25, 50, 50);
+    ctx.clip();
+    ctx.beginPath();
+    ctx.fillRect(0, 0, 100, 100);
+    checkResult([0, 255, 0, 255], 5);                        
+    debug('');
+
+    debug('Testing nonzero clip');
+    ctx.fillStyle = 'rgb(255,0,0)';
+    ctx.fillRect(0, 0, 100, 100);
+    ctx.fillStyle = 'rgb(0,255,0)';
+    ctx.beginPath();
+    ctx.rect(0, 0, 100, 100);
+    ctx.rect(25, 25, 50, 50);
+    ctx.clip('nonzero');
+    ctx.beginPath();
+    ctx.fillRect(0, 0, 100, 100);
+    checkResult([0, 255, 0, 255], 5);
+    debug('');
+	
+    debug('Testing evenodd clip');
+    ctx.fillStyle = 'rgb(255,0,0)';
+    ctx.fillRect(0, 0, 100, 100);
+    ctx.fillStyle = 'rgb(0,255,0)';
+    ctx.beginPath();
+    ctx.rect(0, 0, 100, 100);
+    ctx.rect(25, 25, 50, 50);
+    ctx.clip('evenodd');
+    ctx.beginPath();
+    ctx.fillRect(0, 0, 100, 100);
+    checkResult([255, 0, 0, 255], 5);                        
+    debug('');
+
+}
+
+// Run test and allow variation of results.
+prepareTestScenario();
diff --git a/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-fill-rule.js b/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-fill-rule.js
new file mode 100644
index 0000000..482e03a
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-fill-rule.js
@@ -0,0 +1,66 @@
+description("Series of tests to ensure correct results of the winding rule.");
+
+
+var tmpimg = document.createElement('canvas');
+tmpimg.width = 200;
+tmpimg.height = 200;
+ctx = tmpimg.getContext('2d');
+
+// Create the image for blending test with images.
+var img = document.createElement('canvas');
+img.width = 100;
+img.height = 100;
+var imgCtx = img.getContext('2d');
+
+function pixelDataAtPoint()
+{
+  return ctx.getImageData(50, 50, 1, 1).data;
+}
+
+function checkResult(expectedColors, sigma) {
+    for (var i = 0; i < 4; i++)
+	    shouldBeCloseTo("pixelDataAtPoint()[" + i + "]", expectedColors[i], sigma);
+}
+
+// Execute test.
+function prepareTestScenario() {
+    debug('Testing default fill');
+    ctx.fillStyle = 'rgb(255,0,0)';
+    ctx.beginPath();
+    ctx.fillRect(0, 0, 100, 100);
+    ctx.fillStyle = 'rgb(0,255,0)';
+    ctx.beginPath();
+    ctx.rect(0, 0, 100, 100);
+    ctx.rect(25, 25, 50, 50);
+    ctx.fill();
+    checkResult([0, 255, 0, 255], 5);                        
+    debug('');
+
+    debug('Testing nonzero fill');
+    ctx.fillStyle = 'rgb(255,0,0)';
+    ctx.beginPath();
+    ctx.fillRect(0, 0, 100, 100);
+    ctx.fillStyle = 'rgb(0,255,0)';
+    ctx.beginPath();
+    ctx.rect(0, 0, 100, 100);
+    ctx.rect(25, 25, 50, 50);
+    ctx.fill('nonzero');
+    checkResult([0, 255, 0, 255], 5);
+    debug('');
+	
+    debug('Testing evenodd fill');
+    ctx.fillStyle = 'rgb(255,0,0)';
+    ctx.beginPath();
+    ctx.fillRect(0, 0, 100, 100);
+    ctx.fillStyle = 'rgb(0,255,0)';
+    ctx.beginPath();
+    ctx.rect(0, 0, 100, 100);
+    ctx.rect(25, 25, 50, 50);
+    ctx.fill('evenodd');
+    checkResult([255, 0, 0, 255], 5);                        
+    debug('');
+
+}
+
+// Run test and allow variation of results.
+prepareTestScenario();
diff --git a/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-isPointInPath-winding.js b/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-isPointInPath-winding.js
new file mode 100644
index 0000000..30d0a46
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/fast/canvas/script-tests/canvas-isPointInPath-winding.js
@@ -0,0 +1,40 @@
+description("Series of tests to ensure correct results of the winding rule in isPointInPath.");
+
+
+var tmpimg = document.createElement('canvas');
+tmpimg.width = 200;
+tmpimg.height = 200;
+ctx = tmpimg.getContext('2d');
+
+// Create the image for blending test with images.
+var img = document.createElement('canvas');
+img.width = 100;
+img.height = 100;
+var imgCtx = img.getContext('2d');
+
+// Execute test.
+function prepareTestScenario() {
+    debug('Testing default isPointInPath');
+    ctx.beginPath();
+    ctx.rect(0, 0, 100, 100);
+    ctx.rect(25, 25, 50, 50);
+    shouldBeTrue("ctx.isPointInPath(50, 50)");             
+    debug('');
+
+    debug('Testing nonzero isPointInPath');
+    ctx.beginPath();
+    ctx.rect(0, 0, 100, 100);
+    ctx.rect(25, 25, 50, 50);
+    shouldBeTrue("ctx.isPointInPath(50, 50, 'nonzero')");
+    debug('');
+	
+    debug('Testing evenodd isPointInPath');
+    ctx.beginPath();
+    ctx.rect(0, 0, 100, 100);
+    ctx.rect(25, 25, 50, 50);
+    shouldBeFalse("ctx.isPointInPath(50, 50, 'evenodd')");             
+    debug('');
+}
+
+// Run test and allow variation of results.
+prepareTestScenario();