canvas: pop many clips on restore (#38496)

When restoring context/state we need to pop all clips from current
state, before we just poped one (even if there was none).

Testing: Added new WPT tests

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/canvas/canvas_data.rs

@@ -749,8 +749,10 @@ impl<DrawTarget: GenericDrawTarget> CanvasData<DrawTarget> {
         }
     }
 
-    pub(crate) fn pop_clip(&mut self) {
+    pub(crate) fn pop_clips(&mut self, clips: usize) {
-        self.drawtarget.pop_clip();
+        for _ in 0..clips {
+            self.drawtarget.pop_clip();
+        }
     }
 }
 

components/canvas/canvas_paint_thread.rs

@@ -282,7 +282,7 @@ impl CanvasPaintThread {
                 self.canvas(canvas_id).update_image_rendering();
                 sender.send(()).unwrap();
             },
-            Canvas2dMsg::PopClip => self.canvas(canvas_id).pop_clip(),
+            Canvas2dMsg::PopClips(clips) => self.canvas(canvas_id).pop_clips(clips),
         }
     }
 
@@ -348,14 +348,14 @@ impl Canvas {
         }
     }
 
-    fn pop_clip(&mut self) {
+    fn pop_clips(&mut self, clips: usize) {
         match self {
             #[cfg(feature = "raqote")]
-            Canvas::Raqote(canvas_data) => canvas_data.pop_clip(),
+            Canvas::Raqote(canvas_data) => canvas_data.pop_clips(clips),
             #[cfg(feature = "vello")]
-            Canvas::Vello(canvas_data) => canvas_data.pop_clip(),
+            Canvas::Vello(canvas_data) => canvas_data.pop_clips(clips),
             #[cfg(feature = "vello_cpu")]
-            Canvas::VelloCPU(canvas_data) => canvas_data.pop_clip(),
+            Canvas::VelloCPU(canvas_data) => canvas_data.pop_clips(clips),
             _ => unreachable!(),
         }
     }

components/script/canvas_state.rs

@@ -119,6 +119,9 @@ pub(crate) struct CanvasContextState {
     text_baseline: TextBaseline,
     #[no_trace]
     direction: Direction,
+    /// The number of clips pushed onto the context while in this state.
+    /// When restoring old state, same number of clips will be popped to restore state.
+    clips_pushed: usize,
 }
 
 impl CanvasContextState {
@@ -146,6 +149,7 @@ impl CanvasContextState {
             direction: Default::default(),
             line_dash: Vec::new(),
             line_dash_offset: 0.0,
+            clips_pushed: 0,
         }
     }
 
@@ -1320,12 +1324,15 @@ impl CanvasState {
     }
 
     #[cfg_attr(crown, allow(crown::unrooted_must_root))]
-    // https://html.spec.whatwg.org/multipage/#dom-context-2d-restore
+    /// <https://html.spec.whatwg.org/multipage/#dom-context-2d-restore>
     pub(crate) fn restore(&self) {
         let mut saved_states = self.saved_states.borrow_mut();
         if let Some(state) = saved_states.pop() {
+            let clips_to_pop = self.state.borrow().clips_pushed;
+            if clips_to_pop != 0 {
+                self.send_canvas_2d_msg(Canvas2dMsg::PopClips(clips_to_pop));
+            }
             self.state.borrow_mut().clone_from(&state);
-            self.send_canvas_2d_msg(Canvas2dMsg::PopClip);
         }
     }
 
@@ -1940,6 +1947,7 @@ impl CanvasState {
 
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-clip
     pub(crate) fn clip_(&self, path: Path, fill_rule: CanvasFillRule) {
+        self.state.borrow_mut().clips_pushed += 1;
         self.send_canvas_2d_msg(Canvas2dMsg::ClipPath(
             path,
             fill_rule.convert(),

components/shared/canvas/canvas.rs

@@ -483,7 +483,7 @@ pub enum Canvas2dMsg {
     ),
     ClearRect(Rect<f32>, Transform2D<f32>),
     ClipPath(Path, FillRule, Transform2D<f32>),
-    PopClip,
+    PopClips(usize),
     FillPath(
         FillOrStrokeStyle,
         Path,

tests/wpt/meta/MANIFEST.json

@@ -480322,7 +480322,7 @@
         []
        ],
        "the-canvas-state.yaml": [
-        "230e45f80a5901cae395ed1c4c848556e333073d",
+        "c3f382ef92929aa86f26f5462a7bc6d0e8731854",
         []
        ],
        "the-canvas.yaml": [
@@ -711259,6 +711259,13 @@
          {}
         ]
        ],
+       "2d.state.saverestore.clip.2.html": [
+        "1f1372c2c34847a224434118d864b2431b054e01",
+        [
+         null,
+         {}
+        ]
+       ],
        "2d.state.saverestore.clip.html": [
         "b95a9a38c02740a4025850771c3bb8de5bb68403",
         [
@@ -725464,6 +725471,20 @@
          {}
         ]
        ],
+       "2d.state.saverestore.clip.2.html": [
+        "31805b52bc1ca2a0a3303762bf4d46e068a45e4d",
+        [
+         null,
+         {}
+        ]
+       ],
+       "2d.state.saverestore.clip.2.worker.js": [
+        "f3d49f9511a1c099795aa8fe93955881b761b2a9",
+        [
+         "html/canvas/offscreen/the-canvas-state/2d.state.saverestore.clip.2.worker.html",
+         {}
+        ]
+       ],
        "2d.state.saverestore.clip.html": [
         "08ddd216a8f90c9b4bf81ef04c8cf8829f6ef5e6",
         [

tests/wpt/tests/html/canvas/element/the-canvas-state/2d.state.saverestore.clip.2.html

@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<!-- DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py. -->
+<meta charset="UTF-8">
+<title>Canvas test: 2d.state.saverestore.clip.2</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/html/canvas/resources/canvas-tests.js"></script>
+<link rel="stylesheet" href="/html/canvas/resources/canvas-tests.css">
+<body class="show_output">
+
+<h1>2d.state.saverestore.clip.2</h1>
+<p class="desc">save()/restore() affects the clipping path</p>
+
+
+<p class="output">Actual output:</p>
+<canvas id="c" class="output" width="100" height="50"><p class="fallback">FAIL (fallback content)</p></canvas>
+<p class="output expectedtext">Expected output:<p><img src="/images/green-100x50.png" class="output expected" id="expected" alt="">
+<ul id="d"></ul>
+<script>
+var t = async_test("save()/restore() affects the clipping path");
+_addTest(function(canvas, ctx) {
+
+  ctx.fillStyle = '#f00';
+  ctx.fillRect(0, 0, 100, 50);
+  ctx.save();
+  ctx.rect(0, 0, 1, 1);
+  ctx.clip();
+  ctx.clip();
+  ctx.restore();
+  ctx.fillStyle = '#0f0';
+  ctx.fillRect(0, 0, 100, 50);
+  _assertPixel(canvas, 50,25, 0,255,0,255);
+
+});
+</script>
+

tests/wpt/tests/html/canvas/offscreen/the-canvas-state/2d.state.saverestore.clip.2.html

@@ -0,0 +1,37 @@
+<!DOCTYPE html>
+<!-- DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py. -->
+<meta charset="UTF-8">
+<title>OffscreenCanvas test: 2d.state.saverestore.clip.2</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/html/canvas/resources/canvas-tests.js"></script>
+
+<h1>2d.state.saverestore.clip.2</h1>
+<p class="desc">save()/restore() affects the clipping path</p>
+
+
+<script>
+var t = async_test("save()/restore() affects the clipping path");
+var t_pass = t.done.bind(t);
+var t_fail = t.step_func(function(reason) {
+    throw reason;
+});
+t.step(function() {
+
+  var canvas = new OffscreenCanvas(100, 50);
+  var ctx = canvas.getContext('2d');
+
+  ctx.fillStyle = '#f00';
+  ctx.fillRect(0, 0, 100, 50);
+  ctx.save();
+  ctx.rect(0, 0, 1, 1);
+  ctx.clip();
+  ctx.clip();
+  ctx.restore();
+  ctx.fillStyle = '#0f0';
+  ctx.fillRect(0, 0, 100, 50);
+  _assertPixel(canvas, 50,25, 0,255,0,255);
+  t.done();
+
+});
+</script>

tests/wpt/tests/html/canvas/offscreen/the-canvas-state/2d.state.saverestore.clip.2.worker.js

@@ -0,0 +1,31 @@
+// DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py.
+// OffscreenCanvas test in a worker:2d.state.saverestore.clip.2
+// Description:save()/restore() affects the clipping path
+// Note:
+
+importScripts("/resources/testharness.js");
+importScripts("/html/canvas/resources/canvas-tests.js");
+
+var t = async_test("save()/restore() affects the clipping path");
+var t_pass = t.done.bind(t);
+var t_fail = t.step_func(function(reason) {
+    throw reason;
+});
+t.step(function() {
+
+  var canvas = new OffscreenCanvas(100, 50);
+  var ctx = canvas.getContext('2d');
+
+  ctx.fillStyle = '#f00';
+  ctx.fillRect(0, 0, 100, 50);
+  ctx.save();
+  ctx.rect(0, 0, 1, 1);
+  ctx.clip();
+  ctx.clip();
+  ctx.restore();
+  ctx.fillStyle = '#0f0';
+  ctx.fillRect(0, 0, 100, 50);
+  _assertPixel(canvas, 50,25, 0,255,0,255);
+  t.done();
+});
+done();

tests/wpt/tests/html/canvas/tools/yaml/the-canvas-state.yaml

@@ -25,6 +25,21 @@
     @assert pixel 50,25 == 0,255,0,255;
   expected: green
 
+- name: 2d.state.saverestore.clip.2
+  desc: save()/restore() affects the clipping path
+  code: |
+    ctx.fillStyle = '#f00';
+    ctx.fillRect(0, 0, 100, 50);
+    ctx.save();
+    ctx.rect(0, 0, 1, 1);
+    ctx.clip();
+    ctx.clip();
+    ctx.restore();
+    ctx.fillStyle = '#0f0';
+    ctx.fillRect(0, 0, 100, 50);
+    @assert pixel 50,25 == 0,255,0,255;
+  expected: green
+
 - name: 2d.state.saverestore.path
   desc: save()/restore() does not affect the current path
   code: |