Throw an exception in putImageData if canvas layers are opened #42662
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This API is incompatible with how the 2D canvas is rasterized when it contains unclosed layers. Because layers can have filters that get applied on their final content, they can't be presented until they are closed. Instead, we normally keep the layer content alive after a flush, so that it can be presented in a later frame when the layer is finally closed. putImageData however is supposed to write to the canvas bitmap wholesale, bypassing all render states. This means that we can't write to the layer's content because the written pixels would then get filtered when the layer is closed. We can't write to the main canvas either because these pixels would later be overwritten by the layer's result with draw calls that potentially happened before (e.g. in the sequence `beginLayer(); fillRect(); putImageData(); endLayer();`, `fillRect()` would write over `putImageData()`. This behavior is part of the current 2D Canvas Layer spec draft: Explainer: https://github.com/fserb/canvas2D/blob/master/spec/layers.md Spec draft: whatwg/html#9537 Change-Id: I266a3155c32919a68dbbb093e4aff9b1dd13a3b5 Bug: 1484741 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4943172 Reviewed-by: Fernando Serboncini <[email protected]> Commit-Queue: Jean-Philippe Gravel <[email protected]> Cr-Commit-Position: refs/heads/main@{#1212741}
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This API is incompatible with how the 2D canvas is rasterized when
it contains unclosed layers. Because layers can have filters that get
applied on their final content, they can't be presented until they are
closed. Instead, we normally keep the layer content alive after a
flush, so that it can be presented in a later frame when the layer is
finally closed.
putImageData however is supposed to write to the canvas bitmap
wholesale, bypassing all render states. This means that we can't write
to the layer's content because the written pixels would then get
filtered when the layer is closed. We can't write to the main canvas
either because these pixels would later be overwritten by the layer's
result with draw calls that potentially happened before (e.g. in the
sequence
beginLayer(); fillRect(); putImageData(); endLayer();,fillRect()would write overputImageData().This behavior is part of the current 2D Canvas Layer spec draft:
Explainer: https://github.com/fserb/canvas2D/blob/master/spec/layers.md
Spec draft: whatwg/html#9537
Change-Id: I266a3155c32919a68dbbb093e4aff9b1dd13a3b5
Bug: 1484741
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4943172
Reviewed-by: Fernando Serboncini <[email protected]>
Commit-Queue: Jean-Philippe Gravel <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1212741}