Bug 170408 – Asynchronously decoded image frames should not be destroyed when switching encoded data buffers

• Status: RESOLVED
• Resolution: DUPLICATE
• Component: Images

[Said Abou-Hallawa]

When switching the encoded data buffers, it would be better if we could somehow tell the ImageDecoder to swap in the new contents without destroying anything. But right now the native ImageDecoder does not have a mechanism to do that so WebKit simply destroys all the decoded frames and then deletes the ImageDecoder itself. Then it sets the new data in the ImageSource which will recreate a new ImageDecoder.

For async image decoding, this aggressive flushing mechanism is not actually needed. The asynchronously decoded image frames are owned by WebKit. They are not referenced by the native ImageDecoder. Destroying them and re-decoding them again will generate exactly the same image frames. More importantly, destroying the decoded image frames, can cause flickering because the image can not be drawn till the second decode finish.

[Said Abou-Hallawa]

<rdar://problem/31211672>

[Said Abou-Hallawa]

Created attachment 306095 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 306095 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=306095&action=review

> Source/WebCore/platform/graphics/Image.h:72
> +enum class ImageFrameDestroyScope {

Maybe ImageFramesToDestroy or ImageFrameDestroyBehavior

> Source/WebCore/platform/graphics/Image.h:77
> +    Shared

It's not clear what "Shared" means here. Shared with whom?

[Build Bot]

Comment on attachment 306095 [details]
Patch

Attachment 306095 [details] did not pass mac-debug-ews (mac):
Output: http://webkit-queues.webkit.org/results/3466706

Number of test failures exceeded the failure limit.

[Build Bot]

Created attachment 306102 [details]
Archive of layout-test-results from ews112 for mac-elcapitan

The attached test failures were seen while running run-webkit-tests on the mac-debug-ews.
Bot: ews112  Port: mac-elcapitan  Platform: Mac OS X 10.11.6

[Said Abou-Hallawa]

Created attachment 306122 [details]
Patch

[Said Abou-Hallawa]

Comment on attachment 306095 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=306095&action=review

>> Source/WebCore/platform/graphics/Image.h:72
>> +enum class ImageFrameDestroyScope {
> 
> Maybe ImageFramesToDestroy or ImageFrameDestroyBehavior

I renamed it to ImageFrameDestroyBehavior.

>> Source/WebCore/platform/graphics/Image.h:77
>> +    Shared
> 
> It's not clear what "Shared" means here. Shared with whom?

I renamed Shared to Synchronous.

[Said Abou-Hallawa]

If we prevent deleting the decoded frames of the images in the viewport then there is no need for this bug.

*** This bug has been marked as a duplicate of bug 170640 ***