Bug 170577 – A synchronous DecodingOptions should be compatible with any asynchronous sizeForDrawing DecodingOptions

• Status: RESOLVED
• Resolution: FIXED
• Component: Images

[Said Abou-Hallawa]

This prevents the following repaint infinite loop:

Suppose I have two elements 'x' and 'y' and 'y' is the parent of 'x'. Both 'x' and 'y' are using the image 'm' to draw their background. 'x' does not repeat the background while 'y' does.

1. 'x' draws its background.
2. 'm' is not decoded, so request async image decoding for 'm' since it is a large image.
3. 'm' finishes decoding, it repaints the rectangle of 'x'.
4. Repainting the rectangle of 'x' causes a repaint for 'y' as well.
5. To paint 'y', 'm' will be used to draw a pattern.
6. To draw a pattern of 'm', a synchronous decoded frame has to be obtained so the one that finished decoding is now deleted.
7. Now goto step 1

This loops will runs forever. To prevent this loop from happening, once a synchronous decoded frame is found, there is no need to decode it again. This decoded frame is suitable for any sizeForDrawing.

[Said Abou-Hallawa]

Created attachment 306442 [details]
Patch

[Said Abou-Hallawa]

<rdar://problem/31465804>

[Said Abou-Hallawa]

Created attachment 306451 [details]
To be referenced by the test case

[Said Abou-Hallawa]

Created attachment 306452 [details]
test case

[Simon Fraser (smfr)]

Comment on attachment 306442 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=306442&action=review

> Source/WebCore/ChangeLog:8
> +        Test: fast/images/async-image-background-image-repeated.html

This should go below the paragraph below.

> Source/WebCore/platform/graphics/DecodingOptions.h:76
> +        // Comparing DedocingOptions with isAsynchronous() should not happen.

"DedocingOptions"

[Said Abou-Hallawa]

Created attachment 306584 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 306584 [details]
Patch

Clearing flags on attachment: 306584

Committed r215157: <http://trac.webkit.org/changeset/215157>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.