[webkit-reviews] review granted: [Bug 101787] Zoomed-in scrolling is very slow when deviceScaleFactor > 1 : [Attachment 173437] Patch

[bugzilla-daemon at webkit.org]

Simon Fraser (smfr) <simon.fraser at apple.com> has granted Beth Dakin
<bdakin at apple.com>'s request for review:
Bug 101787: Zoomed-in scrolling is very slow when deviceScaleFactor > 1
https://bugs.webkit.org/show_bug.cgi?id=101787

Attachment 173437: Patch
https://bugs.webkit.org/attachment.cgi?id=173437&action=review

------- Additional Comments from Simon Fraser (smfr) <simon.fraser at apple.com>
View in context: https://bugs.webkit.org/attachment.cgi?id=173437&action=review


> Source/WebCore/ChangeLog:4
> +	   https://bugs.webkit.org/show_bug.cgi?id=101787
> +	   Zoomed-in scrolling is very slow when deviceScaleFactor > 1

Please put the description first, as prepareChangelog does. That means that
browsing short commit messages shows the bug title, rather than just the bug
number.

> Source/WebCore/ChangeLog:9
> +	   whether or not fonts should be subpixel quantized. We want to
default 

subpixel-quantized.

> Source/WebCore/ChangeLog:10
> +	   to quantizing, but we'll turn it off if we're scrolling content that


to subpixel-quantizing.

> Source/WebCore/ChangeLog:14
> +	   State has a new bool shouldQuantizeFonts. It defaults to true since 


shouldSubpixelQuantizeFonts

> Source/WebCore/ChangeLog:18
> +	   (WebCore):

Nuke it!

> Source/WebCore/ChangeLog:26
> +	   whether or not it should try to quantize the fonts.

subpixel-quantize

> Source/WebCore/ChangeLog:32
> +	   Disable quantization for overflow areas, subframes, and content that


etc.

> Source/WebCore/rendering/RenderLayer.cpp:3185
> +    bool didQuantizeFonts = true;

subpixelQuantize

> Source/WebCore/rendering/RenderLayer.cpp:3199
> +    bool needToAdjustSubpixelQuantization = scrollingOnMainThread ||
(renderer()->hasOverflowClip() && !usesCompositedScrolling()) || (frame &&
frame->ownerElement());

We might not want the scrollingOnMainThread here. That could cause a page that
toggles some style (background-attachment) to have jiggling text, but it would
cause slow-scrolling pages to possibly show waviness when scrolling when
zoomed, but it this really an issue?