[webkit-changes] [WebKit/WebKit] e9e9b4: [Cocoa] [Downlevels] Out of bounds optical sizing ...

[Myles C. Maxfield]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: e9e9b4699c26d5e69ffeafd259edcc7e203479fb
      https://github.com/WebKit/WebKit/commit/e9e9b4699c26d5e69ffeafd259edcc7e203479fb
  Author: Myles C. Maxfield <mmaxfield at apple.com>
  Date:   2023-07-12 (Wed, 12 Jul 2023)

  Changed paths:
    A LayoutTests/fast/text/variations/optical-sizing-out-of-bounds-expected.html
    A LayoutTests/fast/text/variations/optical-sizing-out-of-bounds.html
    M Source/WTF/wtf/PlatformUse.h
    M Source/WebCore/platform/graphics/cocoa/FontCacheCoreText.h
    M Source/WebCore/platform/graphics/cocoa/UnrealizedCoreTextFont.cpp
    M Source/WebCore/platform/graphics/cocoa/UnrealizedCoreTextFont.h

  Log Message:
  -----------
  [Cocoa] [Downlevels] Out of bounds optical sizing is rendered as the default value instead of clamping
https://bugs.webkit.org/show_bug.cgi?id=258764
rdar://111535841

Reviewed by Cameron McCormack.

On pre-2023-aligned Apple OSes, Core Text's behavior for optical sizing is that
out of bounds values are ignored, and default optical sizing is used instead of
clamping the specified value. We can work around this by clamping the value
ourself in WebKit, but this is somewhat unfortunate because we only know the
acceptable range after creating a CTFont, but we'd like to specify the values
during CTFont creation time.

This patch solves the problem by doing a 2-phase creation: Create a CTFont,
inspect it, determine if it needs a second phase, and if it does, modify the
CTFont to create a second, derived, CTFont. We already have some support for
this due to the TrueType GX weight/width/slope scales being different than
the CSS scales - but we don't know if a font is a TrueType GX font until we've
created the CTFont object. This patch extends that existing 2-phase creation to
also recreate the font if the optical sizing ended up wrong.

* LayoutTests/fast/text/variations/optical-sizing-out-of-bounds-expected.html: Added.
* LayoutTests/fast/text/variations/optical-sizing-out-of-bounds.html: Added.
* Source/WTF/wtf/PlatformUse.h:
* Source/WebCore/platform/graphics/cocoa/UnrealizedCoreTextFont.cpp:
(WebCore::OpticalSizeRange::isInRange const):
(WebCore::opticalSizeRange):
(WebCore::UnrealizedCoreTextFont::rebuildReason const):
(WebCore::UnrealizedCoreTextFont::realize const):
* Source/WebCore/platform/graphics/cocoa/UnrealizedCoreTextFont.h:
(WebCore::UnrealizedCoreTextFont::RebuildReason::hasEffect const):

Canonical link: https://commits.webkit.org/266000@main