[webkit-changes] [WebKit/WebKit] 9bdb0a: [Cocoa] Use kCTFontVariationAxesAttribute where we...

[Myles C. Maxfield]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 9bdb0a69c53e7c86138c20f222110df8b7ede16f
      https://github.com/WebKit/WebKit/commit/9bdb0a69c53e7c86138c20f222110df8b7ede16f
  Author: Myles C. Maxfield <mmaxfield at apple.com>
  Date:   2023-01-11 (Wed, 11 Jan 2023)

  Changed paths:
    M Source/WTF/wtf/PlatformUse.h
    M Source/WebCore/platform/graphics/cocoa/FontCacheCoreText.cpp

  Log Message:
  -----------
  [Cocoa] Use kCTFontVariationAxesAttribute where we can
https://bugs.webkit.org/show_bug.cgi?id=250370
rdar://104066949

Reviewed by Cameron McCormack.

For https://bugs.webkit.org/show_bug.cgi?id=247987, we want to create as few CTFonts, for
performance. Our current font code converts between CTFonts and CTFontDescriptors fairly
freely; however, all these conversions are somewhat wasteful.

Instead, if we were using the Core Text API properly, we would simply go CFDictionary ->
CTFontDescriptor -> CTFont once. Instead of going back and forth between all these types,
we'd build in everything we need into a single dictionary/descriptor, and have one single
place where we turn that descriptor into a font.

This patch is one step along that journey, and removes one place where we have to create
a font. Currently, we use CTFontCopyVariationAxes(), which requires a whole CTFont, which
causes us to go CTFontDescriptor -> CTFont -> CTFontDescriptor. Instead, we can use
kCTFontVariationAxesAttribute, which operates on a CTFontDescriptor, thereby using a
FontDescriptor more often.

There are more steps along this journey; this is just one step.

No tests because there is no behavior change.

* Source/WTF/wtf/PlatformUse.h:
* Source/WebCore/platform/graphics/cocoa/FontCacheCoreText.cpp:
(WebCore::variationAxes):
(WebCore::variationCapabilitiesForFontDescriptor):

Canonical link: https://commits.webkit.org/258809@main