RFR: 8290866: Apple Color Emoji turns gray after JavaFX version 18

[Andy Goryachev]

On Fri, 24 Feb 2023 19:06:59 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> This fix properly supports colour rendering of Emoji on macOS
>> 
>> 
>> On other platforms the Emoji will be rendered as ordinary greyscale glyphs - if there is font
>> support for the requested code point.
>> 
>> A simple manual test is provided which uses a Text node, Label control
>> and editable TextField control.
>> 
>> Some highlights of the code
>> - To determine if it is a color emoji glyph probe the 'sbix' font table which is what is used by Apple
>> - Text runs now break at an Emoji glyph
>> - The Emoji is retrieved as an BGRA image - ie 4 channel including alpha
>> - It was necessary to retrieve the Emoji glyph bounds via a different CoreText API since
>>    the bounds that were being retrieved were wrong for the Emoji image - causing clipping
>> - It was necessary to retrieve the Emoji code point advance via a CoreText API since
>>    the HMTX metrics were very wrong - causing overlapping glyphs
>> - drawString checks if it is an Emoji run and redirects to a new drawColorGlyph method
>>    which draws the image as a texture
>> - All 3 rendering pipelines have this support and have been verified on all 3 desktop platforms
>
> modules/javafx.graphics/src/main/java/com/sun/javafx/font/PrismFontFile.java line 1456:
> 
>> 1454:    private boolean isSbixGlyph(int glyphID) {
>> 1455:        if (sbixStrikes == null) {
>> 1456:            synchronized (this) {
> 
> This looks like a double-checked locking pattern, which is not guaranteed to be thread-safe.
> 
> Suggestion: move the `synchronized` before the `if`.

or check for null again after synchronized(this)

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PR: https://git.openjdk.org/jfx/pull/1047