See bug 715798 comment 41. According to tryserver results, the Color Emoji font is failing to render (the expected glyph simply doesn't show up) when running the <canvas> reftest (layout/reftests/canvas/text-emoji.html) on 10.7 machines, although Color Emoji in HTML content does work there (compare layout/reftests/text/emoji-01.html), confirming that the font is present. On my local machine, the <canvas> testcase works fine under 10.7, so I'm not sure how to proceed here. If this is a result of some quirk of the test machines, maybe we don't care very much; but if it indicates a wider problem under 10.7, where perhaps many users will experience the failure, it would be good to understand/fix it. Once bug 715798 is in Nightly builds, it would be helpful if OS X 10.7 users could confirm whether the canvas testcase (attached here for reference) successfully displays the Color Emoji glyph.
10.7 is pretty dated at this point. Is this something we still care about? Do the try servers even run 10.7?
Interestingly, with the Skia canvas backend, it seems to fail on all OS X test slaves. It still passes locally for me on 10.10 with Skia canvas. I'm adding a "random-if(cocoaWidget&&azureSkia)" annotation in bug 932958.
This is occurring for me locally on my MBP; running FX41, OS X 10.10.5. Is there any way I can help debug this? :) (I noticed this bug because WordPress uses Canvas to detect whether the browser has emoji support. See https://core.trac.wordpress.org/ticket/34049 for our bug.)
Ryan, can you try setting gfx.canvas.azure.backends back to "cg" in about:config? Does that fix the detection script?
Confirmed that changing the backend pref does fix it. Attached an example that compares emoji rendering in HTML and Canvas; code there is based on our detection script. (The actual detection is done by testing that the color value of the central pixel is non-white.)
Thanks Ryan. I've filed bug 1209480 about this, because it's unrelated to the 10.7-only breakage.
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