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Emoji: Make the UN flag test more accurate.

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Previously, the UN flag test relied on the image being produced to be quite small. Unfortunately, the Chrome PNG encoder seems to have changed recently, and it now produces a relatively large image.

For a better test, we can compare the rendering of [U] + [N] against [U] + zero width space + [N].

Fixes #40616.



git-svn-id: https://develop.svn.wordpress.org/trunk@40582 602fd350-edb4-49c9-b593-d223f7449a82
This commit is contained in:
pento 2017-05-08 05:00:29 +00:00
parent 45b183ea79
commit 491f14540e
1 changed files with 13 additions and 9 deletions
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22
src/wp-includes/js/wp-emoji-loader.js
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@ -39,21 +39,25 @@
switch ( type ) {
case 'flag':
/*
* This works because the image will be one of three things:
* - Two empty squares, if the browser doesn't render emoji
* - Two squares with 'U' and 'N' in them, if the browser doesn't render flag emoji
* - The United Nations flag
* Test for UN flag compatibility. This is the least supported of the letter locale flags,
* so gives us an easy test for full support.
*
* The first two will encode to small images (1-2KB data URLs), the third will encode
* to a larger image (4-5KB data URL).
* To test for support, we try to render it, and compare the rendering to how it would look if
* the browser doesn't render it correctly ([U] + [N]).
*/
context.fillText( stringFromCharCode( 55356, 56826, 55356, 56819 ), 0, 0 );
if ( canvas.toDataURL().length < 3000 ) {
return false;
}
flag = canvas.toDataURL();
context.clearRect( 0, 0, canvas.width, canvas.height );
// Add a zero width space between the characters, to force rendering as characters.
context.fillText( stringFromCharCode( 55356, 57331, 8203, 55356, 57096 ), 0, 0 );
flag2 = canvas.toDataURL();
if ( flag !== flag2 ) {
return false;
}
/*
* Test for rainbow flag compatibility. As the rainbow flag was added out of sequence with
* the usual Unicode release cycle, some browsers support it, and some don't, even if their