Add colored emoji support for TextInputs

[RobinPicard]

Description

This PR aims at answering the following issue: #7995

Currently, Labels render colored emojis correctly but not TextInputs. I believe the origin of the problem is that when a TextInput creates Labels to get the textures for each line, it does not do it in the same way as if it were a standard stand-alone Label. More specifically, the Labels are created without a value for the color property. As a result, the texture is made of pixels in shades of grey (except for emojis). Later, when the textures are added to the Canvas of the TextInput, they are colored by a Color instruction based on the value of the foreground_color property of TextInput. That way, the whome texture is made in shades of that given color. This is not a problem for regular text but that does not work for emojis that end being recolored monochromatically.

The solution is to treat Labels used in TextInputs like regular Labels by setting a value the color property following the same logic that was contained in the Color instruction (the graphic provider will not apply the color to emojis by itself I believe). Then, the Color instruction of the canvas is set to (1, 1, 1, 1) such that the texture's color are not modified.

Testing

The tests test_uix_textinput are successful and the few tests I've done with the example in the issue work fine

Maintainer merge checklist

• Title is descriptive/clear for inclusion in release notes.
• Applied a Component: xxx label.
• Applied the api-deprecation or api-break label.
• Applied the release-highlight label to be highlighted in release notes.
• Added to the milestone version it was merged into.
• Unittests are included in PR.
• Properly documented, including versionadded, versionchanged as needed.

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[tshirtman]

Looks promising! I think it creates an issue with binding, see comment, but shouldn't be too hard to check and fix.

[tshirtman]

The previous version had the advantage of automatically adjusting the rendering if any of the xxx_color properties, or disabled was updated, the new way means lines have to be rerendered, for it to work. so binding on these properties, probably around line 568, of textinput.py, would be necessary, otherwise these color/disabled changes won't be applied until the text (or some other property that is bound) is actually changed.

[RobinPicard]

Ah yes, thanks for the help!

[RobinPicard]

Does it look fine to you now @tshirtman?

[DexerBR]

I recommend binding to update_text_options, binding to refresh_line_options will move the cursor to the end of the text.

So you can move this code below, to the line below line 588

fbind('foreground_color', update_text_options)
fbind('disabled_foreground_color', update_text_options)
fbind('hint_text_color', update_text_options)

[Julian-O]

OP has declared they are not working on Kivy any more. This is an orphan PR that needs fostering.

[misl6]

Superseded by #8491