287339e073
GTK2 code was historically kept around to keep the electron build working. But as of Nov 26, 2017, electron now uses GTK3 [1], so it should now be safe to remove all of the old GTK2-only code. [1] https://github.com/electron/electron/issues/2927#issuecomment-347092515 BUG=876558 R=sky Change-Id: I78402053ae508ccd8fc7ac73697a861bb1ebacf6 Reviewed-on: https://chromium-review.googlesource.com/1183858 Commit-Queue: Thomas Anderson <thomasanderson@chromium.org> Reviewed-by: Scott Violet <sky@chromium.org> Cr-Commit-Position: refs/heads/master@{#585265}
53 lines
1.8 KiB
Markdown
53 lines
1.8 KiB
Markdown
# Linux GTK Theme Integration
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The GTK+ port of Chromium has a mode where we try to match the user's GTK theme
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(which can be enabled under Settings -> Appearance -> Use GTK+ theme).
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## How Chromium determines which colors to use
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GTK3 added a new CSS theming engine which gives fine-tuned control over how
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widgets are styled. Chromium's themes, by contrast, are much simpler: it is
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mostly a list of about 80 colors (see //src/ui/native_theme/native_theme.h)
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overridden by the theme. Chromium usually doesn't use GTK to render entire
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widgets, but instead tries to determine colors from them.
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Chromium needs foreground, background and border colors from widgets. The
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foreground color is simply taken from the CSS "color" property. Backgrounds and
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borders are complicated because in general they might have multiple gradients or
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images. To get the color, Chromium uses GTK to render the background or border
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into a 24x24 bitmap and uses the average color for theming. This mostly gives
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reasonable results, but in case theme authors do not like the resulting color,
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they have the option to theme Chromium widgets specially.
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## Note to GTK theme authors: How to theme Chromium widgets
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Every widget Chromium uses will have a "chromium" style class added to it. For
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example, a textfield selector might look like:
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```
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.window.background.chromium .entry.chromium
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```
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If themes want to handle Chromium textfields specially, for GTK3.0 - GTK3.19,
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they might use:
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```
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/* Normal case */
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.entry {
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color: #ffffff;
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background-color: #000000;
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}
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/* Chromium-specific case */
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.entry.chromium {
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color: #ff0000;
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background-color: #00ff00;
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}
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```
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For GTK3.20 or later, themes will as usual have to replace ".entry" with
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"entry".
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The list of CSS selectors that Chromium uses to determine its colors is in
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//src/chrome/browser/ui/libgtkui/native_theme_gtk.cc.
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