TextPane.background property is not being set in GTKLookAndFeel

[Tiago Daitx]

Hi,

We got a report [1] for a very simple fix so GTKLookAndFeel will
return the right TextPane.background color.

Currently UIManager.getColor("TextPane.background") will ignore the
theme color and always return a white color for GTKLookAndFeel due to
inheritance from BasicLookAndFeel - that is incorrect and fails badly
for dark themes.

Seems to affect various OpenJDK versions - I can confirm it from 8 to
16 after looking at the source code, haven't checked on 7.

Please note that the JTextPane opens using all the correct theme
colors, it's the UIManager.getColor("TextPane.background") call that
fails since GTKLookAndFeel does not currently set it.

If the patch below fails to display correctly the original one can be
fetched directly from the bug report [2].


--- a/src/java.desktop/share/classes/com/sun/java/swing/plaf/gtk/GTKLookAndFeel.java
+++ b/src/java.desktop/share/classes/com/sun/java/swing/plaf/gtk/GTKLookAndFeel.java
@@ -349,6 +349,7 @@
         Double defaultCaretAspectRatio = Double.valueOf(0.025);
         Color caretColor = table.getColor("caretColor");
         Color controlText = table.getColor("controlText");
+        Color text = table.getColor("text");

         Object fieldInputMap = new UIDefaults.LazyInputMap(new Object[] {
                        "ctrl C", DefaultEditorKit.copyAction,
@@ -1150,6 +1151,7 @@
             "TextField.font", new FontLazyValue(Region.TEXT_FIELD),


+            "TextPane.background", text,
             "TextPane.caretForeground", caretColor,
             "TextPane.caretAspectRatio", defaultCaretAspectRatio,
             "TextPane.caretBlinkRate", caretBlinkRate,


References:
[1] https://launchpad.net/bugs/1894419
[2] https://launchpadlibrarian.net/496501072/gtk-laf-textpane-respect-dark-mode.diff

Cheers!

--
Tiago Stürmer Daitx
Software Engineer
tiago.daitx at canonical.com

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