IllegalStateException in AbstractThemeManager.getDefaultTheme()

[ghentschke]

Due to a failed unit test in LSP4E it turns out that since this TM4E commit a IllegalStateException will be thrown by AbstractThemeManager.getDefaultTheme(), when this method gets called from within a non UI thread:

tm4e/org.eclipse.tm4e.ui/src/main/java/org/eclipse/tm4e/ui/internal/themes/AbstractThemeManager.java

Line 57 in 039aed1

return getDefaultTheme(UI.isDarkEclipseTheme());

Exception in thread "org.eclipse.jface.text.reconciler.Reconciler" java.lang.IllegalStateException: No active shell found!
	at org.eclipse.tm4e.ui.internal.utils.UI.isDarkEclipseTheme(UI.java:175)
	at org.eclipse.tm4e.ui.internal.themes.AbstractThemeManager.getDefaultTheme(AbstractThemeManager.java:57)
	at org.eclipse.lsp4e.operations.semanticTokens.TokenTypeMapper.apply(TokenTypeMapper.java:45)
	at org.eclipse.lsp4e.operations.semanticTokens.TokenTypeMapper.apply(TokenTypeMapper.java:1)
	at org.eclipse.lsp4e.operations.semanticTokens.SemanticTokensDataStreamProcessor.textAttribute(SemanticTokensDataStreamProcessor.java:134)
	at org.eclipse.lsp4e.operations.semanticTokens.SemanticTokensDataStreamProcessor.getStyleRanges(SemanticTokensDataStreamProcessor.java:88)
	at org.eclipse.lsp4e.operations.semanticTokens.SemanticHighlightReconcilerStrategy.saveStyle(SemanticHighlightReconcilerStrategy.java:193)
	at org.eclipse.lsp4e.operations.semanticTokens.VersionedSemanticTokens.apply(VersionedSemanticTokens.java:40)
	at org.eclipse.lsp4e.operations.semanticTokens.SemanticHighlightReconcilerStrategy.lambda$5(SemanticHighlightReconcilerStrategy.java:276)
	at java.base/java.util.Optional.ifPresent(Optional.java:178)
	at org.eclipse.lsp4e.operations.semanticTokens.SemanticHighlightReconcilerStrategy.fullReconcile(SemanticHighlightReconcilerStrategy.java:275)
	at org.eclipse.lsp4e.operations.semanticTokens.SemanticHighlightReconcilerStrategy.initialReconcile(SemanticHighlightReconcilerStrategy.java:291)
	at org.eclipse.ui.internal.genericeditor.CompositeReconcilerStrategy.initialReconcile(CompositeReconcilerStrategy.java:48)
	at org.eclipse.jface.text.reconciler.Reconciler.initialProcess(Reconciler.java:223)
	at org.eclipse.jface.text.reconciler.AbstractReconciler$BackgroundThread.run(AbstractReconciler.java:177)

I am not sure if this should be fixed here or in the caller in LSP4E. Should the user be aware, that this method should be called from within a UI thread only?:

 TMUIPlugin.getThemeManager().getDefaultTheme().getToken(tokenType)

[sebthom]

I am not sure if this should be fixed here or in the caller in LSP4E. Should the user be aware, that this method should be called from within a UI thread only?

That is nowhere specified. Most of the code in the tm4e.ui package expects to be running on the UI thread. Anyways, I added a workaround for this case. Can you please give the latest snapshot build a shot? https://download.eclipse.org/tm4e/snapshots/

[ghentschke]

A first check seems very promising. @sebthom Thank you for the fast fix!

Has the default theme changed as well? TMUIPlugin.getThemeManager().getDefaultTheme() returns now the dark theme.

[sebthom]

The default theme depends on the Eclipse UI theme and should only return the dark theme if Eclipse itself is dark.

This is the integration test:

tm4e/org.eclipse.tm4e.ui.tests/src/main/java/org/eclipse/tm4e/ui/tests/themes/ThemeManagerTest.java

Lines 33 to 34 in 33dbe01

	final ITheme theme = manager.getDefaultTheme();
	assertEquals(SolarizedLight, theme.getId());

What has changed is, that we now don't try to guess the Eclipse theme based on theme names but by measuring brightness of the active shell's background color.

tm4e/org.eclipse.tm4e.ui/src/main/java/org/eclipse/tm4e/ui/internal/utils/UI.java

Lines 163 to 181 in 33dbe01

	private static int getBrightness(final int red, final int green, final int blue) {
	// https://www.w3.org/TR/AERT/#color-contrast
	return (int) (0.299 * red + 0.587 * green + 0.114 * blue);
	}
	public static boolean isDarkColor(final RGB color) {
	return getBrightness(color.red, color.green, color.blue) < 128;
	}
	public static boolean isDarkColor(final Color color) {
	return getBrightness(color.getRed(), color.getGreen(), color.getBlue()) < 128;
	}
	public static boolean isDarkEclipseTheme() {
	final var shell = getActiveShell();
	if (shell == null)
	throw new IllegalStateException("No active shell found!");
	return isDarkColor(shell.getBackground());
	}

Maybe this does not work in some scenarios. It is working fine for me on Windows 10.

[sebthom]

I released TM4E 0.10.3 which contains the fix. Thanks for reporting the issue!