Handle zero-width characters properly in code minings

This change improves the rendering of code minings in the presence of
zero-width Unicode characters (e.g., ZWSP, ZWNJ, ZWJ, and BOM). The
`InlinedAnnotationDrawingStrategy` was updated to recognize these
characters, adjust their width calculations, and properly place code
mining annotations without causing layout issues.

This change is needed by
#1437

Author: tobias-melcher

bundles/org.eclipse.jface.text/src/org/eclipse/jface/text/source/inlined/InlinedAnnotationDrawingStrategy.java

@@ -13,6 +13,8 @@
  */
 package org.eclipse.jface.text.source.inlined;
 
+import java.util.Set;
+
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.custom.StyleRange;
 import org.eclipse.swt.custom.StyledText;
@@ -43,6 +45,16 @@ class InlinedAnnotationDrawingStrategy implements IDrawingStrategy {
 
 	private final ITextViewer viewer;
 
+	private static final char ZW_SPACE= '\u200b';
+
+	private static final char ZW_NON_JOINER= '\u200c';
+
+	private static final char ZW_JOINER= '\u200d';
+
+	private static final char ZW_NO_BREAK_SPACE= '\ufeff';
+
+	private static final Set<Character> ZW_CHARACTERS= Set.of(ZW_SPACE, ZW_NON_JOINER, ZW_JOINER, ZW_NO_BREAK_SPACE);
+
 	public InlinedAnnotationDrawingStrategy(ITextViewer viewer) {
 		this.viewer = viewer;
 	}
@@ -436,13 +448,17 @@ protected static void drawAsLeftOf1stCharacter(LineContentAnnotation annotation,
 					// Get size of the character where GlyphMetrics width is added
 					Point charBounds= gc.stringExtent(hostCharacter);
 					int charWidth= charBounds.x;
-					if (charWidth == 0 && ("\r".equals(hostCharacter) || "\n".equals(hostCharacter))) { //$NON-NLS-1$ //$NON-NLS-2$
+					boolean isZeroWidthCharacter= false;
+					if (hostCharacter.length() == 1 && ZW_CHARACTERS.contains(hostCharacter.charAt(0))) {
+						isZeroWidthCharacter= true;
+						charWidth= 0;
+					} else if (charWidth == 0 && ("\r".equals(hostCharacter) || "\n".equals(hostCharacter))) { //$NON-NLS-1$ //$NON-NLS-2$
 						// charWidth is 0 for '\r' on font Consolas, but not on other fonts, why?
 						charWidth= gc.stringExtent(" ").x; //$NON-NLS-1$
 					}
 					// FIXME: remove this code when we need not redraw the character (see https://bugs.eclipse.org/bugs/show_bug.cgi?id=531769)
 					// START TO REMOVE
-					annotation.setRedrawnCharacterWidth(charWidth);
+					annotation.setRedrawnCharacterWidth(charWidth, isZeroWidthCharacter);
 					// END TO REMOVE
 
 					// Annotation takes place, add GlyphMetrics width to the style
@@ -523,6 +539,11 @@ protected static void drawAsRightOfPreviousCharacter(LineContentAnnotation annot
 			char hostCharacter= textWidget.getText(widgetOffset - 1, widgetOffset - 1).charAt(0);
 			// use gc.stringExtent instead of gc.geCharWidth because of bug 548866
 			int redrawnCharacterWidth= hostCharacter != '\t' ? gc.stringExtent(Character.toString(hostCharacter)).x : textWidget.getTabs() * gc.stringExtent(" ").x; //$NON-NLS-1$
+			boolean isZeroWidthCharacter= false;
+			if (ZW_CHARACTERS.contains(hostCharacter)) {
+				redrawnCharacterWidth= 0;
+				isZeroWidthCharacter= true;
+			}
 			Rectangle charBounds= textWidget.getTextBounds(widgetOffset - 1, widgetOffset - 1);
 			Rectangle annotationBounds= new Rectangle(charBounds.x + redrawnCharacterWidth, charBounds.y, annotation.getWidth(), charBounds.height);
 
@@ -539,7 +560,7 @@ protected static void drawAsRightOfPreviousCharacter(LineContentAnnotation annot
 			if (width != 0) {
 				// FIXME: remove this code when we need not redraw the character (see https://bugs.eclipse.org/bugs/show_bug.cgi?id=531769)
 				// START TO REMOVE
-				annotation.setRedrawnCharacterWidth(redrawnCharacterWidth);
+				annotation.setRedrawnCharacterWidth(redrawnCharacterWidth, isZeroWidthCharacter);
 				// END TO REMOVE
 
 				// Annotation takes place, add GlyphMetrics width to the style

bundles/org.eclipse.jface.text/src/org/eclipse/jface/text/source/inlined/LineContentAnnotation.java

@@ -44,6 +44,8 @@ public class LineContentAnnotation extends AbstractInlinedAnnotation {
 
 	private int redrawnCharacterWidth;
 
+	private boolean isZeroWidthCharacter;
+
 	/**
 	 * Line content annotation constructor.
 	 *
@@ -113,8 +115,9 @@ int getRedrawnCharacterWidth() {
 		return redrawnCharacterWidth;
 	}
 
-	void setRedrawnCharacterWidth(int redrawnCharacterWidth) {
+	void setRedrawnCharacterWidth(int redrawnCharacterWidth, boolean isZeroWidthCharacter) {
 		this.redrawnCharacterWidth= redrawnCharacterWidth;
+		this.isZeroWidthCharacter= isZeroWidthCharacter;
 	}
 
 	@Override
@@ -151,7 +154,7 @@ StyleRange updateStyle(StyleRange style, FontMetrics fontMetrics, ITextViewer vi
 		if (!afterPosition) {
 			usePreviousChar= drawRightToPreviousChar(widgetPosition.getOffset(), textWidget);
 		}
-		if (width == 0 || getRedrawnCharacterWidth() == 0) {
+		if (isZeroWidthCharacter == false && (width == 0 || getRedrawnCharacterWidth() == 0)) {
 			return null;
 		}
 		int fullWidth= width + getRedrawnCharacterWidth();

tests/org.eclipse.jface.text.tests/src/org/eclipse/jface/text/tests/codemining/CodeMiningTest.java

@@ -27,7 +27,6 @@
 import org.junit.jupiter.api.Assumptions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.jupiter.api.extension.TestWatcher;
@@ -512,6 +511,53 @@ protected boolean condition() {
 		}.waitForCondition(widget.getDisplay(), 1000), "Code mining is unexpectedly rendered below last line");
 	}
 
+	@Test
+	public void testCodeMiningOnZeroWitdhCharacterAfterPosition() {
+		codeMiningOnZeroWidthCharacter(true);
+	}
+
+	@Test
+	public void testCodeMiningOnZeroWidthCharacterBeforePosition() {
+		codeMiningOnZeroWidthCharacter(false);
+	}
+
+	private void codeMiningOnZeroWidthCharacter(boolean afterPosition) {
+		char ZW_SPACE= '\u200b';
+		String text= "a" + ZW_SPACE + "b";
+		fViewer.getDocument().set(text);
+		fViewer.setCodeMiningProviders(new ICodeMiningProvider[] {
+				new AbstractCodeMiningProvider() {
+					@Override
+					public CompletableFuture<List<? extends ICodeMining>> provideCodeMinings(ITextViewer viewer, IProgressMonitor monitor) {
+						List<ICodeMining> result= new ArrayList<>();
+						result.add(new LineContentCodeMining(new Position(1, 1), afterPosition, this) {
+							@Override
+							public String getLabel() {
+								return "ZWSP";
+							}
+						});
+						return CompletableFuture.completedFuture(result);
+					}
+				}
+		});
+		fViewer.updateCodeMinings();
+		Assertions.assertTrue(new DisplayHelper() {
+			@Override
+			protected boolean condition() {
+				var tw= fViewer.getTextWidget();
+				int off= afterPosition ? 1 : 0;
+				StyleRange styleRange= tw.getStyleRangeAtOffset(off);
+				if (styleRange != null && styleRange.metrics != null) {
+					// code mining applied a style range with metrics at offset 1
+					return true;
+				} else {
+					tw.redraw();
+				}
+				return false;
+			}
+		}.waitForCondition(fViewer.getTextWidget().getDisplay(), 1000), "Line content code mining not rendered at zero width character");
+	}
+
 	@Test
 	public void testCodeMiningSwitchingBetweenInLineAndLineHeader() {
 		String ref= "REF-X";