[StickyScrolling] Move complex line adaption to central handler

Move sticky lines adaptation to the growing sticky lines control into the central sticky scrolling handler. This change simplifies the sticky lines provider, making implementations for specific languages more straightforward and maintainable.

Preparation for eclipse-platform#2398

Author: Christopher-Hermann

bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/DefaultStickyLinesProvider.java

@@ -19,9 +19,6 @@
 
 import org.eclipse.swt.custom.StyledText;
 
-import org.eclipse.jface.text.ITextViewerExtension5;
-import org.eclipse.jface.text.source.ISourceViewer;
-
 /**
  * This class provides sticky lines for the given source code in the source viewer. The
  * implementation is completely based on indentation and therefore works by default for several
@@ -36,83 +33,31 @@ public class DefaultStickyLinesProvider implements IStickyLinesProvider {
 	private StickyLinesProperties fProperties;
 
 	@Override
-	public List<StickyLine> getStickyLines(ISourceViewer sourceViewer, StickyLinesProperties properties) {
-		if (sourceViewer.getTopIndex() == 0) {
-			return Collections.emptyList();
-		}
-
+	public List<StickyLine> getStickyLines(StyledText textWidget, int lineNumber, StickyLinesProperties properties) {
 		this.fProperties= properties;
 		LinkedList<StickyLine> stickyLines= new LinkedList<>();
 
 		try {
-			StyledText textWidget= sourceViewer.getTextWidget();
-			int startLine= textWidget.getTopIndex();
+			int startIndetation= getStartIndentation(lineNumber, textWidget);
 
-			calculateStickyLinesForLineNumber(stickyLines, sourceViewer, startLine);
-			calculateStickyLinesUnderStickyLineControl(stickyLines, sourceViewer, startLine);
-		} catch (IllegalArgumentException e) {
-			stickyLines.clear();
-		}
+			for (int i= lineNumber, previousIndetation= startIndetation; i >= 0; i--) {
+				String line= textWidget.getLine(i);
+				int indentation= getIndentation(line);
 
-		return stickyLines;
-	}
+				if (indentation == IGNORE_LINE_INDENTATION) {
+					continue;
+				}
 
-	private void calculateStickyLinesForLineNumber(LinkedList<StickyLine> stickyLines, ISourceViewer sourceViewer, int lineNumber) {
-		StyledText textWidget= sourceViewer.getTextWidget();
-		int startIndetation= getStartIndentation(lineNumber, textWidget);
-
-		for (int i= lineNumber, previousIndetation= startIndetation; i >= 0; i--) {
-			String line= textWidget.getLine(i);
-			int indentation= getIndentation(line);
-
-			if (indentation == IGNORE_LINE_INDENTATION) {
-				continue;
-			}
-
-			if (indentation < previousIndetation) {
-				previousIndetation= indentation;
-				stickyLines.addFirst(new StickyLine(line, mapLineNumberToSourceViewerLine(i, sourceViewer)));
-			}
-		}
-	}
-
-	private void calculateStickyLinesUnderStickyLineControl(LinkedList<StickyLine> stickyLines, ISourceViewer sourceViewer, int startLine) {
-		int firstBelowControl= startLine + stickyLines.size();
-		StyledText textWidget= sourceViewer.getTextWidget();
-		int lineCount= textWidget.getLineCount();
-
-		for (int i= startLine; i < firstBelowControl && i < lineCount; i++) {
-
-			String line= textWidget.getLine(i);
-			int indentation= getIndentation(line);
-			if (indentation == IGNORE_LINE_INDENTATION) {
-				continue;
-			}
-
-			while (!stickyLines.isEmpty() && indentation <= getLastStickyLineIndentation(stickyLines) && i < firstBelowControl) {
-				stickyLines.removeLast();
-				firstBelowControl--;
-			}
-
-			String nextContentLine= getNextContentLine(i, textWidget);
-			if (getIndentation(nextContentLine) > indentation && i < firstBelowControl) {
-				stickyLines.addLast(new StickyLine(line, mapLineNumberToSourceViewerLine(i, sourceViewer)));
-				firstBelowControl++;
-				continue;
+				if (indentation < previousIndetation) {
+					previousIndetation= indentation;
+					stickyLines.addFirst(new StickyLine(line, i));
+				}
 			}
+		} catch (IllegalArgumentException e) {
+			stickyLines.clear();
 		}
-	}
 
-	private int getLastStickyLineIndentation(LinkedList<StickyLine> stickyLines) {
-		String text= stickyLines.getLast().text();
-		return getIndentation(text);
-	}
-
-	private int mapLineNumberToSourceViewerLine(int lineNumber, ISourceViewer sourceViewer) {
-		if (sourceViewer instanceof ITextViewerExtension5 extension) {
-			return extension.widgetLine2ModelLine(lineNumber);
-		}
-		return lineNumber;
+		return stickyLines;
 	}
 
 	private int getStartIndentation(int startFromLine, StyledText styledText) {

bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/IStickyLinesProvider.java

@@ -28,26 +28,28 @@
 public interface IStickyLinesProvider {
 
 	/**
-	 * Calculate the sticky lines for the source code of the given sourceViewer. Specific
-	 * properties, such as the <code>tabWidht</code> can be retrieved from the
-	 * <code>properties</code>.
+	 * Calculate the sticky lines for the source code of the given textWidget. Specific properties,
+	 * such as the <code>tabWidht</code> can be retrieved from the <code>properties</code>. To get
+	 * access to additional information, the source viewer can be used.
 	 * 
-	 * @param sourceViewer The source viewer containing the source code and information about the
-	 *            first visible line
+	 * @param textWidget The text widget containing the source code
+	 * @param lineNumber The line number to calculate the sticky lines for
+	 * @param properties Properties for additional information
 	 * @return The list of sticky lines to show
 	 * 
 	 * @see ISourceViewer#getTopIndex()
 	 * @see ISourceViewer#getTextWidget()
 	 * @see StyledText#getTopIndex()
 	 */
-	public List<StickyLine> getStickyLines(ISourceViewer sourceViewer, StickyLinesProperties properties);
+	public List<StickyLine> getStickyLines(StyledText textWidget, int lineNumber, StickyLinesProperties properties);
 
 	/**
-	 * Properties required to calculate the sticky lines.
+	 * Additional properties and access in order to calculate the sticky lines.
 	 * 
 	 * @param tabWith The with of a tab
+	 * @param sourceViewer The sourceViewer to access additional information
 	 */
-	record StickyLinesProperties(int tabWith) {
+	record StickyLinesProperties(int tabWith, ISourceViewer sourceViewer) {
 	}
 
 }

bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControl.java

@@ -208,7 +208,8 @@ private void updateStickyScrollingControls() {
 		for (int i= 0; i < getNumberStickyLines(); i++) {
 			StickyLine stickyLine= stickyLines.get(i);
 			stickyLineTextJoiner.add(stickyLine.text());
-			stickyLineNumberJoiner.add(fillLineNumberWithLeadingSpaces(stickyLine.lineNumber() + 1));
+			int lineNumber= getSourceViewerLineNumber(stickyLine.lineNumber());
+			stickyLineNumberJoiner.add(fillLineNumberWithLeadingSpaces(lineNumber + 1));
 		}
 
 		String newStickyLineText= stickyLineTextJoiner.toString();
@@ -223,6 +224,13 @@ private void updateStickyScrollingControls() {
 		}
 	}
 
+	private int getSourceViewerLineNumber(int i) {
+		if (sourceViewer instanceof ITextViewerExtension5 extension) {
+			return extension.widgetLine2ModelLine(i);
+		}
+		return i;
+	}
+
 	private String fillLineNumberWithLeadingSpaces(int lineNumber) {
 		int lineCount= sourceViewer.getDocument().getNumberOfLines();
 		int lineNumberLength= String.valueOf(lineCount).length();
@@ -257,9 +265,6 @@ private void styleStickyLines() {
 
 	private List<StyleRange> getStickyLineStyleRanges(StickyLine stickyLine, int stickyLineTextOffset) {
 		int lineNumber= stickyLine.lineNumber();
-		if (sourceViewer instanceof ITextViewerExtension5 extension) {
-			lineNumber= extension.modelLine2WidgetLine(lineNumber);
-		}
 		try {
 			StyledText textWidget= sourceViewer.getTextWidget();
 			int offsetAtLine= textWidget.getOffsetAtLine(lineNumber);

bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingHandler.java

@@ -22,8 +22,10 @@
 
 import java.time.Duration;
 import java.util.Collections;
+import java.util.LinkedList;
 import java.util.List;
 
+import org.eclipse.swt.custom.StyledText;
 import org.eclipse.swt.graphics.Color;
 import org.eclipse.swt.graphics.RGB;
 
@@ -138,7 +140,7 @@ private StickyScrollingControlSettings loadControlSettings(IPreferenceStore stor
 
 	private StickyLinesProperties loadStickyLinesProperties(IPreferenceStore store) {
 		int tabWidth= store.getInt(EDITOR_TAB_WIDTH);
-		return new StickyLinesProperties(tabWidth);
+		return new StickyLinesProperties(tabWidth, sourceViewer);
 	}
 
 	@Override
@@ -151,13 +153,52 @@ public void viewportChanged(int newVerticalOffset) {
 	}
 
 	private void calculateAndShowStickyLines() {
-		List<StickyLine> stickyLines= stickyLinesProvider.getStickyLines(sourceViewer, stickyLinesProperties);
+		List<StickyLine> stickyLines= Collections.emptyList();
+
+		StyledText textWidget= sourceViewer.getTextWidget();
+		int startLine= textWidget.getTopIndex();
+
+		if (startLine > 0) {
+			stickyLines= stickyLinesProvider.getStickyLines(textWidget, startLine, stickyLinesProperties);
+		}
+
 		if (stickyLines == null) {
 			stickyLines= Collections.emptyList();
 		}
+
+		stickyLines= adaptStickyLinesToVisibleArea(stickyLines, startLine);
+
 		stickyScrollingControl.setStickyLines(stickyLines);
 	}
 
+	private List<StickyLine> adaptStickyLinesToVisibleArea(List<StickyLine> stickyLines, int startLine) {
+		if (stickyLines.isEmpty()) {
+			return stickyLines;
+		}
+
+		LinkedList<StickyLine> adaptedStickyLines= new LinkedList<>(stickyLines);
+
+		int firstVisibleLine= startLine + adaptedStickyLines.size();
+		StyledText textWidget= sourceViewer.getTextWidget();
+		int maximumLines= textWidget.getLineCount();
+
+		for (int i= startLine + 1; i <= firstVisibleLine && i < maximumLines; i++) {
+			List<StickyLine> stickyLinesInLineI= stickyLinesProvider.getStickyLines(textWidget, i, stickyLinesProperties);
+
+			if (stickyLinesInLineI.size() > adaptedStickyLines.size()) {
+				adaptedStickyLines= new LinkedList<>(stickyLinesInLineI);
+				firstVisibleLine= startLine + adaptedStickyLines.size();
+			}
+
+			while (stickyLinesInLineI.size() < adaptedStickyLines.size() && i < firstVisibleLine) {
+				adaptedStickyLines.removeLast();
+				firstVisibleLine--;
+			}
+		}
+
+		return adaptedStickyLines;
+	}
+
 	/**
 	 * Uninstalls the sticky scrolling handler from the source viewer. This completely disposes the
 	 * {@link StickyScrollingControl} and removes all corresponding listeners.