StickyScrolling: Move complex line adaption to central handler

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.