Issue #932: Splitting out drawLineBackground() and drawLineForeground()

Needed to paint entire background in next commit.

Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>

Author: SyntevoAlex

bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledText.java

@@ -5926,18 +5926,16 @@ void handlePaint(Event event) {
 	if (event.width == 0 || event.height == 0) return;
 	if (clientAreaWidth == 0 || clientAreaHeight == 0) return;
 
-	int startLine = getLineIndex(event.y);
-	int y = getLinePixel(startLine);
-	int endY = event.y + event.height;
+	final int endY = event.y + event.height;
 	GC gc = event.gc;
 	Color background = getBackground();
 	Color foreground = getForeground();
 	if (endY > 0) {
-		int lineCount = isSingleLine() ? 1 : content.getLineCount();
-		int x = leftMargin - horizontalScrollOffset;
-		for (int i = startLine; y < endY && i < lineCount; i++) {
-			y += renderer.drawLine(i, x, y, gc, background, foreground);
-		}
+		final int startLine = getLineIndex(event.y);
+		final int endLine = isSingleLine() ? 1 : content.getLineCount();
+		final int x = leftMargin - horizontalScrollOffset;
+		int y = getLinePixel(startLine);
+		y += renderer.drawLines(startLine, endLine, x, y, endY, gc, background, foreground);
 		if (y < endY) {
 			gc.setBackground(background);
 			drawBackground(gc, 0, y, clientAreaWidth, endY - y);

bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledTextRenderer.java

@@ -183,6 +183,11 @@ public LineInfo(LineInfo info) {
 			}
 		}
 	}
+
+	private record LineDrawInfo(int index, TextLayout layout, String text, int offset, int height) {
+
+	}
+
 	static int cap (TextLayout layout, int offset) {
 		if (layout == null) return offset;
 		return Math.min (layout.getText().length() -1, Math.max (0, offset));
@@ -452,32 +457,63 @@ void drawBullet(Bullet bullet, GC gc, int paintX, int paintY, int index, int lin
 	layout.draw(gc, x, paintY);
 	layout.dispose();
 }
-int drawLine(int lineIndex, int paintX, int paintY, GC gc, Color widgetBackground, Color widgetForeground) {
+
+/**
+ * Caches draw-related info that may be expensive to calculate twice when
+ * drawing first background and then foreground.
+ */
+private LineDrawInfo makeLineDrawInfo(int lineIndex) {
 	TextLayout layout = getTextLayout(lineIndex);
-	String line = content.getLine(lineIndex);
-	int lineOffset = content.getOffsetAtLine(lineIndex);
-	int lineLength = line.length();
+	String text = content.getLine(lineIndex);
+	int offset = content.getOffsetAtLine(lineIndex);
+	int height = layout.getBounds().height;
+	return new LineDrawInfo(lineIndex, layout, text, offset, height);
+}
+
+int drawLines(int startLine, int endLine, int begX, int begY, int endY, GC gc, Color widgetBackground, Color widgetForeground) {
+	final boolean drawBackBeforeFore = false;
+
+	if (drawBackBeforeFore) {
+		return 0;
+	}
+
+	int y = begY;
+	for (int iLine = startLine; y < endY && iLine < endLine; iLine++) {
+		LineDrawInfo lineInfo = makeLineDrawInfo(iLine);
+		drawLineBackground(lineInfo, y, gc, widgetBackground);
+		drawLineForeground(lineInfo, begX, y, gc, widgetForeground);
+		disposeTextLayout(lineInfo.layout);
+		y += lineInfo.height;
+	}
+	return y - begY;
+}
+
+private void drawLineBackground(LineDrawInfo lineInfo, int paintY, GC gc, Color widgetBackground) {
 	Rectangle client = styledText.getClientArea();
-	Color lineBackground = getLineBackground(lineIndex, null);
-	StyledTextEvent event = styledText.getLineBackgroundData(lineOffset, line);
+	Color lineBackground = getLineBackground(lineInfo.index, null);
+	StyledTextEvent event = styledText.getLineBackgroundData(lineInfo.offset, lineInfo.text);
 	if (event != null && event.lineBackground != null) lineBackground = event.lineBackground;
-	int height = layout.getBounds().height;
-	int verticalIndent = layout.getVerticalIndent();
+	int verticalIndent = lineInfo.layout.getVerticalIndent();
+
 	if (lineBackground != null) {
 		if (verticalIndent > 0) {
 			gc.setBackground(widgetBackground);
 			gc.fillRectangle(client.x, paintY, client.width, verticalIndent);
 		}
 		gc.setBackground(lineBackground);
-		gc.fillRectangle(client.x, paintY + verticalIndent, client.width, height - verticalIndent);
+		gc.fillRectangle(client.x, paintY + verticalIndent, client.width, lineInfo.height - verticalIndent);
 	} else {
 		gc.setBackground(widgetBackground);
-		styledText.drawBackground(gc, client.x, paintY, client.width, height);
+		styledText.drawBackground(gc, client.x, paintY, client.width, lineInfo.height);
 	}
+}
+
+private void drawLineForeground(LineDrawInfo lineInfo, int paintX, int paintY, GC gc, Color widgetForeground) {
+	int lineLength = lineInfo.text.length();
 	gc.setForeground(widgetForeground);
-	Point[] selection = intersectingRelativeNonEmptySelections(lineOffset, lineOffset + lineLength);
+	Point[] selection = intersectingRelativeNonEmptySelections(lineInfo.offset, lineInfo.offset + lineLength);
 	if (styledText.getBlockSelection() || selection.length == 0) {
-		layout.draw(gc, paintX, paintY);
+		lineInfo.layout.draw(gc, paintX, paintY);
 	} else {
 		Color selectionFg = styledText.getSelectionForeground();
 		Color selectionBg = styledText.getSelectionBackground();
@@ -490,7 +526,7 @@ int drawLine(int lineIndex, int paintX, int paintY, GC gc, Color widgetBackgroun
 				flags |= SWT.LAST_LINE_SELECTION;
 			}
 			// TODO calling draw multiple times here prints line multiple times, overriding some colors
-			layout.draw(gc, paintX, paintY, start, end - 1, selectionFg, selectionBg, flags);
+			lineInfo.layout.draw(gc, paintX, paintY, start, end - 1, selectionFg, selectionBg, flags);
 		}
 	}
 
@@ -499,48 +535,47 @@ int drawLine(int lineIndex, int paintX, int paintY, GC gc, Color widgetBackgroun
 	int bulletIndex = -1;
 	if (bullets != null) {
 		if (bulletsIndices != null) {
-			int index = lineIndex - topIndex;
+			int index = lineInfo.index - topIndex;
 			if (0 <= index && index < CACHE_SIZE) {
 				bullet = bullets[index];
 				bulletIndex = bulletsIndices[index];
 			}
 		} else {
 			for (Bullet b : bullets) {
 				bullet = b;
-				bulletIndex = bullet.indexOf(lineIndex);
+				bulletIndex = bullet.indexOf(lineInfo.index);
 				if (bulletIndex != -1) break;
 			}
 		}
 	}
 	if (bulletIndex != -1 && bullet != null) {
-		FontMetrics metrics = layout.getLineMetrics(0);
+		FontMetrics metrics = lineInfo.layout.getLineMetrics(0);
 		int lineAscent = metrics.getAscent() + metrics.getLeading();
 		if (bullet.type == ST.BULLET_CUSTOM) {
-			bullet.style.start = lineOffset;
+			bullet.style.start = lineInfo.offset;
 			styledText.paintObject(gc, paintX, paintY, lineAscent, metrics.getDescent(), bullet.style, bullet, bulletIndex);
 		} else {
 			drawBullet(bullet, gc, paintX, paintY, bulletIndex, lineAscent, metrics.getDescent());
 		}
 	}
-	TextStyle[] styles = layout.getStyles();
+	TextStyle[] styles = lineInfo.layout.getStyles();
 	int[] ranges = null;
 	for (int i = 0; i < styles.length; i++) {
 		if (styles[i].metrics != null) {
-			if (ranges == null) ranges = layout.getRanges();
+			if (ranges == null) ranges = lineInfo.layout.getRanges();
 			int start = ranges[i << 1];
 			int length = ranges[(i << 1) + 1] - start + 1;
-			Point point = layout.getLocation(start, false);
-			FontMetrics metrics = layout.getLineMetrics(layout.getLineIndex(start));
+			Point point = lineInfo.layout.getLocation(start, false);
+			FontMetrics metrics = lineInfo.layout.getLineMetrics(lineInfo.layout.getLineIndex(start));
 			StyleRange style = (StyleRange)((StyleRange)styles[i]).clone();
-			style.start = start + lineOffset;
+			style.start = start + lineInfo.offset;
 			style.length = length;
 			int lineAscent = metrics.getAscent() + metrics.getLeading();
 			styledText.paintObject(gc, point.x + paintX, point.y + paintY, lineAscent, metrics.getDescent(), style, null, 0);
 		}
 	}
-	disposeTextLayout(layout);
-	return height;
 }
+
 private Point[] intersectingRelativeNonEmptySelections(int fromOffset, int toOffset) {
 	int[] selectionRanges = styledText.getSelectionRanges();
 	int lineLength = toOffset - fromOffset;