Fix caret of raw insert mode of text editor on HiDPI screens

Fixes: #3010

Author: wahlbrink

bundles/org.eclipse.ui.workbench.texteditor/src/org/eclipse/ui/texteditor/AbstractTextEditor.java

@@ -67,6 +67,7 @@
 import org.eclipse.swt.graphics.GC;
 import org.eclipse.swt.graphics.Image;
 import org.eclipse.swt.graphics.ImageData;
+import org.eclipse.swt.graphics.ImageDataProvider;
 import org.eclipse.swt.graphics.PaletteData;
 import org.eclipse.swt.graphics.Point;
 import org.eclipse.swt.graphics.RGB;
@@ -6961,32 +6962,27 @@ private Caret createInsertCaret(StyledText styledText) {
 	}
 
 	private Image createRawInsertModeCaretImage(StyledText styledText) {
-
 		PaletteData caretPalette = new PaletteData(new RGB(0, 0, 0), new RGB(255, 255, 255));
 		int width = getCaretWidthPreference();
-		int widthOffset = width - 1;
-
 		// XXX: Filed request to get a caret with auto-height:
 		// https://bugs.eclipse.org/bugs/show_bug.cgi?id=118612
-		ImageData imageData = new ImageData(4 + widthOffset, styledText.getLineHeight(), 1, caretPalette);
-
-		Display display = styledText.getDisplay();
-		Image bracketImage = new Image(display, imageData);
-		GC gc = new GC(bracketImage);
-		gc.setForeground(display.getSystemColor(SWT.COLOR_WHITE));
-		gc.setLineWidth(0); // NOTE: 0 means width is 1 but with optimized performance
-		int height = imageData.height / 3;
-		// gap between two bars of one third of the height
-		// draw boxes using lines as drawing a line of a certain width produces
-		// rounded corners.
-		for (int i = 0; i < width; i++) {
-			gc.drawLine(i, 0, i, height - 1);
-			gc.drawLine(i, imageData.height - height, i, imageData.height - 1);
-		}
-
-		gc.dispose();
-
-		return bracketImage;
+		int height = styledText.getLineHeight();
+		ImageDataProvider imageDataProvider = zoom -> {
+			double scaleFactor = zoom / 100.0;
+			int w = (int) (width * scaleFactor + 0.5);
+			int h = (int) (height * scaleFactor + 0.5);
+			ImageData imageData = new ImageData(w, h, 1, caretPalette);
+			// gap between two bars of one third of the height
+			int h3 = h / 3;
+			for (int x = 0; x < w; x++) {
+				for (int y = 0; y < h3; y++) {
+					imageData.setPixel(x, y, 1);
+					imageData.setPixel(x, h - y - 1, 1);
+				}
+			}
+			return imageData;
+		};
+		return new Image(styledText.getDisplay(), imageDataProvider);
 	}
 
 	private Caret createRawInsertModeCaret(StyledText styledText) {