Getting rid of getDPI to calculate chevron size

getDPI always returns the points for primary monitor and can produce
faulty behavior. Replacing the logic to calculate the chevron font size.
Visibly 70% size of the font used for CTabItem is now used. Also
adjusting the indent and adding the ZoomChange event to trigger redraw
during DPI change

Author: ShahzaibIbrahim

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

@@ -341,6 +341,7 @@ void init(int style) {
 			case SWT.Selection:        onSelection(event); break;
 			case SWT.Activate:         onActivate(event); break;
 			case SWT.Deactivate:       onDeactivate(event); break;
+			case SWT.ZoomChanged:	   onZoomChange(event); break;
 		}
 	};
 
@@ -362,14 +363,20 @@ void init(int style) {
 		SWT.Resize,
 		SWT.Traverse,
 		SWT.Activate,
-		SWT.Deactivate
+		SWT.Deactivate,
+		SWT.ZoomChanged
 	};
 	for (int folderEvent : folderEvents) {
 		addListener(folderEvent, listener);
 	}
 
 	initAccessible();
 }
+
+void onZoomChange(Event event) {
+	update();
+}
+
 void onDeactivate(Event event) {
 	if (!highlightEnabled) {
 		return;

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

@@ -926,7 +926,8 @@ void drawChevron(GC gc, Rectangle chevronRect, int chevronImageState) {
 		Display display = parent.getDisplay();
 		Font font = getChevronFont(display);
 		int fontHeight = font.getFontData()[0].getHeight();
-		int indent = Math.max(2, (chevronRect.height - fontHeight - 4) /2);
+		int indent = Math.max(2, (chevronRect.height - fontHeight - 8) /2);
+		System.out.println("chevronRect.height - fontHeight " + chevronRect.height + " . " + fontHeight);
 		int x = chevronRect.x + 2;
 		int y = chevronRect.y + indent;
 		int count = parent.getChevronCount();
@@ -1696,11 +1697,12 @@ Color getFillColor() {
 
 	private Font getChevronFont(Display display) {
 		if (chevronFont == null) {
-			Point dpi = display.getDPI();
-			int fontHeight = 72 * CHEVRON_FONT_HEIGHT / dpi.y;
-			FontData fd = parent.getFont().getFontData()[0];
-			fd.setHeight(fontHeight);
-			chevronFont = new Font(display, fd);
+			if (chevronFont == null) {
+				FontData fd = parent.getFont().getFontData()[0];
+				int fontHeight = (int) (parent.getFont().getFontData()[0].height * 0.7);
+				fd.setHeight(fontHeight);
+				chevronFont = new Font(display, fd);
+			}
 		}
 		return chevronFont;
 	}