Design improvement for scaling win32 widgets

This commit improves thes design implementation for widgets in win32 by
moving away from DPIZoomChangeRegistry to an event-driven design using
ZoomChanged event and inheritance. All the classes extending widget must
override handleDPIChange method. The Widget class registers a listener
for ZoomChanged event and Shell (Control) on getting a DPI_CHANGED event
from the OS notifies its ZoomChanged listener as the root of the event
which executes all the handleDPIChange methods for all the parent
classes in hierarchial order and sending the event down in the widget
tree vy notifying ZoomChanged listeners of other associated or children
widgets.

Author: amartya4256

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

@@ -173,6 +173,7 @@ public CCombo (Composite parent, int style) {
 	}
 
 	initAccessible();
+	addListener(SWT.ZoomChanged, this::handleDPIChange);
 }
 static int checkStyle (int style) {
 	int mask = SWT.BORDER | SWT.READ_ONLY | SWT.FLAT | SWT.LEFT_TO_RIGHT | SWT.RIGHT_TO_LEFT | SWT.LEAD | SWT.CENTER | SWT.TRAIL;
@@ -2026,19 +2027,18 @@ public boolean traverse(int event){
 	return super.traverse(event);
 }
 
-/**
- * The method accepts a combo and a callback which takes
- * all the child of the CCombo as the argument and executes it.
- * All children are refreshed after the execution of the callback.
- *
- * @noreference This method is not intended to be referenced by clients.
- * @param combo the Combo to get the children widget from
- * @param childUpdater the callback which works with the child widgets
- */
-public static void updateAndRefreshChildren(CCombo combo, Consumer<Widget> childUpdater) {
-	childUpdater.accept(combo.text);
-	childUpdater.accept(combo.list);
-	childUpdater.accept(combo.arrow);
-	childUpdater.accept(combo.popup);
+private void handleDPIChange(Event event) {
+	if (text != null) {
+		text.notifyListeners(SWT.ZoomChanged, event);
+	}
+	if (list != null) {
+		list.notifyListeners(SWT.ZoomChanged, event);
+	}
+	if (arrow != null) {
+		arrow.notifyListeners(SWT.ZoomChanged, event);
+	}
+	if (popup != null) {
+		popup.notifyListeners(SWT.ZoomChanged, event);
+	}
 }
 }

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

@@ -19,7 +19,6 @@
 
 
 import java.util.*;
-import java.util.function.*;
 import java.util.stream.*;
 
 import org.eclipse.swt.*;
@@ -759,6 +758,7 @@ public StyledText(Composite parent, int style) {
 	initializeAccessible();
 	setData("DEFAULT_DROP_TARGET_EFFECT", new StyledTextDropTargetEffect(this));
 	if (IS_MAC) setData(STYLEDTEXT_KEY);
+	addListener(SWT.ZoomChanged, this::handleDPIChange);
 }
 /**
  * Adds an extended modify listener. An ExtendedModify event is sent by the
@@ -10901,29 +10901,20 @@ void updateSelection(int startOffset, int replacedLength, int newLength) {
 	setCaretLocations();
 }
 
-/**
- * The method accepts a StyledText and a callback which takes
- * all the carets of the StyledText as the argument and executes it.
- * The caret is refreshed after the execution of the callback.
- *
- * @param styledText the StyledText to get the carets from
- * @param caretUpdater the callback which works with the carets
- *
- * @noreference This method is not intended to be referenced by clients.
- */
-public static void updateAndRefreshCarets(StyledText styledText, Consumer<Caret> caretUpdater) {
-	styledText.updateCaretVisibility();
-	styledText.setCaretLocations();
+private void handleDPIChange(Event event) {
+	updateCaretVisibility();
+	setCaretLocations();
 	Set<Caret> caretSet = new LinkedHashSet<>();
-	caretSet.add(styledText.defaultCaret);
-	caretSet.add(styledText.getCaret());
-	if (styledText.carets != null) {
-		for (Caret caret : styledText.carets) {
+	caretSet.add(defaultCaret);
+	caretSet.add(getCaret());
+	if (carets != null) {
+		for (Caret caret : carets) {
 			caretSet.add(caret);
 		}
 	}
-	caretSet.stream().filter(Objects::nonNull).forEach(caretUpdater);
-
+	caretSet.stream().filter(Objects::nonNull).forEach(caretToRefresh -> {
+		caretToRefresh.notifyListeners(SWT.ZoomChanged, event);
+	});
 }
 
 }

bundles/org.eclipse.swt/Eclipse SWT Tests/win32/org/eclipse/swt/internal/DPITestUtil.java

@@ -13,6 +13,7 @@
  *******************************************************************************/
 package org.eclipse.swt.internal;
 
+import org.eclipse.swt.*;
 import org.eclipse.swt.widgets.*;
 
 public final class DPITestUtil {
@@ -22,8 +23,12 @@ private DPITestUtil() {
 
 	public static void changeDPIZoom (Shell shell, int nativeZoom) {
 		DPIUtil.setDeviceZoom(nativeZoom);
-		float scalingFactor = 1f * DPIUtil.getZoomForAutoscaleProperty(nativeZoom) / DPIUtil.getZoomForAutoscaleProperty(shell.nativeZoom);
-		DPIZoomChangeRegistry.applyChange(shell, nativeZoom, scalingFactor);
+		Event event = new Event();
+		event.type = SWT.ZoomChanged;
+		event.widget = shell;
+		event.detail = nativeZoom;
+		event.doit = true;
+		shell.notifyListeners(SWT.ZoomChanged, event);
 	}
 
 }

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/widgets/Item.java

@@ -75,6 +75,7 @@ public abstract class Item extends Widget {
 public Item (Widget parent, int style) {
 	super (parent, style);
 	text = "";
+	this.addListener(SWT.ZoomChanged, this::handleDPIChange);
 }
 
 /**
@@ -224,4 +225,13 @@ boolean updateTextDirection(int textDirection) {
 	return textDirection == AUTO_TEXT_DIRECTION;
 }
 
+
+private void handleDPIChange(Event event) {
+	// Refresh the image
+	Image image = getImage();
+	if (image != null) {
+		setImage(image);
+	}
+}
+
 }

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/internal/CommonWidgetsDPIChangeHandlers.java

@@ -65,8 +65,6 @@ public class Button extends Control {
 		WNDCLASS lpWndClass = new WNDCLASS ();
 		OS.GetClassInfo (0, ButtonClass, lpWndClass);
 		ButtonProc = lpWndClass.lpfnWndProc;
-
-		DPIZoomChangeRegistry.registerHandler(Button::handleDPIChange, Button.class);
 	}
 
 /**
@@ -1561,16 +1559,16 @@ LRESULT wmDrawChild (long wParam, long lParam) {
 	return null;
 }
 
-private static void handleDPIChange(Widget widget, int newZoom, float scalingFactor) {
-	if (!(widget instanceof Button button)) {
-		return;
-	}
+@Override
+void handleDPIChange(Event event, float scalingFactor) {
+	super.handleDPIChange(event, scalingFactor);
 	//Refresh the CheckSize
-	button.refreshCheckSize(newZoom);
+	int newZoom = event.detail;
+	refreshCheckSize(newZoom);
 	// Refresh the image
-	if (button.image != null) {
-		button._setImage(button.image);
-		button.updateImageList();
+	if (image != null) {
+		_setImage(image);
+		updateImageList();
 	}
 }
 }

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/internal/DPIZoomChangeHandler.java

@@ -51,10 +51,6 @@ public class Caret extends Widget {
 	Font font;
 	LOGFONT oldFont;
 
-static {
-	DPIZoomChangeRegistry.registerHandler(Caret::handleDPIChange, Caret.class);
-}
-
 /**
  * Constructs a new instance of this class given its parent
  * and a style value describing its behavior and appearance.
@@ -658,20 +654,18 @@ public void setVisible (boolean visible) {
 	}
 }
 
-private static void handleDPIChange(Widget widget, int newZoom, float scalingFactor) {
-	if (!(widget instanceof Caret caret)) {
-		return;
-	}
-
-	Image image = caret.getImage();
+@Override
+void handleDPIChange(Event event, float scalingFactor) {
+	super.handleDPIChange(event, scalingFactor);
+	Image image = getImage();
 	if (image != null) {
-		caret.setImage(image);
+		setImage(image);
 	}
 
-	if (caret.font != null) {
-		caret.setFont(caret.font);
+	if (font != null) {
+		setFont(font);
 	}
-	if (caret.isVisible && caret.hasFocus ()) caret.resize();
+	if (isVisible && hasFocus ()) resize();
 }
 }