[win32] Handle all scaled font via SWTFontProvider

This commit extends the SWTFontProvider and the SWTFontRegistry to
receive scaled variants of a font where only the handle is available.
Common use case for this is OS.SendMessage (hwnd, OS.WM_GETFONT, 0, 0)
to receive the handle of the current font of a handle. As at this point
the correct zoom the handle was created is not yet know, it is better
to retrieve and manage those fonts via the SWTFontRegistry expecially
when monitor specific scaling is used. When the passed font handle is
not already managed via the SWTFontRegistry it will create the SWT Font
as it was create previously.

Author: akoch-yatta

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/GC.java

@@ -3898,14 +3898,14 @@ void init(Drawable drawable, GCData data, long hDC) {
 		data.background = OS.GetBkColor(hDC);
 	}
 	data.state &= ~(NULL_BRUSH | NULL_PEN);
+	if (data.nativeZoom == 0) {
+		data.nativeZoom = extractZoom(hDC);
+	}
 	Font font = data.font;
 	if (font != null) {
 		data.state &= ~FONT;
 	} else {
-		data.font = Font.win32_new(device, OS.GetCurrentObject(hDC, OS.OBJ_FONT));
-	}
-	if (data.nativeZoom == 0) {
-		data.nativeZoom = extractZoom(hDC);
+		data.font = SWTFontProvider.getFont(device, OS.GetCurrentObject(hDC, OS.OBJ_FONT), data.nativeZoom);
 	}
 	Image image = data.image;
 	if (image != null) {

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

@@ -71,6 +71,11 @@ public Font getFont(FontData fontData, int zoom) {
 		return font;
 	}
 
+	@Override
+	public Font getFont(long fontHandle, int zoom) {
+		return Font.win32_new(device, fontHandle, zoom);
+	}
+
 	private Font registerFont(FontData fontData, Font font) {
 		fontsMap.put(fontData, font);
 		return font;

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

@@ -61,6 +61,21 @@ public static Font getFont(Device device, FontData fontData, int zoom) {
 		return getFontRegistry(device).getFont(fontData, zoom);
 	}
 
+	/**
+	 * Returns the font with the given fontHandle for the given device at the
+	 * specified zoom.
+	 *
+	 * <b>Note:</b> This operation is not thread-safe. It must thus always be called
+	 * from the same thread for the same device, such as the display's UI thread.
+	 *
+	 * @param device     the device to retrieve the font for, must not be {@code null}
+	 * @param fontHandle the handle to an existing font
+	 * @param zoom       the zoom for which the font shall be scaled
+	 */
+	public static Font getFont(Device device, long fontHandle, int zoom) {
+		return getFontRegistry(device).getFont(fontHandle, zoom);
+	}
+
 	/**
 	 * Disposes the font registry for the given device, if one exists.
 	 *

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

@@ -46,6 +46,18 @@ public interface SWTFontRegistry {
 	 */
 	Font getFont(FontData fontData, int zoom);
 
+
+	/**
+	 * Provides a font optimally suited for the specified zoom. If the handle is yet unknown to
+	 * the registry, the font will not be managed by the font registry. Only Fonts created in the
+	 * font registry are managed by it and should not be disposed of externally.
+	 *
+	 * @param fontHandle the handle to an existing font
+	 * @param zoom zoom in % of the standard resolution to determine the appropriate font
+	 * @return the font best suited for the specified zoom
+	 */
+	Font getFont(long fontHandle, int zoom);
+
 	/**
 	 * Disposes all fonts managed by the font registry.
 	 */

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

@@ -44,6 +44,7 @@ private Font getScaledFont(int zoom) {
 
 		private Font createAndCacheFont(int zoom) {
 			Font newFont = createFont(zoom);
+			customFontHandlesKeyMap.put(newFont.handle, this);
 			scaledFonts.put(zoom, newFont);
 			return newFont;
 		}
@@ -112,6 +113,7 @@ protected void dispose() {
 
 	private ScaledFontContainer systemFontContainer;
 	private Map<FontData, ScaledFontContainer> customFontsKeyMap = new HashMap<>();
+	private Map<Long, ScaledFontContainer> customFontHandlesKeyMap = new HashMap<>();
 	private Device device;
 
 	ScalingSWTFontRegistry(Device device) {
@@ -136,6 +138,14 @@ public Font getFont(FontData fontData, int zoom) {
 		return container.getScaledFont(zoom);
 	}
 
+	@Override
+	public Font getFont(long fontHandle, int zoom) {
+		if (customFontHandlesKeyMap.containsKey(fontHandle)) {
+			return customFontHandlesKeyMap.get(fontHandle).getScaledFont(zoom);
+		}
+		return Font.win32_new(device, fontHandle, zoom);
+	}
+
 	@Override
 	public void dispose() {
 		customFontsKeyMap.values().forEach(ScaledFontContainer::dispose);

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Composite.java

@@ -1525,7 +1525,7 @@ LRESULT WM_PAINT (long wParam, long lParam) {
 					Control control = findBackgroundControl ();
 					if (control == null) control = this;
 					data.background = control.getBackgroundPixel ();
-					data.font = Font.win32_new(display, OS.SendMessage (handle, OS.WM_GETFONT, 0, 0), nativeZoom);
+
 					data.uiState = (int)OS.SendMessage (handle, OS.WM_QUERYUISTATE, 0, 0);
 					if ((style & SWT.NO_BACKGROUND) != 0) {
 						/* This code is intentionally commented because it may be slow to copy bits from the screen */
@@ -1536,6 +1536,8 @@ LRESULT WM_PAINT (long wParam, long lParam) {
 						drawBackground (phdc [0], rect);
 					}
 					GC gc = createNewGC(phdc [0], data);
+					data.font = SWTFontProvider.getFont(display, OS.SendMessage (handle, OS.WM_GETFONT, 0, 0), data.nativeZoom);
+
 					Event event = new Event ();
 					event.gc = gc;
 					event.setBounds(DPIUtil.scaleDown(new Rectangle(ps.left, ps.top, width, height), getZoom()));

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Control.java

@@ -1315,7 +1315,7 @@ public Font getFont () {
 	if (font != null) return font;
 	long hFont = OS.SendMessage (handle, OS.WM_GETFONT, 0, 0);
 	if (hFont == 0) hFont = defaultFont ();
-	return Font.win32_new (display, hFont, getShell().nativeZoom);
+	return SWTFontProvider.getFont(display, hFont, getNativeZoom());
 }
 
 /**
@@ -1748,14 +1748,18 @@ public long internal_new_GC (GCData data) {
 			}
 		}
 		data.device = display;
-		data.nativeZoom = nativeZoom;
+		data.nativeZoom = getNativeZoom();
 		int foreground = getForegroundPixel ();
 		if (foreground != OS.GetTextColor (hDC)) data.foreground = foreground;
 		Control control = findBackgroundControl ();
 		if (control == null) control = this;
 		int background = control.getBackgroundPixel ();
 		if (background != OS.GetBkColor (hDC)) data.background = background;
-		data.font = font != null ? font : Font.win32_new (display, OS.SendMessage (hwnd, OS.WM_GETFONT, 0, 0));
+		if (font != null) {
+			data.font = font;
+		} else {
+			data.font = SWTFontProvider.getFont(display, OS.SendMessage (hwnd, OS.WM_GETFONT, 0, 0), data.nativeZoom);
+		}
 		data.uiState = (int)OS.SendMessage (hwnd, OS.WM_QUERYUISTATE, 0, 0);
 	}
 	return hDC;

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Widget.java

@@ -2690,6 +2690,10 @@ GC createNewGC(long hDC, GCData data) {
 	return GC.win32_new(hDC, data);
 }
 
+int getNativeZoom() {
+	return nativeZoom;
+}
+
 int getZoom() {
 	return DPIUtil.getZoomForAutoscaleProperty(nativeZoom);
 }