[win32] Manage Font creation via existing handle via SWTFontProvider

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) {
 		FontData clonedFontData = new FontData(fontData.toString());
 		fontsMap.put(clonedFontData, 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) {
@@ -137,6 +139,14 @@ 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 +1525,6 @@ 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), getNativeZoom());
 					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 +1535,8 @@ 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, getNativeZoom());
+	return SWTFontProvider.getFont(display, hFont, getNativeZoom());
 }
 
 /**
@@ -1753,14 +1753,18 @@ 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;