Calculate Scaling for Font without Device#getDPI()

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

@@ -304,9 +304,11 @@ void cacheLineData(StyledText styledText) {
 				}
 			}
 		}
-		Point screenDPI = styledText.getDisplay().getDPI();
+
 		Point printerDPI = printer.getDPI();
 		resources = new HashMap<> ();
+		int scaleFactorX = printerDPI.x / 100;
+		int scaleFactorY = printerDPI.y / 100;
 		for (int i = 0; i < lineCount; i++) {
 			Color color = printerRenderer.getLineBackground(i, null);
 			if (color != null) {
@@ -323,7 +325,7 @@ void cacheLineData(StyledText styledText) {
 			}
 			int indent = printerRenderer.getLineIndent(i, 0);
 			if (indent != 0) {
-				printerRenderer.setLineIndent(i, 1, indent * printerDPI.x / screenDPI.x);
+				printerRenderer.setLineIndent(i, 1, indent * scaleFactorX);
 			}
 		}
 		StyleRange[] styles = printerRenderer.styles;
@@ -367,17 +369,17 @@ void cacheLineData(StyledText styledText) {
 			if (!printOptions.printTextFontStyle) {
 				style.fontStyle = SWT.NORMAL;
 			}
-			style.rise = style.rise * printerDPI.y / screenDPI.y;
+			style.rise = style.rise * scaleFactorY;
 			GlyphMetrics metrics = style.metrics;
 			if (metrics != null) {
-				metrics.ascent = metrics.ascent * printerDPI.y / screenDPI.y;
-				metrics.descent = metrics.descent * printerDPI.y / screenDPI.y;
-				metrics.width = metrics.width * printerDPI.x / screenDPI.x;
+				metrics.ascent = metrics.ascent * scaleFactorY;
+				metrics.descent = metrics.descent * scaleFactorY;
+				metrics.width = metrics.width * scaleFactorX;
 			}
 		}
-		lineSpacing = styledText.lineSpacing * printerDPI.y / screenDPI.y;
+		lineSpacing = styledText.lineSpacing * scaleFactorY;
 		if (printOptions.printLineNumbers) {
-			printMargin = 3 * printerDPI.x / screenDPI.x;
+			printMargin = 3 * scaleFactorX;
 		}
 	}
 	/**

bundles/org.eclipse.swt/Eclipse SWT Printing/win32/org/eclipse/swt/printing/Printer.java

@@ -268,6 +268,12 @@ protected void create(DeviceData deviceData) {
 	if (handle == 0) SWT.error(SWT.ERROR_NO_HANDLES);
 }
 
+@Override
+protected int getDeviceZoom() {
+	// Printer directly renders on pixel basis, so the zoom must be fixed to 100
+	return 100;
+}
+
 /**
  * Invokes platform specific functionality to allocate a new GC handle.
  * <p>
@@ -295,8 +301,9 @@ public long internal_new_GC(GCData data) {
 			data.style |= SWT.LEFT_TO_RIGHT;
 		}
 		data.device = this;
-		data.font = Font.win32_new(this, OS.GetCurrentObject(handle, OS.OBJ_FONT));
+		data.font = Font.win32_new(this, OS.GetCurrentObject(handle, OS.OBJ_FONT), getDeviceZoom());
 		isGCCreated = true;
+		data.nativeZoom = getDeviceZoom();
 	}
 	return handle;
 }

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

@@ -268,12 +268,20 @@ int computePixels(float height) {
 }
 
 float computePoints(LOGFONT logFont, long hFont) {
-	return computePoints(logFont, hFont, -1);
+	return computePoints(logFont, hFont, SWT.DEFAULT);
 }
 
-float computePoints(LOGFONT logFont, long hFont, int currentFontDPI) {
+float computePoints(LOGFONT logFont, long hFont, int zoom) {
 	long hDC = internal_new_GC (null);
-	int logPixelsY = OS.GetDeviceCaps(hDC, OS.LOGPIXELSY);
+
+	float conversionFactor = 72f;
+	if (isAutoScalable() && zoom != SWT.DEFAULT) {
+		// For auto scalable devices we need to use a dynamic
+		// DPI value that is extracted from the zoom
+		conversionFactor /= DPIUtil.mapZoomToDPI(zoom);
+	} else {
+		conversionFactor /= OS.GetDeviceCaps(hDC, OS.LOGPIXELSY);
+	}
 	int pixels = 0;
 	if (logFont.lfHeight > 0) {
 		/*
@@ -292,14 +300,7 @@ float computePoints(LOGFONT logFont, long hFont, int currentFontDPI) {
 		pixels = -logFont.lfHeight;
 	}
 	internal_dispose_GC (hDC, null);
-	float adjustedZoomFactor = 1.0f;
-	if (currentFontDPI > 0) {
-		// as Device::computePoints will always return point on the basis of the
-		// primary monitor zoom, a custom zoomFactor must be calculated if the font
-		// is used for a different zoom level
-		adjustedZoomFactor *= (float) logPixelsY / (float) currentFontDPI;
-	}
-	return adjustedZoomFactor * pixels * 72f / logPixelsY;
+	return pixels * conversionFactor;
 }
 
 /**

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

@@ -213,7 +213,7 @@ public FontData[] getFontData() {
 	if (isDisposed()) SWT.error(SWT.ERROR_GRAPHIC_DISPOSED);
 	LOGFONT logFont = new LOGFONT ();
 	OS.GetObject(handle, LOGFONT.sizeof, logFont);
-	float heightInPoints = device.computePoints(logFont, handle, DPIUtil.mapZoomToDPI(zoom));
+	float heightInPoints = device.computePoints(logFont, handle, zoom);
 	return new FontData[] {FontData.win32_new(logFont, heightInPoints)};
 }
 
@@ -280,7 +280,7 @@ private static int extractZoom(Device device) {
 	if (device == null) {
 		return DPIUtil.getNativeDeviceZoom();
 	}
-	return DPIUtil.mapDPIToZoom(device._getDPIx());
+	return device.getDeviceZoom();
 }
 
 /**
@@ -331,8 +331,15 @@ public static Font win32_new(Device device, long handle) {
  * @since 3.126
  */
 public static Font win32_new(Device device, long handle, int zoom) {
-	Font font = win32_new(device, handle);
+	Font font = new Font(device);
 	font.zoom = zoom;
+	font.handle = handle;
+	/*
+	 * When created this way, Font doesn't own its .handle, and
+	 * for this reason it can't be disposed. Tell leak detector
+	 * to just ignore it.
+	 */
+	font.ignoreNonDisposed();
 	return font;
 }
 

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

@@ -53,7 +53,9 @@ private Font getScaledFont(int targetZoom) {
 
 		private Font scaleFont(int zoom) {
 			FontData fontData = baseFont.getFontData()[0];
-			fontData.data.lfHeight = computePixels(zoom, fontData);
+			int baseZoom = computeZoom(fontData);
+			int zoomScaleFactor = Math.round(1.0f * zoom / baseZoom);
+			fontData.data.lfHeight *= zoomScaleFactor;
 			Font scaledFont = Font.win32_new(device, fontData, zoom);
 			addScaledFont(zoom, scaledFont);
 			return scaledFont;
@@ -168,24 +170,13 @@ private Font getOrCreateFont(ScaledFontContainer container, int zoom) {
 	}
 
 	private int computeZoom(FontData fontData) {
-		int dpi = device.getDPI().x;
-		int pixelsAtPrimaryMonitorZoom = computePixels(fontData.height);
-		int value = DPIUtil.mapDPIToZoom(dpi) * fontData.data.lfHeight / pixelsAtPrimaryMonitorZoom;
-		return value;
-	}
-
-	private int computePixels(int zoom, FontData fontData) {
-		int dpi = device.getDPI().x;
-		int adjustedLogFontHeight = computePixels(fontData.height);
-		int primaryZoom = DPIUtil.mapDPIToZoom(dpi);
-		if (zoom != primaryZoom) {
-			adjustedLogFontHeight *= (1f * zoom / primaryZoom);
+		int pixelHeight = fontData.data.lfHeight;
+		float currentPointHeight = fontData.height;
+		if (pixelHeight == 0 || Math.abs(currentPointHeight) < 0.001) {
+			// if there is no font yet available, we use a defined zoom
+			return 100;
 		}
-		return adjustedLogFontHeight;
-	}
-
-	private int computePixels(float height) {
-		int dpi = device.getDPI().x;
-		return -(int)(0.5f + (height * dpi / 72f));
+		float pointHeightOn100 = -(pixelHeight / 96f * 72f);
+		return Math.round(100.0f * pointHeightOn100 / currentPointHeight);
 	}
 }