[win32] Make Font#extractZoom device independent

This commit ensures Font#extractZoom is device independent. The previous
logic didn't provide any advantages anymore after the conversion between
points and pixels was changed for Fonts. By using DPIUtil#getNativeZoom
the most probable value for the zoom of a new font a chosen.

Author: akoch-yatta

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

@@ -67,7 +67,7 @@ public final class Font extends Resource {
  */
 Font(Device device) {
 	super(device);
-	this.zoom = extractZoom(this.device);
+	this.zoom = extractZoom(device);
 	this.fontHeight = 0;
 }
 
@@ -100,7 +100,7 @@ private Font(Device device, long handle, int zoom) {
  */
 public Font(Device device, FontData fd) {
 	super(device);
-	this.zoom = extractZoom(this.device);
+	this.zoom = extractZoom(device);
 	init(fd);
 	this.fontHeight = fd.height;
 	init();
@@ -146,7 +146,7 @@ public Font(Device device, FontData[] fds) {
 	for (FontData fd : fds) {
 		if (fd == null) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
 	}
-	this.zoom = extractZoom(this.device);
+	this.zoom = extractZoom(device);
 	FontData fd = fds[0];
 	init(fds[0]);
 	this.fontHeight = fd.height;
@@ -180,7 +180,7 @@ public Font(Device device, FontData[] fds) {
 public Font(Device device, String name, int height, int style) {
 	super(device);
 	if (name == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
-	this.zoom = extractZoom(this.device);
+	this.zoom = extractZoom(device);
 	init(new FontData (name, height, style));
 	this.fontHeight = height;
 	init();
@@ -189,7 +189,7 @@ public Font(Device device, String name, int height, int style) {
 /*public*/ Font(Device device, String name, float height, int style) {
 	super(device);
 	if (name == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
-	this.zoom = extractZoom(this.device);
+	this.zoom = extractZoom(device);
 	init(new FontData (name, height, style));
 	this.fontHeight = height;
 	init();
@@ -296,9 +296,9 @@ public String toString () {
 
 private static int extractZoom(Device device) {
 	if (device == null) {
-		return DPIUtil.getNativeDeviceZoom();
+		System.out.println ("***WARNING: Initializing a font with a null device will use the default device and can lead to errors when this font is used with another device."); //$NON-NLS-1$
 	}
-	return device.getDeviceZoom();
+	return DPIUtil.getNativeDeviceZoom();
 }
 
 /**