Program icon scaling using system DPI #1759

This commit contributes to proper scaling of Program icons. Since these
icons are retrieved by OS.SHGetFileInfo which is System DPI-Aware, it
returns the icon with zoom level of the primary monitor at application
startup. Hence, for initialNativeZoom of the Image object to be created
for the icon, the zoom retrieved from the DPI is considered.

Contributes to
#62 and
#127

Fixes #1759

Author: amartya4256

bundles/org.eclipse.swt/Eclipse SWT Program/win32/org/eclipse/swt/program/Program.java

@@ -19,8 +19,8 @@
 
 import org.eclipse.swt.*;
 import org.eclipse.swt.graphics.*;
+import org.eclipse.swt.internal.*;
 import org.eclipse.swt.internal.win32.*;
-import org.eclipse.swt.widgets.*;
 
 /**
  * Instances of this class represent programs and
@@ -379,9 +379,9 @@ public ImageData getImageData () {
  * @since 3.125
  */
 public ImageData getImageData (int zoom) {
-	// Windows API returns image data according to primary monitor zoom factor
-	// rather than at original scaling
-	int initialNativeZoom = Display.getCurrent().getPrimaryMonitor().getZoom();
+	// OS.SHGetFileInfo is System DPI-aware, hence it retrieves the icon with zoom
+	// of primary monitor at the application startup
+	int initialNativeZoom = getPrimaryMonitorZoomAtStartup();
 	if (extension != null) {
 		SHFILEINFO shfi = new SHFILEINFO ();
 		int flags = OS.SHGFI_ICON | OS.SHGFI_USEFILEATTRIBUTES;
@@ -427,6 +427,13 @@ public ImageData getImageData (int zoom) {
 	return imageData;
 }
 
+private int getPrimaryMonitorZoomAtStartup() {
+	long hDC = OS.GetDC(0);
+	int dpi = OS.GetDeviceCaps(hDC, OS.LOGPIXELSX);
+	OS.ReleaseDC(0, hDC);
+	return DPIUtil.mapDPIToZoom(dpi);
+}
+
 /**
  * Returns the receiver's name.  This is as short and
  * descriptive a name as possible for the program.  If