[GTK] Scale Program.getImageData() to 16x16 pixels

This change ensures Program icons are scaled to 16x16 pixels, to avoid huge icons in platform UI.
The scaling is done only if DPI scaling is 1.

Fixes: #3003

Author: trancexpress

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

@@ -17,13 +17,15 @@
 import java.nio.file.*;
 import java.nio.file.Path;
 import java.util.*;
+import java.util.List;
 
 import org.eclipse.swt.*;
 import org.eclipse.swt.graphics.*;
 import org.eclipse.swt.internal.*;
 import org.eclipse.swt.internal.gtk.*;
 import org.eclipse.swt.internal.gtk3.*;
 import org.eclipse.swt.internal.gtk4.*;
+import org.eclipse.swt.widgets.*;
 
 /**
  * Instances of this class represent programs and
@@ -146,6 +148,7 @@ public ImageData getImageData() {
 public ImageData getImageData(int zoom) {
 	if (iconPath == null) return null;
 	ImageData data = null;
+	int scale = 1;
 
 	long gicon = OS.g_icon_new_for_string(Converter.javaStringToCString(iconPath), null);
 	if (gicon != 0) {
@@ -168,7 +171,15 @@ public ImageData getImageData(int zoom) {
 			OS.g_object_unref(paintable);
 		} else {
 			long icon_theme = GTK3.gtk_icon_theme_get_default();
-			long gicon_info = GTK3.gtk_icon_theme_lookup_by_gicon(icon_theme, gicon, 16/*size*/, 0);
+			Shell shell = Display.getCurrent().getActiveShell();
+			if (shell != null) {
+				long shellHandle = shell.handle;
+				long window = GTK3.gtk_widget_get_window(shellHandle);
+				if (window != 0) {
+					scale = GDK.gdk_window_get_scale_factor(window);
+				}
+			}
+			long gicon_info = GTK3.gtk_icon_theme_lookup_by_gicon_for_scale(icon_theme, gicon, 16/*size*/, scale, 0);
 			if (gicon_info != 0) {
 				pixbuf = GTK3.gtk_icon_info_load_icon(gicon_info, null);
 				OS.g_object_unref(gicon_info);
@@ -204,6 +215,10 @@ public ImageData getImageData(int zoom) {
 					}
 				}
 				data.alphaData = alphaData;
+				if (scale == 1 && height > 16 && width > 16) {
+					ImageData scaled = data.scaledTo(16, 16);
+					data = scaled;
+				}
 			} else {
 				PaletteData palette = new PaletteData(0xFF0000, 0xFF00, 0xFF);
 				data = new ImageData(width, height, 24, palette, 4, srcData);