[GTK] Scale external program icons to 16x16 #3004

trancexpress · 2026-01-23T16:12:01Z

GTK3 API gtk_icon_theme_lookup_by_gicon() returns 48x48 icons, despite specifying size 16x16 in the arguments.

This change scales the retrieved icon to 16x16,
to avoid unexpected program icon sizes.

trancexpress · 2026-01-23T16:12:49Z

@akurtakov any better ideas here?

I'll try to get a 16x16 icon with GTK3 APIs, somehow. I do have such sizes available... I'm not sure why 48x48 is always returned.

trancexpress · 2026-01-23T16:23:20Z

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

 					}
 				}
 				data.alphaData = alphaData;
+				ImageData scaled = data.scaledTo(16, 16);


I guess we can check if the height or width are higher than 16 and only then scale...

Makes sense.

Did you found the commit that changed this icons size?

Probably its this commit in platform UI:

eclipse-platform/eclipse.platform.ui@f0b1071

For too large icons, we used to show a default. After this commit we don't.

github-actions · 2026-01-23T16:24:45Z

Test Results (linux)

59 files - 29 59 suites - 29 8m 23s ⏱️ - 6m 4s
4 562 tests ± 0 4 342 ✅ ± 0 220 💤 ±0 0 ❌ ±0
141 runs - 70 139 ✅ - 69 2 💤 - 1 0 ❌ ±0

Results for commit 4ca6879. ± Comparison against base commit 8c1409a.

♻️ This comment has been updated with latest results.

akurtakov · 2026-01-23T16:39:20Z

Is there 16x16 icon available at all (/usr/share/icons/themename/... or smth similar)? If not what are the available sizes? I believe Gtk returns the closest bigger size if the requested size is not available. If this is on HiDPI system it becomes even more complicated as 16x16 with scale=2 will try to return 32x32 which in case of not available might give you the next one 48x48.
On a HiDPI screen I see too small icon - both with and without the patch

akurtakov · 2026-01-23T16:40:56Z

I don't believe there would be such a "simple" fix.

trancexpress · 2026-01-23T16:53:05Z

Is there 16x16 icon available at all (/usr/share/icons/themename/... or smth similar)? If not what are the available sizes? I believe Gtk returns the closest bigger size if the requested size is not available.

I think there is:

#include <gtk/gtk.h>

// gcc -g icon.c  `pkg-config --cflags --libs gtk+-3.0`  -o IconExample && ./IconExample


int
main (int argc, char **argv)
{
	GtkWidget *window, *scrolled_window;
	GtkListStore *liststore;
	GtkTreeIter iter;

	gtk_init(&argc, &argv);

	window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
	g_signal_connect(window, "delete_event", gtk_main_quit, NULL);
	gtk_window_set_default_size(GTK_WINDOW(window), 200, 100);

	scrolled_window = gtk_scrolled_window_new(NULL, NULL);

	GIcon *gicon = g_icon_new_for_string("kate", NULL);
	GtkIconTheme *icon_theme = gtk_icon_theme_get_default();
	GtkIconInfo *gicon_info = gtk_icon_theme_lookup_by_gicon(icon_theme, gicon, 16/*size*/, 0);
	GdkPixbuf *pixbuf = gtk_icon_info_load_icon(gicon_info, NULL);

	int height = gdk_pixbuf_get_height(pixbuf);
	int width = gdk_pixbuf_get_width(pixbuf);
	g_print("height=%d, width=%d\n", height, width);

	gtk_container_add (GTK_CONTAINER (window), scrolled_window);

	gtk_widget_show_all(window);

	gtk_main();

	return 0;
}

$ gcc -g icon.c  `pkg-config --cflags --libs gtk+-3.0`  -o IconExample && ./IconExample
height=48, width=48

$ find /usr/share/icons/ -name "kate.png"  | sort -V
/usr/share/icons/hicolor/16x16/apps/kate.png
/usr/share/icons/hicolor/22x22/apps/kate.png
/usr/share/icons/hicolor/32x32/apps/kate.png
/usr/share/icons/hicolor/44x44/apps/kate.png
/usr/share/icons/hicolor/48x48/apps/kate.png
/usr/share/icons/hicolor/64x64/apps/kate.png
/usr/share/icons/hicolor/128x128/apps/kate.png
/usr/share/icons/hicolor/150x150/apps/kate.png
/usr/share/icons/hicolor/256x256/apps/kate.png
/usr/share/icons/hicolor/310x310/apps/kate.png
/usr/share/icons/hicolor/512x512/apps/kate.png

If this is on HiDPI system it becomes even more complicated as 16x16 with scale=2 will try to return 32x32 which in case of not available might give you the next one 48x48. On a HiDPI screen I see too small icon - both with and without the patch

What is the difference for HiDPI? Will the zoom level argument be different?

The GTK3 documentation does say this: https://docs.gtk.org/gtk3/method.IconTheme.lookup_by_gicon.html

When rendering on displays with high pixel densities you should not use a size multiplied by the scaling factor returned by functions like gdk_window_get_scale_factor(). Instead, you should use gtk_icon_theme_lookup_by_gicon_for_scale(), as the assets loaded for a given scaling factor may be different.

akurtakov · 2026-01-23T16:57:12Z

Yes, looks like gtk_icon_theme_lookup_by_gicon_for_scale https://docs.gtk.org/gtk3/method.IconTheme.lookup_by_gicon_for_scale.html has to be used.

trancexpress · 2026-01-23T17:02:14Z

Slightly modifying the prints:

g_print("height=%d, width=%d, %s\n", height, width, gtk_icon_info_get_filename(gicon_info));

Then I see:

$ gcc -g icon.c  `pkg-config --cflags --libs gtk+-3.0`  -o IconExample && ./IconExample
height=48, width=48, /usr/share/icons/breeze-dark/apps/48/kate.svg

$ find  /usr/share/icons/breeze-dark/apps/ -name "*kate*"
/usr/share/icons/breeze-dark/apps/22/kate-symbolic.svg
/usr/share/icons/breeze-dark/apps/16/kate-symbolic.svg
/usr/share/icons/breeze-dark/apps/48/kate.svg
/usr/share/icons/breeze-dark/apps/24/kate-symbolic.svg
/usr/share/icons/breeze-dark/apps/32/kate-symbolic.svg

In the Advantest environment, emacs is used to open the external file... There I see:

$ find  /usr/share/icons/breeze/apps/ -name "*emacs*"
/usr/share/icons/breeze/apps/48/emacs.svg

So we must be missing icons... at least for breeze...

trancexpress · 2026-01-23T17:14:09Z

Yes, looks like gtk_icon_theme_lookup_by_gicon_for_scale https://docs.gtk.org/gtk3/method.IconTheme.lookup_by_gicon_for_scale.html has to be used.

OK, I'll try to in the next few days.

I assume for the scale parameter we use DPIUtil.getScalingFactor(int)?

And the scaling down we can do for scale 1, when hopefully we are not in the HiDPI case. Considering that breeze supplies a 48x48 SVG icon, that should be scalable however we want... I don't think we want to request more icon sizes for the theme.

Though SWT won't be scaling the SVG in a sensible way... Unless we try to open the SVG by using the path to the icon. Which will make things even more complicated, so I won't be trying that.

trancexpress · 2026-01-24T14:58:06Z

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

+				long shellHandle = shell.handle;
+				long window = GTK3.gtk_widget_get_window(shellHandle);
+				if (window != 0) {
+					scale = GDK.gdk_window_get_scale_factor(window);


Looks like to get the scaling argument we need a window.

Any better way to get the window @akurtakov ?

Thinking about this, we are requesting icon data that is likely cached by platform UI.

Depending on the screen scaling doesn't seem like a good idea. E.g. if two screens have different scaling, we would be caching the icon for one of them...

@HeikoKlare maybe you have insights here? Where do we handle different DPI for icons in platform UI? Maybe doing the fix in SWT is not the best place...

This change ensures Program icons are scaled to 16x16 pixels, to avoid huge icons in platform UI. Fixes: eclipse-platform#3003

trancexpress commented Jan 23, 2026

View reviewed changes

trancexpress marked this pull request as draft January 23, 2026 16:53

trancexpress force-pushed the gh3003 branch from bdb507f to 9fae876 Compare January 24, 2026 14:56

trancexpress commented Jan 24, 2026

View reviewed changes

trancexpress changed the title ~~Scale external program icons to 16x16~~ [GTK] Scale external program icons to 16x16 Jan 25, 2026

trancexpress force-pushed the gh3003 branch from 9fae876 to cbf6f67 Compare January 25, 2026 11:22

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

4ca6879

This change ensures Program icons are scaled to 16x16 pixels, to avoid huge icons in platform UI. Fixes: eclipse-platform#3003

trancexpress force-pushed the gh3003 branch from cbf6f67 to 4ca6879 Compare January 25, 2026 11:24

[GTK] Scale external program icons to 16x16 #3004

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