[GTK] Program.findProgram() always returns null

[HeikoKlare]

Describe the bug
The Program.findProgram() implementation for GTK always returns null.
This was found when adding an according test in: #3187

To Reproduce
Extend the test Test_org_eclipse_swt_program_Program.test_findProgramLjava_lang_String to print the program found the registered extensions or just execute this according snippet:

public static void main (String [] args) {
	String[] extensions = Program.getExtensions();
	if (extensions != null) {
		for (String extension : extensions) {
			System.out.println(Program.findProgram(extension));
		}
	}
}

It just prints null.

Expected behavior
I expect the method to return the actual program representations registered for the mime type of the given extensions.

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

2. Additional OS info (e.g. OS version, Linux Desktop, etc)
   Ubuntu 22.04.5 LTS on WSL, Glib 2.72.4
   But also happens on other (in particular non-WSL) installations (as it was found via CI in [Cocoa] Replace deprecated LSGetApplicationForInfo in Program.findProgram #3187).

Version since
Found in current master state; I did not check when that started to happen (may rather be a change in GLib than in Eclipse code).

[akurtakov]

Running on my Gnome desktop I end up with the very lenghty output of:

Program {Collabora Office}
Program {Text Editor}
Program {Web}
Program {LibreOffice Writer}
Program {Image Viewer}
Program {Text Editor}
Program {GNU Image Manipulation Program}
Program {Video Player}
...

[HeikoKlare]

Thank you! Very interesting. Could you please check explicitly check what it returns for extensions .jpg and .txt? Those have been tested via CI in #3187. Just to see if I just used bad extensions there and the overall "null" results are an issue of my WSL environment.
And maybe you can share some information about you environment (such as the glib version that provides the involved methods)?

[akurtakov]

.jpg:Program {Image Viewer}
.txt:Program {Text Editor}

[akurtakov]

My guess would be that there is no mime-database (~/.local/share/applications/,/usr/share/applications/) in WSL . What does xdg-mime query default text/plain gives you (org.gnome.TextEditor.desktop for me)?

[akurtakov]

Note: SWT's Program parses manually /usr/share/mime/globs as it was faster and required less ifs compared to supporting multiple glib versions (not relevant anymore as all needed api should be in supported versions). This manual parsing could potentially hurt as WSL probably does smth "clever" to figure mimetypes from windows apis.

[HeikoKlare]

My guess would be that there is no mime-database (~/.local/share/applications/,/usr/share/applications/) in WSL . What does xdg-mime query default text/plain gives you (org.gnome.TextEditor.desktop for me)?

That gives me: vim.desktop

I was just checking different types with gio mime (like gio mime text/plain), which always says that there is no default application for that type.

[akurtakov]

gio mime text/plain
Default application for “text/plain”: org.gnome.TextEditor.desktop
Registered applications:
	libreoffice-writer.desktop
	org.gnome.TextEditor.desktop
	org.kde.kate.desktop
Recommended applications:
	libreoffice-writer.desktop
	org.gnome.TextEditor.desktop
	org.kde.kate.desktop

First thought would be that xdg-mime has been adapted to WSL but gio wasn't yet.

[HeikoKlare]

Note: SWT's Program parses manually /usr/share/mime/globs as it was faster and required less ifs compared to supporting multiple glib versions (not relevant anymore as all needed api should be in supported versions). This manual parsing could potentially hurt as WSL probably does smth "clever" to figure mimetypes from windows apis.

I see. But note that not only WSL is affected but also the CI environments. Here are test failures when retrieving the program for jpeg type: https://github.com/eclipse-platform/eclipse.platform.swt/pull/3187/checks?check_run_id=69771565537
I will undraft that PR once to have the Jenkins pipeline run as well to if it only happens in GHA runs or also on Jenkins.

[akurtakov]

I would bet it's some missing package . Packages (Fedora names) shared-mime-info and xdg-utils have to be there for sure for findProgram to work. A program that registers as handler for text/plain (e.g. gnome-text-editor) should be installed too.

[HeikoKlare]

One additional note: the mime type for the given extension is properly found. Just the retrieval of the according program fails in this line:

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

Line 281 in 98062b7

long application = OS.g_app_info_get_default_for_type (mimeTypeBuffer, false);

On my (WSL) system, there have been no mimeapps.list at the common places. Explicitly registering one for text/plain (gio mime text/plain) makes Program.getProgram(".txt") work.

A consequence of this behavior is that all tests for the Program class using findProgram effectively don't test anything at all as those tests silently accept that this method always returns null. So we would not notice a regression that makes the method fail independent from the environmental setup.
But it also seems difficult to guarantee that on machines used for testing there is at least one extension / mime type for which this method suceeds so that we could use it for testing. So we can also accept the situation and I will adapt the test in https://github.com/eclipse-platform/eclipse.platform.swt/pull/3187/checks?check_run_id=69831529916 to not be executed for GTK.

[HeikoKlare]

Closing this as per previous comment.