appimagetool don't configure loaders.cache

[brunvonlope]

Similar to #282

---

When bundling GTK apps, appimagetool copy the loaders.cache file required by GdkPixbuf. But inside the file the paths aren't adapted to be relative to AppDir/usr/lib... which makes the system loaders be called by GdkPixbuf.

I suggest changing the paths inside the loaders.cache file when calling deploy in a similar way that we do manually with GIMP: https://gitlab.gnome.org/GNOME/gimp/-/blob/master/build/linux/appimage/bundle-gimp-appimage.sh?ref_type=heads#L170. Otherwise, some apps can even not display the GUI at all.

[probonopd]

Hello @brunvonlope, apparently you know a lot about the inner workings of GTK (well, at least compared to me, anyways). Would you be able to send a pull request? Thanks for your suggestion.

[brunvonlope]

Hello @brunvonlope, apparently you know a lot about the inner workings of GTK (well, at least compared to me, anyways). Would you be able to send a pull request? Thanks for your suggestion.

I know almost nothing, specially about Go ☹️. To be fair, this bug was discovered by accident while using testing AppImage in some distros.

[probonopd]

We already have some code related to it:

go-appimage/src/appimagetool/appdirtool.go

Lines 625 to 675 in 6866993

	func handleGdk(appdir helpers.AppDir) {
	// If there is a .so with the name libgdk_pixbuf inside the AppDir, then we need to
	// bundle Gdk pixbuf loaders without which the bundled Gtk does not work
	// cp /usr/lib/x86_64-linux-gnu/gdk-pixbuf-*/*/loaders/* usr/lib/x86_64-linux-gnu/gdk-pixbuf-*/*/loaders/
	// cp /usr/lib/x86_64-linux-gnu/gdk-pixbuf-*/*/loaders.cache usr/lib/x86_64-linux-gnu/gdk-pixbuf-*/*/ -
	// this file must also be patched not to contain paths to the libraries
	for _, lib := range allELFs {
	if strings.HasPrefix(filepath.Base(lib), "libgdk_pixbuf") {
	log.Println("Determining Gdk pixbuf loaders (for GDK_PIXBUF_MODULEDIR and GDK_PIXBUF_MODULE_FILE)...")
	locs, err := findWithPrefixInLibraryLocations("gdk-pixbuf")
	if err != nil {
	log.Println("Could not find Gdk pixbuf loaders")
	os.Exit(1)
	} else {
	for _, loc := range locs {
	determineELFsInDirTree(appdir, loc)
	// We need to patch away the path to libpixbufloader-png.so from the file loaders.cache, similar to:
	// sed -i -e 's|/usr/lib/x86_64-linux-gnu/gdk-pixbuf-2.0/2.10.0/loaders/||g' usr/lib/x86_64-linux-gnu/gdk-pixbuf-*/*/loaders.cache
	// the patched file must not contain paths to the libraries
	loadersCaches := helpers.FilesWithSuffixInDirectoryRecursive(loc, "loaders.cache")
	if len(loadersCaches) < 1 {
	helpers.PrintError("loadersCaches", errors.New("could not find loaders.cache"))
	os.Exit(1)
	}
	err = copy.Copy(loadersCaches[0], appdir.Path+loadersCaches[0])
	if err != nil {
	helpers.PrintError("Could not copy loaders.cache", err)
	os.Exit(1)
	}
	whatToPatchAway := helpers.FilesWithSuffixInDirectoryRecursive(loc, "libpixbufloader-png.so")
	if len(whatToPatchAway) < 1 {
	helpers.PrintError("whatToPatchAway", errors.New("could not find directory that contains libpixbufloader-png.so"))
	break // os.Exit(1)
	}
	log.Println("Patching", appdir.Path+loadersCaches[0], "removing", filepath.Dir(whatToPatchAway[0])+"/")
	err = PatchFile(appdir.Path+loadersCaches[0], filepath.Dir(whatToPatchAway[0])+"/", "")
	if err != nil {
	helpers.PrintError("PatchFile loaders.cache", err)
	break // os.Exit(1)
	}
	}
	}
	break
	}
	}
	}

Maybe it is not working properly?

[pbs3141]

Indeed it's not working:

ERROR whatToPatchAway: could not find directory that contains libpixbufloader-png.so

My system doesn't even have a libpixbufloader-png.so anymore. PNG support is baked into gdk-pixbuf itself, not implemented as a loader module.

This could either be fixed by assuming the following directory layout

loaders.cache
loaders/
    *.so

so that the loaders can be found from the location of loaders.cache, or searching other formats, e.g. svg, webp, until one succeeds.

[probonopd]

Thanks @pbs3141. I'd appreciate code contributions from someone knowledgeable about Gtk here.

Has https://github.com/linuxdeploy/linuxdeploy-plugin-gtk/blob/3b67a1d1c1b0c8268f57f2bce40fe2d33d409cea/linuxdeploy-plugin-gtk.sh#L312-L332 the correct logic?