Test building Windows without GTK2

[greg-hellings]

• Move to long-deprecated WEBKIT1 backend, but at least it gives us a
  shot at GTK3
• Use GTKTVEDITOR in the builds

TODO: Something is still pulling in gtk-2 in the images. That should be
sorted out before everything is fully merged

[LAfricain]

Windows GTK3 build (test/windows-build-gtk3) — icons & Preferences dialog fix

Context

After moving to GTK3/GtkBuilder/WebKit1 on this branch, two blocking issues showed up at runtime on Windows (tested via Wine): icons weren't rendering, and opening the Preferences dialog silently crashed the app.

Diagnosis

The initial suspicion — leftover GTK2/libglade dependencies — was ruled out. Verified via objdump, source grep, and CI build logs: the build is fully GTK3/GtkBuilder, no libglade anywhere in the binary or the compile flags.

The actual problem: win32/CMakeLists.txt installs the GTK3 DLLs correctly, but was missing three runtime resources GTK3 needs:

1. The system icon theme (hicolor/Adwaita)
2. gdk-pixbuf loaders (needed to render SVG icons)
3. Compiled GSettings schemas (used internally by GtkFileChooserButton, which is used in the Preferences dialog)

Missing #3 caused a fatal error (GLib-GIO-ERROR: No GSettings schemas are installed) that killed the process the moment Preferences tried to open — hence the silent crash.

Fix applied (commit on test-nogtk2, needs rebasing onto Greg's branch)

Added three install() blocks to win32/CMakeLists.txt, right after the existing SVG icon install section:

• ${SYS_ROOT_SHARE}/icons → full icon theme
• ${SYS_ROOT_LIB}/gdk-pixbuf-2.0 → pixbuf loaders
• ${SYS_ROOT_SHARE}/glib-2.0/schemas + compiled via glib-compile-schemas at install time → GSettings schemas

Verified in CI (GitHub Actions): build succeeds, all files confirmed present in the installed package.

Remaining work (not done yet)

The resources are now bundled correctly, but GTK/GLib don't discover them automatically at runtime on Windows. Two environment variables need to be set for things to work:

• GSETTINGS_SCHEMA_DIR → path to share/glib-2.0/schemas
• XDG_DATA_DIRS → path to share (Windows-style path, C:\...)

Manually confirmed working (icons visible, Preferences dialog fully functional) once these are forced before launching xiphos.exe.

Next step: set both variables programmatically in src/main/main.c, before the gtk_init() call, computing the install path dynamically via g_win32_get_package_installation_directory_of_module() — rather than relying on GLib's automatic detection, which doesn't work reliably for this MinGW cross-compiled configuration.