Snap: fix theming (#3057)

Use gtk3 file chooser dialogs, mouse coursor theme if available and force fallback icon theme, fixes issue #2966

snap/local/launchers/README.md

@@ -0,0 +1,11 @@
+# /snap/local/launchers
+Here are the launchers, or wrapper programs to deal with some runtime-fixable problems for the snapped applications, like setting proper environmental variables in snap.
+
+In convention launchers are named _something_-launch, for dealing certain problem with _something_, and usually can be called in a stacked manner to consolidate their modifications.
+
+```yaml
+apps:
+  _app_name_:
+    command: foo-launch bar-launch _app_command_
+```
+

snap/local/launchers/gtk3-env-launch

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+# This is the maintainence launcher for the snap, make necessary runtime environment changes to make the snap work here.  You may also insert security confinement/deprecation/obsoletion notice of the snap here.
+
+set \
+	-o errexit \
+	-o errtrace \
+	-o nounset \
+	-o pipefail
+
+# gtk-common-themes support
+export QT_QPA_PLATFORMTHEME=gtk3
+
+# Finally run the next part of the command chain
+exec "${@}"

snap/snapcraft.yaml

@@ -9,15 +9,27 @@ description: |
 confinement: strict
 base: core18
 
-plugs:
-  icon-themes: # fix mouse cursor theme
+plugs: # plugs for theming, font settings, cursor and to use gtk3 file chooser
+  gtk-3-themes:
+    interface: content
+    target: $SNAP/data-dir/themes
+    default-provider: gtk-common-themes:gtk-3-themes
+  icon-themes:
     interface: content
     target: $SNAP/data-dir/icons
-    default-provider: gtk-common-themes
+    default-provider: gtk-common-themes:icon-themes
+  sound-themes:
+    interface: content
+    target: $SNAP/data-dir/sounds
+    default-provider: gtk-common-themes:sounds-themes
 
 apps:
   keepassxc:
-    command: desktop-launch keepassxc
+    adapter: full
+    command: usr/bin/keepassxc -style fusion
+    command-chain:
+      - bin/desktop-launch
+      - bin/gtk3-env-launch
     plugs: [unity7, x11, opengl, gsettings, home, network, network-bind, removable-media, raw-usb, wayland, desktop-legacy, desktop]
     desktop: usr/share/applications/org.keepassxc.KeePassXC.desktop
     environment:
@@ -73,7 +85,7 @@ parts:
       - libquazip5-1
       - libusb-1.0-0
       - qtwayland5
-      - qt5-style-plugins # for mouse cursor theme fix
+      - qt5-gtk-platformtheme # for theming, font settings, cursor and to use gtk3 file chooser
     override-build: |
       snapcraftctl build
       sed -i 's|Icon=keepassxc|Icon=${SNAP}/usr/share/icons/hicolor/256x256/apps/keepassxc.png|g' $SNAPCRAFT_PART_INSTALL/usr/share/applications/org.keepassxc.KeePassXC.desktop
@@ -83,6 +95,14 @@ parts:
       - -opt
     after: [desktop-qt5]
 
+  launchers: # custom launcher to set QT_QPA_PLATFORMTHEME=gtk3 correctly
+    source: snap/local/launchers
+    plugin: dump
+    organize:
+      '*': bin/
+    stage:
+      - -bin/README.*
+
   desktop-qt5:
       source: https://github.com/ubuntu/snapcraft-desktop-helpers.git
       source-subdir: qt

src/core/Bootstrap.cpp

@@ -85,6 +85,12 @@ namespace Bootstrap
         bootstrap();
         MessageBox::initializeButtonDefs();
 
+#ifdef KEEPASSXC_DIST_SNAP
+        // snap: force fallback theme to avoid using system theme (gtk integration)
+        // with missing actions just like on Windows and macOS
+        QIcon::setThemeSearchPaths(QStringList() << ":/icons");
+#endif
+
 #ifdef Q_OS_MACOS
         // Don't show menu icons on OSX
         QApplication::setAttribute(Qt::AA_DontShowIconsInMenus);