Announce the desktop file name as the window identity

A window is matched to its desktop file, and so to its icon, by the
identity it advertises: app_id on Wayland, WM_CLASS on X11. GTK derives
both from the program name, which defaults to the executable, so the
window announced slic3r-app-launcher while the desktop file installed for
it is com.prusa3d.PrusaSlicer. Nothing matched and the window was drawn
with a generic icon.

Set the program name to the desktop file name, and take both it and
StartupWMClass from one CMake variable so they cannot drift apart.

This only showed up once the application started running on Wayland
directly instead of through XWayland.

Author: xarbit

CMakeLists.txt

@@ -96,10 +96,13 @@ include(GNUInstallDirs)
 include(CMakeDependentOption)
 include(Utils)
 
+# Also the app id the window announces, see g_set_prgname() in DesktopApp.cpp.
+set(SLIC3R_DESKTOP_FILE_NAME "com.prusa3d.PrusaSlicer")
+
 if (UNIX AND NOT APPLE)
     configure_file(
-        ${CMAKE_SOURCE_DIR}/src/platform/unix/com.prusa3d.PrusaSlicer.desktop.in
-        ${CMAKE_BINARY_DIR}/com.prusa3d.PrusaSlicer.desktop
+        ${CMAKE_SOURCE_DIR}/src/platform/unix/${SLIC3R_DESKTOP_FILE_NAME}.desktop.in
+        ${CMAKE_BINARY_DIR}/${SLIC3R_DESKTOP_FILE_NAME}.desktop
         @ONLY
     )
 endif ()

src/platform/unix/com.prusa3d.PrusaSlicer.desktop.in

@@ -9,4 +9,4 @@ MimeType=model/stl;application/vnd.ms-3mfdocument;application/prs.wavefront-obj;
 Categories=Graphics;3DGraphics;Engineering;
 Keywords=3D;Printing;Slicer;slice;3D;printer;convert;gcode;stl;obj;amf;SLA
 StartupNotify=false
-StartupWMClass=prusa-slicer
+StartupWMClass=@SLIC3R_DESKTOP_FILE_NAME@

src/slic3r-app-desktop/src/Slic3r/App/Desktop/DesktopApp.cpp

@@ -1,5 +1,11 @@
 #include "DesktopApp.hpp"
 
+#ifdef __WXGTK__
+#include <glib.h>
+
+#include "Slic3r/Version.hpp"
+#endif
+
 #include "MainFrame.hpp"
 #include "Slic3r/App/Undo/Store.hpp"
 #include "SplashScreen.hpp"
@@ -169,6 +175,11 @@ int run(const Slic3r::App::InitParams& init_params, AppServices& app_services)
         ::setenv("GDK_BACKEND", "x11", /* replace */ false);
     }
 
+    // A compositor finds a window's icon through the desktop file named after
+    // the app id the window announces. GTK takes that from the program name,
+    // which defaults to the executable, so it has to be set before GTK starts.
+    ::g_set_prgname(SLIC3R_DESKTOP_FILE_NAME);
+
     if (app_services.app_config().get<Theme::Style>("theme") == Theme::Style::Light) {
         setenv("GTK_THEME", "Adwaita:light", 1);
     } else {

src/slic3r-base/include/Slic3r/Version.hpp.in

@@ -4,10 +4,12 @@
 #define SLIC3R_APP_KEY "@SLIC3R_APP_KEY@"
 #define SLIC3R_VERSION "@SLIC3R_VERSION@"
 #define SLIC3R_BUILD_ID "@SLIC3R_BUILD_ID@"
+#define SLIC3R_DESKTOP_FILE_NAME "@SLIC3R_DESKTOP_FILE_NAME@"
 
 namespace Slic3r {
     constexpr const char* APP_NAME = SLIC3R_APP_NAME;
     constexpr const char* APP_KEY = SLIC3R_APP_KEY;
     constexpr const char* VERSION = SLIC3R_VERSION;
     constexpr const char* BUILD_ID = SLIC3R_BUILD_ID;
+    constexpr const char* DESKTOP_FILE_NAME = SLIC3R_DESKTOP_FILE_NAME;
 }