Disable GNOME CSD header bar by default

closes cypherstack#1248

Author: sneurlax

scripts/app_config/templates/linux/my_application.cc

@@ -1,9 +1,6 @@
 #include "my_application.h"
 
 #include <flutter_linux/flutter_linux.h>
-#ifdef GDK_WINDOWING_X11
-#include <gdk/gdkx.h>
-#endif
 
 #include "flutter/generated_plugin_registrant.h"
 
@@ -26,26 +23,15 @@ static void my_application_activate(GApplication* application) {
   GtkWindow* window =
       GTK_WINDOW(gtk_application_window_new(GTK_APPLICATION(application)));
 
-  // Use a header bar when running in GNOME as this is the common style used
-  // by applications and is the setup most users will be using (e.g. Ubuntu
-  // desktop).
-  // If running on X and not using GNOME then just use a traditional title bar
-  // in case the window manager does more exotic layout, e.g. tiling.
-  // If running on Wayland assume the header bar will work (may need changing
-  // if future cases occur).
-  gboolean use_header_bar = TRUE;
-#ifdef GDK_WINDOWING_X11
-  GdkScreen* screen = gtk_window_get_screen(window);
-  if (GDK_IS_X11_SCREEN(screen)) {
-    const gchar* wm_name = gdk_x11_screen_get_window_manager_name(screen);
-    if (g_strcmp0(wm_name, "GNOME Shell") != 0) {
-      use_header_bar = FALSE;
-    }
-  }
-#endif
+  // Use a traditional title bar by default for best compatibility across
+  // desktop environments (KDE, XFCE, tiling WMs, etc.).
+  // Set GTK_CSD=1 to use a GNOME-style header bar instead.
+  gboolean use_header_bar = FALSE;
   const char* gtk_csd_env_var = getenv("GTK_CSD");
-  gboolean use_gtk_csd = !gtk_csd_env_var || strcmp(gtk_csd_env_var, "0") != 0;
-  if (use_header_bar && use_gtk_csd) {
+  if (gtk_csd_env_var && strcmp(gtk_csd_env_var, "1") == 0) {
+    use_header_bar = TRUE;
+  }
+  if (use_header_bar) {
     GtkHeaderBar* header_bar = GTK_HEADER_BAR(gtk_header_bar_new());
     gtk_widget_show(GTK_WIDGET(header_bar));
     gtk_header_bar_set_title(header_bar, "PlaceHolderName");