load Gtk CSS much earlier

This allows the splash screen to be properly styled from the
beginning, so that it does not change color/font in the middle of
startup.

src/common/darktable.c

@@ -1345,6 +1345,10 @@ int dt_init(int argc, char *argv[], const gboolean init_gui, const gboolean load
     // make sure that we have no stale global progress bar
     // visible. thus it's run as early as possible
     dt_control_progress_init(darktable.control);
+
+    // ensure that we can load the Gtk theme early enough that the splash screen
+    // doesn't change as we progress through startup
+    darktable.gui = (dt_gui_gtk_t *)calloc(1, sizeof(dt_gui_gtk_t));
   }
 
 #ifdef _OPENMP
@@ -1393,6 +1397,7 @@ int dt_init(int argc, char *argv[], const gboolean init_gui, const gboolean load
     gtk_init(&argc, &argv);
 
     darktable.themes = NULL;
+    dt_gui_theme_init(darktable.gui);
     darktable_splash_screen_create(NULL);
   }
 
@@ -1487,7 +1492,6 @@ int dt_init(int argc, char *argv[], const gboolean init_gui, const gboolean load
   // idem for folder reachability
   if(init_gui)
   {
-    darktable.gui = (dt_gui_gtk_t *)calloc(1, sizeof(dt_gui_gtk_t));
     darktable.gui->grouping = dt_conf_get_bool("ui_last/grouping");
     dt_film_set_folder_status();
   }

src/gui/gtk.c

@@ -1152,6 +1152,25 @@ static void _open_url(GtkWidget *widget, gpointer url)
 }
 #endif
 
+int dt_gui_theme_init(dt_gui_gtk_t *gui)
+{
+  if(gui->gtkrc[0] != '\0')
+    return 0;	// avoid duplicate initializatoin
+  if(!gui->ui)
+    gui->ui = g_malloc0(sizeof(dt_ui_t));
+
+  const char *css_theme = dt_conf_get_string_const("ui_last/theme");
+  if(css_theme)
+  {
+    g_strlcpy(gui->gtkrc, css_theme, sizeof(gui->gtkrc));
+  }
+  else
+    g_snprintf(gui->gtkrc, sizeof(gui->gtkrc), "darktable");
+  // actually load the theme
+  dt_gui_load_theme(gui->gtkrc);
+  return 1;
+}
+
 int dt_gui_gtk_init(dt_gui_gtk_t *gui)
 {
   /* lets zero mem */
@@ -1178,14 +1197,6 @@ int dt_gui_gtk_init(dt_gui_gtk_t *gui)
   dt_loc_get_sharedir(sharedir, sizeof(sharedir));
   dt_loc_get_user_config_dir(configdir, sizeof(configdir));
 
-  const char *css_theme = dt_conf_get_string_const("ui_last/theme");
-  if(css_theme)
-  {
-    g_strlcpy(gui->gtkrc, css_theme, sizeof(gui->gtkrc));
-  }
-  else
-    g_snprintf(gui->gtkrc, sizeof(gui->gtkrc), "darktable");
-
 #ifdef MAC_INTEGRATION
 #ifdef GTK_TYPE_OSX_APPLICATION
   GtkOSXApplication *OSXApp = g_object_new(GTK_TYPE_OSX_APPLICATION, NULL);
@@ -1268,7 +1279,8 @@ int dt_gui_gtk_init(dt_gui_gtk_t *gui)
 #endif
 
   GtkWidget *widget;
-  gui->ui = g_malloc0(sizeof(dt_ui_t));
+  if(!gui->ui)
+    gui->ui = g_malloc0(sizeof(dt_ui_t));
   gui->surface = NULL;
   gui->center_tooltip = 0;
   gui->grouping = dt_conf_get_bool("ui_last/grouping");
@@ -1284,6 +1296,10 @@ int dt_gui_gtk_init(dt_gui_gtk_t *gui)
   g_object_set(G_OBJECT(settings), "gtk-theme-name", "Adwaita", (gchar *)0);
   g_object_unref(settings);
 
+  // Initializing widgets
+  _init_widgets(gui);
+  dt_gui_apply_theme(gui);
+
   // smooth scrolling must be enabled to handle trackpad/touch events
   gui->scroll_mask = GDK_SCROLL_MASK | GDK_SMOOTH_SCROLL_MASK;
 
@@ -1293,9 +1309,6 @@ int dt_gui_gtk_init(dt_gui_gtk_t *gui)
   // Init focus peaking
   gui->show_focus_peaking = dt_conf_get_bool("ui/show_focus_peaking");
 
-  // Initializing widgets
-  _init_widgets(gui);
-
   //init overlay colors
   dt_guides_set_overlay_colors();
 
@@ -1425,9 +1438,6 @@ int dt_gui_gtk_init(dt_gui_gtk_t *gui)
 
   darktable.gui->reset = 0;
 
-  // load theme
-  dt_gui_load_theme(gui->gtkrc);
-
   // let's try to support pressure sensitive input devices like tablets for mask drawing
   dt_print(DT_DEBUG_INPUT, "[input device] Input devices found:\n\n");
 
@@ -3256,7 +3266,10 @@ void dt_gui_load_theme(const char *theme)
   g_free(themecss);
 
   g_object_unref(themes_style_provider);
+}
 
+void dt_gui_apply_theme()
+{
   // setup the colors
 
   GdkRGBA *c = darktable.gui->colors;

src/gui/gtk.h

@@ -200,6 +200,7 @@ void dt_gui_add_class(GtkWidget *widget, const gchar *class_name);
 void dt_gui_remove_class(GtkWidget *widget, const gchar *class_name);
 
 void dt_open_url(const char *url);
+int dt_gui_theme_init(dt_gui_gtk_t *gui);
 int dt_gui_gtk_init(dt_gui_gtk_t *gui);
 void dt_gui_gtk_run(dt_gui_gtk_t *gui);
 void dt_gui_gtk_cleanup(dt_gui_gtk_t *gui);
@@ -449,7 +450,8 @@ void dt_gui_dialog_add_help(GtkDialog *dialog,
 void dt_gui_show_help(GtkWidget *widget);
 
 // load a CSS theme
-void dt_gui_load_theme(const char *theme);
+void dt_gui_load_theme(const char *theme); // read them and add user tweaks
+void dt_gui_apply_theme();                 // apply the loaded theme to darktable's windows
 
 // reload GUI scalings
 void dt_configure_ppd_dpi(dt_gui_gtk_t *gui);