[evolution] Change when symbolic icons are forced in the application

[Milan Crha <mcrha src gnome org>]

commit fb9003cfa60690106e9bfe1e832fb28b1f60d062
Author: Milan Crha <mcrha redhat com>
Date:   Mon Jul 18 15:35:33 2022 +0200

    Change when symbolic icons are forced in the application
    
    Rather than forcing symbolic icons in GNOME, check whether only symbolic
    icons are available for the current icon theme and if so, then force
    the symbolic icons, otherwise use colored icons.
    
    The test can be still inaccurate, but the gtk+ API doesn't have a way to
    check whether the icon theme is symbolic-only or not.
    
    Related to https://gitlab.gnome.org/GNOME/evolution/-/issues/1848

 src/shell/e-shell-window.c | 15 --------
 src/shell/main.c           | 96 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+), 15 deletions(-)
---
diff --git a/src/shell/e-shell-window.c b/src/shell/e-shell-window.c
index 805e2d30fb..e7be30feee 100644
--- a/src/shell/e-shell-window.c
+++ b/src/shell/e-shell-window.c
@@ -92,11 +92,6 @@ toolbar {\
        border-top: 1px solid @borders;\
 }\
 ";
-static const char *css_icons =
-"* {\
-       -gtk-icon-style:symbolic;\
-}\
-";
 
 static void
 shell_window_menubar_update_new_menu (EShellWindow *shell_window)
@@ -1165,16 +1160,6 @@ e_shell_window_init (EShellWindow *shell_window)
                GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
        g_clear_object (&css_provider);
 
-       /* If running on GNOME, force symbolic icons */
-       if (e_util_is_running_gnome ()) {
-               css_provider = gtk_css_provider_new ();
-               gtk_css_provider_load_from_data (css_provider, css_icons, -1, NULL);
-               gtk_style_context_add_provider_for_screen (gdk_screen_get_default (),
-                       GTK_STYLE_PROVIDER (css_provider),
-                       GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
-               g_clear_object (&css_provider);
-       }
-
        g_signal_connect (shell_window, "delete-event",
                G_CALLBACK (shell_window_delete_event_cb), NULL);
 }
diff --git a/src/shell/main.c b/src/shell/main.c
index ac7b2a3a9e..566f629439 100644
--- a/src/shell/main.c
+++ b/src/shell/main.c
@@ -103,6 +103,100 @@ static gchar **remaining_args;
 void e_convert_local_mail (EShell *shell);
 void e_migrate_base_dirs (EShell *shell);
 
+static void
+e_setup_theme_icons_theme_changed_cb (GtkSettings *settings)
+{
+       GtkCssProvider *symbolic_icons_css_provider;
+       GtkIconTheme *icon_theme;
+       gboolean use_symbolic_icons = FALSE;
+       gboolean using_symbolic_icons;
+       gchar **paths = NULL;
+       gchar *icon_theme_name = NULL;
+       guint n_symbolic = 0, n_non_symbolic = 0;
+       guint ii;
+
+       if (!settings)
+               return;
+
+       g_object_get (settings,
+               "gtk-icon-theme-name", &icon_theme_name,
+               NULL);
+
+       icon_theme = gtk_icon_theme_get_default ();
+       gtk_icon_theme_get_search_path (icon_theme, &paths, NULL);
+
+       for (ii = 0; paths && paths[ii]; ii++) {
+               GDir *dir;
+               gchar *dirname;
+
+               dirname = g_build_filename (paths[ii], icon_theme_name, "16x16", "actions", NULL);
+               dir = g_dir_open (dirname, 0, NULL);
+               if (dir) {
+                       const gchar *filename;
+
+                       for (filename = g_dir_read_name (dir);
+                            filename;
+                            filename = g_dir_read_name (dir)) {
+                               /* pick few common action icons and check whether they are
+                                  only symbolic in the current theme */
+                               if (g_str_has_prefix (filename, "appointment-new") ||
+                                   g_str_has_prefix (filename, "edit-cut") ||
+                                   g_str_has_prefix (filename, "edit-copy")) {
+                                       if (strstr (filename, "-symbolic.") ||
+                                           strstr (filename, ".symbolic.")) {
+                                               n_symbolic++;
+                                       } else {
+                                               n_non_symbolic++;
+                                       }
+                               }
+                       }
+                       g_dir_close (dir);
+               }
+               g_free (dirname);
+       }
+
+       g_strfreev (paths);
+       g_free (icon_theme_name);
+
+       use_symbolic_icons = !n_non_symbolic && n_symbolic > 0;
+
+       /* using the same key on both objects, to save one quark */
+       #define KEY_NAME "e-symbolic-icons-css-provider"
+
+       symbolic_icons_css_provider = g_object_get_data (G_OBJECT (icon_theme), KEY_NAME);
+       using_symbolic_icons = symbolic_icons_css_provider && GINT_TO_POINTER (
+               g_object_get_data (G_OBJECT (symbolic_icons_css_provider), KEY_NAME)) != 0;
+
+       if (use_symbolic_icons && !using_symbolic_icons) {
+               if (!symbolic_icons_css_provider) {
+                       symbolic_icons_css_provider = gtk_css_provider_new ();
+                       g_object_set_data_full (G_OBJECT (icon_theme), KEY_NAME, symbolic_icons_css_provider, 
g_object_unref);
+
+                       gtk_style_context_add_provider_for_screen (gdk_screen_get_default (),
+                               GTK_STYLE_PROVIDER (symbolic_icons_css_provider),
+                               GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
+               }
+               gtk_css_provider_load_from_data (symbolic_icons_css_provider, "* { -gtk-icon-style:symbolic; 
}", -1, NULL);
+               g_object_set_data (G_OBJECT (symbolic_icons_css_provider), KEY_NAME, GINT_TO_POINTER (1));
+       } else if (!use_symbolic_icons && using_symbolic_icons) {
+               gtk_css_provider_load_from_data (symbolic_icons_css_provider, "", -1, NULL);
+               g_object_set_data (G_OBJECT (symbolic_icons_css_provider), KEY_NAME, GINT_TO_POINTER (0));
+       }
+
+       #undef KEY_NAME
+}
+
+static void
+e_setup_theme_icons (void)
+{
+       GtkSettings *settings = gtk_settings_get_default ();
+
+       e_signal_connect_notify (settings, "notify::gtk-icon-theme-name",
+               G_CALLBACK (e_setup_theme_icons_theme_changed_cb), NULL);
+
+       e_setup_theme_icons_theme_changed_cb (settings);
+}
+
 static void
 categories_icon_theme_hack (void)
 {
@@ -681,6 +775,8 @@ main (gint argc,
         * as both shell backends and certain plugins hook into this. */
        e_shell_migrate_attempt (shell);
 
+       e_setup_theme_icons ();
+
        e_shell_event (shell, "ready-to-start", NULL);
 
        g_idle_add ((GSourceFunc) idle_cb, remaining_args);