[gnome-control-center] display: Show insensitive apply button for invalid configurations

[Benjamin Berg <bberg src gnome org>]

commit adf5a42f01e112ec5c294b52ffb838c9177c61f5
Author: Benjamin Berg <bberg redhat com>
Date:   Fri Nov 24 15:39:38 2017 +0100

    display: Show insensitive apply button for invalid configurations
    
    When the user creates temporary invalid configurations the dialog used
    to hide the apply button as if no change had been done so far. Change
    this to show the normal "Apply"/"Cancel" titlebar but make the "Apply"
    button insensitive and modify the title to indicate the error.
    
    Unfortunately we don't currently get the reason in a way that we could
    translate it. Ideally we would special case common error scenarios and
    present the user with a better explanation or even correct the mistake.
    
    See https://bugzilla.gnome.org/show_bug.cgi?id=790891 for the related
    mutter bug.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=790792

 panels/display/cc-display-panel.c | 82 ++++++++++++++++++++++-----------------
 1 file changed, 46 insertions(+), 36 deletions(-)
---
diff --git a/panels/display/cc-display-panel.c b/panels/display/cc-display-panel.c
index 2f372fd7e..13f5332e9 100644
--- a/panels/display/cc-display-panel.c
+++ b/panels/display/cc-display-panel.c
@@ -87,6 +87,8 @@ struct _CcDisplayPanelPrivate
 
   GtkWidget *main_titlebar;
   GtkWidget *apply_titlebar;
+  GtkWidget *apply_titlebar_apply;
+  GtkWidget *apply_titlebar_warning;
 };
 
 typedef struct
@@ -283,6 +285,8 @@ reset_titlebar (CcDisplayPanel *self)
     }
 
   g_clear_object (&priv->apply_titlebar);
+  g_clear_object (&priv->apply_titlebar_apply);
+  g_clear_object (&priv->apply_titlebar_warning);
 }
 
 static void
@@ -2590,47 +2594,59 @@ on_toplevel_key_press (GtkWidget   *button,
 }
 
 static void
-show_apply_titlebar (CcDisplayPanel *panel)
+show_apply_titlebar (CcDisplayPanel *panel, gboolean is_applicable)
 {
   CcDisplayPanelPrivate *priv = panel->priv;
-  GtkWidget *header, *button, *toplevel;
   GtkSizeGroup *size_group;
 
-  if (priv->apply_titlebar)
-    return;
+  if (!priv->apply_titlebar)
+    {
+      GtkWidget *header, *button, *toplevel;
+      priv->apply_titlebar = header = gtk_header_bar_new ();
 
-  priv->apply_titlebar = header = gtk_header_bar_new ();
-  gtk_header_bar_set_title (GTK_HEADER_BAR (header), _("Apply Changes?"));
+      size_group = gtk_size_group_new (GTK_SIZE_GROUP_VERTICAL);
 
-  size_group = gtk_size_group_new (GTK_SIZE_GROUP_VERTICAL);
+      button = gtk_button_new_with_mnemonic (_("_Cancel"));
+      gtk_header_bar_pack_start (GTK_HEADER_BAR (header), button);
+      gtk_size_group_add_widget (size_group, button);
+      g_signal_connect_object (button, "clicked", G_CALLBACK (on_screen_changed),
+                               panel, G_CONNECT_SWAPPED);
 
-  button = gtk_button_new_with_mnemonic (_("_Cancel"));
-  gtk_header_bar_pack_start (GTK_HEADER_BAR (header), button);
-  gtk_size_group_add_widget (size_group, button);
-  g_signal_connect_object (button, "clicked", G_CALLBACK (on_screen_changed),
-                           panel, G_CONNECT_SWAPPED);
+      toplevel = cc_shell_get_toplevel (cc_panel_get_shell (CC_PANEL (panel)));
+      g_signal_connect_object (toplevel, "key-press-event", G_CALLBACK (on_toplevel_key_press),
+                               button, G_CONNECT_SWAPPED);
 
-  toplevel = cc_shell_get_toplevel (cc_panel_get_shell (CC_PANEL (panel)));
-  g_signal_connect_object (toplevel, "key-press-event", G_CALLBACK (on_toplevel_key_press),
-                           button, G_CONNECT_SWAPPED);
+      priv->apply_titlebar_apply = button = gtk_button_new_with_mnemonic (_("_Apply"));
+      gtk_header_bar_pack_end (GTK_HEADER_BAR (header), button);
+      gtk_size_group_add_widget (size_group, button);
+      g_signal_connect_object (button, "clicked", G_CALLBACK (apply_current_configuration),
+                               panel, G_CONNECT_SWAPPED);
+      gtk_style_context_add_class (gtk_widget_get_style_context (button),
+                                   GTK_STYLE_CLASS_SUGGESTED_ACTION);
 
-  button = gtk_button_new_with_mnemonic (_("_Apply"));
-  gtk_header_bar_pack_end (GTK_HEADER_BAR (header), button);
-  gtk_size_group_add_widget (size_group, button);
-  g_signal_connect_object (button, "clicked", G_CALLBACK (apply_current_configuration),
-                           panel, G_CONNECT_SWAPPED);
-  gtk_style_context_add_class (gtk_widget_get_style_context (button),
-                               GTK_STYLE_CLASS_SUGGESTED_ACTION);
+      gtk_widget_show_all (header);
+      g_object_unref (size_group);
 
-  gtk_widget_show_all (header);
-  g_object_unref (size_group);
+      header = gtk_window_get_titlebar (GTK_WINDOW (toplevel));
+      if (header)
+        priv->main_titlebar = g_object_ref (header);
 
-  header = gtk_window_get_titlebar (GTK_WINDOW (toplevel));
-  if (header)
-    priv->main_titlebar = g_object_ref (header);
+      gtk_window_set_titlebar (GTK_WINDOW (toplevel), priv->apply_titlebar);
+      g_object_ref (priv->apply_titlebar);
+      g_object_ref (priv->apply_titlebar_apply);
+    }
 
-  gtk_window_set_titlebar (GTK_WINDOW (toplevel), priv->apply_titlebar);
-  g_object_ref (priv->apply_titlebar);
+  if (is_applicable)
+    {
+      gtk_header_bar_set_title (GTK_HEADER_BAR (priv->apply_titlebar), _("Apply Changes?"));
+      gtk_header_bar_set_subtitle (GTK_HEADER_BAR (priv->apply_titlebar), NULL);
+    }
+  else
+    {
+      gtk_header_bar_set_title (GTK_HEADER_BAR (priv->apply_titlebar), _("Changes Cannot be Applied"));
+      gtk_header_bar_set_subtitle (GTK_HEADER_BAR (priv->apply_titlebar), _("This could be due to hardware 
limitations."));
+    }
+  gtk_widget_set_sensitive (priv->apply_titlebar_apply, is_applicable);
 }
 
 static void
@@ -2640,12 +2656,6 @@ update_apply_button (CcDisplayPanel *panel)
   gboolean config_equal;
   CcDisplayConfig *applied_config;
 
-  if (!cc_display_config_is_applicable (priv->current_config))
-    {
-      reset_titlebar (panel);
-      return;
-    }
-
   applied_config = cc_display_config_manager_get_current (priv->manager);
 
   config_equal = cc_display_config_equal (priv->current_config,
@@ -2655,7 +2665,7 @@ update_apply_button (CcDisplayPanel *panel)
   if (config_equal)
     reset_titlebar (panel);
   else
-    show_apply_titlebar (panel);
+    show_apply_titlebar (panel, cc_display_config_is_applicable (priv->current_config));
 }
 
 static void