[gnome-control-center/gnome-2-28] RANDR - Sensitize 'Mirror Screens' depending on whether mirror mode is actually supported

[Federico Mena Quintero <federico src gnome org>]

commit b24e10480d9675e8f09331087f0234d421718b3d
Author: Federico Mena Quintero <federico novell com>
Date:   Thu Dec 10 12:06:01 2009 -0600

    RANDR - Sensitize 'Mirror Screens' depending on whether mirror mode is actually supported
    
    Previously it was always sensitive, even if there were not enough connected outputs
    for mirroring, or if those those outputs didn't support the same resolution for
    mirroring.
    
    Signed-off-by: Federico Mena Quintero <federico novell com>

 capplets/display/xrandr-capplet.c |   70 ++++++++++++++++++++++++++++++++++---
 1 files changed, 65 insertions(+), 5 deletions(-)
---
diff --git a/capplets/display/xrandr-capplet.c b/capplets/display/xrandr-capplet.c
index 49458ad..69b95f1 100644
--- a/capplets/display/xrandr-capplet.c
+++ b/capplets/display/xrandr-capplet.c
@@ -78,12 +78,15 @@ struct App
 };
 
 static void rebuild_gui (App *app);
+static void on_clone_changed (GtkWidget *box, gpointer data);
 static void on_rate_changed (GtkComboBox *box, gpointer data);
 static gboolean output_overlaps (GnomeOutputInfo *output, GnomeRRConfig *config);
 static void select_current_output_from_dialog_position (App *app);
 static void monitor_on_off_toggled_cb (GtkToggleButton *toggle, gpointer data);
 static void get_geometry (GnomeOutputInfo *output, int *w, int *h);
 static void apply_configuration_returned_cb (DBusGProxy *proxy, DBusGProxyCall *call_id, void *data);
+static gboolean get_clone_size (GnomeRRScreen *screen, int *width, int *height);
+static gboolean output_info_supports_mode (App *app, GnomeOutputInfo *info, int width, int height);
 
 static void
 error_message (App *app, const char *primary_text, const char *secondary_text)
@@ -420,6 +423,67 @@ count_all_outputs (GnomeRRConfig *config)
 }
 #endif
 
+/* Computes whether "Mirror Screens" (clone mode) is supported based on these criteria:
+ *
+ * 1. There is an available size for cloning.
+ *
+ * 2. There are 2 or more connected outputs that support that size.
+ */
+static gboolean
+mirror_screens_is_supported (App *app)
+{
+    int clone_width, clone_height;
+    gboolean have_clone_size;
+    gboolean mirror_is_supported;
+
+    mirror_is_supported = FALSE;
+
+    have_clone_size = get_clone_size (app->screen, &clone_width, &clone_height);
+
+    if (have_clone_size) {
+	int i;
+	int num_outputs_with_clone_size;
+
+	num_outputs_with_clone_size = 0;
+
+	for (i = 0; app->current_configuration->outputs[i] != NULL; i++)
+	{
+	    GnomeOutputInfo *output = app->current_configuration->outputs[i];
+
+	    /* We count the connected outputs that support the clone size.  It
+	     * doesn't matter if those outputs aren't actually On currently; we
+	     * will turn them on in on_clone_changed().
+	     */
+	    if (output->connected && output_info_supports_mode (app, output, clone_width, clone_height))
+		num_outputs_with_clone_size++;
+	}
+
+	if (num_outputs_with_clone_size >= 2)
+	    mirror_is_supported = TRUE;
+    }
+
+    return mirror_is_supported;
+}
+
+static void
+rebuild_mirror_screens (App *app)
+{
+    gboolean mirror_is_active;
+    gboolean mirror_is_supported;
+
+    g_signal_handlers_block_by_func (app->clone_checkbox, G_CALLBACK (on_clone_changed), app);
+
+    mirror_is_active = app->current_configuration && app->current_configuration->clone;
+
+    /* If mirror_is_active, then it *must* be possible to turn mirroring off */
+    mirror_is_supported = mirror_is_active || mirror_screens_is_supported (app);
+    
+    gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (app->clone_checkbox), mirror_is_active);
+    gtk_widget_set_sensitive (app->clone_checkbox, mirror_is_supported);
+
+    g_signal_handlers_unblock_by_func (app->clone_checkbox, G_CALLBACK (on_clone_changed), app);
+}
+
 static void
 rebuild_current_monitor_label (App *app)
 {
@@ -597,6 +661,7 @@ rebuild_gui (App *app)
     g_debug ("rebuild gui, is on: %d", app->current_output->on);
 #endif
 
+    rebuild_mirror_screens (app);
     rebuild_current_monitor_label (app);
     rebuild_on_off_radios (app);
     rebuild_resolution_combo (app);
@@ -609,11 +674,6 @@ rebuild_gui (App *app)
     gtk_widget_set_sensitive (app->panel_checkbox, sensitive);
 
     app->ignore_gui_changes = FALSE;
-
-    if (app->current_configuration && app->current_configuration->clone)
-	gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (app->clone_checkbox), TRUE);
-    else
-	gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (app->clone_checkbox), FALSE);
 }
 
 static gboolean