libgimpwidgets: Fix GUI twitching due to bold label sizing

Resolves #10026

Selecting a checkbutton makes the label bold. This increases the
width of its label, and if it's the longest item in a box, this
causes minor "twitching" and resizing of the dialogue.
This patch calculates the size of the label when bold and then
requests the label width be set accordingly to resolve the issue.

app/dialogs/item-options-dialog.c

@@ -472,6 +472,7 @@ check_button_with_icon_new (const gchar *label,
   GtkWidget *hbox;
   GtkWidget *button;
   GtkWidget *image;
+  GtkWidget *label_widget;
 
   hbox = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 6);
   gtk_box_pack_start (vbox, hbox, FALSE, FALSE, 0);
@@ -485,5 +486,9 @@ check_button_with_icon_new (const gchar *label,
   gtk_box_pack_start (GTK_BOX (hbox), button, TRUE, TRUE, 0);
   gtk_widget_show (button);
 
+  /* size the label to its bold size, avoiding a GUI twitch */
+  label_widget = gtk_bin_get_child (GTK_BIN (button));
+  gtk_widget_set_size_request (label_widget, gimp_get_bold_label_width (label), -1);
+
   return button;
 }

libgimpwidgets/gimppropwidgets.c

@@ -122,6 +122,7 @@ gimp_prop_check_button_new (GObject     *config,
   GParamSpec  *param_spec;
   GtkWidget   *button;
   const gchar *blurb;
+  GtkWidget   *label_widget;
 
   g_return_val_if_fail (G_IS_OBJECT (config), NULL);
   g_return_val_if_fail (property_name != NULL, NULL);
@@ -137,6 +138,10 @@ gimp_prop_check_button_new (GObject     *config,
   button = gtk_check_button_new_with_mnemonic (label);
   gtk_widget_show (button);
 
+  /* size the label to its bold size, avoiding a GUI twitch */
+  label_widget = gtk_bin_get_child (GTK_BIN (button));
+  gtk_widget_set_size_request (label_widget, gimp_get_bold_label_width (label), -1);
+
   blurb = g_param_spec_get_blurb (param_spec);
   if (blurb)
     gimp_help_set_help_data (button, blurb, NULL);

libgimpwidgets/gimpwidgets.def

@@ -201,6 +201,7 @@ EXPORTS
 	gimp_float_adjustment_update
 	gimp_frame_get_type
 	gimp_frame_new
+	gimp_get_bold_label_width
 	gimp_get_monitor_at_pointer
 	gimp_grid_attach_aligned
 	gimp_help_connect

libgimpwidgets/gimpwidgetsutils.c

@@ -1279,3 +1279,23 @@ gimp_widget_set_handle_on_mapped (GtkWidget    *widget,
 
   return FALSE;
 }
+
+/* get the width of the label when it is bold */
+gint
+gimp_get_bold_label_width (const gchar *text)
+  {
+    GtkWidget      *temp_label = gtk_label_new (NULL);
+    GtkRequisition  natural_size;
+
+    gtk_label_set_text (GTK_LABEL (temp_label), text);
+    gtk_widget_set_visible (temp_label, TRUE);
+
+    gimp_label_set_attributes (GTK_LABEL (temp_label),
+                               PANGO_ATTR_WEIGHT, PANGO_WEIGHT_BOLD,
+                               -1);
+
+    gtk_widget_get_preferred_size (temp_label, NULL, &natural_size);
+    gtk_widget_destroy (temp_label);
+
+    return natural_size.width;
+}

libgimpwidgets/gimpwidgetsutils.h

@@ -70,6 +70,7 @@ const Babl         * gimp_widget_get_render_space    (GtkWidget       *widget,
 void                 gimp_widget_set_native_handle   (GtkWidget        *widget,
                                                       GBytes          **handle);
 
+gint                 gimp_get_bold_label_width       (const gchar      *text);
 
 /* Internal use */