[gimp] libgimpwidgets: add a "mnemonic-widget-changed" signal to GimpLabeled.

[Jehan <jehanp src gnome org>]

commit 97b81118aab68a7c78c1b1747dbaa6d9e5929a43
Author: Jehan <jehan girinstud io>
Date:   Thu Feb 17 23:24:05 2022 +0100

    libgimpwidgets: add a "mnemonic-widget-changed" signal to GimpLabeled.
    
    This allows to track changes of mnemonic widgets, as we do in
    GimpLabelColor when we switch from editable to non-editable (or
    reverse).

 libgimpwidgets/gimplabelcolor.c |  1 +
 libgimpwidgets/gimplabeled.c    | 59 +++++++++++++++++++++++++++++++----------
 libgimpwidgets/gimplabeled.h    | 16 +++++++----
 3 files changed, 57 insertions(+), 19 deletions(-)
---
diff --git a/libgimpwidgets/gimplabelcolor.c b/libgimpwidgets/gimplabelcolor.c
index ac0a2061ff..19a95d65e1 100644
--- a/libgimpwidgets/gimplabelcolor.c
+++ b/libgimpwidgets/gimplabelcolor.c
@@ -246,6 +246,7 @@ gimp_label_color_set_property (GObject      *object,
             {
               gtk_grid_attach (GTK_GRID (lcolor), priv->area, 1, 0, 1, 1);
               gtk_widget_show (priv->area);
+              g_signal_emit_by_name (object, "mnemonic-widget-changed", priv->area);
             }
         }
       break;
diff --git a/libgimpwidgets/gimplabeled.c b/libgimpwidgets/gimplabeled.c
index 19c088c1e2..550356b635 100644
--- a/libgimpwidgets/gimplabeled.c
+++ b/libgimpwidgets/gimplabeled.c
@@ -40,6 +40,12 @@
  * another widget.
  **/
 
+enum
+{
+  MNEMONIC_WIDGET_CHANGED,
+  LAST_SIGNAL
+};
+
 enum
 {
   PROP_0,
@@ -48,25 +54,29 @@ enum
 
 typedef struct _GimpLabeledPrivate
 {
-  GtkWidget     *label;
-  GtkWidget     *mnemonic_widget;
+  GtkWidget *label;
 } GimpLabeledPrivate;
 
 
-static void       gimp_labeled_constructed       (GObject       *object);
-static void       gimp_labeled_set_property      (GObject       *object,
-                                                  guint          property_id,
-                                                  const GValue  *value,
-                                                  GParamSpec    *pspec);
-static void       gimp_labeled_get_property      (GObject       *object,
-                                                  guint          property_id,
-                                                  GValue        *value,
-                                                  GParamSpec    *pspec);
+static void       gimp_labeled_constructed            (GObject       *object);
+static void       gimp_labeled_set_property           (GObject       *object,
+                                                       guint          property_id,
+                                                       const GValue  *value,
+                                                       GParamSpec    *pspec);
+static void       gimp_labeled_get_property           (GObject       *object,
+                                                       guint          property_id,
+                                                       GValue        *value,
+                                                       GParamSpec    *pspec);
+
+static void gimp_labeled_real_mnemonic_widget_changed (GimpLabeled   *labeled,
+                                                       GtkWidget     *widget);
+
 
 G_DEFINE_TYPE_WITH_PRIVATE (GimpLabeled, gimp_labeled, GTK_TYPE_GRID)
 
 #define parent_class gimp_labeled_parent_class
 
+static guint signals[LAST_SIGNAL] = { 0 };
 
 static void
 gimp_labeled_class_init (GimpLabeledClass *klass)
@@ -77,6 +87,17 @@ gimp_labeled_class_init (GimpLabeledClass *klass)
   object_class->set_property = gimp_labeled_set_property;
   object_class->get_property = gimp_labeled_get_property;
 
+  signals[MNEMONIC_WIDGET_CHANGED] =
+    g_signal_new ("mnemonic-widget-changed",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_FIRST,
+                  G_STRUCT_OFFSET (GimpLabeledClass, mnemonic_widget_changed),
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 1,
+                  GTK_TYPE_WIDGET);
+
+  klass->mnemonic_widget_changed = gimp_labeled_real_mnemonic_widget_changed;
+
   /**
    * GimpLabeled:label:
    *
@@ -103,6 +124,7 @@ gimp_labeled_constructed (GObject *object)
   GimpLabeledClass   *klass;
   GimpLabeled        *labeled = GIMP_LABELED (object);
   GimpLabeledPrivate *priv    = gimp_labeled_get_instance_private (labeled);
+  GtkWidget          *mnemonic_widget;
   gint                x       = 0;
   gint                y       = 0;
   gint                width   = 1;
@@ -115,10 +137,10 @@ gimp_labeled_constructed (GObject *object)
 
   klass = GIMP_LABELED_GET_CLASS (labeled);
   g_return_if_fail (klass->populate);
-  priv->mnemonic_widget = klass->populate (labeled, &x, &y, &width, &height);
+  mnemonic_widget = klass->populate (labeled, &x, &y, &width, &height);
 
-  if (priv->mnemonic_widget)
-    gtk_label_set_mnemonic_widget (GTK_LABEL (priv->label), priv->mnemonic_widget);
+  g_signal_emit (object, signals[MNEMONIC_WIDGET_CHANGED], 0,
+                 mnemonic_widget);
 
   gtk_grid_attach (GTK_GRID (labeled), priv->label, x, y, width, height);
   gtk_widget_show (priv->label);
@@ -175,6 +197,15 @@ gimp_labeled_get_property (GObject    *object,
     }
 }
 
+static void
+gimp_labeled_real_mnemonic_widget_changed (GimpLabeled *labeled,
+                                           GtkWidget   *widget)
+{
+  GimpLabeledPrivate *priv  = gimp_labeled_get_instance_private (labeled);
+
+  gtk_label_set_mnemonic_widget (GTK_LABEL (priv->label), widget);
+}
+
 /* Public functions */
 
 /**
diff --git a/libgimpwidgets/gimplabeled.h b/libgimpwidgets/gimplabeled.h
index e0a5aa019b..65c33e5b86 100644
--- a/libgimpwidgets/gimplabeled.h
+++ b/libgimpwidgets/gimplabeled.h
@@ -35,6 +35,11 @@ struct _GimpLabeledClass
 {
   GtkGridClass       parent_class;
 
+  /*  Signals        */
+
+  void (* mnemonic_widget_changed) (GimpLabeled *labeled,
+                                    GtkWidget   *widget);
+
   /*  Class methods  */
 
   /**
@@ -50,11 +55,12 @@ struct _GimpLabeledClass
    * Returns: (transfer none): the #GtkWidget which the label must be
    *                           set as mnemonic to.
    **/
-  GtkWidget     * (* populate) (GimpLabeled *labeled,
-                                gint        *x,
-                                gint        *y,
-                                gint        *width,
-                                gint        *height);
+  GtkWidget     * (* populate)     (GimpLabeled *labeled,
+                                    gint        *x,
+                                    gint        *y,
+                                    gint        *width,
+                                    gint        *height);
+
 
   /* Padding for future expansion */
   void (* _gimp_reserved1) (void);