[gtk/stack-fixes: 3/8] stack: Provide a selection model

[Matthias Clasen <matthiasc src gnome org>]

commit b39558938dcf8d7eb8f92db76676db24381b45e1
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Feb 8 20:36:58 2019 -0500

    stack: Provide a selection model
    
    Make GtkStack expose a selection model for its children.
    The model can be used to track changes to the children
    and the visible child, and to change what child is
    visible.

 gtk/gtkstack.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gtk/gtkstack.h |  5 ++++
 2 files changed, 90 insertions(+)
---
diff --git a/gtk/gtkstack.c b/gtk/gtkstack.c
index 338199c319..a473cc2a09 100644
--- a/gtk/gtkstack.c
+++ b/gtk/gtkstack.c
@@ -30,6 +30,7 @@
 #include "gtksettingsprivate.h"
 #include "gtksnapshot.h"
 #include "gtkwidgetprivate.h"
+#include "gtksingleselection.h"
 #include "a11y/gtkstackaccessible.h"
 #include "a11y/gtkstackaccessibleprivate.h"
 #include <math.h>
@@ -138,6 +139,8 @@ typedef struct {
 
   GtkStackTransitionType active_transition_type;
 
+  GtkSelectionModel *pages;
+
 } GtkStackPrivate;
 
 static void gtk_stack_buildable_interface_init (GtkBuildableIface *iface);
@@ -2294,3 +2297,85 @@ gtk_stack_init (GtkStack *stack)
   priv->transition_duration = 200;
   priv->transition_type = GTK_STACK_TRANSITION_TYPE_NONE;
 }
+
+static gboolean
+transform_to (GBinding *binding,
+              const GValue *from_value,
+              GValue *to_value,
+              gpointer user_data)
+{
+  GtkStack *stack = user_data;
+  GtkStackPrivate *priv = gtk_stack_get_instance_private (stack);
+  GtkWidget *child;
+  guint i;
+  guint pos = GTK_INVALID_LIST_POSITION;
+
+  child = g_value_get_object (from_value);
+  for (i = 0; i < g_list_model_get_n_items (G_LIST_MODEL (priv->pages)); i++)
+    {
+      GtkWidget *widget;
+      widget = g_list_model_get_item (G_LIST_MODEL (priv->pages), i);
+      if (widget == child)
+        pos = i;
+      g_object_unref (widget);
+      if (pos != GTK_INVALID_LIST_POSITION)
+        break;
+    }
+
+  g_value_set_uint (to_value, pos);
+  return TRUE;
+}
+
+static gboolean
+transform_from (GBinding *binding,
+              const GValue *from_value,
+              GValue *to_value,
+              gpointer user_data)
+{
+  GtkStack *stack = user_data;
+  GtkStackPrivate *priv = gtk_stack_get_instance_private (stack);
+  guint selected;
+
+  selected = g_value_get_uint (from_value);
+  if (selected < g_list_model_get_n_items (G_LIST_MODEL (priv->pages)))
+    {
+      GtkWidget *child;
+      child = g_list_model_get_item (G_LIST_MODEL (priv->pages), selected);
+      g_value_set_object (to_value, child);
+      g_object_unref (child);
+      return TRUE;
+    }
+  else
+    return FALSE;
+}
+
+/**
+ * gtk_stack_get_pages:
+ * @stack: a #GtkStack
+ *
+ * Returns a #GListModel that contains the children of the stack,
+ * and can be used to keep and up-to-date view. The model also
+ * implements #GtkSelectionModel and can be used to track and
+ * modify the visible child.
+ *
+ * Returns: (transfer full): a #GtkSelectionModel for the stack's children
+ */
+GtkSelectionModel *
+gtk_stack_get_pages (GtkStack *stack)
+{
+  GtkStackPrivate *priv = gtk_stack_get_instance_private (stack);
+
+  g_return_val_if_fail (GTK_IS_STACK (stack), NULL);
+
+  if (priv->pages)
+    return g_object_ref (priv->pages);
+
+  priv->pages = GTK_SELECTION_MODEL (gtk_single_selection_new (gtk_widget_observe_children (GTK_WIDGET 
(stack))));
+  g_object_add_weak_pointer (G_OBJECT (priv->pages), (gpointer *)&priv->pages);
+  g_object_bind_property_full (stack, "visible-child",
+                               priv->pages, "selected",
+                               G_BINDING_BIDIRECTIONAL|G_BINDING_SYNC_CREATE,
+                               transform_to, transform_from, stack, NULL);
+
+  return priv->pages;
+}
diff --git a/gtk/gtkstack.h b/gtk/gtkstack.h
index 6379328041..658ef8bb6a 100644
--- a/gtk/gtkstack.h
+++ b/gtk/gtkstack.h
@@ -27,6 +27,7 @@
 #endif
 
 #include <gtk/gtkcontainer.h>
+#include <gtk/gtkselectionmodel.h>
 
 G_BEGIN_DECLS
 
@@ -155,6 +156,10 @@ void                   gtk_stack_set_interpolate_size    (GtkStack *stack,
                                                           gboolean  interpolate_size);
 GDK_AVAILABLE_IN_ALL
 gboolean               gtk_stack_get_interpolate_size    (GtkStack *stack);
+
+GDK_AVAILABLE_IN_ALL
+GtkSelectionModel *    gtk_stack_get_pages               (GtkStack *stack);
+
 G_END_DECLS
 
 #endif