[gtk/wip/layout-manager] Add GtkLegacyLayout

[Emmanuele Bassi <ebassi src gnome org>]

commit 423d5e166eb6dade38382cb3ecd84c6ad1979106
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Mon Jan 28 14:03:25 2019 +0000

    Add GtkLegacyLayout
    
    GtkLegacyLayout is a layout manager for the transitional period between
    the introduction of layout managers and the removal of GtkWidget virtual
    functions for the size negotiation.

 gtk/gtklegacylayout.c        | 129 +++++++++++++++++++++++++++++++++++++++++++
 gtk/gtklegacylayoutprivate.h |  33 +++++++++++
 gtk/meson.build              |   1 +
 3 files changed, 163 insertions(+)
---
diff --git a/gtk/gtklegacylayout.c b/gtk/gtklegacylayout.c
new file mode 100644
index 0000000000..17596a7f6e
--- /dev/null
+++ b/gtk/gtklegacylayout.c
@@ -0,0 +1,129 @@
+/*< private >
+ * SECTION:gtklegacylayout
+ * @Title: GtkLegacyLayout
+ * @Short_description: A legacy layout manager
+ *
+ * #GtkLegacyLayout is a convenience type meant to be used as a transition
+ * mechanism between #GtkContainers implementing a layout policy, and
+ * #GtkLayoutManager classes.
+ *
+ * A #GtkLegacyLayout uses closures matching to the old #GtkWidget virtual
+ * functions for size negotiation, to ease the porting towards the
+ * corresponding #GtkLayoutManager virtual functions.
+ */
+
+#include "config.h"
+
+#include "gtklegacylayoutprivate.h"
+
+struct _GtkLegacyLayout
+{
+  GtkLayoutManager parent_instance;
+
+  GtkLegacyRequestModeFunc request_mode_func;
+  GtkLegacyMeasureFunc measure_func;
+  GtkLegacyAllocateFunc allocate_func;
+};
+
+G_DEFINE_TYPE (GtkLegacyLayout, gtk_legacy_layout, GTK_TYPE_LAYOUT_MANAGER)
+
+static GtkSizeRequestMode
+gtk_legacy_layout_get_request_mode (GtkLayoutManager *manager,
+                                    GtkWidget        *widget)
+{
+  GtkLegacyLayout *self = GTK_LEGACY_LAYOUT (manager);
+
+  if (self->request_mode_func != NULL)
+    return self->request_mode_func (widget);
+
+  return GTK_SIZE_REQUEST_CONSTANT_SIZE;
+}
+
+static void
+gtk_legacy_layout_measure (GtkLayoutManager *manager,
+                           GtkWidget        *widget,
+                           GtkOrientation    orientation,
+                           int               for_size,
+                           int              *minimum_p,
+                           int              *natural_p,
+                           int              *minimum_baseline_p,
+                           int              *natural_baseline_p)
+{
+  GtkLegacyLayout *self = GTK_LEGACY_LAYOUT (manager);
+  int minimum = 0, natural = 0;
+  int minimum_baseline = 0, natural_baseline = 0;
+
+  if (self->measure_func != NULL)
+    self->measure_func (widget, orientation, for_size,
+                        &minimum, &natural,
+                        &minimum_baseline, &natural_baseline);
+
+  if (minimum_p != NULL)
+    *minimum_p = minimum;
+  if (natural_p != NULL)
+    *natural_p = natural;
+
+  if (minimum_baseline_p != NULL)
+    *minimum_baseline_p = minimum_baseline;
+  if (natural_baseline_p != NULL)
+    *natural_baseline_p = natural_baseline;
+}
+
+static void
+gtk_legacy_layout_allocate (GtkLayoutManager *manager,
+                            GtkWidget        *widget,
+                            int               width,
+                            int               height,
+                            int               baseline)
+{
+  GtkLegacyLayout *self = GTK_LEGACY_LAYOUT (manager);
+
+  if (self->allocate_func != NULL)
+    self->allocate_func (widget, width, height, baseline);
+}
+
+static void
+gtk_legacy_layout_class_init (GtkLegacyLayoutClass *klass)
+{
+  GtkLayoutManagerClass *layout_class = GTK_LAYOUT_MANAGER_CLASS (klass);
+
+  layout_class->get_request_mode = gtk_legacy_layout_get_request_mode;
+  layout_class->measure = gtk_legacy_layout_measure;
+  layout_class->allocate = gtk_legacy_layout_allocate;
+}
+
+static void
+gtk_legacy_layout_init (GtkLegacyLayout *self)
+{
+}
+
+/*< private >
+ * gtk_legacy_layout_new:
+ * @request_mode: (nullable): a function to retrieve
+ *   the #GtkSizeRequestMode of the widget using the layout
+ * @measure: (nullable): a fucntion to measure the widget
+ *   using the layout
+ * @allocate: (nullable): a function to allocate the children
+ *   of the widget using the layout
+ *
+ * Creates a new legacy layout manager.
+ *
+ * Legacy layout managers map to the old #GtkWidget size negotiation
+ * virtual functions, and are meant to be used during the transition
+ * from layout containers to layout manager delegates.
+ *
+ * Returns: (transfer full): the newly created #GtkLegacyLayout
+ */
+GtkLayoutManager *
+gtk_legacy_layout_new (GtkLegacyRequestModeFunc request_mode,
+                       GtkLegacyMeasureFunc measure,
+                       GtkLegacyAllocateFunc allocate)
+{
+  GtkLegacyLayout *self = g_object_new (GTK_TYPE_LEGACY_LAYOUT, NULL);
+
+  self->request_mode_func = request_mode;
+  self->measure_func = measure;
+  self->allocate_func = allocate;
+
+  return GTK_LAYOUT_MANAGER (self);
+}
diff --git a/gtk/gtklegacylayoutprivate.h b/gtk/gtklegacylayoutprivate.h
new file mode 100644
index 0000000000..47fe5d6998
--- /dev/null
+++ b/gtk/gtklegacylayoutprivate.h
@@ -0,0 +1,33 @@
+#pragma once
+
+#include <gtk/gtklayoutmanager.h>
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_LEGACY_LAYOUT (gtk_legacy_layout_get_type ())
+
+typedef GtkSizeRequestMode (* GtkLegacyRequestModeFunc) (GtkWidget *widget);
+
+typedef void (* GtkLegacyMeasureFunc) (GtkWidget      *widget,
+                                       GtkOrientation  orientation,
+                                       int             for_size,
+                                       int            *minimum,
+                                       int            *natural,
+                                       int            *minimum_baseline,
+                                       int            *natural_baseline);
+
+typedef void (* GtkLegacyAllocateFunc) (GtkWidget *widget,
+                                        int        width,
+                                        int        height,
+                                        int        baseline);
+
+GDK_AVAILABLE_IN_ALL
+G_DECLARE_FINAL_TYPE (GtkLegacyLayout, gtk_legacy_layout, GTK, LEGACY_LAYOUT, GtkLayoutManager)
+
+GDK_AVAILABLE_IN_ALL
+GtkLayoutManager *
+gtk_legacy_layout_new (GtkLegacyRequestModeFunc request_mode,
+                       GtkLegacyMeasureFunc measure,
+                       GtkLegacyAllocateFunc allocate);
+
+G_END_DECLS
diff --git a/gtk/meson.build b/gtk/meson.build
index f580f205f7..80a3b8c3c4 100644
--- a/gtk/meson.build
+++ b/gtk/meson.build
@@ -116,6 +116,7 @@ gtk_private_sources = files([
   'gtkiconhelper.c',
   'gtkkineticscrolling.c',
   'gtkkeyhash.c',
+  'gtklegacylayout.c',
   'gtkmagnifier.c',
   'gtkmenusectionbox.c',
   'gtkmenutracker.c',