[gtk/wip/ebassi/fixed-layout-v2: 3/3] Add API to access child transformations to GtkFixed

[Emmanuele Bassi <ebassi src gnome org>]

commit 6e7748b2661cac76565485ab4f1497f3563f1a7f
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Apr 2 15:48:46 2019 +0100

    Add API to access child transformations to GtkFixed
    
    This is mostly convenience API around GtkFixedLayoutChild, but it should
    push people towards using transformations with GtkFixed instead of just
    using fixed positioning.

 gtk/gtkfixed.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++------
 gtk/gtkfixed.h | 37 ++++++++++++++++++++------------
 2 files changed, 84 insertions(+), 20 deletions(-)
---
diff --git a/gtk/gtkfixed.c b/gtk/gtkfixed.c
index e41c887cb3..4f0ae14241 100644
--- a/gtk/gtkfixed.c
+++ b/gtk/gtkfixed.c
@@ -27,7 +27,6 @@
  * @Short_description: A container which allows you to position
  * widgets at fixed coordinates
  * @Title: GtkFixed
- * @See_also: #GtkLayout
  *
  * The #GtkFixed widget is a container which can place child widgets
  * at fixed positions and with fixed sizes, given in pixels. #GtkFixed
@@ -52,7 +51,7 @@
  *
  * In addition, #GtkFixed does not pay attention to text direction and thus may
  * produce unwanted results if your app is run under right-to-left languages
- * such as Hebrew or Arabic. That is: normally GTK+ will order containers
+ * such as Hebrew or Arabic. That is: normally GTK will order containers
  * appropriately for the text direction, e.g. to put labels to the right of the
  * thing they label when using an RTL language, but it can’t do that with
  * #GtkFixed. So if you need to reorder widgets depending on the text direction,
@@ -142,7 +141,8 @@ gtk_fixed_new (void)
  * @x: the horizontal position to place the widget at.
  * @y: the vertical position to place the widget at.
  *
- * Adds a widget to a #GtkFixed container at the given position.
+ * Adds a widget to a #GtkFixed container and assigns a translation
+ * transformation to the given @x and @y coordinates to it.
  */
 void
 gtk_fixed_put (GtkFixed  *fixed,
@@ -174,8 +174,10 @@ gtk_fixed_put (GtkFixed  *fixed,
  * @x: (out): the horizontal position of the @widget
  * @y: (out): the vertical position of the @widget
  *
- * Retrieves the position of the given child #GtkWidget in the given
- * #GtkFixed container.
+ * Retrieves the translation transformation of the given child #GtkWidget
+ * in the given #GtkFixed container.
+ *
+ * See also: gtk_fixed_get_child_transform().
  */
 void
 gtk_fixed_get_child_position (GtkFixed  *fixed,
@@ -202,6 +204,58 @@ gtk_fixed_get_child_position (GtkFixed  *fixed,
     *y = floorf (pos_y);
 }
 
+/**
+ * gtk_fixed_set_child_transform:
+ * @fixed: a #GtkFixed
+ * @widget: a #GtkWidget, child of @fixed
+ * @transform: (nullable): the transformation assigned to @widget
+ *
+ * Sets the transformation for @widget.
+ *
+ * This is a convenience function that retrieves the #GtkFixedLayoutChild
+ * instance associated to @widget and calls gtk_fixed_layout_child_set_position().
+ */
+void
+gtk_fixed_set_child_transform (GtkFixed     *fixed,
+                               GtkWidget    *widget,
+                               GskTransform *transform)
+{
+  GtkFixedPrivate *priv = gtk_fixed_get_instance_private (fixed);
+  GtkFixedLayoutChild *child_info;
+
+  g_return_if_fail (GTK_IS_FIXED (fixed));
+  g_return_if_fail (GTK_IS_WIDGET (widget));
+  g_return_if_fail (gtk_widget_get_parent (widget) == GTK_WIDGET (fixed));
+
+  child_info = GTK_FIXED_LAYOUT_CHILD (gtk_layout_manager_get_layout_child (priv->layout, widget));
+  gtk_fixed_layout_child_set_position (child_info, transform);
+}
+
+/**
+ * gtk_fixed_get_child_transform:
+ * @fixed: a #GtkFixed
+ * @widget: a #GtkWidget, child of @fixed
+ *
+ * Retrieves the transformation for @widget set using
+ * gtk_fixed_set_child_transform().
+ *
+ * Returns: (transfer none) (nullable): a #GskTransform
+ */
+GskTransform *
+gtk_fixed_get_child_transform (GtkFixed  *fixed,
+                               GtkWidget *widget)
+{
+  GtkFixedPrivate *priv = gtk_fixed_get_instance_private (fixed);
+  GtkFixedLayoutChild *child_info;
+
+  g_return_val_if_fail (GTK_IS_FIXED (fixed), NULL);
+  g_return_val_if_fail (GTK_IS_WIDGET (widget), NULL);
+  g_return_val_if_fail (gtk_widget_get_parent (widget) == GTK_WIDGET (fixed), NULL);
+
+  child_info = GTK_FIXED_LAYOUT_CHILD (gtk_layout_manager_get_layout_child (priv->layout, widget));
+  return gtk_fixed_layout_child_get_position (child_info);
+}
+
 /**
  * gtk_fixed_move:
  * @fixed: a #GtkFixed.
@@ -209,7 +263,8 @@ gtk_fixed_get_child_position (GtkFixed  *fixed,
  * @x: the horizontal position to move the widget to.
  * @y: the vertical position to move the widget to.
  *
- * Moves a child of a #GtkFixed container to the given position.
+ * Sets a translation transformation to the given @x and @y coordinates to
+ * the child @widget of the given #GtkFixed container.
  */
 void
 gtk_fixed_move (GtkFixed  *fixed,
diff --git a/gtk/gtkfixed.h b/gtk/gtkfixed.h
index 758eac6e49..3127193439 100644
--- a/gtk/gtkfixed.h
+++ b/gtk/gtkfixed.h
@@ -62,24 +62,33 @@ struct _GtkFixedClass
 };
 
 GDK_AVAILABLE_IN_ALL
-GType      gtk_fixed_get_type           (void) G_GNUC_CONST;
+GType gtk_fixed_get_type (void) G_GNUC_CONST;
+
+GDK_AVAILABLE_IN_ALL
+GtkWidget *     gtk_fixed_new                (void);
 GDK_AVAILABLE_IN_ALL
-GtkWidget* gtk_fixed_new                (void);
+void            gtk_fixed_put                   (GtkFixed     *fixed,
+                                                 GtkWidget    *widget,
+                                                 gint          x,
+                                                 gint          y);
 GDK_AVAILABLE_IN_ALL
-void       gtk_fixed_put                (GtkFixed  *fixed,
-                                         GtkWidget *widget,
-                                         gint       x,
-                                         gint       y);
+void            gtk_fixed_move                  (GtkFixed     *fixed,
+                                                 GtkWidget    *widget,
+                                                 gint          x,
+                                                 gint          y);
+GDK_AVAILABLE_IN_ALL
+void            gtk_fixed_get_child_position    (GtkFixed     *fixed,
+                                                 GtkWidget    *widget,
+                                                 gint         *x,
+                                                 gint         *y);
+
 GDK_AVAILABLE_IN_ALL
-void       gtk_fixed_move               (GtkFixed  *fixed,
-                                         GtkWidget *widget,
-                                         gint       x,
-                                         gint       y);
+void            gtk_fixed_set_child_transform   (GtkFixed     *fixed,
+                                                 GtkWidget    *widget,
+                                                 GskTransform *transform);
 GDK_AVAILABLE_IN_ALL
-void       gtk_fixed_get_child_position (GtkFixed  *fixed,
-                                         GtkWidget *widget,
-                                         gint      *x,
-                                         gint      *y);
+GskTransform *  gtk_fixed_get_child_transform   (GtkFixed     *fixed,
+                                                 GtkWidget    *widget);
 
 G_END_DECLS