Introduce gtk_tree_view_is_blank_at_pos()

This function is useful to figure out whether the tree view is "blank"
at a given location.  For such locations you might want to popup a
custom popup menu, clear the current selection or start rubber banding.
In the future, we are planning on updating GtkTreeView's user
interactions to take advantage of this new function.

Part of bug 350618.

1 files changed, 103 insertions, 0 deletions

diff --git a/gtk/gtktreeview.c b/gtk/gtktreeview.c
index fc599c996f..76b748fc1c 100644
--- a/gtk/gtktreeview.c
+++ b/gtk/gtktreeview.c
@@ -14039,6 +14039,109 @@ gtk_tree_view_get_visible_range (GtkTreeView  *tree_view,
   return retval;
 }
 
+/**
+ * gtk_tree_view_is_blank_at_pos:
+ * @tree_view: A #GtkTreeView
+ * @x: The x position to be identified (relative to bin_window)
+ * @y: The y position to be identified (relative to bin_window)
+ * @path: (out) (allow-none): A pointer to a #GtkTreePath pointer to be filled in, or %NULL
+ * @column: (out) (allow-none): A pointer to a #GtkTreeViewColumn pointer to be filled in, or %NULL
+ * @cell_x: (out) (allow-none): A pointer where the X coordinate relative to the cell can be placed, or %NULL
+ * @cell_y: (out) (allow-none): A pointer where the Y coordinate relative to the cell can be placed, or %NULL
+ *
+ * Determine whether the point (@x, @y) in @tree_view is blank, that is no
+ * cell content nor an expander arrow is drawn at the location. If so, the
+ * location can be considered as the background. You might wish to take
+ * special action on clicks on the background, such as clearing a current
+ * selection, having a custom context menu or starting rubber banding.
+ *
+ * The @x and @y coordinate that are provided must be relative to bin_window
+ * coordinates.  That is, @x and @y must come from an event on @tree_view
+ * where <literal>event->window == gtk_tree_view_get_bin_window (<!-- -->)</literal>.
+ *
+ * For converting widget coordinates (eg. the ones you get from
+ * GtkWidget::query-tooltip), please see
+ * gtk_tree_view_convert_widget_to_bin_window_coords().
+ *
+ * The @path, @column, @cell_x and @cell_y arguments will be filled in
+ * likewise as for gtk_tree_view_get_path_at_pos().  Please see
+ * gtk_tree_view_get_path_at_pos() for more information.
+ *
+ * Return value: %TRUE if the area at the given coordinates is blank,
+ * %FALSE otherwise.
+ *
+ * Since: 3.0
+ */
+gboolean
+gtk_tree_view_is_blank_at_pos (GtkTreeView       *tree_view,
+                               gint                x,
+                               gint                y,
+                               GtkTreePath       **path,
+                               GtkTreeViewColumn **column,
+                               gint               *cell_x,
+                               gint               *cell_y)
+{
+  GtkRBTree *tree;
+  GtkRBNode *node;
+  GtkTreeIter iter;
+  GtkTreePath *real_path;
+  GtkTreeViewColumn *real_column;
+  GdkRectangle cell_area, background_area;
+
+  g_return_val_if_fail (GTK_IS_TREE_VIEW (tree_view), FALSE);
+
+  if (!gtk_tree_view_get_path_at_pos (tree_view, x, y,
+                                      &real_path, &real_column,
+                                      cell_x, cell_y))
+    /* If there's no path here, it is blank */
+    return TRUE;
+
+  if (path)
+    *path = real_path;
+
+  if (column)
+    *column = real_column;
+
+  gtk_tree_model_get_iter (tree_view->priv->model, &iter, real_path);
+  _gtk_tree_view_find_node (tree_view, real_path, &tree, &node);
+
+  /* Check if there's an expander arrow at (x, y) */
+  if (real_column == tree_view->priv->expander_column
+      && gtk_tree_view_draw_expanders (tree_view))
+    {
+      gboolean over_arrow;
+
+      over_arrow = coords_are_over_arrow (tree_view, tree, node, x, y);
+
+      if (over_arrow)
+        {
+          if (!path)
+            gtk_tree_path_free (real_path);
+          return FALSE;
+        }
+    }
+
+  /* Otherwise, have the column see if there's a cell at (x, y) */
+  gtk_tree_view_column_cell_set_cell_data (real_column,
+                                           tree_view->priv->model,
+                                           &iter,
+                                           GTK_RBNODE_FLAG_SET (node, GTK_RBNODE_IS_PARENT),
+                                           node->children ? TRUE : FALSE);
+
+  gtk_tree_view_get_background_area (tree_view, real_path, real_column,
+                                     &background_area);
+  gtk_tree_view_get_cell_area (tree_view, real_path, real_column,
+                               &cell_area);
+
+  if (!path)
+    gtk_tree_path_free (real_path);
+
+  return _gtk_tree_view_column_is_blank_at_pos (real_column,
+                                                &cell_area,
+                                                &background_area,
+                                                x, y);
+}
+
 static void
 unset_reorderable (GtkTreeView *tree_view)
 {