Treeview Drag: allow to use single column as drag-widget

1 files changed, 64 insertions, 0 deletions

diff --git a/libs/gtkmm2ext/dndtreeview.cc b/libs/gtkmm2ext/dndtreeview.cc
index 53b212d711..be53482603 100644
--- a/libs/gtkmm2ext/dndtreeview.cc
+++ b/libs/gtkmm2ext/dndtreeview.cc
@@ -33,6 +33,7 @@ DnDTreeViewBase::DragData DnDTreeViewBase::drag_data;
 
 DnDTreeViewBase::DnDTreeViewBase ()
 	: TreeView ()
+	, _drag_column (-1)
 {
 	draggable.push_back (TargetEntry ("GTK_TREE_MODEL_ROW", TARGET_SAME_WIDGET));
 	data_column = -1;
@@ -44,6 +45,69 @@ DnDTreeViewBase::DnDTreeViewBase ()
 }
 
 void
+DnDTreeViewBase::on_drag_begin (Glib::RefPtr<Gdk::DragContext> const & context) {
+	if (_drag_column >= 0) {
+		/* this code is a customized drop-in replacement for
+		 * Gtk::TreeView::on_drag_begin().
+		 * We can use it's cleanup function for the generated Pixmap
+		 */
+
+		TreeModel::Path path;
+		TreeViewColumn* column;
+		int cell_x;
+		int cell_y;
+
+		if (!get_path_at_pos ((int)press_start_x, (int)press_start_y, path, column, cell_x, cell_y)) {
+			return;
+		}
+
+		TreeIter iter = get_model()->get_iter (path);
+		int x_offset, y_offset, width, height;
+
+		Gdk::Rectangle unused;
+		TreeViewColumn* clm = get_column(_drag_column);
+
+		clm->cell_set_cell_data (get_model(), iter, false, false);
+		clm->cell_get_size (unused, x_offset, y_offset, width, height);
+
+		Glib::RefPtr<Gdk::Pixmap> pixmap = Gdk::Pixmap::create (get_root_window(), width, height);
+
+		CellRenderer* cell_renderer = clm->get_first_cell ();
+		Gdk::Rectangle cell_background (0, 0, width, height);
+		Gdk::Rectangle cell_size (x_offset, y_offset, width, height);
+
+		// the cell-renderer only clears the background if
+		// cell->cell_background_set and priv->cell_background
+		Gdk::Color clr = get_style()->get_bg(STATE_NORMAL);
+		// code dup from gtk_cell_renderer_render() to clear the background:
+		cairo_t *cr = gdk_cairo_create (Glib::unwrap(pixmap));
+		gdk_cairo_rectangle (cr, (cell_background).gobj());
+		gdk_cairo_set_source_color (cr, clr.gobj());
+		cairo_fill (cr);
+		cairo_destroy (cr);
+
+		// gtkmm wants a "window", gtk itself is happy with a "drawable",
+		// cell_renderer->render (pixmap, *this, cell_area, cell_area, cell_area, 0);
+		// We ain't got no window, so use gtk directly:
+		gtk_cell_renderer_render (cell_renderer->gobj(),
+				Glib::unwrap(pixmap), ((Gtk::Widget*)this)->gobj(),
+				(cell_background).gobj(),
+				(cell_size).gobj(),
+				(cell_size).gobj(),
+				((GtkCellRendererState)(0)));
+
+		context->set_icon (pixmap->get_colormap(),
+				pixmap, Glib::RefPtr<Gdk::Bitmap>(NULL),
+				width / 2 + 1, cell_y + 1);
+
+	} else {
+		Gtk::TreeView::on_drag_begin (context);
+	}
+	start_object_drag ();
+}
+
+
+void
 DnDTreeViewBase::add_drop_targets (list<TargetEntry>& targets)
 {
 	for (list<TargetEntry>::iterator i = targets.begin(); i != targets.end(); ++i) {