Tree View Scrolling

[Eric Pastoor <epastoor vt edu>]

I am trying to get a GtkTree to show all of the children if possible  
when the user expands the parent.  This is my callback routine on the  
row-expanded signal. The technique I thought I would use is to first  
scroll the tree to the last row. Then scroll it back to the parent.  
This would make sure that the parent is always visible and at least  
at the top.


The gtk_tree_view_scroll_to_cell has an alignment boolean that seems  
to make the change. However, I am getting a repainting effect when no  
scrolling movement is necessary because everything is displayed.    
Does anyone have a method to do this.  When I tried using both of my  
scroll for false on the alignment, nothing changed.   The second  
scroll back to the parent has to be true for any scrolling to take  
place, but this is also what causes the screen to flash.


        GtkTreeStore* treeStore = ftw->getGtkTreeStore();
        GtkTreeModel* treeModel = GTK_TREE_MODEL(treeStore);
        GtkTreeView*  treeView  = GTK_TREE_VIEW(ftw->getGtkTreeView());

        GtkTreePath* iterPath =
                gtk_tree_model_get_path(treeModel, startIter);
        bool isRowExpanded = gtk_tree_view_row_expanded(treeView, iterPath);
        gtk_tree_path_free(iterPath);

        // This row should have been expanded already.
        FATAL_ERROR_IF (NOT isRowExpanded);

        bool iterHasChild = gtk_tree_model_iter_has_child(treeModel,
                                                          startIter);
        if (iterHasChild)
        {
		int numChildren = gtk_tree_model_iter_n_children(treeModel,  
startIter);
                FATAL_ERROR_IF (numChildren <= 0);

                GtkTreeIter iter;
                bool valid =
                        gtk_tree_model_iter_nth_child(treeModel,
                                                      &iter,
                                                      startIter,
                                                      numChildren-1);

		// valid is false when numChildren is too big, or startIter has no  
children.
                FATAL_ERROR_IF (NOT valid);

                // Scroll to the last child to get it visible
                iterPath = gtk_tree_model_get_path(treeModel, &iter);
                gtk_tree_view_scroll_to_cell(treeView,
                                             iterPath,
                                             NULL,
                                             false, // do not use align
                                             0,     // row align is ignored
                                             0);    // col align is ignored
                gtk_tree_path_free(iterPath);

		// Now scroll to the parent where we started. The effect of this is  
to try
		// to show the last child if possible while being able to see the  
parent at
                // the top.
                iterPath = gtk_tree_model_get_path(treeModel, startIter);
                gtk_tree_view_scroll_to_cell(treeView,
                                             iterPath,
                                             NULL,
                                             true, // use align or these 2 scrolls cancel out
                                             0,    // row align is ignored
                                             0.0); // col align is ignored
                gtk_tree_path_free(iterPath);
        }

Thanks for any help.
Eric