Coalesce visual changes to canvas/items and allow canvas to render

First visual change will be processed as normal and then blocked until the
canvas renders the change. If further visual changes need processing then
Editor::pre_render callback will schedule another expose/redraw/render.

This prevents an issue where idle_visual_changer is called many times in
response to events(keys/motion/etc) but the canvas does not get a chance to
render any but the last one which results in a big pause/jump.

This results in a more responsive canvas and in particular a smoother and more
predictable zooming experience.

diff --git a/gtk2_ardour/editor.cc b/gtk2_ardour/editor.cc
index 248c4713fe99adf50e658e0f9fbd091e5c5e40c2..37e55aded040b106ae37dea2e54f4464f659dd23 100644 (file)
--- a/gtk2_ardour/editor.cc
+++ b/gtk2_ardour/editor.cc
@@ -345,6 +345,7 @@ Editor::Editor ()
        , _full_canvas_height (0)
        , edit_controls_left_menu (0)
        , edit_controls_right_menu (0)
+       , visual_change_queued(false)
        , _last_update_time (0)
        , _err_screen_engine (0)
        , cut_buffer_start (0)
@@ -4578,9 +4579,23 @@ Editor::_idle_visual_changer (void* arg)
        return static_cast<Editor*>(arg)->idle_visual_changer ();
 }
 
+void
+Editor::pre_render ()
+{
+       visual_change_queued = false;
+
+       if (pending_visual_change.pending != 0) {
+               ensure_visual_change_idle_handler();
+       }
+}
+
 int
 Editor::idle_visual_changer ()
 {
+       if (pending_visual_change.pending == 0) {
+               return 0;
+       }
+
        /* set_horizontal_position() below (and maybe other calls) call
           gtk_main_iteration(), so it's possible that a signal will be handled
           half-way through this method.  If this signal wants an
@@ -4592,6 +4607,11 @@ Editor::idle_visual_changer ()
        */
 
        pending_visual_change.idle_handler_id = -1;
+
+       if (visual_change_queued) {
+               return 0;
+       }
+
        pending_visual_change.being_handled = true;
 
        VisualChange vc = pending_visual_change;
@@ -4602,6 +4622,8 @@ Editor::idle_visual_changer ()
 
        pending_visual_change.being_handled = false;
 
+       visual_change_queued = true;
+
        return 0; /* this is always a one-shot call */
 }
 

diff --git a/gtk2_ardour/editor.h b/gtk2_ardour/editor.h
index 60bf93494d83e5f5d7f3e2f47ef737b78f9f7e8f..bce6caa912f9ae9072fb5416a5f6b289ce919c96 100644 (file)
--- a/gtk2_ardour/editor.h
+++ b/gtk2_ardour/editor.h
@@ -1148,6 +1148,9 @@ private:
        };
 
        VisualChange pending_visual_change;
+       bool visual_change_queued;
+
+       void pre_render ();
 
        static int _idle_visual_changer (void *arg);
        int idle_visual_changer ();

diff --git a/gtk2_ardour/editor_canvas.cc b/gtk2_ardour/editor_canvas.cc
index 72d0c2b0632cde721ade62394885f8e229fd1ad7..3b38f12df04b5b5602952ef798adf4dc2662e4b8 100644 (file)
--- a/gtk2_ardour/editor_canvas.cc
+++ b/gtk2_ardour/editor_canvas.cc
@@ -241,6 +241,8 @@ Editor::initialize_canvas ()
        _track_canvas->signal_enter_notify_event().connect (sigc::mem_fun(*this, &Editor::entered_track_canvas), false);
        _track_canvas->set_flags (CAN_FOCUS);
 
+       _track_canvas->PreRender.connect (sigc::mem_fun(*this, &Editor::pre_render));
+
        /* set up drag-n-drop */
 
        vector<TargetEntry> target_table;