[pitivi] elements: Lazy create the KeyFrame curves

[Thibault Saunier <tsaunier src gnome org>]

commit 536e99c73aa9cda5cbbc2e6eeabcdd9ebb6d8dfd
Author: Thibault Saunier <tsaunier gnome org>
Date:   Wed Aug 9 10:58:02 2017 -0400

    elements: Lazy create the KeyFrame curves
    
    Creating the UI representation of the keyframe is expensive (on big
    projects it can take several seconds to create them - 25s for the
    project provided in T7793).
    
    We do not need to create them when creating the clip UI but only once
    the clip is selected, so make sure to create them until actually
    requred.
    
    Fixes T7793
    
    Reviewed-by: Alex Băluț <<alexandru balut gmail com>>
    Differential Revision: https://phabricator.freedesktop.org/D1823

 pitivi/timeline/elements.py |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)
---
diff --git a/pitivi/timeline/elements.py b/pitivi/timeline/elements.py
index a34dcea..6b976d4 100644
--- a/pitivi/timeline/elements.py
+++ b/pitivi/timeline/elements.py
@@ -506,7 +506,8 @@ class TimelineElement(Gtk.Layout, Zoomable, Loggable):
         self.keyframe_curve = None
 
     # Private methods
-    def __createKeyframeCurve(self, binding):
+    def __ensure_keyframes(self, binding):
+        """Ensures that we have at least 2 keyframes (at inpoint and end)."""
         source = binding.props.control_source
         values = source.get_all()
 
@@ -519,7 +520,10 @@ class TimelineElement(Gtk.Layout, Zoomable, Loggable):
             assert source.set(inpoint, val)
             assert source.set(inpoint + self._ges_elem.props.duration, val)
 
+    def __create_keyframe_curve(self):
+        """Creates required keyframe curve."""
         self.__removeKeyframes()
+        binding = self._ges_elem.get_control_binding(self.__controlledProperty.name)
         self.keyframe_curve = KeyframeCurve(self.timeline, binding)
         self.keyframe_curve.connect("enter", self.__curveEnterCb)
         self.keyframe_curve.connect("leave", self.__curveLeaveCb)
@@ -528,6 +532,7 @@ class TimelineElement(Gtk.Layout, Zoomable, Loggable):
         self.__update_keyframe_curve_visibility()
 
     def __createControlBinding(self, element):
+        """Creates the required ControlBinding and keyframes."""
         if self.__controlledProperty:
             element.connect("control-binding-added",
                             self.__controlBindingAddedCb)
@@ -535,7 +540,7 @@ class TimelineElement(Gtk.Layout, Zoomable, Loggable):
                 element.get_control_binding(self.__controlledProperty.name)
 
             if binding:
-                self.__createKeyframeCurve(binding)
+                self.__ensure_keyframes(binding)
 
                 return
 
@@ -546,7 +551,7 @@ class TimelineElement(Gtk.Layout, Zoomable, Loggable):
 
     def __controlBindingAddedCb(self, unused_ges_elem, binding):
         if binding.props.name == self.__controlledProperty.name:
-            self.__createKeyframeCurve(binding)
+            self.__ensure_keyframes(binding)
 
     def do_draw(self, cr):
         self.propagate_draw(self.__background, cr)
@@ -561,6 +566,9 @@ class TimelineElement(Gtk.Layout, Zoomable, Loggable):
 
     # Callbacks
     def __selectedChangedCb(self, unused_selected, selected):
+        if not self.keyframe_curve and self.__controlledProperty:
+            self.__create_keyframe_curve()
+
         if self.keyframe_curve:
             self.__update_keyframe_curve_visibility()