[pitivi] timeline: Disable previewers while removing clips

[Thibault Saunier <tsaunier src gnome org>]

commit 22e9418769c2e134cf072e202344d2fd91719378
Author: Thibault Saunier <tsaunier gnome org>
Date:   Tue Nov 7 16:58:19 2017 -0300

    timeline: Disable previewers while removing clips
    
    Without that we will go crazy about starting/stoping preview generation
    while removing clips.
    
    Reviewed-by: Alex Băluț <<alexandru balut gmail com>>
    Differential Revision: https://phabricator.freedesktop.org/D1877

 pitivi/timeline/previewers.py |   26 +++++++++++++------
 pitivi/timeline/timeline.py   |   56 ++++++++++++++++++++--------------------
 2 files changed, 46 insertions(+), 36 deletions(-)
---
diff --git a/pitivi/timeline/previewers.py b/pitivi/timeline/previewers.py
index b40f7f7..26ab468 100644
--- a/pitivi/timeline/previewers.py
+++ b/pitivi/timeline/previewers.py
@@ -17,6 +17,7 @@
 # Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
 # Boston, MA 02110-1301, USA.
 """Previewers for the timeline."""
+import contextlib
 import os
 import random
 import sqlite3
@@ -330,10 +331,10 @@ class PreviewGeneratorManager():
         previewer.connect("done", self.__previewer_done_cb)
         previewer.startGeneration()
 
-    def start_flushing(self):
-        """Flushes all previewers and start ignoring any update."""
-        if self._running:
-            self._running = False
+    @contextlib.contextmanager
+    def paused(self, interrupt=False):
+        """Pauses (and flushes if interrupt=True) managed previewers."""
+        if interrupt:
             for previewer in list(self._current_previewers.values()):
                 previewer.stopGeneration()
 
@@ -341,12 +342,21 @@ class PreviewGeneratorManager():
                 for previewer in previewers:
                     previewer.stopGeneration()
 
-    def stop_flushing(self):
-        """Stop ignoring managed previewers updates."""
-        self._running = True
+        try:
+            self._running = False
+            yield
+        except:
+            self.warning("An exception occurred while the previewer was paused")
+            raise
+        finally:
+            self._running = True
+            for track_type in self._previewers:
+                self.__start_next_previewer(track_type)
 
     def __previewer_done_cb(self, previewer):
-        track_type = previewer.track_type
+        self.__start_next_previewer(previewer.track_type)
+
+    def __start_next_previewer(self, track_type):
         next_previewer = self._current_previewers.pop(track_type, None)
         if next_previewer:
             next_previewer.disconnect_by_func(self.__previewer_done_cb)
diff --git a/pitivi/timeline/timeline.py b/pitivi/timeline/timeline.py
index 9cf0064..3407f45 100644
--- a/pitivi/timeline/timeline.py
+++ b/pitivi/timeline/timeline.py
@@ -439,26 +439,25 @@ class Timeline(Gtk.EventBox, Zoomable, Loggable):
     def setProject(self, project):
         """Connects to the GES.Timeline holding the project."""
         # Avoid starting/closing preview generation like crazy while tearing down project
-        Previewer.manager.start_flushing()
-        if self.ges_timeline is not None:
-            self.disconnect_by_func(self._button_press_event_cb)
-            self.disconnect_by_func(self._button_release_event_cb)
-            self.disconnect_by_func(self._motion_notify_event_cb)
-
-            self.ges_timeline.disconnect_by_func(self._durationChangedCb)
-            self.ges_timeline.disconnect_by_func(self._layer_added_cb)
-            self.ges_timeline.disconnect_by_func(self._layer_removed_cb)
-            self.ges_timeline.disconnect_by_func(self._snapCb)
-            self.ges_timeline.disconnect_by_func(self._snapEndedCb)
-            for ges_layer in self.ges_timeline.get_layers():
-                self._remove_layer(ges_layer)
-
-            self.ges_timeline.ui = None
-            self.ges_timeline = None
-
-        if self._project:
-            self._project.pipeline.disconnect_by_func(self._positionCb)
-        Previewer.manager.stop_flushing()
+        with Previewer.manager.paused(True):
+            if self.ges_timeline is not None:
+                self.disconnect_by_func(self._button_press_event_cb)
+                self.disconnect_by_func(self._button_release_event_cb)
+                self.disconnect_by_func(self._motion_notify_event_cb)
+
+                self.ges_timeline.disconnect_by_func(self._durationChangedCb)
+                self.ges_timeline.disconnect_by_func(self._layer_added_cb)
+                self.ges_timeline.disconnect_by_func(self._layer_removed_cb)
+                self.ges_timeline.disconnect_by_func(self._snapCb)
+                self.ges_timeline.disconnect_by_func(self._snapEndedCb)
+                for ges_layer in self.ges_timeline.get_layers():
+                    self._remove_layer(ges_layer)
+
+                self.ges_timeline.ui = None
+                self.ges_timeline = None
+
+            if self._project:
+                self._project.pipeline.disconnect_by_func(self._positionCb)
 
         self._project = project
         if self._project:
@@ -1631,14 +1630,15 @@ class TimelineContainer(Gtk.Grid, Zoomable, Loggable):
 
     def _deleteSelected(self, unused_action, unused_parameter):
         if self.ges_timeline:
-            with self.app.action_log.started("delete clip",
-                                             
finalizing_action=CommitTimelineFinalizingAction(self._project.pipeline),
-                                             toplevel=True):
-                for clip in self.timeline.selection:
-                    layer = clip.get_layer()
-                    if isinstance(clip, GES.TransitionClip):
-                        continue
-                    layer.remove_clip(clip)
+            with Previewer.manager.paused():
+                with self.app.action_log.started("delete clip",
+                                                
finalizing_action=CommitTimelineFinalizingAction(self._project.pipeline),
+                                                toplevel=True):
+                    for clip in self.timeline.selection:
+                        layer = clip.get_layer()
+                        if isinstance(clip, GES.TransitionClip):
+                            continue
+                        layer.remove_clip(clip)
 
             self.timeline.selection.setSelection([], SELECT)