[pitivi] project_: Interact directly with the proxy manager

[Alexandru Băluț <alexbalut src gnome org>]

commit 6cc0e1dfc2138dbaa816b3aa1ffa0dd5a1669732
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Tue Dec 20 00:59:42 2016 +0100

    project_: Interact directly with the proxy manager
    
    This is preparatory work. The same call will be needed when redoing an
    asset proxying operation. This avoids the duplication of the logic which
    removes and adds an asset from the project just to start proxy
    generation.
    
    Reviewed-by: Thibault Saunier <tsaunier gnome org>
    Differential Revision: https://phabricator.freedesktop.org/D1567

 pitivi/project.py |   19 +++++++++++--------
 1 files changed, 11 insertions(+), 8 deletions(-)
---
diff --git a/pitivi/project.py b/pitivi/project.py
index ad72653..38f9db3 100644
--- a/pitivi/project.py
+++ b/pitivi/project.py
@@ -1063,15 +1063,19 @@ class Project(Loggable, GES.Project):
             # Ignore for example the assets producing GES.TitleClips.
             return
 
-        if not self.loading_assets:
-            # Progress == 0 means "starting to import"
-            self.emit("asset-loading-progress", 0, 0)
+        self._prepare_asset_processing(asset)
 
+    def _prepare_asset_processing(self, asset):
         asset.creation_progress = 0
         asset.error = None
         asset.ready = False
         asset.force_proxying = False
         asset.proxying_error = None
+
+        if not self.loading_assets:
+            # Progress == 0 means "starting to import"
+            self.emit("asset-loading-progress", 0, 0)
+
         self.loading_assets.append(asset)
 
     def do_asset_removed(self, asset):
@@ -1184,19 +1188,18 @@ class Project(Loggable, GES.Project):
         if originals:
             self.app.action_log.begin("Adding assets")
             for asset in originals:
-                # Add and remove the asset to
-                # trigger the proxy creation code path
-                self.remove_asset(asset)
-                self.emit("asset-loading", asset)
+                self._prepare_asset_processing(asset)
                 asset.force_proxying = True
-                self.add_asset(asset)
+                self.app.proxy_manager.add_job(asset)
 
     def disableProxiesForAssets(self, assets, delete_proxy_file=False):
         for asset in assets:
             proxy_target = asset.get_proxy_target()
             if proxy_target:
+                # The asset is a proxy for the proxy_target original asset.
                 self.debug("Stop proxying %s", proxy_target.props.id)
                 proxy_target.set_proxy(None)
+                proxy_target.force_proxying = False
                 if delete_proxy_file:
                     if not self.app.proxy_manager.is_proxy_asset(asset):
                         raise RuntimeError("Trying to remove proxy %s"