[pitivi] timeline: Show vertical scrollbar only when needed

[Alexandru Băluț <alexbalut src gnome org>]

commit beb3cce31305f3a66d2ae1fe6031fb6f4d4cf871
Author: Harish Fulara <harish14143 iiitd ac in>
Date:   Sun Mar 18 03:05:01 2018 +0530

    timeline: Show vertical scrollbar only when needed
    
    Fixes #1811

 pitivi/timeline/timeline.py | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)
---
diff --git a/pitivi/timeline/timeline.py b/pitivi/timeline/timeline.py
index c92ce538..1ef1fbfa 100644
--- a/pitivi/timeline/timeline.py
+++ b/pitivi/timeline/timeline.py
@@ -1353,6 +1353,7 @@ class TimelineContainer(Gtk.Grid, Zoomable, Loggable):
 
         self.app.project_manager.connect("new-project-loaded",
                                          self._projectLoadedCb)
+        self.timeline.connect("size-allocate", self.__timeline_size_allocate_cb)
 
     # Public API
 
@@ -1499,9 +1500,11 @@ class TimelineContainer(Gtk.Grid, Zoomable, Loggable):
 
         self.timeline = Timeline(self.app, left_size_group)
 
-        vscrollbar = Gtk.Scrollbar(orientation=Gtk.Orientation.VERTICAL,
-                                   adjustment=self.timeline.vadj)
-        vscrollbar.get_style_context().add_class("background")
+        # Vertical Scrollbar. It will be displayed only when needed.
+        self.vscrollbar = Gtk.Scrollbar(orientation=Gtk.Orientation.VERTICAL,
+                                        adjustment=self.timeline.vadj)
+        self.vscrollbar.get_style_context().add_class("background")
+
         hscrollbar = Gtk.Scrollbar(orientation=Gtk.Orientation.HORIZONTAL,
                                    adjustment=self.timeline.hadj)
         hscrollbar.get_style_context().add_class("background")
@@ -1522,7 +1525,7 @@ class TimelineContainer(Gtk.Grid, Zoomable, Loggable):
         self.attach(zoom_box, 0, 0, 1, 1)
         self.attach(self.ruler, 1, 0, 1, 1)
         self.attach(self.timeline, 0, 1, 2, 1)
-        self.attach(vscrollbar, 2, 1, 1, 1)
+        self.attach(self.vscrollbar, 2, 1, 1, 1)
         self.attach(hscrollbar, 1, 2, 1, 1)
         self.attach(self.toolbar, 3, 1, 1, 1)
 
@@ -1946,6 +1949,10 @@ class TimelineContainer(Gtk.Grid, Zoomable, Loggable):
         self._framerate = videorate
         self.ruler.setProjectFrameRate(self._framerate)
 
+    def __timeline_size_allocate_cb(self, unused_widget, allocation):
+        fits = self.timeline.layout.props.height <= allocation.height
+        self.vscrollbar.set_opacity(0 if fits else 1)
+
     def _projectLoadedCb(self, unused_project_manager, project):
         """Connects to the project's timeline and pipeline."""
         if self._project: