improve video generation

Speed up by removing Python threading and solely using the signals
emitted by gtkfractal.

Clarify that a video is made up of keyframes and transitions
consisting of a number of frames defined by the duration parameter.
By default the keyframe is shown for one frame but this is
configurable using the stopped parameter.

doc/gnofract4d-manual/C/gnofract4d-manual.xml

@@ -336,15 +336,15 @@ are. </para></listitem>
 <title>Director</title>
 <para>
 
-The <emphasis>Director</emphasis> allows you to create fractal movies.
-You first define keyframes (including base keyframes) which are stops
-in video.  Then, for each of them, you define for how long they last
-(<guilabel>duration</guilabel> - in frames), how long still image of
-keyframe will stay in video (<guilabel>stopped for</guilabel>) and
-interpolation type between several possibilities. When you hit
-<guibutton>Render</guibutton> button, Director will render all frames
-and put them in directory you selected and then it will try to create
-a video using <ulink url="https://www.ffmpeg.org/">
+The <emphasis>Director</emphasis> allows you to create fractal videos.
+You first define keyframes which are points in the video.
+Then, for each of them, you specify how long a still image of the keyframe will
+stay in the video (<guilabel>stopped for</guilabel>), how long the transition
+is to the next keyframe (<guilabel>transition duration</guilabel> - in frames)
+and the interpolation type used for the transition from several possibilities.
+When you hit <guibutton>Render</guibutton> button, Director will render all
+frames and put them in the directory you selected and then it will create
+the video using <ulink url="https://www.ffmpeg.org/">
 <emphasis>FFmpeg</emphasis></ulink>.</para>
 
 <para>

fract4d/animation.py

@@ -258,14 +258,15 @@ def get_mu(self, int_type, x):
     # create a list containing all the filenames of the frames
     def create_list(self):
         framelist = []
-        current = 1
+        current = 0
         for i in range(self.keyframes_count()):
             for j in range(self.get_keyframe_stop(i)):  # output keyframe 'stop' times
-                framelist.append(self.get_image_filename(current-1))
+                framelist.append(self.get_image_filename(current))
+            current += 1
 
-            if i < self.keyframes_count()-1:
-                # final frame has no transitions following it
-                for j in range(self.get_keyframe_duration(i)):  # output all transition files
+            if i < self.keyframes_count() - 1:
+                # skip final frame which has no transitions following it
+                for j in range(self.get_keyframe_duration(i)):  # output all transition files minus keyframe
                     framelist.append(self.get_image_filename(current))
                     current += 1
 

fract4d/test_animation.py

@@ -132,7 +132,7 @@ def testCreateList(self):
         # then a sequence of 10 changing frames
         self.assertEqual([os.path.join(Test.tmpdir.name, "image_%07d.png") % n for n in range(1,11)], list[4:14])
         # then 3 more unchanging frames
-        self.assertEqual([os.path.join(Test.tmpdir.name, "image_0000010.png")] * 3, list[14:17])
+        self.assertEqual([os.path.join(Test.tmpdir.name, "image_0000011.png")] * 3, list[14:17])
 
     def testFilenames(self):
         self.assertEqual(