Camera tracking: made some options more easy to understand

- Changed some names so now people who aren't really familiar with
  motion tracking can understand what they exactly means
- Also cleaned up and rephraded some descriptions
- Changed behavior of operator which creates empty for 2d tracks:
  now it operates on all selected tracks rather than active track only
- Added checkbox to enable/disable rotation stabilization

release/scripts/startup/bl_operators/clip.py

@@ -24,27 +24,27 @@ from bpy.types import Operator
 from bpy_extras.io_utils import unpack_list
 
 
+def CLIP_track_view_selected(sc, track):
+    if track.select_anchor:
+        return True
+
+    if sc.show_marker_pattern and track.select_pattern:
+        return True
+
+    if sc.show_marker_search and track.select_search:
+        return True
+
+    return False
+
 class CLIP_OT_track_to_empty(Operator):
     """Create an Empty object which will be copying movement of active track"""
 
     bl_idname = "clip.track_to_empty"
-    bl_label = "2D Track to Empty"
+    bl_label = "Link Empty to Track"
     bl_options = {'UNDO', 'REGISTER'}
 
-    @classmethod
-    def poll(cls, context):
-        if context.space_data.type != 'CLIP_EDITOR':
-            return False
-
+    def _link_track(self, context, track):
         sc = context.space_data
-        clip = sc.clip
-
-        return clip and clip.tracking.tracks.active
-
-    def execute(self, context):
-        sc = context.space_data
-        clip = sc.clip
-        track = clip.tracking.tracks.active
         constraint = None
         ob = None
 
@@ -65,6 +65,14 @@ class CLIP_OT_track_to_empty(Operator):
         constraint.track = track.name
         constraint.use_3d_position = False
 
+    def execute(self, context):
+        sc = context.space_data
+        clip = sc.clip
+
+        for track in clip.tracking.tracks:
+            if CLIP_track_view_selected(sc, track):
+                self._link_track(context, track)
+
         return {'FINISHED'}
 
 
@@ -179,7 +187,7 @@ class CLIP_OT_delete_proxy(Operator):
 
 
 class CLIP_OT_set_viewport_background(Operator):
-    """Set current movie clip as a camera background in 3D viewport"""
+    """Set current movie clip as a camera background in 3D viewport (works only when a 3D viewport is visible)"""
 
     bl_idname = "clip.set_viewport_background"
     bl_label = "Set as Background"