Add background processing (redux)

Author: siddhantwahal

stage7.1_background_proc/pycasa/model/image_folder.py

@@ -7,7 +7,10 @@
 
 # ETS imports
 from traits.api import (
-    Directory, Event, HasStrictTraits, Instance, List, observe,
+    Bool, Directory, Event, HasStrictTraits, Instance, List, observe, Property
+)
+from traits_futures.api import (
+    CallFuture, submit_call, TraitsExecutor
 )
 
 # Local imports
@@ -28,6 +31,12 @@ class ImageFolder(HasStrictTraits):
 
     data_updated = Event
 
+    traits_executor = Instance(TraitsExecutor)
+
+    future = Instance(CallFuture)
+
+    executor_idle = Property(Bool, depends_on="future.done")
+
     def __init__(self, **traits):
         # Don't forget this!
         super(ImageFolder, self).__init__(**traits)
@@ -62,8 +71,25 @@ def _create_metadata_df(self):
                 for img in self.images
         ])
 
-    def compute_num_faces(self, **kwargs):
-        for i, image in enumerate(self.images):
-            faces = image.detect_faces(**kwargs)
-            self.data[NUM_FACE_COL].iat[i] = len(faces)
-            self.data_updated = True
+    def compute_num_faces_background(self, **kwargs):
+        self.future = submit_call(
+            self.traits_executor,
+            self._compute_num_faces,
+            **kwargs
+        )
+
+    def _compute_num_faces(self, **kwargs):
+        return [
+            len(img_file.detect_faces(**kwargs))
+            for img_file in self.images
+        ]
+
+    @observe("future:done")
+    def _update_data(self, event):
+        num_faces_all_images = self.future.result
+        for idx, num_faces in enumerate(num_faces_all_images):
+            self.data[NUM_FACE_COL].iat[idx] = num_faces
+        self.data_updated = True
+
+    def _get_executor_idle(self):
+        return self.future is None or self.future.done

stage7.1_background_proc/pycasa/ui/image_folder_view.py

@@ -68,8 +68,7 @@ def traits_view(self):
                 visible_when="view_filter_controls",
             ),
             Item("filtered_data",
-                 editor=DataFrameEditor(columns=DISPLAYED_COLUMNS,
-                                        update="data_updated"),
+                 editor=DataFrameEditor(columns=DISPLAYED_COLUMNS),
                  show_label=False, visible_when="len(model.data) > 0"),
             HGroup(
                 Spring(),
@@ -79,8 +78,11 @@ def traits_view(self):
             ),
             HGroup(
                 Spring(),
-                Item("scan", show_label=False,
-                     enabled_when="len(model.data) > 0"),
+                Item(
+                    "scan",
+                    show_label=False,
+                    enabled_when="len(model.data) > 0 and model.executor_idle"
+                ),
                 Spring(),
             ),
         )
@@ -90,8 +92,12 @@ def traits_view(self):
 
     @observe("scan")
     def scan_for_faces(self, event):
-        self.model.compute_num_faces()
+        self.model.compute_num_faces_background()
+
+    @observe("model:data_updated")
+    def _update_all_data(self, event):
         self.all_data.update(self.model.data)
+        self.update_filtered_data(None)
 
     @observe("selected_years")
     def update_years(self, event):

stage7.1_background_proc/pycasa/ui/tasks/pycasa_task.py

@@ -3,6 +3,7 @@
 
 # ETS imports
 from traits.api import Instance
+from traits_futures.api import TraitsExecutor
 from pyface.api import error, ImageResource
 from pyface.action.api import StatusBarManager
 from pyface.tasks.api import PaneItem, SplitEditorAreaPane, Task, TaskLayout
@@ -27,6 +28,9 @@ class PycasaTask(Task):
     #: The human-readable name of the task.
     name = "Pycasa"
 
+    #: An executor for background tasks
+    traits_executor = Instance(TraitsExecutor, ())
+
     central_pane = Instance(SplitEditorAreaPane)
 
     # Task interface ----------------------------------------------------------
@@ -57,14 +61,21 @@ def open_in_central_pane(self, filepath):
             obj = ImageFile(filepath=filepath)
             self.central_pane.edit(obj, factory=ImageFileEditor)
         elif file_ext == "":
-            obj = ImageFolder(directory=filepath)
+            obj = ImageFolder(
+                directory=filepath,
+                traits_executor=self.traits_executor
+            )
             self.central_pane.edit(obj, factory=ImageFolderEditor)
         else:
             print("Unsupported file format: {}".format(file_ext))
             obj = None
 
         return obj
 
+    def prepare_destroy(self):
+        self.traits_executor.shutdown()
+        return super().prepare_destroy()
+
     # Menu action methods -----------------------------------------------------
 
     def request_open_new_path(self):