scanner: Create a custom ProgressBar widget

For use tracking the progress we make through the TaskQueue

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

scanner/__init__.py

@@ -2,3 +2,4 @@
 from . import metadata
 from . import queue
 from . import task
+from . import widgets

scanner/test_widgets.py

@@ -0,0 +1,28 @@
+# Copyright 2021 (c) Anna Schumaker.
+import unittest
+from gi.repository import Gtk
+from . import queue
+from . import task
+from . import widgets
+
+class FakeTask(task.Task):
+    def run_task(self): return None
+
+class TestScannerProgressBar(unittest.TestCase):
+    def test_progress_bar(self):
+        q  = queue.TaskQueue()
+        pb = widgets.ProgressBar(q)
+
+        self.assertIsInstance(pb, Gtk.ProgressBar)
+        self.assertTrue( pb.get_hexpand())
+        self.assertFalse(pb.get_visible())
+        self.assertEqual(pb.get_valign(), Gtk.Align.CENTER)
+        self.assertEqual(pb.queue, q)
+
+        for i in range(3): q.push(FakeTask())
+        self.assertTrue(pb.get_visible())
+
+        for i in [ 1, 2, 0 ]:
+            q.run()
+            self.assertEqual(pb.get_fraction(), i/3)
+        self.assertFalse(pb.get_visible())

scanner/widgets.py

@@ -0,0 +1,24 @@
+# Copyright 2021 (c) Anna Schumaker.
+from gi.repository import Gtk
+
+class ProgressBar(Gtk.ProgressBar):
+    def __init__(self, queue):
+        Gtk.ProgressBar.__init__(self)
+
+        self.queue = queue
+        self.queue.connect("task-pushed", self.on_task_pushed)
+        self.queue.connect("run-task", self.on_run_task)
+        self.queue.connect("tasks-finished", self.on_tasks_finished)
+
+        self.set_valign(Gtk.Align.CENTER)
+        self.set_hexpand(True)
+        self.set_visible(False)
+
+    def on_task_pushed(self, queue, task):
+        self.set_visible(True)
+
+    def on_run_task(self, queue, task):
+        self.set_fraction(queue.progress)
+
+    def on_tasks_finished(self, queue):
+        self.set_visible(False)