all clocks: Add a preview() method ready for a watch face chooser

One benefit from wasp-os' dirt simple drawing model is that it is very
easy for apps to provide full screen previews of themselves. Add this
for all clocks ready for us to add a watch face chooser application.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

1 files changed, 12 insertions, 0 deletions

diff --git a/wasp/apps/template.py b/wasp/apps/template.py
index e611545..3027599 100644
--- a/wasp/apps/template.py
+++ b/wasp/apps/template.py
@@ -63,6 +63,18 @@ class TemplateApp():
         """Notify the application the device is waking up."""
         pass
 
+    def preview(self):
+        """Provide a preview for the watch face selection.
+
+        preview() must be implemented by watch face applications because it
+        is called by the watch face selector. When called the application should
+        redraw the screen as through it was the foreground() application. The
+        application will not be active after the preview.
+
+        Other applications should not implement this entry point.
+        """
+        pass
+
     def press(self, button, state):
         """Notify the application of a button-press event."""
         draw = wasp.watch.drawable