Work around the candidate popup position issue

Some applications (most notably Firefox) fail to correctly position the
candidate popup.

This is because we don't use a pre-edit text at all, and it seems those
applications (or maybe the toolkits?) get confused by the absence of a
pre-edit text. :(

This is a gross hack. The real issue needs to be fixed in the
apps/toolkits, but we need to do something in the meantime, as this is
just too much of a bad UX issue for us.

The idea comes from FrÃdÃric Péter.

Fixes #60

src/engine.py

@@ -434,6 +434,20 @@ def update_auxiliary_text(self):
         text = IBus.Text.new_from_string(self.current_radicals)
         super(Engine, self).update_auxiliary_text(text, len(self.current_radicals)>0)
 
+        # We don't use pre-edit at all for Cangjie or Quick
+        #
+        # However, some applications (most notably Firefox) fail to correctly
+        # position the candidate popup, as if they got confused by the absence
+        # of a pre-edit text. :(
+        #
+        # This is a horrible hack, but it fixes the immediate problem.
+        if self.current_radicals:
+            super(Engine, self).update_preedit_text(IBus.Text.new_from_string('\u200B'), 0, True)
+
+        else:
+            super(Engine, self).update_preedit_text(IBus.Text.new_from_string(''), 0, False)
+        # End of the horrible workaround
+
     def update_lookup_table(self):
         """Update the lookup table."""
         if not self.current_input:

tests/run_tests.in

@@ -47,6 +47,12 @@ class MockEngine:
         # We don't need anything here for the unit tests
         pass
 
+    def update_preedit_text(self, text, cursor_pos, visible):
+        # We don't need anything here for the unit tests
+        #
+        # We only have this for an ugly workaround.
+        pass
+
 
 class MockLookupTable:
     def __init__(self):