Add a tilt transition

The tilt transition is like pan, only vertical instead of
horizontal.

3 files changed, 23 insertions, 5 deletions

diff --git a/example/demo.rst b/example/demo.rst
index bafd9ba..c105e7d 100644
--- a/example/demo.rst
+++ b/example/demo.rst
@@ -2,11 +2,11 @@
    The following directives, when used at the top of the file, set default
    values for all slides:
 
-   This sets the transition style.  Values are: 'dissolve', 'pan', or
-   'cut'.  The optional argument of 'duration' sets the duration of
-   the transition in seconds (0.4 seconds by default).  The same
-   syntax may be used within a slide to override the transition for
-   that slide alone.
+   This sets the transition style.  Values are: 'dissolve', 'pan',
+   'tilt', or 'cut'.  The optional argument of 'duration' sets the
+   duration of the transition in seconds (0.4 seconds by default).
+   The same syntax may be used within a slide to override thes
+   transition for that slide alone.
 
    .. transition:: dissolve
       :duration: 0.4
@@ -77,6 +77,13 @@ Pan Transition
 ...or "pan," where the slides appear horizontally adjacent and move
 right to left...
 
+Tilt Transition
+===============
+.. transition:: tilt
+
+...or "tilt," where the slides appear vertically adjacent and move
+bottom to top...
+
 Cut Transition
 ==============
 .. transition:: cut
diff --git a/presentty/rst.py b/presentty/rst.py
index e96ff21..ab06f76 100644
--- a/presentty/rst.py
+++ b/presentty/rst.py
@@ -65,6 +65,7 @@ class UrwidTranslator(docutils.nodes.GenericNodeVisitor):
     transition_map = {'dissolve': transition_mod.DissolveTransition,
                       'cut': transition_mod.CutTransition,
                       'pan': transition_mod.PanTransition,
+                      'tilt': transition_mod.TiltTransition,
                       }
 
     def __init__(self, document, palette, hinter=None, basedir='.'):
diff --git a/presentty/transition.py b/presentty/transition.py
index c699ddb..5592cd9 100644
--- a/presentty/transition.py
+++ b/presentty/transition.py
@@ -46,6 +46,16 @@ class PanTransition(Transition):
         c.pad_trim_left_right(0-offset, 0-(size[0]-offset))
         return c
 
+class TiltTransition(Transition):
+    def render(self, size, focus=False):
+        old = self.old.render((size[0], size[1]))
+        new = self.new.render((size[0], size[1]))
+        c = urwid.CanvasCombine([(old, None, False),
+                              (new, None, False)])
+        offset = int(size[1] * self.progress)
+        c.pad_trim_top_bottom(0-offset, 0-(size[1]-offset))
+        return c
+
 class DissolveTransition(Transition):
     def __init__(self, *args, **kw):
         super(DissolveTransition, self).__init__(*args, **kw)