add visual diff idea

README.md

@@ -24,6 +24,7 @@
 
 [Use ref-counting to handle object lifetimes](#use-ref-counting-to-handle-object-lifetimes)
 
+[Visual Diff](#visual-diff)
 
 Inject Purr Data Directly into the Web
 --------------------------------------
@@ -591,3 +592,27 @@ or unbind symbols even within a single call stack.
 
 ### Languages
 C.
+
+
+Visual/Animated Diff
+-----------
+
+### Goal
+Make a tool to visually show the changes in a Purr Data patch.
+
+### Details
+Pd has a source file format that is difficult to read. Furthermore,
+changes in z-order in the GUI can make changes in the source nearly
+impossible to convey. This makes it difficult to glean anything of
+substance by viewing a diff of a Pd file in git.
+
+
+### Challenges
+This is a general problem with visual programming languages. There may
+be some prior art with some languages that attempt to solve the problem.
+But unlike Pd, those languages were probably built from the ground up
+to solve that problem, whereas Pd's file format doesn't lend itself to
+solving that problem.
+
+### Languages
+C, possibly HTML5.