From 2b1ba37c195761b32f7126a874067e7549925ddd Mon Sep 17 00:00:00 2001
From: timb <opuscule@gmail.com>
Date: Thu, 30 Jul 2015 02:59:28 -0700
Subject: make a note of data structure for sanity purposes if code is read
 years later

---
 js/png.js  |  8 ++++++++
 js/undo.js | 12 +++++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/js/png.js b/js/png.js
index df9960c..e9b326e 100644
--- a/js/png.js
+++ b/js/png.js
@@ -60,6 +60,14 @@ var crc32 = function(u8){
 var signature = new Uint8Array([137, 80, 78, 71, 13, 10, 26, 10])
 var te, td
 
+// decodes chunks in png
+// see http://www.w3.org/TR/PNG/#5Chunk-layout
+// returns something like
+// [{length: Number,
+//   type: String[4],
+//   crc: Number,
+//   data: Uint8Array[]  // optional
+// }, ...]
 var decode = function(buf, err){
   var u8a = new Uint8Array(buf)
   var dv = new DataView(buf)
diff --git a/js/undo.js b/js/undo.js
index 436422f..44b137a 100644
--- a/js/undo.js
+++ b/js/undo.js
@@ -33,6 +33,12 @@ var update_dom = function(){
   update_dom_visibility('redo')
 }
 
+// state is an undo or redo state that might contain these props
+// {lexs: {'0,0': LexState, ...},
+//  focus: {x:, y: },
+//  size: {w:, h: },
+//  rects: [{x:, y:, w:, h:, lexs: [LexState, ...]}, ...]
+// }
 var new_state = function(){
   var state = {lexs:{}};
   save_focus(canvas.focus_x, canvas.focus_y, state)
@@ -98,20 +104,20 @@ var save_resize = function(w, h, old_w, old_h, state){
   state = state || current_undo
   save_size(old_w, old_h, state)
   if (old_w > w){
-    // .----.
+    // .---XX
     // |   XX
     // |___XX
     save_rect(w, 0, old_w - w, old_h, state)
     if (old_h > h){
       // .----.
       // |    |
-      // |XXX_|
+      // XXXX_|
       save_rect(0, h, w, old_h - h, state)
     }
   } else if (old_h > h){
     // .----.
     // |    |
-    // |XXXX|
+    // XXXXXX
     save_rect(0, h, old_w, old_h - h, state)
   }
 }
-- 
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