From 393e42b439a3762d5d203d6084c51c1c4d611f2f Mon Sep 17 00:00:00 2001
From: nightwing <amirjanyan@gmail.com>
Date: Sat, 8 Sep 2012 16:26:42 +0400
Subject: [PATCH] emacs recenter-top-bottom

---
 lib/ace/keyboard/emacs.js   | 17 ++++++++++++++++-
 lib/ace/virtual_renderer.js |  4 +++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/lib/ace/keyboard/emacs.js b/lib/ace/keyboard/emacs.js
index 5fa7a315..9e3b5d89 100644
--- a/lib/ace/keyboard/emacs.js
+++ b/lib/ace/keyboard/emacs.js
@@ -212,7 +212,8 @@ exports.emacsKeys = {
     "S-C-Home"        : "selecttostart",
     "S-C-End"         : "selecttoend",
 
-    "C-l|M-s" : "centerselection",
+    "C-l" : "recenterTopBottom",
+    "M-s" : "centerselection",
     "M-g": "gotoline",
     "C-x C-p": "selectall",
 
@@ -270,6 +271,20 @@ exports.emacsKeys = {
 exports.handler.bindKeys(exports.emacsKeys);
 
 exports.handler.addCommands({
+    recenterTopBottom: function(editor) {
+        var renderer = editor.renderer;
+        var pos = renderer.$cursorLayer.getPixelPosition();
+        var h = renderer.$size.scrollerHeight - renderer.lineHeight;       
+        var scrollTop = renderer.scrollTop;
+        if (Math.abs(pos.top - scrollTop) < 2) {
+            scrollTop = pos.top - h;
+        } else if (Math.abs(pos.top - scrollTop - h * 0.5) < 2) {
+            scrollTop = pos.top;
+        } else {
+            scrollTop = pos.top - h * 0.5;
+        }
+        editor.session.setScrollTop(scrollTop);
+    },
     selectRectangularRegion:  function(editor) {
         editor.multiSelect.toggleBlockSelection();
     },
diff --git a/lib/ace/virtual_renderer.js b/lib/ace/virtual_renderer.js
index a97860d1..5ec1ffc5 100644
--- a/lib/ace/virtual_renderer.js
+++ b/lib/ace/virtual_renderer.js
@@ -1038,9 +1038,11 @@ var VirtualRenderer = function(container, theme) {
             cursor = {row: cursor, column: 0};
 
         var pos = this.$cursorLayer.getPixelPosition(cursor);
-        var offset = pos.top - this.$size.scrollerHeight * (alignment || 0);
+        var h = this.$size.scrollerHeight - this.lineHeight;
+        var offset = pos.top - h * (alignment || 0);
 
         this.session.setScrollTop(offset);
+        return offset;
     };
 
     this.STEPS = 8;