From 64a55719b20f1d0d3098e343160a5104f3608a05 Mon Sep 17 00:00:00 2001
From: nightwing <amirjanyan@gmail.com>
Date: Mon, 23 May 2011 13:20:17 +0500
Subject: [PATCH] eliminate scrollbar jitter while typing at the bottom of
 screen

---
 lib/ace/virtual_renderer.js | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/lib/ace/virtual_renderer.js b/lib/ace/virtual_renderer.js
index a9687660..31a9eeff 100644
--- a/lib/ace/virtual_renderer.js
+++ b/lib/ace/virtual_renderer.js
@@ -95,7 +95,7 @@ var VirtualRenderer = function(container, theme) {
     this.scrollBar = new ScrollBar(container);
     this.scrollBar.addEventListener("scroll", this.onScroll.bind(this));
 
-    this.scrollTop = 0;
+    this.scrollTop = this.desiredScrollTop = 0;
 
     this.cursorPos = {
         row : 0,
@@ -384,7 +384,7 @@ var VirtualRenderer = function(container, theme) {
     };
 
     this.$updateScrollBar = function() {
-        this.scrollBar.setInnerHeight(this.session.getScreenLength() * this.lineHeight);
+        this.scrollBar.setInnerHeight(this.layerConfig.maxHeight);
         this.scrollBar.setScrollTop(this.scrollTop);
     };
 
@@ -469,6 +469,10 @@ var VirtualRenderer = function(container, theme) {
         if (horizScrollChanged)
             this.scroller.style.overflowX = horizScroll ? "scroll" : "hidden";
 
+        var maxHeight = this.session.getScreenLength() * this.lineHeight;
+        this.scrollTop = this.desiredScrollTop =
+                Math.max(0, Math.min(this.desiredScrollTop, maxHeight - this.$size.scrollerHeight));
+
         var lineCount = Math.ceil(minHeight / this.lineHeight) - 1;
         var firstRow = Math.max(0, Math.round((this.scrollTop - offset) / this.lineHeight));
         var lastRow = firstRow + lineCount;
@@ -494,7 +498,7 @@ var VirtualRenderer = function(container, theme) {
 
         offset = this.scrollTop - firstRowScreen * this.lineHeight;
 
-        var layerConfig = this.layerConfig = {
+        this.layerConfig = {
             width : longestLine,
             padding : this.$padding,
             firstRow : firstRow,
@@ -503,12 +507,13 @@ var VirtualRenderer = function(container, theme) {
             lineHeight : this.lineHeight,
             characterWidth : this.characterWidth,
             minHeight : minHeight,
+            maxHeight : maxHeight,
             offset : offset,
             height : this.$size.scrollerHeight
         };
 
         // For debugging.
-        // console.log(JSON.stringify(layerConfig));
+        // console.log(JSON.stringify(this.layerConfig));
 
         this.$gutterLayer.element.style.marginTop = (-offset) + "px";
         this.content.style.marginTop = (-offset) + "px";
@@ -662,12 +667,11 @@ var VirtualRenderer = function(container, theme) {
     };
 
     this.scrollToY = function(scrollTop) {
-        var maxHeight = this.session.getScreenLength() * this.lineHeight - this.$size.scrollerHeight;
-        var scrollTop = Math.max(0, Math.min(maxHeight, scrollTop));
-
+        // after calling scrollBar.setScrollTop
+        // scrollbar sends us event with same scrollTop. ignore it
         if (this.scrollTop !== scrollTop) {
-            this.scrollTop = scrollTop;
             this.$loop.schedule(this.CHANGE_SCROLL);
+            this.desiredScrollTop = scrollTop;
         }
     };