From b97496009b800e843c91893da374cf886b0a420f Mon Sep 17 00:00:00 2001
From: nightwing <amirjanyan@gmail.com>
Date: Sun, 7 Jul 2013 12:48:53 +0400
Subject: [PATCH 1/3] scrollPastEnd

---
 lib/ace/virtual_renderer.js | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/lib/ace/virtual_renderer.js b/lib/ace/virtual_renderer.js
index 6ed5a01d..b70d6906 100644
--- a/lib/ace/virtual_renderer.js
+++ b/lib/ace/virtual_renderer.js
@@ -848,7 +848,7 @@ var VirtualRenderer = function(container, theme) {
         
         var hideScrollbars = this.$size.height <= 2 * this.lineHeight;
         var screenLines = this.session.getScreenLength()
-        var maxHeight =  screenLines * this.lineHeight;
+        var maxHeight = screenLines * this.lineHeight;
 
         var offset = this.scrollTop % this.lineHeight;
         var minHeight = this.$size.scrollerHeight + this.lineHeight;
@@ -864,6 +864,9 @@ var VirtualRenderer = function(container, theme) {
             this.scrollBarH.setVisible(horizScroll);
         }
         
+        if (!this.$maxLines && this.$scrollPastEnd)
+            maxHeight += (this.$size.scrollerHeight - this.lineHeight) * this.$scrollPastEnd;
+
         var vScroll = !hideScrollbars && (this.$vScrollBarAlwaysVisible ||
             this.$size.scrollerHeight - maxHeight < 0);
         var vScrollChanged = this.$vScroll !== vScroll;
@@ -1579,9 +1582,23 @@ config.defineOptions(VirtualRenderer.prototype, "renderer", {
         }
     },
     minLines: {
-        set: function(name) {        
+        set: function(val) {
             this.updateFull();
         }
+    },
+    scrollPastEnd: {
+        set: function(val) {
+            if (val == true)
+                val = 1;
+            else if (val == false)
+                val = 0;
+            if (this.$scrollPastEnd == val)
+                return;
+            this.$scrollPastEnd = val;
+            this.$loop.schedule(this.CHANGE_SCROLL);
+        },
+        initialValue: 1,
+        handlesSet: true
     }
 });
 

From 8a6320bfd1fb5033f98411ea14b82a4d493a92ee Mon Sep 17 00:00:00 2001
From: nightwing <amirjanyan@gmail.com>
Date: Sun, 7 Jul 2013 12:50:24 +0400
Subject: [PATCH 2/3] resize scrollbar for scrollPastEnd only when needed

---
 lib/ace/virtual_renderer.js | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/lib/ace/virtual_renderer.js b/lib/ace/virtual_renderer.js
index b70d6906..3e9a535d 100644
--- a/lib/ace/virtual_renderer.js
+++ b/lib/ace/virtual_renderer.js
@@ -864,9 +864,14 @@ var VirtualRenderer = function(container, theme) {
             this.scrollBarH.setVisible(horizScroll);
         }
         
-        if (!this.$maxLines && this.$scrollPastEnd)
-            maxHeight += (this.$size.scrollerHeight - this.lineHeight) * this.$scrollPastEnd;
-
+        if (!this.$maxLines && this.$scrollPastEnd) {
+            if (this.scrollTop > maxHeight - this.$size.scrollerHeight)
+                maxHeight += Math.min(
+                    (this.$size.scrollerHeight - this.lineHeight) * this.$scrollPastEnd,
+                    this.scrollTop - maxHeight + this.$size.scrollerHeight
+                );
+        }
+        
         var vScroll = !hideScrollbars && (this.$vScrollBarAlwaysVisible ||
             this.$size.scrollerHeight - maxHeight < 0);
         var vScrollChanged = this.$vScroll !== vScroll;
@@ -1271,7 +1276,8 @@ var VirtualRenderer = function(container, theme) {
         if (deltaY < 0 && this.session.getScrollTop() >= 1 - this.scrollMargin.top)
            return true;
         if (deltaY > 0 && this.session.getScrollTop() + this.$size.scrollerHeight
-            - this.layerConfig.maxHeight < -1 + this.scrollMargin.bottom)
+            - this.layerConfig.maxHeight - (this.$size.scrollerHeight - this.lineHeight) * this.$scrollPastEnd
+            < -1 + this.scrollMargin.bottom)
            return true;
         // todo: better handle horizontal scrolling
         if (deltaX)

From 1ad2602f8b2d02ae10d0feed2b959f8c1d62bed4 Mon Sep 17 00:00:00 2001
From: nightwing <amirjanyan@gmail.com>
Date: Sun, 7 Jul 2013 13:02:57 +0400
Subject: [PATCH 3/3] add scrollPastEnd to demo

---
 demo/kitchen-sink/demo.js | 3 +++
 kitchen-sink.html         | 8 ++++++++
 lib/ace/editor.js         | 1 +
 3 files changed, 12 insertions(+)

diff --git a/demo/kitchen-sink/demo.js b/demo/kitchen-sink/demo.js
index abd5deb8..88d5fa0e 100644
--- a/demo/kitchen-sink/demo.js
+++ b/demo/kitchen-sink/demo.js
@@ -430,6 +430,9 @@ bindCheckbox("fade_fold_widgets", function(checked) {
 bindCheckbox("read_only", function(checked) {
     env.editor.setReadOnly(checked);
 });
+bindCheckbox("scrollPastEnd", function(checked) {
+    env.editor.setOption("scrollPastEnd", checked);
+});
 
 bindDropdown("split", function(value) {
     var sp = env.split;
diff --git a/kitchen-sink.html b/kitchen-sink.html
index bb534835..586b317e 100644
--- a/kitchen-sink.html
+++ b/kitchen-sink.html
@@ -274,6 +274,14 @@
         <input type="checkbox" id="read_only">
       </td>
     </tr>
+    <tr>
+      <td >
+        <label for="scrollPastEnd">Scroll Past End</label>
+      </td>
+      <td>
+        <input type="checkbox" id="scrollPastEnd" checked>
+      </td>
+    </tr>
     <tr>
       <td colspan="2">
         <input type="button" value="Edit Snippets" onclick="env.editSnippets()">
diff --git a/lib/ace/editor.js b/lib/ace/editor.js
index 088fbaae..d92666b8 100644
--- a/lib/ace/editor.js
+++ b/lib/ace/editor.js
@@ -2261,6 +2261,7 @@ config.defineOptions(Editor.prototype, "editor", {
     fontFamily: "renderer",
     maxLines: "renderer",
     minLines: "renderer",
+    scrollPastEnd: "renderer",
 
     scrollSpeed: "$mouseHandler",
     dragDelay: "$mouseHandler",