From 6899e01fc1e5c0b5639faefddbe6f1c63f5f1ede Mon Sep 17 00:00:00 2001
From: Daniel Imms <daimms@microsoft.com>
Date: Tue, 12 Sep 2017 15:05:47 -0700
Subject: [PATCH] Improve scrolling while user has scrolled up

Fixes #953
---
 src/Terminal.ts | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/Terminal.ts b/src/Terminal.ts
index e19887cb..f4d10dc4 100644
--- a/src/Terminal.ts
+++ b/src/Terminal.ts
@@ -1071,7 +1071,16 @@ export class Terminal extends EventEmitter implements ITerminal, IInputHandlingT
       // Only adjust ybase and ydisp when the buffer is not trimmed
       if (!willBufferBeTrimmed) {
         this.buffer.ybase++;
-        this.buffer.ydisp++;
+        // Only scroll the ydisp with ybase if the user has not scrolled up
+        if (!this.userScrolling) {
+          this.buffer.ydisp++;
+        }
+      } else {
+        // When the buffer is full and the user has scrolled up, keep the text
+        // stable unless ydisp is right at the top
+        if (this.userScrolling) {
+          this.buffer.ydisp = Math.max(this.buffer.ydisp - 1, 0);
+        }
       }
     } else {
       // scrollTop is non-zero which means no line will be going to the