From 526838c498310083108c2dce3c2d9a71dd924d89 Mon Sep 17 00:00:00 2001
From: Kevin Walzer <kw@codebykevin.com>
Date: Sun, 4 Jan 2015 23:24:23 +0000
Subject: Improved scrolling for text under Cocoa; thanks to Marc Culler for
 patch.

---
 generic/tkTextDisp.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/generic/tkTextDisp.c b/generic/tkTextDisp.c
index a0cbc52..4391f0c 100644
--- a/generic/tkTextDisp.c
+++ b/generic/tkTextDisp.c
@@ -3885,6 +3885,21 @@ TkTextUpdateOneLine(
  *
  *----------------------------------------------------------------------
  */
+#ifdef MAC_OSX_TK
+static void
+RedisplayText(
+    ClientData clientData )
+{
+    register TkText *textPtr = (TkText *) clientData;
+    TextDInfo *dInfoPtr = textPtr->dInfoPtr;
+    TkRegion damageRegion = TkCreateRegion();
+    XRectangle rectangle = {0, 0, dInfoPtr->maxX, dInfoPtr->maxY};
+    TkUnionRectWithRegion(&rectangle, damageRegion, damageRegion);
+    
+    TextInvalidateRegion(textPtr, damageRegion);
+    DisplayText(clientData);
+}
+#endif
 
 static void
 DisplayText(
@@ -3899,6 +3914,9 @@ DisplayText(
     int bottomY = 0;		/* Initialization needed only to stop compiler
 				 * warnings. */
     Tcl_Interp *interp;
+#ifdef MAC_OSX_TK
+    Tcl_TimerToken macRefreshTimer = NULL; 
+#endif
 
     if ((textPtr->tkwin == NULL) || (textPtr->flags & DESTROYED)) {
 	/*
@@ -4100,6 +4118,22 @@ DisplayText(
 		oldY, dInfoPtr->maxX-dInfoPtr->x, height, 0, y-oldY,
 		damageRgn)) {
 	    TextInvalidateRegion(textPtr, damageRgn);
+
+#ifdef MAC_OSX_TK
+
+	    /*
+	     * On OS X large scrolls sometimes leave garbage on the screen.
+	     * This attempts to clean it up by redisplaying the Text window
+	     * after 200 milliseconds.
+	     */
+	    if ( abs(y-oldY) > 14 ) {
+		Tcl_DeleteTimerHandler(macRefreshTimer);
+		macRefreshTimer = Tcl_CreateTimerHandler(200,
+							 RedisplayText,
+							 clientData);
+	    }
+#endif
+
 	}
 	numCopies++;
 	TkDestroyRegion(damageRgn);
-- 
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