From 8713a1a4977a211504657d65a3d134b7c85bf0d3 Mon Sep 17 00:00:00 2001
From: culler <culler>
Date: Sat, 31 Jul 2021 21:41:51 +0000
Subject: Use the correct coordinates to compute the damage region.  This makes
 the tests pass again.

---
 macosx/tkMacOSXDraw.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/macosx/tkMacOSXDraw.c b/macosx/tkMacOSXDraw.c
index 2830fa1..3d8f26e 100644
--- a/macosx/tkMacOSXDraw.c
+++ b/macosx/tkMacOSXDraw.c
@@ -1144,7 +1144,7 @@ TkScrollWindow(
     TKContentView *view = (TKContentView *)TkMacOSXGetNSViewForDrawable(macDraw);
     HIShapeRef srcRgn, dstRgn;
     HIMutableShapeRef dmgRgn = HIShapeCreateMutable();
-    NSRect bounds, scrollSrc, scrollDst;
+    NSRect bounds, viewSrcRect, srcRect, dstRect;
     int result = 0;
 
     if (view) {
@@ -1154,29 +1154,31 @@ TkScrollWindow(
 	 */
 
   	bounds = [view bounds];
- 	scrollSrc = NSMakeRect(macDraw->xOff + x,
+ 	viewSrcRect = NSMakeRect(macDraw->xOff + x,
 		bounds.size.height - height - (macDraw->yOff + y),
 		width, height);
- 	scrollDst = NSOffsetRect(scrollSrc, dx, -dy);
 
 	/*
-	 * Compute the damage.
+	 * Scroll the rectangle.
 	 */
 
-	srcRgn = HIShapeCreateWithRect(&scrollSrc);
-	dstRgn = HIShapeCreateWithRect(&scrollDst);
-	ChkErr(HIShapeDifference, srcRgn, dstRgn, dmgRgn);
-	result = HIShapeIsEmpty(dmgRgn) ? 0 : 1;
+	[view scrollRect:viewSrcRect by:NSMakeSize(dx, -dy)];
 
 	/*
-	 * Scroll the rectangle.
+	 * Compute the damage region, using Tk coordinates (origin at top left).
 	 */
 
-	[view scrollRect:scrollSrc by:NSMakeSize(dx, -dy)];
+	srcRect = CGRectMake(x, y, width, height);
+	dstRect = CGRectOffset(srcRect, dx, dy);
+	srcRgn = HIShapeCreateWithRect(&srcRect);
+	dstRgn = HIShapeCreateWithRect(&dstRect);
+	ChkErr(HIShapeDifference, srcRgn, dstRgn, dmgRgn);
+	result = HIShapeIsEmpty(dmgRgn) ? 0 : 1;
+
     }
 
     /*
-     * Convert dmgRgn to Tk coordinates and store the result.
+     * Convert the HIShape dmgRgn into a TkRegion and store it.
      */
 
     TkMacOSXSetWithNativeRegion(damageRgn, dmgRgn);
-- 
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