1 files changed, 38 insertions, 7 deletions

diff --git a/generic/tkTextDisp.c b/generic/tkTextDisp.c
index 39a57eb..238ae1a 100644
--- a/generic/tkTextDisp.c
+++ b/generic/tkTextDisp.c
@@ -4274,7 +4274,6 @@ DisplayText(
 	    }
 	    dlPtr = dlPtr->nextPtr;
 	}
-
 	/*
 	 * Scan through the lines following the copied ones to see if we are
 	 * going to overwrite them with the copy operation. If so, mark them
@@ -4298,9 +4297,7 @@ DisplayText(
 	if (TkScrollWindow(textPtr->tkwin, dInfoPtr->scrollGC, dInfoPtr->x,
 		oldY, dInfoPtr->maxX-dInfoPtr->x, height, 0, y-oldY,
 		damageRgn)) {
-#ifndef MAC_OSX_TK
 	    TextInvalidateRegion(textPtr, damageRgn);
-#endif
 	}
 	numCopies++;
 	TkDestroyRegion(damageRgn);
@@ -4442,11 +4439,38 @@ DisplayText(
 		}
 		dlPtr->oldY = dlPtr->y;
 		dlPtr->flags &= ~(NEW_LAYOUT | OLD_Y_INVALID);
+#ifdef MAC_OSX_TK
+	    } else if (dlPtr->chunkPtr != NULL) {
+		/*
+		 * On macOS we need to redisplay all embedded windows which
+		 * were moved by the call to TkScrollWindows above.  This is
+		 * not necessary on Unix or Windows because XScrollWindow will
+		 * have included the bounding rectangles of all of these
+		 * windows in the damage region.  The macosx implementation of
+		 * TkScrollWindow does not do this.  It simply generates a
+		 * damage region which is the scroll source rectangle minus
+		 * the scroll destination rectangle.  This is because there is
+		 * no efficient process available for iterating through the
+		 * subwindows which meet the scrolled area.  (On Unix this is
+		 * handled by GraphicsExpose events generated by XCopyArea and
+		 * on Windows by ScrollWindowEx.  On macOS the low level
+		 * scrolling is accomplished by calling [view scrollRect:by:].
+		 * This method does not provide any damage information and, in
+		 * any case, could not be aware of Tk windows which were not
+		 * based on NSView objects.
+		 *
+		 * On the other hand, this loop is already iterating through
+		 * all embedded windows which could possibly have been moved
+		 * by the scrolling.  So it is as efficient to redisplay them
+		 * here as it would have been if they had been redisplayed by
+		 * the call to TextInvalidateRegion above.
+		 */
+#else
 	    } else if (dlPtr->chunkPtr != NULL && ((dlPtr->y < 0)
 		    || (dlPtr->y + dlPtr->height > dInfoPtr->maxY))) {
-		register TkTextDispChunk *chunkPtr;
-
-		/*
+		/* 
+		 * On platforms other than the Mac:
+		 *
 		 * It's the first or last DLine which are also overlapping the
 		 * top or bottom of the window, but we decided above it wasn't
 		 * necessary to display them (we were able to update them by
@@ -4460,6 +4484,8 @@ DisplayText(
 		 * So, we loop through all the chunks, calling the display
 		 * proc of embedded windows only.
 		 */
+#endif
+		register TkTextDispChunk *chunkPtr;
 
 		for (chunkPtr = dlPtr->chunkPtr; (chunkPtr != NULL);
 			chunkPtr = chunkPtr->nextPtr) {
@@ -4482,13 +4508,18 @@ DisplayText(
 
 			x = -chunkPtr->width;
 		    }
+		    if (tkTextDebug) {
+			char string[TK_POS_CHARS];
+
+			TkTextPrintIndex(textPtr, &dlPtr->index, string);
+			LOG("tk_textEmbWinDisplay", string);
+		    }
 		    TkTextEmbWinDisplayProc(textPtr, chunkPtr, x,
 			    dlPtr->spaceAbove,
 			    dlPtr->height-dlPtr->spaceAbove-dlPtr->spaceBelow,
 			    dlPtr->baseline - dlPtr->spaceAbove, NULL,
 			    (Drawable) None, dlPtr->y + dlPtr->spaceAbove);
 		}
-
 	    }
 	}
 #ifndef TK_NO_DOUBLE_BUFFERING