Don't draw any lines above the visible range. Their descenders can hang down...

Don't draw any lines above the visible range. Their descenders can hang down into the display when vertical spacing is less than 100%. Issue 6223

sources/iTermTextDrawingHelper.m

@@ -217,11 +217,13 @@ typedef struct iTermTextColorContext {
     NSInteger yLimit = _numberOfLines;
     VT100GridCoordRange boundingCoordRange = [self coordRangeForRect:rect];
+    NSRange visibleLines = [self rangeOfVisibleRows];
+
     // Start at 0 because ligatures can draw incorrectly otherwise. When a font has a ligature for
     // -> and >-, then a line like ->->-> needs to start at the beginning since drawing only a
     // suffix of it could draw a >- ligature at the start of the range being drawn. Issue 5030.
     boundingCoordRange.start.x = 0;
-    boundingCoordRange.start.y = MAX(0, boundingCoordRange.start.y - 1);
+    boundingCoordRange.start.y = MAX(MAX(0, boundingCoordRange.start.y - 1), visibleLines.location);
     boundingCoordRange.end.x = MIN(_gridSize.width, boundingCoordRange.end.x + haloWidth);
     boundingCoordRange.end.y = MIN(yLimit, boundingCoordRange.end.y + 1);
     
@@ -252,7 +254,10 @@ typedef struct iTermTextColorContext {
         }
     }
-    [self drawRanges:ranges count:numRowsInRect origin:boundingCoordRange.start boundingRect:[self rectForCoordRange:boundingCoordRange]];
+    [self drawRanges:ranges count:numRowsInRect
+              origin:boundingCoordRange.start
+        boundingRect:[self rectForCoordRange:boundingCoordRange]
+        visibleLines:visibleLines];
     
     if (_showDropTargets) {
         [self drawDropTargets];
@@ -296,7 +301,11 @@ typedef struct iTermTextColorContext {
     return count;
 }
-- (void)drawRanges:(NSRange *)ranges count:(NSInteger)numRanges origin:(VT100GridCoord)origin boundingRect:(NSRect)boundingRect {
+- (void)drawRanges:(NSRange *)ranges
+             count:(NSInteger)numRanges
+            origin:(VT100GridCoord)origin
+      boundingRect:(NSRect)boundingRect
+      visibleLines:(NSRange)visibleLines {
     // Configure graphics
     [[NSGraphicsContext currentContext] setCompositingOperation:NSCompositeCopy];
@@ -304,7 +313,6 @@ typedef struct iTermTextColorContext {
     _blinkingFound = NO;
     NSMutableArray<iTermBackgroundColorRunsInLine *> *backgroundRunArrays = [NSMutableArray array];
-    NSRange visibleLines = [self rangeOfVisibleRows];
     for (NSInteger i = 0; i < numRanges; i++) {
         const int line = origin.y + i;