Call refresh after changing font size to avoid doing a double redraw at two...

Call refresh after changing font size to avoid doing a double redraw at two different scroll positions. Issue 5836

sources/PTYTextView.m

@@ -718,13 +718,16 @@ static const int kDragThreshold = 3;
     _secondaryFont.boldItalicVersion = [_secondaryFont computedBoldItalicVersion];
     [self updateMarkedTextAttributes];
-    [self setNeedsDisplay:YES];
     NSScrollView* scrollview = [self enclosingScrollView];
     [scrollview setLineScroll:[self lineHeight]];
     [scrollview setPageScroll:2 * [self lineHeight]];
     [self updateNoteViewFrames];
     [_delegate textViewFontDidChange];
+
+    // Refresh to avoid drawing before and after resize.
+    [self refresh];
+    [self setNeedsDisplay:YES];
 }
 - (void)changeFont:(id)fontManager
@@ -1128,6 +1131,8 @@ static const int kDragThreshold = 3;
     _drawingHelper.copyModeSelecting = _delegate.textViewCopyModeSelecting;
     _drawingHelper.copyModeCursorCoord = _delegate.textViewCopyModeCursorCoord;
     _drawingHelper.passwordInput = _delegate.textViewPasswordInput;
+
+    DLog(@"drawing document visible rect %@", NSStringFromRect(self.enclosingScrollView.documentVisibleRect));
     
     const NSRect *rectArray;
     NSInteger rectCount;

sources/iTermTextDrawingHelper.m

@@ -335,7 +335,7 @@ typedef struct iTermTextColorContext {
         const double y = line * _cellSize.height;
         // An array of PTYTextViewBackgroundRunArray objects (one element per line).
         
-//        NSLog(@"    draw line %d", line);
+//        NSLog(@"Draw line %d at %f", line, y);
         NSData *matches = [_delegate drawingHelperMatchesOnLine:line];
         screen_char_t* theLine = [self.delegate drawingHelperLineAtIndex:line];
         NSIndexSet *selectedIndexes =