Clip to cell when drawing insertion point

This fixes an issue where the cursor would spill over into the
neighboring cells on Retina displays (only).

src/MacVim/MMCoreTextView.m

@@ -1241,6 +1241,9 @@ recurseDraw(const unichar *chars, CGGlyph *glyphs, CGSize *advances,
 {
     CGContextRef context = [[NSGraphicsContext currentContext] graphicsPort];
     NSRect rect = [self rectForRow:row column:col numRows:1 numColumns:1];
+    CGRect clipRect = *(CGRect *)▭
+
+    CGContextSaveGState(context);
 
     if (MMInsertionPointHorizontal == shape) {
         int frac = (cellSize.height * percent + 99)/100;
@@ -1259,6 +1262,12 @@ recurseDraw(const unichar *chars, CGGlyph *glyphs, CGSize *advances,
     // over into adjacent display cells and it may look ugly.
     CGContextSetShouldAntialias(context, NO);
 
+    // Even though antialiasing is disabled and we adjust the rect to fit
+    // inside the display cell it still happens on Retina displays (only) that
+    // the cursor bleeds over into the neighboring cells.  To work around this
+    // issue we enable clipping.
+    CGContextClipToRect(context, clipRect);
+
     if (MMInsertionPointHollow == shape) {
         // When stroking a rect its size is effectively 1 pixel wider/higher
         // than we want so make it smaller to avoid having it bleed over into
@@ -1275,7 +1284,7 @@ recurseDraw(const unichar *chars, CGGlyph *glyphs, CGSize *advances,
         CGContextFillRect(context, *(CGRect*)&rect);
     }
 
-    CGContextSetShouldAntialias(context, antialias);
+    CGContextRestoreGState(context);
 }
 
 - (void)drawInvertedRectAtRow:(int)row column:(int)col numRows:(int)nrows