Mask two cells for double width characters being drawn over a box cursor.

Issue 5884

sources/iTermCursor.h

@@ -19,6 +19,7 @@ typedef struct {
 - (iTermCursorNeighbors)cursorNeighbors;
 - (void)cursorDrawCharacterAt:(VT100GridCoord)coord
+                  doubleWidth:(BOOL)doubleWidth
                 overrideColor:(NSColor*)overrideColor
                       context:(CGContextRef)ctx
               backgroundColor:(NSColor *)backgroundColor;

sources/iTermCursor.m

@@ -193,12 +193,14 @@
         CGContextRef ctx = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
         if (smart && focused) {
             [self drawSmartCursorCharacter:screenChar
+                               doubleWidth:doubleWidth
                            backgroundColor:backgroundColor
                                        ctx:ctx
                                      coord:coord];
         } else {
             // Non-smart
             [self.delegate cursorDrawCharacterAt:coord
+                                     doubleWidth:doubleWidth
                                    overrideColor:foregroundColor
                                          context:ctx
                                  backgroundColor:backgroundColor];
@@ -207,6 +209,7 @@
 }
 - (void)drawSmartCursorCharacter:(screen_char_t)screenChar
+                     doubleWidth:(BOOL)doubleWidth
                  backgroundColor:(NSColor *)backgroundColor
                              ctx:(CGContextRef)ctx
                            coord:(VT100GridCoord)coord {
@@ -218,6 +221,7 @@
                                                                   backgroundColor:backgroundColor];
     [self.delegate cursorDrawCharacterAt:coord
+                             doubleWidth:doubleWidth
                            overrideColor:overrideColor
                                  context:ctx
                          backgroundColor:nil];

sources/iTermTextDrawingHelper.m

@@ -2702,6 +2702,7 @@ static BOOL iTermTextDrawingHelperIsCharacterDrawable(screen_char_t *c,
 }
 - (void)cursorDrawCharacterAt:(VT100GridCoord)coord
+                  doubleWidth:(BOOL)doubleWidth
                 overrideColor:(NSColor *)overrideColor
                       context:(CGContextRef)ctx
               backgroundColor:(NSColor *)backgroundColor {
@@ -2709,7 +2710,8 @@ static BOOL iTermTextDrawingHelperIsCharacterDrawable(screen_char_t *c,
     [context saveGraphicsState];
     int row = coord.y + _numberOfScrollbackLines;
-    VT100GridCoordRange coordRange = VT100GridCoordRangeMake(coord.x, row, coord.x + 1, row + 1);
+    int width = doubleWidth ? 2 : 1;
+    VT100GridCoordRange coordRange = VT100GridCoordRangeMake(coord.x, row, coord.x + width, row + 1);
     NSRect innerRect = [self rectForCoordRange:coordRange];
     NSRectClip(innerRect);