fixes for transparency + cgLayer code

Author: Ben Osheroff

src/MacVim/MMCoreTextView.m

@@ -607,7 +607,11 @@ - (void)drawRect:(NSRect)rect
                 cgLayerSize.width,
                 cgLayerSize.height);
 
-        CGContextDrawLayerInRect([context graphicsPort], drawRect, l);
+        CGContextRef cgContext = [context graphicsPort];
+        CGContextSaveGState(cgContext);
+        CGContextSetBlendMode(cgContext, kCGBlendModeCopy);
+        CGContextDrawLayerInRect(cgContext, drawRect, l);
+        CGContextRestoreGState(cgContext);
     }
 }
 
@@ -1487,6 +1491,7 @@ - (void)scrollRect:(NSRect)rect lineCount:(int)count
         // draw self on top of self, offset so as to "scroll" lines vertically
         CGContextSaveGState(context);
         CGContextClipToRect(context, clipRect);
+        CGContextSetBlendMode(context, kCGBlendModeCopy);
         CGContextDrawLayerAtPoint(
                 context, CGPointMake(0, -yOffset), [self getCGLayer]);
         CGContextRestoreGState(context);