winemac: Work around poor-quality downscaling in high-res/retina mode on macOS 10.13 and earlier.

dlls/winemac.drv/cocoa_window.m

@@ -680,6 +680,22 @@ static CVReturn WineDisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTi
         [self layer].contentsScale = mode ? 2.0 : 1.0;
         [self layer].minificationFilter = mode ? kCAFilterLinear : kCAFilterNearest;
         [self layer].magnificationFilter = mode ? kCAFilterLinear : kCAFilterNearest;
+
+        /* On macOS 10.13 and earlier, the desired minificationFilter seems to be
+         * ignored and "nearest" filtering is used, which looks terrible.
+         * Enabling rasterization seems to work around this, only enable
+         * it when there may be down-scaling (retina mode enabled).
+         */
+        if (floor(NSAppKitVersionNumber) < 1671 /*NSAppKitVersionNumber10_14*/)
+        {
+            if (mode)
+            {
+                [self layer].shouldRasterize = YES;
+                [self layer].rasterizationScale = 2.0;
+            }
+            else
+                [self layer].shouldRasterize = NO;
+        }
     }
 
     - (void) setRetinaMode:(int)mode