macOS: Expose more display modes on retina screens. Fixes an issue found in BZFlag.

src/video/cocoa/SDL_cocoamodes.m

@@ -100,15 +100,47 @@ CG_SetError(const char *prefix, CGDisplayErr result)
 }
 
 static SDL_bool
-GetDisplayMode(_THIS, CGDisplayModeRef vidmode, CVDisplayLinkRef link, SDL_DisplayMode *mode)
+GetDisplayMode(_THIS, CGDisplayModeRef vidmode, CFArrayRef modelist, CVDisplayLinkRef link, SDL_DisplayMode *mode)
 {
     SDL_DisplayModeData *data;
-    int width = 0;
-    int height = 0;
+    int width = (int) CGDisplayModeGetWidth(vidmode);
+    int height = (int) CGDisplayModeGetHeight(vidmode);
     int bpp = 0;
     int refreshRate = 0;
     CFStringRef fmt;
 
+    /* Ignore this mode if it's low-dpi (@1x) and we have a high-dpi mode in the
+     * list with the same size in points.
+     */
+#ifdef MAC_OS_X_VERSION_10_8
+    if (modelist != NULL && floor(NSAppKitVersionNumber) > NSAppKitVersionNumber10_7) {
+        int pixelW = (int) CGDisplayModeGetPixelWidth(vidmode);
+        int pixelH = (int) CGDisplayModeGetPixelHeight(vidmode);
+
+        if (width == pixelW && height == pixelH) {
+            CFIndex modescount = CFArrayGetCount(modelist);
+
+            for (int i = 0; i < modescount; i++) {
+                CGDisplayModeRef othermode = (CGDisplayModeRef) CFArrayGetValueAtIndex(modelist, i);
+
+                if (CFEqual(vidmode, othermode)) {
+                    continue;
+                }
+
+                int otherW = (int) CGDisplayModeGetWidth(othermode);
+                int otherH = (int) CGDisplayModeGetHeight(othermode);
+
+                int otherpixelW = (int) CGDisplayModeGetPixelWidth(othermode);
+                int otherpixelH = (int) CGDisplayModeGetPixelHeight(othermode);
+
+                if (width == otherW && height == otherH && (otherpixelW != otherW || otherpixelH != otherH)) {
+                    return SDL_FALSE;
+                }
+            }
+        }
+    }
+#endif
+
     data = (SDL_DisplayModeData *) SDL_malloc(sizeof(*data));
     if (!data) {
         return SDL_FALSE;
@@ -116,8 +148,6 @@ GetDisplayMode(_THIS, CGDisplayModeRef vidmode, CVDisplayLinkRef link, SDL_Displ
     data->moderef = vidmode;
 
     fmt = CGDisplayModeCopyPixelEncoding(vidmode);
-    width = (int) CGDisplayModeGetWidth(vidmode);
-    height = (int) CGDisplayModeGetHeight(vidmode);
     refreshRate = (int) (CGDisplayModeGetRefreshRate(vidmode) + 0.5);
 
     if (CFStringCompare(fmt, CFSTR(IO32BitDirectPixels),
@@ -243,7 +273,7 @@ Cocoa_InitModes(_THIS)
             SDL_zero(display);
             /* this returns a stddup'ed string */
             display.name = (char *)Cocoa_GetDisplayName(displays[i]);
-            if (!GetDisplayMode(_this, moderef, link, &mode)) {
+            if (!GetDisplayMode(_this, moderef, NULL, link, &mode)) {
                 CVDisplayLinkRelease(link);
                 CGDisplayModeRelease(moderef);
                 SDL_free(display.name);
@@ -340,7 +370,29 @@ void
 Cocoa_GetDisplayModes(_THIS, SDL_VideoDisplay * display)
 {
     SDL_DisplayData *data = (SDL_DisplayData *) display->driverdata;
-    CFArrayRef modes = CGDisplayCopyAllDisplayModes(data->display, NULL);
+    CFDictionaryRef dict = NULL;
+    CFArrayRef modes;
+
+    /* By default, CGDisplayCopyAllDisplayModes will only get a subset of the
+     * system's available modes. For example on a 15" 2016 MBP, users can
+     * choose 1920x1080@2x in System Preferences but it won't show up here,
+     * unless we specify the option below.
+     */
+#ifdef MAC_OS_X_VERSION_10_8
+    if (floor(NSAppKitVersionNumber) > NSAppKitVersionNumber10_7) {
+        const CFStringRef dictkeys[] = {kCGDisplayShowDuplicateLowResolutionModes};
+        const CFBooleanRef dictvalues[] = {kCFBooleanTrue};
+        dict = CFDictionaryCreate(NULL,
+                                  (const void **)dictkeys,
+                                  (const void **)dictvalues,
+                                  1,
+                                  &kCFCopyStringDictionaryKeyCallBacks,
+                                  &kCFTypeDictionaryValueCallBacks);
+    }
+#endif
+
+    modes = CGDisplayCopyAllDisplayModes(data->display, dict);
+    CFRelease(dict);
 
     if (modes) {
         CVDisplayLinkRef link = NULL;
@@ -352,7 +404,7 @@ Cocoa_GetDisplayModes(_THIS, SDL_VideoDisplay * display)
         for (i = 0; i < count; i++) {
             CGDisplayModeRef moderef = (CGDisplayModeRef) CFArrayGetValueAtIndex(modes, i);
             SDL_DisplayMode mode;
-            if (GetDisplayMode(_this, moderef, link, &mode)) {
+            if (GetDisplayMode(_this, moderef, modes, link, &mode)) {
                 CGDisplayModeRetain(moderef);
                 SDL_AddDisplayMode(display, &mode);
             }