macOS: 10.13 should use OpenGL renderer

There appears to be a problem with SDL's Metal renderer under 10.13 (segfault on window creation).

src/macos.h

@@ -26,6 +26,8 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
 
 /* Platform-specific functionality for macOS */
 
+iBool   shouldDefaultToMetalRenderer_MacOS  (void);
+
 void    setupApplication_MacOS  (void);
 void    insertMenuItems_MacOS   (const char *menuLabel, int atIndex, const iMenuItem *items, size_t count);
 void    handleCommand_MacOS     (const char *cmd);

src/macos.m

@@ -38,14 +38,25 @@
     default_TouchBarVariant,
 };
 
+static iInt2 macVer_(void) {
+    if ([[NSProcessInfo processInfo] respondsToSelector:@selector(operatingSystemVersion)]) {
+        const NSOperatingSystemVersion ver = [[NSProcessInfo processInfo] operatingSystemVersion];
+        return init_I2(ver.majorVersion, ver.minorVersion);
+    }
+    return init_I2(10, 10);
+}
+
 static NSString *currentSystemAppearance_(void) {
     /* This API does not exist on 10.13. */
-    @try {
+    if ([NSApp respondsToSelector:@selector(effectiveAppearance)]) {
         return [[NSApp effectiveAppearance] name];
     }
-    @catch (NSException *) {
-        return @"NSAppearanceNameAqua";
-    }
+    return @"NSAppearanceNameAqua";
+}
+
+iBool shouldDefaultToMetalRenderer_MacOS(void) {
+    const iInt2 ver = macVer_();
+    return ver.x > 10 || ver.y > 13;
 }
 
 /*----------------------------------------------------------------------------------------------*/

src/ui/window.c

@@ -522,7 +522,7 @@ void init_Window(iWindow *d, iRect rect) {
     d->isDrawFrozen = iTrue;
     uint32_t flags = 0;
 #if defined (iPlatformApple)
-    SDL_SetHint(SDL_HINT_RENDER_DRIVER, "metal");
+    SDL_SetHint(SDL_HINT_RENDER_DRIVER, shouldDefaultToMetalRenderer_MacOS() ? "metal" : "opengl");
 #else
     flags |= SDL_WINDOW_OPENGL;
 #endif