Use fixed size rather than nsscreen (#174)

Author: noahsmartin

DemoApp/DemoApp.xcodeproj/project.pbxproj

@@ -829,6 +829,11 @@
 		};
 		FA8F8B802C66C4C4007CEA33 /* PBXTargetDependency */ = {
 			isa = PBXTargetDependency;
+			platformFilters = (
+				ios,
+				maccatalyst,
+				macos,
+			);
 			target = FA1671BE2A5367A800A42DB0 /* DemoApp */;
 			targetProxy = FA8F8B7F2C66C4C4007CEA33 /* PBXContainerItemProxy */;
 		};
@@ -1245,6 +1250,8 @@
 				PRODUCT_BUNDLE_IDENTIFIER = com.emerge.DemoAppTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = iphoneos;
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTS_MACCATALYST = YES;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
@@ -1265,6 +1272,8 @@
 				PRODUCT_BUNDLE_IDENTIFIER = com.emerge.DemoAppTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = iphoneos;
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTS_MACCATALYST = YES;
 				SWIFT_EMIT_LOC_STRINGS = NO;
 				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = "1,2";

Sources/SnapshotPreviewsCore/AppKitRenderingStrategy.swift

@@ -99,7 +99,7 @@ final class AppKitContainer: NSHostingController<EmergeModifierView> {
       heightAnchor = view.heightAnchor.constraint(equalToConstant: height)
       heightAnchor?.isActive = true
     default:
-      let fittingSize = sizeThatFits(in: NSScreen.main!.frame.size)
+      let fittingSize = sizeThatFits(in: NSSize(width: 800, height: 200))
       widthAnchor = view.widthAnchor.constraint(greaterThanOrEqualToConstant: fittingSize.width)
       widthAnchor?.isActive = true
       heightAnchor = view.heightAnchor.constraint(greaterThanOrEqualToConstant: fittingSize.height)