Reduce amount of unsafe on iOS (#2579)

* Use objc2::foundation CG types

* Add safe abstraction over UIApplication

* Add safe abstraction over UIDevice

* Add safe abstraction over UIScreen

* Add safe abstraction over UIWindow

* Add safe abstraction over UIViewController

* Add safe abstraction over UIView

* Appease clippy

src/platform_impl/ios/uikit/screen.rs

@@ -0,0 +1,79 @@
+use objc2::encode::{Encode, Encoding};
+use objc2::foundation::{CGFloat, CGRect, MainThreadMarker, NSArray, NSInteger, NSObject};
+use objc2::rc::{Id, Shared};
+use objc2::{extern_class, extern_methods, msg_send_id, ClassType};
+
+use super::{UICoordinateSpace, UIScreenMode};
+
+extern_class!(
+    #[derive(Debug, PartialEq, Eq, Hash)]
+    pub(crate) struct UIScreen;
+
+    unsafe impl ClassType for UIScreen {
+        type Super = NSObject;
+    }
+);
+
+extern_methods!(
+    unsafe impl UIScreen {
+        pub fn main(_mtm: MainThreadMarker) -> Id<Self, Shared> {
+            unsafe { msg_send_id![Self::class(), mainScreen] }
+        }
+
+        pub fn screens(_mtm: MainThreadMarker) -> Id<NSArray<Self, Shared>, Shared> {
+            unsafe { msg_send_id![Self::class(), screens] }
+        }
+
+        #[sel(bounds)]
+        pub fn bounds(&self) -> CGRect;
+
+        #[sel(scale)]
+        pub fn scale(&self) -> CGFloat;
+
+        #[sel(nativeBounds)]
+        pub fn nativeBounds(&self) -> CGRect;
+
+        #[sel(nativeScale)]
+        pub fn nativeScale(&self) -> CGFloat;
+
+        #[sel(maximumFramesPerSecond)]
+        pub fn maximumFramesPerSecond(&self) -> NSInteger;
+
+        pub fn mirroredScreen(&self) -> Id<Self, Shared> {
+            unsafe { msg_send_id![Self::class(), mirroredScreen] }
+        }
+
+        pub fn preferredMode(&self) -> Option<Id<UIScreenMode, Shared>> {
+            unsafe { msg_send_id![self, preferredMode] }
+        }
+
+        #[sel(setCurrentMode:)]
+        pub fn setCurrentMode(&self, mode: Option<&UIScreenMode>);
+
+        pub fn availableModes(&self) -> Id<NSArray<UIScreenMode, Shared>, Shared> {
+            unsafe { msg_send_id![self, availableModes] }
+        }
+
+        #[sel(setOverscanCompensation:)]
+        pub fn setOverscanCompensation(&self, overscanCompensation: UIScreenOverscanCompensation);
+
+        pub fn coordinateSpace(&self) -> Id<UICoordinateSpace, Shared> {
+            unsafe { msg_send_id![self, coordinateSpace] }
+        }
+    }
+);
+
+#[repr(transparent)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct UIScreenOverscanCompensation(NSInteger);
+
+unsafe impl Encode for UIScreenOverscanCompensation {
+    const ENCODING: Encoding = NSInteger::ENCODING;
+}
+
+#[allow(dead_code)]
+impl UIScreenOverscanCompensation {
+    pub const Scale: Self = Self(0);
+    pub const InsetBounds: Self = Self(1);
+    pub const None: Self = Self(2);
+}