Add macOS support using Core Graphics

Cargo.toml

@@ -16,6 +16,10 @@ x11-dl = "2.19.1"
 [target.'cfg(target_os = "windows")'.dependencies]
 winapi = "0.3.9"
 
+[target.'cfg(target_os = "macos")'.dependencies]
+core-graphics = "0.22.3"
+objc = "0.2.7"
+
 [dev-dependencies]
 winit = "0.26.1"
 image = "0.23.14"

src/cg.rs

@@ -0,0 +1,64 @@
+use crate::{GraphicsContextImpl, SoftBufferError};
+use raw_window_handle::{HasRawWindowHandle, AppKitHandle};
+use objc::runtime::Object;
+use core_graphics::base::{kCGBitmapByteOrder32Little, kCGImageAlphaNoneSkipFirst, kCGRenderingIntentDefault};
+use core_graphics::color_space::CGColorSpace;
+use core_graphics::context::CGContext;
+use core_graphics::data_provider::CGDataProvider;
+use core_graphics::geometry::{CGPoint, CGSize, CGRect};
+use core_graphics::image::CGImage;
+use core_graphics::sys;
+
+pub struct CGImpl {
+    view: *mut Object,
+}
+
+impl CGImpl {
+    pub unsafe fn new<W: HasRawWindowHandle>(handle: AppKitHandle) -> Result<Self, SoftBufferError<W>> {
+        let window = handle.ns_window as *mut Object;
+        let view = handle.ns_view as *mut Object;
+        let cls = class!(NSGraphicsContext);
+        let graphics_context: *mut Object = msg_send![cls, graphicsContextWithWindow:window];
+        if graphics_context.is_null() {
+            return Err(SoftBufferError::PlatformError(Some("Graphics context is null".into()), None));
+        }
+        let _: () = msg_send![cls, setCurrentContext:graphics_context];
+        Ok(
+            Self {
+                view,
+            }
+        )
+    }
+}
+
+impl GraphicsContextImpl for CGImpl {
+    unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
+        let cls = class!(NSGraphicsContext);
+        let graphics_context: *mut Object = msg_send![cls, currentContext];
+        let context_ptr: *mut sys::CGContext = msg_send![graphics_context, CGContext];
+        let context = CGContext::from_existing_context_ptr(context_ptr);
+        let color_space = CGColorSpace::create_device_rgb();
+        let slice = std::slice::from_raw_parts(
+            buffer.as_ptr() as *const u8,
+            buffer.len() * 4);
+        let data_provider = CGDataProvider::from_slice(slice);
+        let image = CGImage::new(
+            width as usize,
+            height as usize,
+            8,
+            32,
+            (width * 4) as usize,
+            &color_space,
+            kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipFirst,
+            &data_provider,
+            false,
+            kCGRenderingIntentDefault,
+        );
+        let frame: CGRect = msg_send![self.view, frame];
+        // In Core Graphics, (0, 0) is bottom left, not top left
+        let origin = CGPoint { x: 0f64, y: frame.size.height };
+        let size = CGSize { width: width as f64, height: -(height as f64) };
+        let rect = CGRect { origin, size };
+        context.draw_image(rect, &image);
+    }
+}

src/lib.rs

@@ -1,7 +1,13 @@
 #![doc = include_str!("../README.md")]
 
+#[cfg(target_os = "macos")]
+#[macro_use]
+extern crate objc;
+
 #[cfg(target_os = "windows")]
 mod win32;
+#[cfg(target_os = "macos")]
+mod cg;
 #[cfg(target_os = "linux")]
 mod x11;
 
@@ -32,6 +38,8 @@ impl<W: HasRawWindowHandle> GraphicsContext<W> {
             RawWindowHandle::Xlib(xlib_handle) => Box::new(x11::X11Impl::new(xlib_handle)?),
             #[cfg(target_os = "windows")]
             RawWindowHandle::Win32(win32_handle) => Box::new(win32::Win32Impl::new(&win32_handle)?),
+            #[cfg(target_os = "macos")]
+            RawWindowHandle::AppKit(appkit_handle) => Box::new(cg::CGImpl::new(appkit_handle)?),
             unimplemented_handle_type => return Err(SoftBufferError::UnsupportedPlatform {
                 window,
                 human_readable_platform_name: window_handle_type_name(&unimplemented_handle_type),