Use static dispatch

Author: notgull

src/cg.rs

@@ -1,4 +1,4 @@
-use crate::{GraphicsContextImpl, SwBufError};
+use crate::SwBufError;
 use raw_window_handle::AppKitWindowHandle;
 use core_graphics::base::{kCGBitmapByteOrder32Little, kCGImageAlphaNoneSkipFirst, kCGRenderingIntentDefault};
 use core_graphics::color_space::CGColorSpace;
@@ -32,10 +32,8 @@ impl CGImpl {
         let _: () = msg_send![subview, release]; // releases subview (-1) = 1
         Ok(Self{layer})
     }
-}
 
-impl GraphicsContextImpl for CGImpl {
-    unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
+    pub(crate) unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
         let color_space = CGColorSpace::create_device_rgb();
         let data = std::slice::from_raw_parts(
             buffer.as_ptr() as *const u8,

src/lib.rs

@@ -27,7 +27,54 @@ use raw_window_handle::{HasRawDisplayHandle, HasRawWindowHandle, RawDisplayHandl
 /// An instance of this struct contains the platform-specific data that must be managed in order to
 /// write to a window on that platform.
 pub struct GraphicsContext {
-    graphics_context_impl: Box<dyn GraphicsContextImpl>,
+    /// The inner static dispatch object.
+    /// 
+    /// This is boxed so that `GraphicsContext` is the same size on every platform, which should
+    /// hopefully prevent surprises.
+    graphics_context_impl: Box<Dispatch>
+}
+
+/// A macro for creating the enum used to statically dispatch to the platform-specific implementation.
+macro_rules! make_dispatch {
+    (
+        $(
+            $(#[$attr:meta])*
+            $name: ident ($inner_ty: ty),
+        )*
+    ) => {
+        enum Dispatch {
+            $(
+                $(#[$attr])*
+                $name($inner_ty),
+            )*
+        }
+
+        impl Dispatch {
+            unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
+                match self {
+                    $(
+                        $(#[$attr])*
+                        Self::$name(inner) => inner.set_buffer(buffer, width, height),
+                    )*
+                }
+            }
+        }
+    };
+}
+
+make_dispatch! {
+    #[cfg(all(feature = "x11", any(target_os = "linux", target_os = "freebsd")))]
+    X11(x11::X11Impl),
+    #[cfg(all(feature = "wayland", any(target_os = "linux", target_os = "freebsd")))]
+    Wayland(wayland::WaylandImpl),
+    #[cfg(target_os = "windows")]
+    Win32(win32::Win32Impl),
+    #[cfg(target_os = "macos")]
+    CG(cg::CGImpl),
+    #[cfg(target_arch = "wasm32")]
+    Web(web::WebImpl),
+    #[cfg(target_os = "redox")]
+    Orbital(orbital::OrbitalImpl),
 }
 
 impl GraphicsContext {
@@ -48,19 +95,19 @@ impl GraphicsContext {
     ///  - Ensure that the provided handles are valid to draw a 2D buffer to, and are valid for the
     ///    lifetime of the GraphicsContext
     pub unsafe fn from_raw(raw_window_handle: RawWindowHandle, raw_display_handle: RawDisplayHandle) -> Result<Self, SwBufError> {
-        let imple: Box<dyn GraphicsContextImpl> = match (raw_window_handle, raw_display_handle) {
+        let imple: Dispatch = match (raw_window_handle, raw_display_handle) {
             #[cfg(all(feature = "x11", any(target_os = "linux", target_os = "freebsd")))]
-            (RawWindowHandle::Xlib(xlib_window_handle), RawDisplayHandle::Xlib(xlib_display_handle)) => Box::new(x11::X11Impl::new(xlib_window_handle, xlib_display_handle)?),
+            (RawWindowHandle::Xlib(xlib_window_handle), RawDisplayHandle::Xlib(xlib_display_handle)) => Dispatch::X11(x11::X11Impl::new(xlib_window_handle, xlib_display_handle)?),
             #[cfg(all(feature = "wayland", any(target_os = "linux", target_os = "freebsd")))]
-            (RawWindowHandle::Wayland(wayland_window_handle), RawDisplayHandle::Wayland(wayland_display_handle)) => Box::new(wayland::WaylandImpl::new(wayland_window_handle, wayland_display_handle)?),
+            (RawWindowHandle::Wayland(wayland_window_handle), RawDisplayHandle::Wayland(wayland_display_handle)) => Dispatch::Wayland(wayland::WaylandImpl::new(wayland_window_handle, wayland_display_handle)?), 
             #[cfg(target_os = "windows")]
-            (RawWindowHandle::Win32(win32_handle), _) => Box::new(win32::Win32Impl::new(&win32_handle)?),
+            (RawWindowHandle::Win32(win32_handle), _) => Dispatch::Win32(win32::Win32Impl::new(&win32_handle)?),
             #[cfg(target_os = "macos")]
-            (RawWindowHandle::AppKit(appkit_handle), _) => Box::new(cg::CGImpl::new(appkit_handle)?),
+            (RawWindowHandle::AppKit(appkit_handle), _) => Dispatch::CG(cg::CGImpl::new(appkit_handle)?),
             #[cfg(target_arch = "wasm32")]
-            (RawWindowHandle::Web(web_handle), _) => Box::new(web::WebImpl::new(web_handle)?),
+            (RawWindowHandle::Web(web_handle), _) => Dispatch::Web(web::WebImpl::new(web_handle)?),
             #[cfg(target_os = "redox")]
-            (RawWindowHandle::Orbital(orbital_handle), _) => Box::new(orbital::OrbitalImpl::new(orbital_handle)?),
+            (RawWindowHandle::Orbital(orbital_handle), _) => Dispatch::Orbital(orbital::OrbitalImpl::new(orbital_handle)?),
             (unimplemented_window_handle, unimplemented_display_handle) => return Err(SwBufError::UnsupportedPlatform {
                 human_readable_window_platform_name: window_handle_type_name(&unimplemented_window_handle),
                 human_readable_display_platform_name: display_handle_type_name(&unimplemented_display_handle),
@@ -70,7 +117,7 @@ impl GraphicsContext {
         };
 
         Ok(Self {
-            graphics_context_impl: imple,
+            graphics_context_impl: Box::new(imple)
         })
     }
 
@@ -109,10 +156,6 @@ impl GraphicsContext {
     }
 }
 
-trait GraphicsContextImpl {
-    unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16);
-}
-
 fn window_handle_type_name(handle: &RawWindowHandle) -> &'static str {
     match handle {
         RawWindowHandle::Xlib(_) => "Xlib",

src/orbital.rs

@@ -5,7 +5,6 @@ use std::{
     str,
 };
 
-use crate::GraphicsContextImpl;
 use crate::SwBufError;
 
 struct OrbitalMap {
@@ -49,10 +48,8 @@ impl OrbitalImpl {
     pub fn new(handle: OrbitalWindowHandle) -> Result<Self, SwBufError> {
         Ok(Self { handle })
     }
-}
 
-impl GraphicsContextImpl for OrbitalImpl {
-    unsafe fn set_buffer(&mut self, buffer: &[u32], width_u16: u16, height_u16: u16) {
+    pub(crate) unsafe fn set_buffer(&mut self, buffer: &[u32], width_u16: u16, height_u16: u16) {
         let window_fd = self.handle.window as usize;
 
         // Read the current width and size

src/wayland/mod.rs

@@ -1,4 +1,4 @@
-use crate::{error::unwrap, GraphicsContextImpl, SwBufError};
+use crate::{error::unwrap, SwBufError};
 use raw_window_handle::{WaylandDisplayHandle, WaylandWindowHandle};
 use std::collections::VecDeque;
 use wayland_client::{
@@ -78,10 +78,8 @@ impl WaylandImpl {
         self.buffers.push_back(buffer);
         self.buffers.back().unwrap()
     }
-}
 
-impl GraphicsContextImpl for WaylandImpl {
-    unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
+    pub(super) unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
         let _ = self.event_queue.dispatch_pending(&mut State);
 
         let surface = self.surface.clone();

src/web.rs

@@ -5,7 +5,6 @@ use web_sys::CanvasRenderingContext2d;
 use web_sys::HtmlCanvasElement;
 use web_sys::ImageData;
 
-use crate::GraphicsContextImpl;
 use crate::SwBufError;
 
 pub struct WebImpl {
@@ -60,10 +59,8 @@ impl WebImpl {
 
         Ok(Self { canvas, ctx })
     }
-}
 
-impl GraphicsContextImpl for WebImpl {
-    unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
+    pub(crate) unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
         self.canvas.set_width(width.into());
         self.canvas.set_height(height.into());
 

src/win32.rs

@@ -1,12 +1,12 @@
 //! Implementation of software buffering for Windows.
-//! 
+//!
 //! This module converts the input buffer into a bitmap and then stretches it to the window.
 
-use crate::{GraphicsContextImpl, SwBufError};
+use crate::SwBufError;
 use raw_window_handle::Win32WindowHandle;
 
-use std::mem;
 use std::io;
+use std::mem;
 use std::os::raw::c_int;
 
 use windows_sys::Win32::Foundation::HWND;
@@ -33,9 +33,9 @@ struct BitmapInfo {
 
 impl Win32Impl {
     /// Create a new `Win32Impl` from a `Win32WindowHandle`.
-    /// 
+    ///
     /// # Safety
-    /// 
+    ///
     /// The `Win32WindowHandle` must be a valid window handle.
     pub unsafe fn new(handle: &Win32WindowHandle) -> Result<Self, crate::SwBufError> {
         // It is valid for the window handle to be null here. Error out if it is.
@@ -56,17 +56,12 @@ impl Win32Impl {
             ));
         }
 
-        Ok(Self {
-            dc,
-            window: hwnd,
-        })
+        Ok(Self { dc, window: hwnd })
     }
-}
 
-impl GraphicsContextImpl for Win32Impl {
-    unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
+    pub(crate) unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
         // Create a new bitmap info struct.
-        let mut bitmap_info: BitmapInfo =mem::zeroed();
+        let mut bitmap_info: BitmapInfo = mem::zeroed();
 
         bitmap_info.bmi_header.biSize = mem::size_of::<BITMAPINFOHEADER>() as u32;
         bitmap_info.bmi_header.biPlanes = 1;

src/x11.rs

@@ -1,10 +1,10 @@
 //! Implementation of software buffering for X11.
-//! 
+//!
 //! This module converts the input buffer into an XImage and then sends it over the wire to be
 //! drawn. A more effective implementation would use shared memory instead of the wire. In
 //! addition, we may also want to blit to a pixmap instead of a window.
 
-use crate::{GraphicsContextImpl, SwBufError};
+use crate::SwBufError;
 use raw_window_handle::{XlibDisplayHandle, XlibWindowHandle};
 use std::os::raw::{c_char, c_uint};
 use x11_dl::xlib::{Display, Visual, Xlib, ZPixmap, GC};
@@ -32,9 +32,9 @@ pub struct X11Impl {
 
 impl X11Impl {
     /// Create a new `X11Impl` from a `XlibWindowHandle` and `XlibDisplayHandle`.
-    /// 
+    ///
     /// # Safety
-    /// 
+    ///
     /// The `XlibWindowHandle` and `XlibDisplayHandle` must be valid.
     pub unsafe fn new(
         window_handle: XlibWindowHandle,
@@ -83,10 +83,8 @@ impl X11Impl {
             depth,
         })
     }
-}
 
-impl GraphicsContextImpl for X11Impl {
-    unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
+    pub(crate) unsafe fn set_buffer(&mut self, buffer: &[u32], width: u16, height: u16) {
         // Create the image from the buffer.
         let image = (self.lib.XCreateImage)(
             self.display_handle.display as *mut Display,