gfx: Rename WebrenderSurfman to RenderingContext and move to gfx (#31184)

This is a small cleanup that moves and renames this class. The rename is
simply because we are exposing a lot about the details of Servo's
rendering in the API and it makes sense to start thinking about
abstracting that away a bit.

This also moves the struct to `gfx`, which does have an effect on
Servo's dependency graph. This adds a new dependency on gfx to
`compositing`, but `compositing` had a transitive dependency on
gfx before through `canvas`.

components/gfx/rendering_context.rs

@@ -0,0 +1,243 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#![deny(unsafe_code)]
+
+use std::cell::RefCell;
+use std::ffi::c_void;
+use std::rc::Rc;
+
+use euclid::default::Size2D;
+use surfman::chains::{PreserveBuffer, SwapChain};
+use surfman::{
+    Adapter, Connection, Context, ContextAttributeFlags, ContextAttributes, Device, Error, GLApi,
+    GLVersion, NativeContext, NativeDevice, NativeWidget, Surface, SurfaceAccess, SurfaceInfo,
+    SurfaceTexture, SurfaceType,
+};
+
+/// A Servo rendering context, which holds all of the information needed
+/// to render Servo's layout, and bridges WebRender and surfman.
+#[derive(Clone)]
+pub struct RenderingContext(Rc<RenderingContextData>);
+
+struct RenderingContextData {
+    device: RefCell<Device>,
+    context: RefCell<Context>,
+    // We either render to a swap buffer or to a native widget
+    swap_chain: Option<SwapChain<Device>>,
+}
+
+impl Drop for RenderingContextData {
+    fn drop(&mut self) {
+        let ref mut device = self.device.borrow_mut();
+        let ref mut context = self.context.borrow_mut();
+        if let Some(ref swap_chain) = self.swap_chain {
+            let _ = swap_chain.destroy(device, context);
+        }
+        let _ = device.destroy_context(context);
+    }
+}
+
+impl RenderingContext {
+    pub fn create(
+        connection: &Connection,
+        adapter: &Adapter,
+        surface_type: SurfaceType<NativeWidget>,
+    ) -> Result<Self, Error> {
+        let mut device = connection.create_device(&adapter)?;
+        let flags = ContextAttributeFlags::ALPHA |
+            ContextAttributeFlags::DEPTH |
+            ContextAttributeFlags::STENCIL;
+        let version = match connection.gl_api() {
+            GLApi::GLES => GLVersion { major: 3, minor: 0 },
+            GLApi::GL => GLVersion { major: 3, minor: 2 },
+        };
+        let context_attributes = ContextAttributes { flags, version };
+        let context_descriptor = device.create_context_descriptor(&context_attributes)?;
+        let mut context = device.create_context(&context_descriptor, None)?;
+        let surface_access = SurfaceAccess::GPUOnly;
+        let headless = match surface_type {
+            SurfaceType::Widget { .. } => false,
+            SurfaceType::Generic { .. } => true,
+        };
+        let surface = device.create_surface(&context, surface_access, surface_type)?;
+        device
+            .bind_surface_to_context(&mut context, surface)
+            .map_err(|(err, mut surface)| {
+                let _ = device.destroy_surface(&mut context, &mut surface);
+                err
+            })?;
+
+        device.make_context_current(&context)?;
+
+        let swap_chain = if headless {
+            Some(SwapChain::create_attached(
+                &mut device,
+                &mut context,
+                surface_access,
+            )?)
+        } else {
+            None
+        };
+        let device = RefCell::new(device);
+        let context = RefCell::new(context);
+        let data = RenderingContextData {
+            device,
+            context,
+            swap_chain,
+        };
+        Ok(RenderingContext(Rc::new(data)))
+    }
+
+    pub fn create_surface_texture(
+        &self,
+        surface: Surface,
+    ) -> Result<SurfaceTexture, (Error, Surface)> {
+        let ref device = self.0.device.borrow();
+        let ref mut context = self.0.context.borrow_mut();
+        device.create_surface_texture(context, surface)
+    }
+
+    pub fn destroy_surface_texture(
+        &self,
+        surface_texture: SurfaceTexture,
+    ) -> Result<Surface, (Error, SurfaceTexture)> {
+        let ref device = self.0.device.borrow();
+        let ref mut context = self.0.context.borrow_mut();
+        device.destroy_surface_texture(context, surface_texture)
+    }
+
+    pub fn make_gl_context_current(&self) -> Result<(), Error> {
+        let ref device = self.0.device.borrow();
+        let ref context = self.0.context.borrow();
+        device.make_context_current(context)
+    }
+
+    pub fn swap_chain(&self) -> Result<&SwapChain<Device>, Error> {
+        self.0.swap_chain.as_ref().ok_or(Error::WidgetAttached)
+    }
+
+    pub fn resize(&self, size: Size2D<i32>) -> Result<(), Error> {
+        let ref mut device = self.0.device.borrow_mut();
+        let ref mut context = self.0.context.borrow_mut();
+        if let Some(swap_chain) = self.0.swap_chain.as_ref() {
+            return swap_chain.resize(device, context, size);
+        }
+        let mut surface = device.unbind_surface_from_context(context)?.unwrap();
+        device.resize_surface(context, &mut surface, size)?;
+        device
+            .bind_surface_to_context(context, surface)
+            .map_err(|(err, mut surface)| {
+                let _ = device.destroy_surface(context, &mut surface);
+                err
+            })
+    }
+
+    pub fn present(&self) -> Result<(), Error> {
+        let ref mut device = self.0.device.borrow_mut();
+        let ref mut context = self.0.context.borrow_mut();
+        if let Some(ref swap_chain) = self.0.swap_chain {
+            return swap_chain.swap_buffers(device, context, PreserveBuffer::No);
+        }
+        let mut surface = device.unbind_surface_from_context(context)?.unwrap();
+        device.present_surface(context, &mut surface)?;
+        device
+            .bind_surface_to_context(context, surface)
+            .map_err(|(err, mut surface)| {
+                let _ = device.destroy_surface(context, &mut surface);
+                err
+            })
+    }
+
+    /// Invoke a closure with the surface associated with the current front buffer.
+    /// This can be used to create a surfman::SurfaceTexture to blit elsewhere.
+    pub fn with_front_buffer<F: FnMut(&Device, Surface) -> Surface>(&self, mut f: F) {
+        let ref mut device = self.0.device.borrow_mut();
+        let ref mut context = self.0.context.borrow_mut();
+        let surface = device
+            .unbind_surface_from_context(context)
+            .unwrap()
+            .unwrap();
+        let surface = f(device, surface);
+        device.bind_surface_to_context(context, surface).unwrap();
+    }
+
+    pub fn device(&self) -> std::cell::Ref<Device> {
+        self.0.device.borrow()
+    }
+
+    pub fn connection(&self) -> Connection {
+        let ref device = self.0.device.borrow();
+        device.connection()
+    }
+
+    pub fn adapter(&self) -> Adapter {
+        let ref device = self.0.device.borrow();
+        device.adapter()
+    }
+
+    pub fn native_context(&self) -> NativeContext {
+        let ref device = self.0.device.borrow();
+        let ref context = self.0.context.borrow();
+        device.native_context(context)
+    }
+
+    pub fn native_device(&self) -> NativeDevice {
+        let ref device = self.0.device.borrow();
+        device.native_device()
+    }
+
+    pub fn context_attributes(&self) -> ContextAttributes {
+        let ref device = self.0.device.borrow();
+        let ref context = self.0.context.borrow();
+        let ref descriptor = device.context_descriptor(context);
+        device.context_descriptor_attributes(descriptor)
+    }
+
+    pub fn context_surface_info(&self) -> Result<Option<SurfaceInfo>, Error> {
+        let ref device = self.0.device.borrow();
+        let ref context = self.0.context.borrow();
+        device.context_surface_info(context)
+    }
+
+    pub fn surface_info(&self, surface: &Surface) -> SurfaceInfo {
+        let ref device = self.0.device.borrow();
+        device.surface_info(surface)
+    }
+
+    pub fn surface_texture_object(&self, surface: &SurfaceTexture) -> u32 {
+        let ref device = self.0.device.borrow();
+        device.surface_texture_object(surface)
+    }
+
+    pub fn get_proc_address(&self, name: &str) -> *const c_void {
+        let ref device = self.0.device.borrow();
+        let ref context = self.0.context.borrow();
+        device.get_proc_address(context, name)
+    }
+
+    pub fn unbind_native_surface_from_context(&self) -> Result<(), Error> {
+        let device = self.0.device.borrow_mut();
+        let mut context = self.0.context.borrow_mut();
+        let mut surface = device.unbind_surface_from_context(&mut context)?.unwrap();
+        let _ = device.destroy_surface(&mut context, &mut surface)?;
+        Ok(())
+    }
+
+    pub fn bind_native_surface_to_context(&self, native_widget: NativeWidget) -> Result<(), Error> {
+        let mut device = self.0.device.borrow_mut();
+        let mut context = self.0.context.borrow_mut();
+        let surface_access = SurfaceAccess::GPUOnly;
+        let surface_type = SurfaceType::Widget { native_widget };
+        let surface = device.create_surface(&context, surface_access, surface_type)?;
+        device
+            .bind_surface_to_context(&mut context, surface)
+            .map_err(|(err, mut surface)| {
+                let _ = device.destroy_surface(&mut context, &mut surface);
+                err
+            })?;
+        device.make_context_current(&context)?;
+        Ok(())
+    }
+}