api/context: add make_not_current_as_possibly_current

Allow making the context not current by reference.

Author: mickvangelderen

CHANGELOG.md

@@ -1,5 +1,7 @@
 # Unreleased
 
+- Add `PossiblyCurrentContext::make_not_current_in_place(&self)` for when `Send` capability of `NotCurrentContext` is not required.
+
 # Version 0.32.1
 
 - Fixed EGL's `Device::query_devices()` being too strict about required extensions.

glutin/src/api/cgl/context.rs

@@ -148,10 +148,14 @@ impl PossiblyCurrentGlContext for PossiblyCurrentContext {
     type Surface<T: SurfaceTypeTrait> = Surface<T>;
 
     fn make_not_current(self) -> Result<Self::NotCurrentContext> {
-        self.inner.make_not_current()?;
+        self.make_not_current_in_place()?;
         Ok(NotCurrentContext::new(self.inner))
     }
 
+    fn make_not_current_in_place(&self) -> Result<()> {
+        self.inner.make_not_current()
+    }
+
     fn is_current(&self) -> bool {
         if let Some(current) = NSOpenGLContext::currentContext() {
             current == self.inner.raw

glutin/src/api/egl/context.rs

@@ -259,10 +259,14 @@ impl PossiblyCurrentGlContext for PossiblyCurrentContext {
     type Surface<T: SurfaceTypeTrait> = Surface<T>;
 
     fn make_not_current(self) -> Result<Self::NotCurrentContext> {
-        self.inner.make_not_current()?;
+        self.make_not_current_in_place()?;
         Ok(NotCurrentContext::new(self.inner))
     }
 
+    fn make_not_current_in_place(&self) -> Result<()> {
+        self.inner.make_not_current()
+    }
+
     fn is_current(&self) -> bool {
         unsafe {
             self.inner.bind_api();

glutin/src/api/glx/context.rs

@@ -302,10 +302,14 @@ impl PossiblyCurrentGlContext for PossiblyCurrentContext {
     type Surface<T: SurfaceTypeTrait> = Surface<T>;
 
     fn make_not_current(self) -> Result<Self::NotCurrentContext> {
-        self.inner.make_not_current()?;
+        self.make_not_current_in_place()?;
         Ok(NotCurrentContext::new(self.inner))
     }
 
+    fn make_not_current_in_place(&self) -> Result<()> {
+        self.inner.make_not_current()
+    }
+
     fn is_current(&self) -> bool {
         unsafe { self.inner.display.inner.glx.GetCurrentContext() == *self.inner.raw }
     }

glutin/src/api/wgl/context.rs

@@ -288,16 +288,20 @@ impl PossiblyCurrentGlContext for PossiblyCurrentContext {
     type Surface<T: SurfaceTypeTrait> = Surface<T>;
 
     fn make_not_current(self) -> Result<Self::NotCurrentContext> {
+        self.make_not_current_in_place()?;
+        Ok(NotCurrentContext::new(self.inner))
+    }
+
+    fn make_not_current_in_place(&self) -> Result<()> {
         unsafe {
             if self.is_current() {
                 let hdc = wgl::GetCurrentDC();
                 if wgl::MakeCurrent(hdc, std::ptr::null()) == 0 {
                     return Err(IoError::last_os_error().into());
                 }
             }
-
-            Ok(NotCurrentContext::new(self.inner))
         }
+        Ok(())
     }
 
     fn is_current(&self) -> bool {

glutin/src/context.rs

@@ -97,6 +97,11 @@ pub trait PossiblyCurrentGlContext: Sealed {
     /// - **macOS: this will block if your main thread is blocked.**
     fn make_not_current(self) -> Result<Self::NotCurrentContext>;
 
+    /// Make the context not current to the current thread. If you need to
+    /// send the context to another thread, use [`Self::make_not_current`]
+    /// instead.
+    fn make_not_current_in_place(&self) -> Result<()>;
+
     /// Make [`Self::Surface`] current on the calling thread.
     ///
     /// # Platform specific
@@ -517,6 +522,10 @@ impl PossiblyCurrentGlContext for PossiblyCurrentContext {
         )
     }
 
+    fn make_not_current_in_place(&self) -> Result<()> {
+        Ok(gl_api_dispatch!(self; Self(context) => context.make_not_current_in_place()?))
+    }
+
     fn make_current<T: SurfaceTypeTrait>(&self, surface: &Self::Surface<T>) -> Result<()> {
         match (self, surface) {
             #[cfg(egl_backend)]

glutin_examples/examples/switch_render_thread.rs

@@ -7,7 +7,6 @@ use std::thread;
 use glutin::config::ConfigTemplateBuilder;
 use glutin::context::{ContextAttributesBuilder, PossiblyCurrentContext};
 use glutin::display::GetGlDisplay;
-use glutin::error::{Error as GlutinError, ErrorKind};
 use glutin::prelude::*;
 use glutin::surface::{Surface, WindowSurface};
 use glutin_examples::gl::types::GLfloat;
@@ -148,7 +147,7 @@ impl AppState {
 
 /// A rendering context that can be shared between tasks.
 struct RenderContext {
-    context: Option<PossiblyCurrentContext>,
+    context: PossiblyCurrentContext,
     surface: Surface<WindowSurface>,
     renderer: Renderer,
 }
@@ -161,44 +160,27 @@ impl RenderContext {
         surface: Surface<WindowSurface>,
         renderer: Renderer,
     ) -> Self {
-        Self { context: Some(context), surface, renderer }
+        Self { context, surface, renderer }
     }
 
     fn make_current(&mut self) -> Result<(), impl Error> {
-        let ctx =
-            self.context.take().ok_or_else(|| GlutinError::from(ErrorKind::BadContextState))?;
-        let result = ctx.make_current(&self.surface);
-        self.context = Some(ctx);
-        result
+        self.context.make_current(&self.surface)
     }
 
     fn make_not_current(&mut self) -> Result<(), impl Error> {
-        let ctx =
-            self.context.take().ok_or_else(|| GlutinError::from(ErrorKind::BadContextState))?;
-        let not_current_ctx = ctx.make_not_current()?;
-        self.context = Some(not_current_ctx.treat_as_possibly_current());
-        Ok::<(), GlutinError>(())
+        self.context.make_not_current_in_place()
     }
 
     fn swap_buffers(&mut self) -> Result<(), impl Error> {
-        let ctx =
-            self.context.take().ok_or_else(|| GlutinError::from(ErrorKind::BadContextState))?;
-        let result = self.surface.swap_buffers(&ctx);
-        self.context = Some(ctx);
-        result
+        self.surface.swap_buffers(&self.context)
     }
 
     fn draw_with_clear_color(&self, red: GLfloat, green: GLfloat, blue: GLfloat, alpha: GLfloat) {
         self.renderer.draw_with_clear_color(red, green, blue, alpha)
     }
 
     fn resize(&mut self, size: PhysicalSize<NonZeroU32>) {
-        let Some(ctx) = self.context.take() else {
-            return;
-        };
-        self.surface.resize(&ctx, size.width, size.height);
-        self.context = Some(ctx);
-
+        self.surface.resize(&self.context, size.width, size.height);
         self.renderer.resize(size.width.get() as i32, size.height.get() as i32);
     }
 }