Improve the OpenGL context request system

src/android/mod.rs

@@ -11,7 +11,9 @@ use events::MouseButton;
 
 use std::collections::RingBuf;
 
+use Api;
 use BuilderAttribs;
+use GlRequest;
 
 pub struct Window {
     display: ffi::egl::types::EGLDisplay,
@@ -157,7 +159,10 @@ impl Window {
         android_glue::write_log("eglInitialize succeeded");
 
         let use_gles2 = match builder.gl_version {
-            Some((2, 0)) => true,
+            GlRequest::Specific(Api::OpenGlEs, (2, _)) => true,
+            GlRequest::Specific(Api::OpenGlEs, _) => false,
+            GlRequest::Specific(_, _) => panic!("Only OpenGL ES is supported"),     // FIXME: return a result
+            GlRequest::GlThenGles { opengles_version: (2, _), .. } => true,
             _ => false,
         };
 

src/cocoa/mod.rs

@@ -5,7 +5,9 @@ use {CreationError, Event, MouseCursor};
 use CreationError::OsError;
 use libc;
 
+use Api;
 use BuilderAttribs;
+use GlRequest;
 
 use cocoa::base::{Class, id, YES, NO, NSUInteger, nil, objc_allocateClassPair, class, objc_registerClassPair};
 use cocoa::base::{selector, msg_send, msg_send_stret, class_addMethod, class_addIvar};
@@ -453,11 +455,18 @@ impl Window {
         }
     }
 
-    fn create_context(view: id, vsync: bool, gl_version: Option<(u32, u32)>) -> Option<id> {
+    fn create_context(view: id, vsync: bool, gl_version: GlRequest) -> Option<id> {
         let profile = match gl_version {
-            None | Some((0...2, _)) | Some((3, 0)) => NSOpenGLProfileVersionLegacy as u32,
+            GlRequest::Latest => NSOpenGLProfileVersion4_1Core as u32,
-            Some((3, 1...2)) => NSOpenGLProfileVersion3_2Core as u32,
+            GlRequest::Specific(Api::OpenGl, (1 ... 2, _)) => NSOpenGLProfileVersionLegacy as u32,
-            Some((_, _)) => NSOpenGLProfileVersion4_1Core as u32,
+            GlRequest::Specific(Api::OpenGl, (3, 0)) => NSOpenGLProfileVersionLegacy as u32,
+            GlRequest::Specific(Api::OpenGl, (3, 1 ... 2)) => NSOpenGLProfileVersion3_2Core as u32,
+            GlRequest::Specific(Api::OpenGl, _) => NSOpenGLProfileVersion4_1Core as u32,
+            GlRequest::Specific(_, _) => panic!("Only the OpenGL API is supported"),    // FIXME: return Result
+            GlRequest::GlThenGles { opengl_version: (1 ... 2, _), .. } => NSOpenGLProfileVersionLegacy as u32,
+            GlRequest::GlThenGles { opengl_version: (3, 0), .. } => NSOpenGLProfileVersionLegacy as u32,
+            GlRequest::GlThenGles { opengl_version: (3, 1 ... 2), .. } => NSOpenGLProfileVersion3_2Core as u32,
+            GlRequest::GlThenGles { .. } => NSOpenGLProfileVersion4_1Core as u32,
         };
         unsafe {
             let attributes = [

src/headless.rs

@@ -1,6 +1,7 @@
 use Api;
 use BuilderAttribs;
 use CreationError;
+use GlRequest;
 
 use gl_common;
 use libc;
@@ -24,12 +25,16 @@ impl HeadlessRendererBuilder {
         }
     }
 
-    /// Requests to use a specific OpenGL version.
+    /// THIS FUNCTION IS DEPRECATED
-    ///
+    #[deprecated = "Use with_gl instead"]
-    /// Version is a (major, minor) pair. For example to request OpenGL 3.3
-    ///  you would pass `(3, 3)`.
     pub fn with_gl_version(mut self, version: (u32, u32)) -> HeadlessRendererBuilder {
-        self.attribs.gl_version = Some(version);
+        self.attribs.gl_version = GlRequest::Specific(::Api::OpenGl, (version.0 as u8, version.1 as u8));
+        self
+    }
+
+    /// Sets how the backend should choose the OpenGL API and version.
+    pub fn with_gl(mut self, request: GlRequest) -> HeadlessRendererBuilder {
+        self.attribs.gl_version = request;
         self
     }
 

src/lib.rs

@@ -114,6 +114,30 @@ pub enum Api {
     WebGl,
 }
 
+/// Describes the OpenGL API and version that are being requested when a context is created.
+#[derive(Debug, Copy, Clone)]
+pub enum GlRequest {
+    /// Request the latest version of the "best" API of this platform.
+    ///
+    /// On desktop, will try OpenGL.
+    Latest,
+
+    /// Request a specific version of a specific API.
+    ///
+    /// Example: `GlRequest::Specific(Api::OpenGl, (3, 3))`.
+    Specific(Api, (u8, u8)),
+
+    /// If OpenGL is available, create an OpenGL context with the specified `opengl_version`.
+    /// Else if OpenGL ES or WebGL is available, create a context with the
+    /// specified `opengles_version`.
+    GlThenGles {
+        /// The version to use for OpenGL.
+        opengl_version: (u8, u8),
+        /// The version to use for OpenGL ES.
+        opengles_version: (u8, u8),
+    },
+}
+
 #[derive(Debug, Copy)]
 pub enum MouseCursor {
     /// The platform-dependent default cursor.
@@ -194,7 +218,7 @@ struct BuilderAttribs<'a> {
     dimensions: Option<(u32, u32)>,
     title: String,
     monitor: Option<winimpl::MonitorID>,
-    gl_version: Option<(u32, u32)>,
+    gl_version: GlRequest,
     gl_debug: bool,
     vsync: bool,
     visible: bool,
@@ -215,7 +239,7 @@ impl BuilderAttribs<'static> {
             dimensions: None,
             title: "glutin window".to_string(),
             monitor: None,
-            gl_version: None,
+            gl_version: GlRequest::Latest,
             gl_debug: cfg!(ndebug),
             vsync: false,
             visible: true,

src/win32/init.rs

@@ -5,9 +5,12 @@ use std::os;
 use super::callback;
 use super::Window;
 use super::MonitorID;
+
+use Api;
 use BuilderAttribs;
 use CreationError;
 use CreationError::OsError;
+use GlRequest;
 use PixelFormat;
 
 use std::ffi::CString;
@@ -353,12 +356,21 @@ fn create_context(extra: Option<(&gl::wgl_extra::Wgl, &BuilderAttribs<'static>)>
         if extra_functions.CreateContextAttribsARB.is_loaded() {
             let mut attributes = Vec::new();
 
-            if builder.gl_version.is_some() {
+            match builder.gl_version {
-                let version = builder.gl_version.as_ref().unwrap();
+                GlRequest::Latest => {},
-                attributes.push(gl::wgl_extra::CONTEXT_MAJOR_VERSION_ARB as libc::c_int);
+                GlRequest::Specific(Api::OpenGl, (major, minor)) => {
-                attributes.push(version.0 as libc::c_int);
+                    attributes.push(gl::wgl_extra::CONTEXT_MAJOR_VERSION_ARB as libc::c_int);
-                attributes.push(gl::wgl_extra::CONTEXT_MINOR_VERSION_ARB as libc::c_int);
+                    attributes.push(major as libc::c_int);
-                attributes.push(version.1 as libc::c_int);
+                    attributes.push(gl::wgl_extra::CONTEXT_MINOR_VERSION_ARB as libc::c_int);
+                    attributes.push(minor as libc::c_int);
+                },
+                GlRequest::Specific(_, _) => panic!("Only OpenGL is supported"),
+                GlRequest::GlThenGles { opengl_version: (major, minor), .. } => {
+                    attributes.push(gl::wgl_extra::CONTEXT_MAJOR_VERSION_ARB as libc::c_int);
+                    attributes.push(major as libc::c_int);
+                    attributes.push(gl::wgl_extra::CONTEXT_MINOR_VERSION_ARB as libc::c_int);
+                    attributes.push(minor as libc::c_int);
+                },
             }
 
             if builder.gl_debug {

src/window.rs

@@ -5,6 +5,7 @@ use Api;
 use BuilderAttribs;
 use CreationError;
 use Event;
+use GlRequest;
 use MouseCursor;
 
 use gl_common;
@@ -56,12 +57,16 @@ impl<'a> WindowBuilder<'a> {
         self
     }
 
-    /// Requests to use a specific OpenGL version.
+    /// THIS FUNCTION IS DEPRECATED
-    ///
+    #[deprecated = "Use with_gl instead"]
-    /// Version is a (major, minor) pair. For example to request OpenGL 3.3
-    ///  you would pass `(3, 3)`.
     pub fn with_gl_version(mut self, version: (u32, u32)) -> WindowBuilder<'a> {
-        self.attribs.gl_version = Some(version);
+        self.attribs.gl_version = GlRequest::Specific(::Api::OpenGl, (version.0 as u8, version.1 as u8));
+        self
+    }
+
+    /// Sets how the backend should choose the OpenGL API and version.
+    pub fn with_gl(mut self, request: GlRequest) -> WindowBuilder<'a> {
+        self.attribs.gl_version = request;
         self
     }
 

src/x11/window/mod.rs

@@ -10,6 +10,9 @@ use super::ffi;
 use std::sync::{Arc, Mutex, Once, ONCE_INIT, Weak};
 use std::sync::{StaticMutex, MUTEX_INIT};
 
+use Api;
+use GlRequest;
+
 pub use self::monitor::{MonitorID, get_available_monitors, get_primary_monitor};
 
 mod events;
@@ -483,12 +486,21 @@ impl Window {
         let (context, extra_functions) = unsafe {
             let mut attributes = Vec::new();
 
-            if builder.gl_version.is_some() {
+            match builder.gl_version {
-                let version = builder.gl_version.as_ref().unwrap();
+                GlRequest::Latest => {},
-                attributes.push(ffi::GLX_CONTEXT_MAJOR_VERSION);
+                GlRequest::Specific(Api::OpenGl, (major, minor)) => {
-                attributes.push(version.0 as libc::c_int);
+                    attributes.push(ffi::GLX_CONTEXT_MAJOR_VERSION);
-                attributes.push(ffi::GLX_CONTEXT_MINOR_VERSION);
+                    attributes.push(major as libc::c_int);
-                attributes.push(version.1 as libc::c_int);
+                    attributes.push(ffi::GLX_CONTEXT_MINOR_VERSION);
+                    attributes.push(minor as libc::c_int);
+                },
+                GlRequest::Specific(_, _) => panic!("Only OpenGL is supported"),
+                GlRequest::GlThenGles { opengl_version: (major, minor), .. } => {
+                    attributes.push(ffi::GLX_CONTEXT_MAJOR_VERSION);
+                    attributes.push(major as libc::c_int);
+                    attributes.push(ffi::GLX_CONTEXT_MINOR_VERSION);
+                    attributes.push(minor as libc::c_int);
+                },
             }
 
             if builder.gl_debug {