Add the windows-static-egl Cargo feature

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Unreleased
 
 - Fix android activity life cycle
+- Add the `windows-static-egl` Cargo feature. (See crate’s doc-comment.)
 
 # Version 0.13.0 (2018-02-28)
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "glutin"
-version = "0.13.0"
+version = "0.13.1"
 authors = ["The glutin contributors, Pierre Krieger <pierre.krieger1708@gmail.com>"]
 description = "Cross-platform OpenGL context provider."
 keywords = ["windowing", "opengl"]
@@ -10,6 +10,9 @@ repository = "https://github.com/tomaka/glutin"
 documentation = "https://docs.rs/glutin"
 build = "build.rs"
 
+[features]
+windows-static-egl = []
+
 [dependencies]
 lazy_static = "1"
 libc = "0.2"

appveyor.yml

@@ -15,3 +15,4 @@ build: false
 
 test_script:
   - cargo test --verbose
+  - cargo build --features windows-static-egl --example windows_static_egl

examples/windows_static_egl.rs

@@ -0,0 +1,20 @@
+//! This incomplete example will likely crash at runtime on Windows
+//! when the `windows-static-egl` feature is enabled,
+//! but it should still compile and link.
+
+extern crate glutin;
+
+use std::os::raw::{c_char, c_void};
+
+#[allow(non_snake_case)]
+#[no_mangle]
+pub extern fn eglGetProcAddress(_name: *const c_char) -> *const c_void {
+    0 as _
+}
+
+fn main() {
+    let events_loop = glutin::EventsLoop::new();
+    let window = glutin::WindowBuilder::new().with_title("A fantastic window!");
+    let context = glutin::ContextBuilder::new();
+    let _gl_window = glutin::GlWindow::new(window, context, &events_loop).unwrap();
+}

src/lib.rs

@@ -23,13 +23,15 @@
 //!
 //! # Features
 //!
-//! This crate has two Cargo features: `window` and `headless`.
+//! This crate has one Cargo feature: `windows-static-egl`.
 //!
-//!  - `window` allows you to create regular windows and enables the `WindowBuilder` object.
-//!  - `headless` allows you to do headless rendering, and enables
-//!     the `HeadlessRendererBuilder` object.
+//! On Windows, when the `windows-static-egl` feature is enabled,
+//! glutin assumes that `libEGL` is statically linked into the program, and uses it.
+//! Specifically, it will look for this `extern` symbol:
 //!
-//! By default only `window` is enabled.
+//! ```ignore
+//! fn eglGetProcAddress(name: *const c_char) -> *const c_void;
+//! ```
 
 #[cfg(target_os = "windows")]
 #[macro_use]

src/platform/windows/mod.rs

@@ -31,9 +31,28 @@ pub enum RawHandle {
 struct EglWrapper(Egl);
 unsafe impl Sync for EglWrapper {}
 
+#[cfg(feature = "windows-static-egl")]
+fn static_egl() -> Option<EglWrapper> {
+    use std::os::raw::{c_char, c_void};
+
+    extern {
+        fn eglGetProcAddress(name: *const c_char) -> *const c_void;
+    }
+
+    Some(EglWrapper(Egl::load_with(|name| {
+        let name = CString::new(name).unwrap();
+        unsafe { eglGetProcAddress(name.as_ptr()) }
+    })))
+}
+
+#[cfg(not(feature = "windows-static-egl"))]
+fn static_egl() -> Option<EglWrapper> {
+    None
+}
+
 lazy_static! {
     // An EGL implementation available on the system.
-    static ref EGL: Option<EglWrapper> = {
+    static ref EGL: Option<EglWrapper> = static_egl().or_else(|| {
         // the ATI drivers provide an EGL implementation in their DLLs
         let ati_dll_name = if cfg!(target_pointer_width = "64") {
             b"atio6axx.dll\0"
@@ -56,7 +75,7 @@ lazy_static! {
         }
 
         None
-    };
+    });
 }
 
 /// The Win32 implementation of the main `Context` object.