libsimpleservo: OpenGL support for Linux (glx)

Cargo.lock

@@ -3941,6 +3941,7 @@ dependencies = [
  "core-foundation 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "gl_generator 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.44 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libloading 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "libservo 0.0.1",
  "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",

ports/libsimpleservo/api/Cargo.toml

@@ -20,6 +20,9 @@ core-foundation = "0.6"
 [target.'cfg(target_os = "windows")'.dependencies]
 winapi = "0.3.2"
 
+[target.'cfg(any(target_os = "linux", target_os = "dragonfly", target_os = "freebsd", target_os = "openbsd"))'.dependencies]
+libloading = "0.5"
+
 [build-dependencies]
 gl_generator = "0.10"
 

ports/libsimpleservo/api/build.rs

@@ -5,15 +5,16 @@
 use gl_generator::{Api, Fallbacks, Profile, Registry};
 use std::env;
 use std::fs::File;
-use std::path::Path;
+use std::path::PathBuf;
 
 fn main() {
     let target = env::var("TARGET").unwrap();
+    let dest = PathBuf::from(&env::var("OUT_DIR").unwrap());
+
     // Generate GL bindings
     // For now, we only support EGL, and only on Windows and Android.
     if target.contains("android") || target.contains("windows") {
-        let dest = env::var("OUT_DIR").unwrap();
-        let mut file = File::create(&Path::new(&dest).join("egl_bindings.rs")).unwrap();
+        let mut file = File::create(&dest.join("egl_bindings.rs")).unwrap();
         if target.contains("android") {
             Registry::new(Api::Egl, (1, 5), Profile::Core, Fallbacks::All, [])
                 .write_bindings(gl_generator::StaticStructGenerator, &mut file)
@@ -25,4 +26,15 @@ fn main() {
                 .unwrap();
         };
     }
+
+    if target.contains("linux") ||
+        target.contains("dragonfly") ||
+        target.contains("freebsd") ||
+        target.contains("openbsd")
+    {
+        let mut file = File::create(&dest.join("glx_bindings.rs")).unwrap();
+        Registry::new(Api::Glx, (1, 4), Profile::Core, Fallbacks::All, [])
+            .write_bindings(gl_generator::StructGenerator, &mut file)
+            .unwrap();
+    }
 }

ports/libsimpleservo/api/src/gl_glue.rs

@@ -75,7 +75,7 @@ pub mod egl {
     }
 }
 
-#[cfg(any(target_os = "windows", target_os = "linux"))]
+#[cfg(target_os = "windows")]
 pub mod gl {
     pub fn init() -> Result<crate::gl_glue::ServoGl, &'static str> {
         unimplemented!();
@@ -110,3 +110,45 @@ pub mod gl {
         Ok(gl)
     }
 }
+
+#[cfg(any(
+    target_os = "linux",
+    target_os = "dragonfly",
+    target_os = "freebsd",
+    target_os = "openbsd"
+))]
+pub mod gl {
+    use libloading::{Library, Symbol};
+    use servo::gl::GlFns;
+    use std::ffi::CString;
+    use std::os::raw::c_void;
+
+    pub fn init() -> Result<crate::gl_glue::ServoGl, &'static str> {
+        info!("Loading OpenGL");
+
+        pub mod glx {
+            include!(concat!(env!("OUT_DIR"), "/glx_bindings.rs"));
+        }
+
+        let lib = match Library::new("libGL.so.1").or_else(|_| Library::new("libGL.so")) {
+            Ok(lib) => lib,
+            Err(_) => return Err("Can't find libGL.so, OpenGL isn't configured/installed"),
+        };
+
+        let glx = glx::Glx::load_with(|sym| unsafe {
+            let symbol: Symbol<*const c_void> = lib.get(sym.as_bytes()).unwrap();
+            *symbol.into_raw()
+        });
+
+        let gl = unsafe {
+            GlFns::load_with(|addr| {
+                let addr = CString::new(addr.as_bytes()).unwrap();
+                glx.GetProcAddress(addr.as_ptr() as *const _) as *const _
+            })
+        };
+
+        info!("OpenGL is loaded");
+
+        Ok(gl)
+    }
+}