Merge pull request #48 from simartin/servo_issue_9097

New GLLimits struct to access GL "limit values".

Author: emilio

src/gl_context.rs

@@ -6,6 +6,7 @@ use NativeGLContextMethods;
 use GLContextAttributes;
 use GLContextCapabilities;
 use GLFormats;
+use GLLimits;
 use DrawBuffer;
 use ColorAttachmentType;
 
@@ -21,6 +22,7 @@ pub struct GLContext<Native> {
     attributes: GLContextAttributes,
     capabilities: GLContextCapabilities,
     formats: GLFormats,
+    limits: GLLimits,
 }
 
 impl<Native> GLContext<Native>
@@ -30,13 +32,15 @@ impl<Native> GLContext<Native>
         try!(native_context.make_current());
         let attributes = GLContextAttributes::any();
         let formats = GLFormats::detect(&attributes);
+        let limits = GLLimits::detect();
 
         Ok(GLContext {
             native_context: native_context,
             draw_buffer: None,
             attributes: attributes,
             capabilities: GLContextCapabilities::detect(),
             formats: formats,
+            limits: limits,
         })
     }
 
@@ -110,6 +114,10 @@ impl<Native> GLContext<Native>
         &self.formats
     }
 
+    pub fn borrow_limits(&self) -> &GLLimits {
+        &self.limits
+    }
+
     pub fn borrow_draw_buffer(&self) -> Option<&DrawBuffer> {
         self.draw_buffer.as_ref()
     }

src/gl_limits.rs

@@ -0,0 +1,15 @@
+use gleam::gl::types::GLint;
+use gleam::gl;
+
+#[derive(Clone, Deserialize, Serialize)]
+pub struct GLLimits {
+    pub max_vertex_attribs: GLint,
+}
+
+impl GLLimits {
+    pub fn detect() -> GLLimits {
+        GLLimits {
+            max_vertex_attribs: gl::get_integer_v(gl::MAX_VERTEX_ATTRIBS),
+        }
+    }
+}

src/lib.rs

@@ -34,6 +34,9 @@ pub use gl_feature::GLFeature;
 mod gl_formats;
 pub use gl_formats::GLFormats;
 
+mod gl_limits;
+pub use gl_limits::GLLimits;
+
 #[macro_use]
 extern crate log;
 

src/tests.rs

@@ -159,3 +159,13 @@ fn test_sharing() {
 
     test_pixels(&vec);
 }
+
+#[test]
+fn test_limits() {
+    let size = Size2D::new(256, 256);
+    let context = GLContext::<NativeGLContext>::new(size,
+                                                    GLContextAttributes::default(),
+                                                    ColorAttachmentType::Texture,
+                                                    None).unwrap();
+    assert!(context.borrow_limits().max_vertex_attribs != 0);
+}