From 9b39d99f6efa45bb6629f9f819c7e8589281e61e Mon Sep 17 00:00:00 2001
From: Pierre Krieger <pierre.krieger1708@gmail.com>
Date: Fri, 14 Nov 2014 15:59:45 +0100
Subject: Detect OSMesa errors

---
 src/x11/headless.rs | 15 +++++++++++----
 tests/headless.rs   |  3 ++-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/x11/headless.rs b/src/x11/headless.rs
index 71232e5..977305a 100644
--- a/src/x11/headless.rs
+++ b/src/x11/headless.rs
@@ -1,5 +1,5 @@
 use HeadlessRendererBuilder;
-use CreationError;
+use {CreationError, OsError};
 use libc;
 use std::{mem, ptr};
 use super::ffi;
@@ -18,16 +18,23 @@ impl HeadlessContext {
             height: builder.dimensions.1,
             buffer: Vec::from_elem(builder.dimensions.0 * builder.dimensions.1, unsafe { mem::uninitialized() }),
             context: unsafe {
-                // TODO: check errors
-                ffi::OSMesaCreateContext(0x1908, ptr::null())
+                let ctxt = ffi::OSMesaCreateContext(0x1908, ptr::null());
+                if ctxt.is_null() {
+                    return Err(OsError("OSMesaCreateContext failed".to_string()));
+                }
+                ctxt
             }
         })
     }
 
     pub unsafe fn make_current(&self) {
-        ffi::OSMesaMakeCurrent(self.context,
+        let ret = ffi::OSMesaMakeCurrent(self.context,
             self.buffer.as_ptr() as *mut libc::c_void,
             0x1401, self.width as libc::c_int, self.height as libc::c_int);
+
+        if ret == 0 {
+            panic!("OSMesaMakeCurrent failed")
+        }
     }
 
     pub fn get_proc_address(&self, addr: &str) -> *const () {
diff --git a/tests/headless.rs b/tests/headless.rs
index fe82c1d..084f228 100644
--- a/tests/headless.rs
+++ b/tests/headless.rs
@@ -32,6 +32,7 @@ fn main() {
         gl.ReadPixels(0, 0, 1, 1, gl::RGBA, gl::UNSIGNED_BYTE, std::mem::transmute(&mut value));
         
         assert!(value == (0, 255, 0, 255) || value == (0, 64, 0, 255) ||
-            value == (0, 64, 0, 255) || value == (0, 64, 0, 0));
+                value == (0, 64, 0, 255) || value == (0, 64, 0, 0),
+                "value is: {}", value);
     }
 }
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