Make EGL function eglCreateContext spec-conformant and actually read the EGL_CONTEXT_CLIENT_VERSION field when creating a context. Require the version number 2, since WebGL1 maps to GLES2.

2 files changed, 30 insertions, 1 deletions

diff --git a/src/library_egl.js b/src/library_egl.js
index 73d5e544..11cf8951 100644
--- a/src/library_egl.js
+++ b/src/library_egl.js
@@ -264,6 +264,26 @@ var LibraryEGL = {
       return 0;
     }
 
+    // EGL 1.4 spec says default EGL_CONTEXT_CLIENT_VERSION is GLES1, but this is not supported by Emscripten.
+    // So user must pass EGL_CONTEXT_CLIENT_VERSION == 2 to initialize EGL.
+    var glesContextVersion = 1;
+    for(;;) {
+        var param = {{{ makeGetValue('contextAttribs', '0', 'i32') }}};
+        if (!param) break;
+        var value = {{{ makeGetValue('contextAttribs', '4', 'i32') }}};
+        if (param == 0x3098 /*EGL_CONTEXT_CLIENT_VERSION*/) {
+          glesContextVersion = value;
+        }
+        contextAttribs += 8;
+    }
+    if (glesContextVersion != 2) {
+#if GL_ASSERTIONS
+      Module.printErr('When initializing GLES2/WebGL1 via EGL, one must pass EGL_CONTEXT_CLIENT_VERSION = 2 to GL context attributes! GLES version ' + glesContextVersion + ' is not supported!');
+#endif
+      EGL.setErrorCode(0x3005 /* EGL_BAD_CONFIG */);
+      return 0; /* EGL_NO_CONTEXT */
+    }
+
     _glutInitDisplayMode(0x92 /* GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH | GLUT_MULTISAMPLE */);
     EGL.windowID = _glutCreateWindow();
     if (EGL.windowID != 0) {
diff --git a/tests/test_egl.c b/tests/test_egl.c
index 5864a797..d66949d0 100644
--- a/tests/test_egl.c
+++ b/tests/test_egl.c
@@ -37,12 +37,21 @@ int main(int argc, char *argv[])
     assert(eglGetError() == EGL_SUCCESS);
     assert(surface != 0);
 
+    // WebGL maps to GLES2. GLES1 is not supported.
+    EGLint contextAttribsOld[] =
+    {
+        EGL_CONTEXT_CLIENT_VERSION, 1,
+        EGL_NONE
+    };
+    EGLContext context = eglCreateContext(display, config, NULL, contextAttribsOld);
+    assert(eglGetError() != EGL_SUCCESS);
+
     EGLint contextAttribs[] =
     {
         EGL_CONTEXT_CLIENT_VERSION, 2,
         EGL_NONE
     };
-    EGLContext context = eglCreateContext(display, config, NULL, contextAttribs);
+    context = eglCreateContext(display, config, NULL, contextAttribs);
     assert(eglGetError() == EGL_SUCCESS);
     assert(context != 0);