Properly resolve and use glMapBuffer / glUnmapBuffer on GLES2.

Even though we're able to resolve the function pointers, the spec says
we have to check for the GL_OES_mapbuffer extension before we use them.
Fixes a crash on a platform that doesn't advertise the extension but
still resolves the function pointers.

Reviewed-by: Kim

3 files changed, 28 insertions, 13 deletions

diff --git a/src/opengl/qglbuffer.cpp b/src/opengl/qglbuffer.cpp
index a1ec3ef..b5c6b83 100644
--- a/src/opengl/qglbuffer.cpp
+++ b/src/opengl/qglbuffer.cpp
@@ -543,6 +543,10 @@ void *QGLBuffer::map(QGLBuffer::Access access)
         return 0;
     if (!glMapBufferARB)
         return 0;
+#ifdef QT_OPENGL_ES_2
+    if (access != QGLBuffer::WriteOnly)
+        return 0;
+#endif
     return glMapBufferARB(d->type, access);
 }
 
diff --git a/src/opengl/qglextensions.cpp b/src/opengl/qglextensions.cpp
index 98d2960..64f7526 100644
--- a/src/opengl/qglextensions.cpp
+++ b/src/opengl/qglextensions.cpp
@@ -191,23 +191,30 @@ bool qt_resolve_frag_program_extensions(QGLContext *ctx)
 
 bool qt_resolve_buffer_extensions(QGLContext *ctx)
 {
+    if (!QGLContextPrivate::extensionFuncs(ctx).qt_bufferFuncsResolved) {
 #if defined(QGL_RESOLVE_BUFFER_FUNCS)
-    if (glBindBuffer && glDeleteBuffers && glGenBuffers && glBufferData
-            && glBufferSubData && glGetBufferParameteriv)
-        return true;
+        glBindBuffer = (_glBindBuffer) qt_gl_getProcAddressARB(ctx, "glBindBuffer");
+        glDeleteBuffers = (_glDeleteBuffers) qt_gl_getProcAddressARB(ctx, "glDeleteBuffers");
+        glGenBuffers = (_glGenBuffers) qt_gl_getProcAddressARB(ctx, "glGenBuffers");
+        glBufferData = (_glBufferData) qt_gl_getProcAddressARB(ctx, "glBufferData");
+        glBufferSubData = (_glBufferSubData) qt_gl_getProcAddressARB(ctx, "glBufferSubData");
+        glGetBufferSubData = (_glGetBufferSubData) qt_gl_getProcAddressARB(ctx, "glGetBufferSubData");
+        glGetBufferParameteriv = (_glGetBufferParameteriv) qt_gl_getProcAddressARB(ctx, "glGetBufferParameteriv");
 #endif
 
-#if defined(QGL_RESOLVE_BUFFER_FUNCS)
-    glBindBuffer = (_glBindBuffer) qt_gl_getProcAddressARB(ctx, "glBindBuffer");
-    glDeleteBuffers = (_glDeleteBuffers) qt_gl_getProcAddressARB(ctx, "glDeleteBuffers");
-    glGenBuffers = (_glGenBuffers) qt_gl_getProcAddressARB(ctx, "glGenBuffers");
-    glBufferData = (_glBufferData) qt_gl_getProcAddressARB(ctx, "glBufferData");
-    glBufferSubData = (_glBufferSubData) qt_gl_getProcAddressARB(ctx, "glBufferSubData");
-    glGetBufferSubData = (_glGetBufferSubData) qt_gl_getProcAddressARB(ctx, "glGetBufferSubData");
-    glGetBufferParameteriv = (_glGetBufferParameteriv) qt_gl_getProcAddressARB(ctx, "glGetBufferParameteriv");
+#ifdef QT_OPENGL_ES_2
+        QGLExtensionMatcher extensions;
+        if (extensions.match("GL_OES_mapbuffer")) {
+            glMapBufferARB = (_glMapBufferARB) qt_gl_getProcAddressARB(ctx, "glMapBufferOES");
+            glUnmapBufferARB = (_glUnmapBufferARB) qt_gl_getProcAddressARB(ctx, "glUnmapBufferOES");
+        }
+#else
+        glMapBufferARB = (_glMapBufferARB) qt_gl_getProcAddressARB(ctx, "glMapBuffer");
+        glUnmapBufferARB = (_glUnmapBufferARB) qt_gl_getProcAddressARB(ctx, "glUnmapBuffer");
 #endif
-    glMapBufferARB = (_glMapBufferARB) qt_gl_getProcAddressARB(ctx, "glMapBuffer");
-    glUnmapBufferARB = (_glUnmapBufferARB) qt_gl_getProcAddressARB(ctx, "glUnmapBuffer");
+
+        QGLContextPrivate::extensionFuncs(ctx).qt_bufferFuncsResolved = true;
+    }
 
 #if defined(QGL_RESOLVE_BUFFER_FUNCS)
     return glBindBuffer
diff --git a/src/opengl/qglextensions_p.h b/src/opengl/qglextensions_p.h
index 98433c3..f85c89b 100644
--- a/src/opengl/qglextensions_p.h
+++ b/src/opengl/qglextensions_p.h
@@ -332,6 +332,8 @@ struct QGLExtensionFuncs
         qt_glMapBufferARB = 0;
         qt_glUnmapBufferARB = 0;
 
+        qt_bufferFuncsResolved = false;
+
         qt_glProgramParameteriEXT = 0;
         qt_glFramebufferTextureEXT = 0;
         qt_glFramebufferTextureLayerEXT = 0;
@@ -457,6 +459,8 @@ struct QGLExtensionFuncs
     _glMapBufferARB qt_glMapBufferARB;
     _glUnmapBufferARB qt_glUnmapBufferARB;
 
+    bool qt_bufferFuncsResolved;
+
     // Geometry shaders...
     _glProgramParameteriEXT qt_glProgramParameteriEXT;
     _glFramebufferTextureEXT qt_glFramebufferTextureEXT;