Support using OpenGL ES context on desktop

src/gpu/gl/unix/SkNativeGLContext_unix.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "gl/SkNativeGLContext.h"
 
 #include <GL/glu.h>
@@ skipping 48 matching lines @@
         if (fPixmap) {
             XFreePixmap(fDisplay, fPixmap);
             fPixmap = 0;
         }
 
         XCloseDisplay(fDisplay);
         fDisplay = NULL;
     }
 }
 
-const GrGLInterface* SkNativeGLContext::createGLContext() {
+const GrGLInterface* SkNativeGLContext::createGLContext(GrGLStandard forcedGpuAPI) {
     fDisplay = XOpenDisplay(0);
 
     if (!fDisplay) {
         SkDebugf("Failed to open X display.\n");
         this->destroyGLContext();
         return NULL;
     }
 
     // Get a matching FB config
     static int visual_attribs[] = {
@@ skipping 100 matching lines @@
     // error handler, so be sure to guard against other threads issuing
     // X commands while this code is running.
     ctxErrorOccurred = false;
     int (*oldHandler)(Display*, XErrorEvent*) =
         XSetErrorHandler(&ctxErrorHandler);
 
     // Get the default screen's GLX extension list
     const char *glxExts = glXQueryExtensionsString(
         fDisplay, DefaultScreen(fDisplay)
     );
+
+
     // Check for the GLX_ARB_create_context extension string and the function.
     // If either is not present, use GLX 1.3 context creation method.
-    if (!gluCheckExtension(
-          reinterpret_cast<const GLubyte*>("GLX_ARB_create_context")
-          , reinterpret_cast<const GLubyte*>(glxExts)))
-    {
-        //SkDebugf("GLX_ARB_create_context not found."
-        //       " Using old-style GLX context.\n");
+
+    if (!gluCheckExtension(reinterpret_cast<const GLubyte*>("GLX_ARB_create_context"),
+                           reinterpret_cast<const GLubyte*>(glxExts))) {
+        if (kGLES_GrGLStandard != forcedGpuAPI) {
 #ifdef GLX_1_3
-        fContext = glXCreateNewContext(fDisplay, bestFbc, GLX_RGBA_TYPE, 0, True);
+            fContext = glXCreateNewContext(fDisplay, bestFbc, GLX_RGBA_TYPE, 0, True);
 #else
-        fContext = glXCreateContext(fDisplay, vi, 0, True);
+            fContext = glXCreateContext(fDisplay, vi, 0, True);
 #endif
-
+        }
     }
 #ifdef GLX_1_3
     else {
         //SkDebugf("Creating context.\n");
-
         PFNGLXCREATECONTEXTATTRIBSARBPROC glXCreateContextAttribsARB =
             (PFNGLXCREATECONTEXTATTRIBSARBPROC) glXGetProcAddressARB((GrGLubyte*)"glXCreateContextAttribsARB");
-        int context_attribs[] = {
+
+        static const int context_attribs_gl[] = {
             GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
             GLX_CONTEXT_MINOR_VERSION_ARB, 0,
-            //GLX_CONTEXT_FLAGS_ARB        , GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
             None
         };
-        fContext = glXCreateContextAttribsARB(
-            fDisplay, bestFbc, 0, True, context_attribs
-        );
+        static const int context_attribs_gl_fallback[] = {
+            GLX_CONTEXT_MAJOR_VERSION_ARB, 1,
+            GLX_CONTEXT_MINOR_VERSION_ARB, 0,
+            None
+        };
+        static const int context_attribs_gles[] = {
+            GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
+            GLX_CONTEXT_MINOR_VERSION_ARB, 0,
+            GLX_CONTEXT_PROFILE_MASK_ARB, GLX_CONTEXT_ES2_PROFILE_BIT_EXT,
+            None
+        };
 
-        // Sync to ensure any errors generated are processed.
-        XSync(fDisplay, False);
-        if (!ctxErrorOccurred && fContext) {
-           //SkDebugf( "Created GL 3.0 context.\n" );
+        if (kGLES_GrGLStandard == forcedGpuAPI) {
+            if (gluCheckExtension(
+                    reinterpret_cast<const GLubyte*>("GLX_EXT_create_context_es2_profile"),
+                    reinterpret_cast<const GLubyte*>(glxExts))) {
+                fContext = glXCreateContextAttribsARB(fDisplay, bestFbc, 0, True,
+                                                      context_attribs_gles);
+            }
         } else {
-            // Couldn't create GL 3.0 context.
-            // Fall back to old-style 2.x context.
-            // When a context version below 3.0 is requested,
-            // implementations will return the newest context version compatible
-            // with OpenGL versions less than version 3.0.
+            fContext = glXCreateContextAttribsARB(fDisplay, bestFbc, 0, True, context_attribs_gl);
 
-            // GLX_CONTEXT_MAJOR_VERSION_ARB = 1
-            context_attribs[1] = 1;
-            // GLX_CONTEXT_MINOR_VERSION_ARB = 0
-            context_attribs[3] = 0;
+            // Sync to ensure any errors generated are processed.
+            XSync(fDisplay, False);
+            if (ctxErrorOccurred || !fContext) {
+                // Couldn't create GL 3.0 context.
+                // Fall back to old-style 2.x context.
+                // When a context version below 3.0 is requested,
+                // implementations will return the newest context version
+                // compatible with OpenGL versions less than version 3.0.
 
-            ctxErrorOccurred = false;
+                ctxErrorOccurred = false;
 
-            //SkDebugf("Failed to create GL 3.0 context."
-            //       " Using old-style GLX context.\n");
-            fContext = glXCreateContextAttribsARB(
-                fDisplay, bestFbc, 0, True, context_attribs
-            );
+                fContext = glXCreateContextAttribsARB(fDisplay, bestFbc, 0, True,
+                                                      context_attribs_gl_fallback);
+            }
         }
     }
 #endif
 
     // Sync to ensure any errors generated are processed.
     XSync(fDisplay, False);
 
     // Restore the original error handler
     XSetErrorHandler(oldHandler);
 
@@ skipping 28 matching lines @@
 
 void SkNativeGLContext::makeCurrent() const {
     if (!glXMakeCurrent(fDisplay, fGlxPixmap, fContext)) {
         SkDebugf("Could not set the context.\n");
     }
 }
 
 void SkNativeGLContext::swapBuffers() const {
     glXSwapBuffers(fDisplay, fGlxPixmap);
 }