Enabled internal GL API loader as GLEW alternative

At build time, the preprocessor symbols: OSD_USES_GLEW or
OSD_USES_INTERNAL_GLAPILOADER determine the GL API loader
that will be used by the OSD library.

CMakeLists.txt

@@ -306,6 +306,7 @@ option(NO_METAL "Disable Metal support" OFF)
 option(NO_DX "Disable DirectX support")
 option(NO_TESTS "Disable all tests")
 option(NO_GLTESTS "Disable GL tests")
+option(NO_GLEW "Disable use of GLEW" OFF)
 option(NO_GLFW "Disable components depending on GLFW" OFF)
 option(NO_GLFW_X11 "Disable GLFW components depending on X11" OFF)
 
@@ -351,13 +352,17 @@ if (OPENGL_FOUND AND NOT IOS)
     add_definitions(
         -DOPENSUBDIV_HAS_OPENGL
     )
-    if (APPLE)
-        find_package(GLEW)
-    else()
-        find_package(GLEW REQUIRED)
+    if (NOT NO_GLEW)
+        if (APPLE)
+            find_package(GLEW)
+        else()
+            find_package(GLEW REQUIRED)
+        endif()
     endif()
     if(GLEW_FOUND)
         add_definitions( -DOSD_USES_GLEW )
+    else()
+        add_definitions( -DOSD_USES_INTERNAL_GLAPILOADER )
     endif()
 endif()
 
@@ -457,9 +462,9 @@ if(GLEW_FOUND AND GLEW_INCLUDE_DIR)
         ${GLEW_LIBRARY}
         ${OPENGL_gl_LIBRARY})
 
-elseif(OPENGL_FOUND AND OPENGL_INCLUDE_DIR)
+elseif(OPENGL_FOUND)
 
-    osd_detect_gl_version(${OPENGL_INCLUDE_DIR}/GL/glext.h)
+    osd_detect_gl_version(${PROJECT_SOURCE_DIR}/glLoader/glApi.h)
     set(OPENGL_LOADER_INCLUDE_DIRS
         ${OPENGL_INCLUDE_DIR}
         ${PROJECT_SOURCE_DIR}/glLoader)

glLoader/CMakeLists.txt

@@ -28,10 +28,13 @@ endif()
 
 list(APPEND GLLOADER_SOURCE_FILES
     glLoader.cpp
+    glApi.cpp
 )
 
 list(APPEND GLLOADER_HEADER_FILES
     glLoader.h
+    glApi.h
+    khrplatform.h
 )
 
 include_directories(

glLoader/glLoader.cpp

@@ -36,7 +36,12 @@ namespace GLLoader {
 bool
 applicationInitializeGL()
 {
-#if defined(OSD_USES_GLEW)
+#if defined(OSD_USES_INTERNAL_GLAPILOADER)
+    // -- GLAPILOADER
+    return OpenSubdiv::internal::GLApi::glApiLoad();
+
+#elif defined(OSD_USES_GLEW)
+    // -- GLEW
 #define CORE_PROFILE
 #ifdef CORE_PROFILE
     // this is the only way to initialize GLEW (before GLEW 1.13)
@@ -60,8 +65,12 @@ applicationInitializeGL()
 bool
 libraryInitializeGL()
 {
-    // do nothing
+#if defined(OSD_USES_INTERNAL_GLAPILOADER)
+    return OpenSubdiv::internal::GLApi::glApiLoad();
+#else
+    // otherwise do nothing
     return true;
+#endif
 }
 
 

glLoader/glLoader.h

@@ -31,6 +31,11 @@
 /// function entry points at run-time and to define types, enum values,
 /// and function prototypes needed at compile-time.
 ///
+/// There are three components to this library:
+///   glLoader.h        -- interface (this header file)
+///   glApi.h           -- low-level generated OpenGL API loader
+///   khrplatform.h     -- khronos.org abstraction for low-level platform types
+///
 /// To use:
 ///   - Include "glloader.h"
 ///
@@ -132,36 +137,18 @@
 /// The boolean variables described here are defined in an internal namespace.
 ///
 
-#if defined(OSD_USES_GLEW)
+#if defined(OSD_USES_INTERNAL_GLAPILOADER)
+    // -- GLAPILOADER
+    #include "glApi.h"
+
+    #define OSD_OPENGL_HAS(token) (GLAPILOADER_GL_##token)
+
+#elif defined(OSD_USES_GLEW)
     // -- GLEW
     #include <GL/glew.h>
 
     #define OSD_OPENGL_HAS(token) (GLEW_##token)
 
-#else
-
-    // -- PLATFORM
-    #if defined(__APPLE__)
-        #include "TargetConditionals.h"
-        #if TARGET_OS_IPHONE || TARGET_IPHONE_SIMULATOR
-            #include <OpenGLES/ES2/gl.h>
-        #else
-            #include <OpenGL/gl3.h>
-        #endif
-    #elif defined(ANDROID)
-        #include <GLES2/gl2.h>
-    #elif defined(_WIN32)
-        #define WIN32_LEAN_AND_MEAN
-        #include <GL/gl.h>
-        #include <windows.h>
-    #else
-        #define GL_GLEXT_PROTOTYPES
-        #include <GL/gl.h>
-        #include <GL/glext.h>
-    #endif
-
-    #define OSD_OPENGL_HAS(token) (GL_##token)
-
 #endif
 
 namespace OpenSubdiv {
@@ -184,4 +171,9 @@ extern bool libraryInitializeGL();
 }  // namespace OpenSubdiv
 
 
+#if defined(OSD_USES_INTERNAL_GLAPILOADER)
+using namespace OpenSubdiv::internal::GLApi;
+#endif
+
+
 #endif  // OPENSUBDIV3_GLLOADER_H

opensubdiv/osd/clGLVertexBuffer.cpp

@@ -38,6 +38,9 @@ CLGLVertexBuffer::CLGLVertexBuffer(int numElements,
                                          cl_context /* clContext */)
     : _numElements(numElements), _numVertices(numVertices),
       _vbo(0), _clQueue(0), _clMemory(0), _clMapped(false) {
+
+    // Initialize internal OpenGL loader library if necessary
+    OpenSubdiv::internal::GLLoader::libraryInitializeGL();
 }
 
 CLGLVertexBuffer::~CLGLVertexBuffer() {

opensubdiv/osd/cpuGLVertexBuffer.cpp

@@ -37,6 +37,9 @@ namespace Osd {
 CpuGLVertexBuffer::CpuGLVertexBuffer(int numElements, int numVertices)
     : _numElements(numElements), _numVertices(numVertices),
       _vbo(0), _cpuBuffer(0), _dataDirty(true) {
+
+    // Initialize internal OpenGL loader library if necessary
+    OpenSubdiv::internal::GLLoader::libraryInitializeGL();
 }
 
 CpuGLVertexBuffer::~CpuGLVertexBuffer() {

opensubdiv/osd/cudaGLVertexBuffer.cpp

@@ -40,6 +40,9 @@ namespace Osd {
 CudaGLVertexBuffer::CudaGLVertexBuffer(int numElements, int numVertices)
     : _numElements(numElements), _numVertices(numVertices),
       _vbo(0), _devicePtr(0), _cudaResource(0) {
+
+    // Initialize internal OpenGL loader library if necessary
+    OpenSubdiv::internal::GLLoader::libraryInitializeGL();
 }
 
 CudaGLVertexBuffer::~CudaGLVertexBuffer() {

opensubdiv/osd/glComputeEvaluator.cpp

@@ -130,6 +130,9 @@ GLComputeEvaluator::GLComputeEvaluator()
       _patchArraysSSBO(0) {
     memset (&_stencilKernel, 0, sizeof(_stencilKernel));
     memset (&_patchKernel, 0, sizeof(_patchKernel));
+
+    // Initialize internal OpenGL loader library if necessary
+    OpenSubdiv::internal::GLLoader::libraryInitializeGL();
 }
 
 GLComputeEvaluator::~GLComputeEvaluator() {

opensubdiv/osd/glLegacyGregoryPatchTable.cpp

@@ -35,6 +35,9 @@ GLLegacyGregoryPatchTable::GLLegacyGregoryPatchTable() :
     _vertexTextureBuffer(0), _vertexValenceTextureBuffer(0),
     _quadOffsetsTextureBuffer(0) {
     _quadOffsetsBase[0] = _quadOffsetsBase[1] = 0;
+
+    // Initialize internal OpenGL loader library if necessary
+    OpenSubdiv::internal::GLLoader::libraryInitializeGL();
 }
 
 GLLegacyGregoryPatchTable::~GLLegacyGregoryPatchTable() {

opensubdiv/osd/glPatchTable.cpp

@@ -37,6 +37,9 @@ namespace Osd {
 GLPatchTable::GLPatchTable() :
     _patchIndexBuffer(0), _patchParamBuffer(0),
     _patchIndexTexture(0), _patchParamTexture(0) {
+
+    // Initialize internal OpenGL loader library if necessary
+    OpenSubdiv::internal::GLLoader::libraryInitializeGL();
 }
 
 GLPatchTable::~GLPatchTable() {

opensubdiv/osd/glVertexBuffer.cpp

@@ -35,6 +35,9 @@ GLVertexBuffer::GLVertexBuffer(int numElements, int numVertices)
     : _numElements(numElements),
       _numVertices(numVertices),
       _vbo(0) {
+
+    // Initialize internal OpenGL loader library if necessary
+    OpenSubdiv::internal::GLLoader::libraryInitializeGL();
 }
 
 GLVertexBuffer::~GLVertexBuffer() {

opensubdiv/osd/glXFBEvaluator.cpp

@@ -157,6 +157,9 @@ GLXFBEvaluator::GLXFBEvaluator(bool interleavedDerivativeBuffers)
     : _srcBufferTexture(0),
       _patchArraysUBO(0),
       _interleavedDerivativeBuffers(interleavedDerivativeBuffers) {
+
+    // Initialize internal OpenGL loader library if necessary
+    OpenSubdiv::internal::GLLoader::libraryInitializeGL();
 }
 
 GLXFBEvaluator::~GLXFBEvaluator() {