[OpenGL] use GLAD as API loader (replace GLEW)

.gitmodules

@@ -10,3 +10,7 @@
 	path = external/glfw
 	url = https://github.com/glfw/glfw
 	shallow = true
+[submodule "external/glad"]
+	path = external/glad
+	url = https://github.com/taichi-dev/taichi_glad_ready
+	shallow = true

appveyor.yml

@@ -61,5 +61,5 @@ build_script:
   - cd ..
   - '%PYTHON% -c "import taichi"'
   - "%PYTHON% examples/laplace.py"
-  - "%PYTHON% bin/taichi test -t 2"
+  - "%PYTHON% bin/taichi test -t 2 -a x64"
   - "cd python && %PYTHON% build.py try_upload"

cmake/TaichiCore.cmake

@@ -3,18 +3,26 @@ set(CORE_LIBRARY_NAME taichi_core)
 option(USE_STDCPP "Use -stdlib=libc++" OFF)
 option(TI_WITH_CUDA "Build with the CUDA backend" ON)
 option(TI_WITH_OPENGL "Build with the OpenGL backend" ON)
-option(GLEW_USE_STATIC_LIBS OFF)
 
 if (APPLE)
     if (TI_WITH_CUDA)
         set(TI_WITH_CUDA OFF)
         message(WARNING "CUDA not supported on OS X. Setting TI_WITH_CUDA to OFF.")
     endif()
+    if (TI_WITH_OPENGL)
+        set(TI_WITH_OPENGL OFF)
+        message(WARNING "OpenGL not supported on OS X. Setting TI_WITH_OPENGL to OFF.")
+    endif()
+endif()
+
+if (NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/external/glad/src/glad.c")
+    set(TI_WITH_OPENGL OFF)
+    message(WARNING "external/glad submodule not detected. Settings TI_WITH_OPENGL to OFF.")
 endif()
 
 file(GLOB TAICHI_CORE_SOURCE
         "taichi/*/*/*/*.cpp" "taichi/*/*/*.cpp" "taichi/*/*.cpp" "taichi/*.cpp"
-        "taichi/*/*/*/*.h" "taichi/*/*/*.h" "taichi/*/*.h" "taichi/*.h" "external/*.c" "tests/cpp/*.cpp")
+        "taichi/*/*/*/*.h" "taichi/*/*/*.h" "taichi/*/*.h" "taichi/*.h" "tests/cpp/*.cpp")
 
 file(GLOB TAICHI_BACKEND_SOURCE "taichi/backends/**/*.cpp" "taichi/backends/**/*.h")
 
@@ -25,8 +33,8 @@ file(GLOB TAICHI_OPENGL_SOURCE "taichi/backends/opengl/*.h" "taichi/backends/ope
 list(REMOVE_ITEM TAICHI_CORE_SOURCE ${TAICHI_BACKEND_SOURCE})
 
 if (TI_WITH_CUDA)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DTI_WITH_CUDA")
-    list(APPEND TAICHI_CORE_SOURCE ${TAICHI_CUDA_SOURCE})
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DTI_WITH_CUDA")
+  list(APPEND TAICHI_CORE_SOURCE ${TAICHI_CUDA_SOURCE})
 endif()
 
 if(NOT CUDA_VERSION)
@@ -37,6 +45,14 @@ endif()
 list(APPEND TAICHI_CORE_SOURCE ${TAICHI_METAL_SOURCE})
 list(APPEND TAICHI_CORE_SOURCE ${TAICHI_OPENGL_SOURCE})
 
+if (TI_WITH_OPENGL)
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DTI_WITH_OPENGL")
+  # Q: Why not external/glad/src/*.c?
+  # A: To ensure glad submodule exists when TI_WITH_OPENGL is ON.
+  file(GLOB TAICHI_GLAD_SOURCE "external/glad/src/glad.c")
+  list(APPEND TAICHI_CORE_SOURCE ${TAICHI_GLAD_SOURCE})
+endif()
+
 add_library(${CORE_LIBRARY_NAME} SHARED ${TAICHI_CORE_SOURCE} ${PROJECT_SOURCES})
 
 if (APPLE)
@@ -47,32 +63,20 @@ endif()
 include_directories(${CMAKE_SOURCE_DIR})
 include_directories(external/include)
 include_directories(external/spdlog/include)
+if (TI_WITH_OPENGL)
+  include_directories(external/glad/include)
+endif()
 
 set(LIBRARY_NAME ${CORE_LIBRARY_NAME})
 
 if (TI_WITH_OPENGL)
-  if(NOT GLEW_VERSION)
-    set(GLEW_VERSION 2.0.0)
-  endif()
-  find_package(GLEW ${GLEW_VERSION})
-  if (GLEW_FOUND)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DTI_WITH_OPENGL")
-    message("Building with GLEW ${GLEW_VERSION}")
-    message("Using GLEW: ${GLEW_LIBRARIES}")
-    target_include_directories(${LIBRARY_NAME} PUBLIC ${GLEW_INCLUDE_DIRS})
-    target_link_libraries(${LIBRARY_NAME} ${GLEW_LIBRARIES} GLEW)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DGLEW_STATIC")
-
-    set(GLFW_BUILD_DOCS OFF CACHE BOOL "" FORCE)
-    set(GLFW_BUILD_TESTS OFF CACHE BOOL "" FORCE)
-    set(GLFW_BUILD_EXAMPLES OFF CACHE BOOL "" FORCE)
-
-    message("Building with GLFW")
-    add_subdirectory(external/glfw)
-    target_link_libraries(${LIBRARY_NAME} glfw)
-  else()
-    message(WARNING "GLEW not found, ignoring TI_WITH_OPENGL.")
-  endif()
+  set(GLFW_BUILD_DOCS OFF CACHE BOOL "" FORCE)
+  set(GLFW_BUILD_TESTS OFF CACHE BOOL "" FORCE)
+  set(GLFW_BUILD_EXAMPLES OFF CACHE BOOL "" FORCE)
+
+  message("Building with GLFW")
+  add_subdirectory(external/glfw)
+  target_link_libraries(${LIBRARY_NAME} glfw)
 endif()
 
 # http://llvm.org/docs/CMake.html#embedding-llvm-in-your-project

taichi/backends/opengl/opengl_api.cpp

@@ -6,7 +6,7 @@
 #include "taichi/program/program.h"
 
 #ifdef TI_WITH_OPENGL
-#include "GL/glew.h"
+#include "glad/glad.h"
 #include "GLFW/glfw3.h"
 #endif
 
@@ -245,7 +245,6 @@ void initialize_opengl() {
   static bool gl_inited = false;
   if (gl_inited)
     return;
-  TI_WARN("OpenGL backend currently WIP, MAY NOT WORK");
   gl_inited = true;
 
   glfwInit();
@@ -257,7 +256,7 @@ void initialize_opengl() {
   // And the best way to make context is by creating a window
   // Then hide it immediately, LOL
   GLFWwindow *window =
-      glfwCreateWindow(1, 1, "Make GLEW Happy", nullptr, nullptr);
+      glfwCreateWindow(1, 1, "Make OpenGL Context", nullptr, nullptr);
   if (!window) {
     const char *desc = nullptr;
     int status = glfwGetError(&desc);
@@ -267,16 +266,13 @@ void initialize_opengl() {
   }
   glfwHideWindow(window);
   glfwMakeContextCurrent(window);
-  int status = glewInit();
-  if (status != GLEW_OK) {
-    TI_ERROR("[glsl] cannot initialize GLEW: {}", glewGetErrorString(status));
-  }
-  TI_INFO("[glsl] OpenGL {}", (const char *)glGetString(GL_VERSION));
-  TI_INFO("[glsl] GLSL {}",
-          (const char *)glGetString(GL_SHADING_LANGUAGE_VERSION));
-#define PER_OPENGL_EXTENSION(x)                \
-  if ((opengl_has_##x = glewGetExtension(#x))) \
-    TI_INFO("[glsl] Found " #x);
+
+  if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
+    TI_ERROR("[glsl] cannot initialize GLAD");
+  }
+#define PER_OPENGL_EXTENSION(x)    \
+  if ((opengl_has_##x = GLAD_##x)) \
+    TI_TRACE("[glsl] Found " #x);
 #include "taichi/inc/opengl_extension.inc.h"
 #undef PER_OPENGL_EXTENSION
   if (!opengl_has_GL_ARB_compute_shader)

taichi/program/program.cpp

@@ -289,8 +289,8 @@ void Program::materialize_layout() {
   } else if (config.arch == Arch::opengl) {
     opengl::OpenglStructCompiler scomp;
     opengl_struct_compiled_ = scomp.run(*snode_root);
-    TI_INFO("OpenGL root buffer size: {} B",
-            opengl_struct_compiled_->root_size);
+    TI_TRACE("OpenGL root buffer size: {} B",
+             opengl_struct_compiled_->root_size);
     opengl_kernel_launcher_ = std::make_unique<opengl::GLSLLauncher>(
         opengl_struct_compiled_->root_size);
   }