Add support for GLAD

CMakeLists.txt

@@ -38,6 +38,7 @@ option(EXPERIMENTAL "Enable Experimental Features" OFF)
 option(SNAPSHOT "Create dev snapshot, uses nightly icons" OFF)
 option(HEADLESS "Build without GUI frontend" OFF)
 option(ENABLE_EGL "Enable EGL instead of GLX support if available" OFF)
+option(USE_GLAD "Use GLAD instead of glew" OFF)
 option(WASM "Build WebAssembly, (implies NULLGL=ON) " OFF)
 option(NULLGL "Build without OpenGL, (implies HEADLESS=ON) " OFF)
 option(IDPREFIX "Prefix CSG nodes with index # (debugging purposes only, will break node cache)" OFF)
@@ -111,6 +112,12 @@ if(WASM)
   target_compile_definitions(OpenSCAD PRIVATE CGAL_DISABLE_ROUNDING_MATH_CHECK)
 endif()
 
+if(USE_GLAD)
+  target_compile_definitions(OpenSCAD PRIVATE USE_GLAD)
+else()
+  target_compile_definitions(OpenSCAD PRIVATE USE_GLEW)
+endif()
+
 if(NULLGL)
   set(HEADLESS ON CACHE BOOL "" FORCE)
 endif()
@@ -160,6 +167,9 @@ add_subdirectory(submodules)
 
 if (MXECROSS)
   target_compile_definitions(OpenSCAD PRIVATE GLEW_STATIC LIBXML_STATIC STATIC_QT_SVG_PLUGIN)
+  if (NOT USE_GLAD)
+    target_compile_definitions(OpenSCAD PRIVATE GLEW_STATIC)
+  endif()
   target_link_libraries(OpenSCAD PRIVATE bcrypt)
 endif()
 
@@ -175,18 +185,23 @@ macro(find_graphics)
     target_compile_definitions(OpenSCAD PRIVATE ENABLE_OPENCSG)
 
     if(MSVC)
-      find_package(GLEW CONFIG REQUIRED QUIET)
+      if (NOT USE_GLAD)
+        find_package(GLEW CONFIG REQUIRED QUIET)
+        message(STATUS "GLEW: Using target GLEW::GLEW")
+        target_link_libraries(OpenSCAD PRIVATE GLEW::GLEW)
+      endif()
       find_path(OPENCSG_INCLUDE_DIRS opencsg/opencsg.h)
-      message(STATUS "GLEW: Using target GLEW::GLEW")
       target_include_directories(OpenSCAD SYSTEM PRIVATE "${OPENCSG_INCLUDE_DIRS}/opencsg")
-      target_link_libraries(OpenSCAD PRIVATE GLEW::GLEW)
     else()
-      find_package(GLEW REQUIRED)
+      if (NOT USE_GLAD)
+        find_package(GLEW REQUIRED)
+        message(STATUS "GLEW_INCLUDE_DIR: ${GLEW_INCLUDE_DIR}")
+        message(STATUS "GLEW_LIBRARY: ${GLEW_LIBRARY}")
+        target_include_directories(OpenSCAD SYSTEM PRIVATE ${GLEW_INCLUDE_DIR})
+        target_link_libraries(OpenSCAD PRIVATE ${GLEW_LIBRARY})
+      endif()
+      target_include_directories(OpenSCAD SYSTEM PRIVATE ${OPENCSG_INCLUDE_DIRS})
       find_path(OPENCSG_INCLUDE_DIRS opencsg.h)
-      message(STATUS "GLEW_INCLUDE_DIR: ${GLEW_INCLUDE_DIR}")
-      message(STATUS "GLEW_LIBRARY: ${GLEW_LIBRARY}")
-      target_include_directories(OpenSCAD SYSTEM PRIVATE ${GLEW_INCLUDE_DIR} ${OPENCSG_INCLUDE_DIRS})
-      target_link_libraries(OpenSCAD PRIVATE ${GLEW_LIBRARY})
     endif()
 
     find_package(OpenGL REQUIRED QUIET)
@@ -534,7 +549,9 @@ elseif(UNIX)
       set(OFFSCREEN_METHOD "Unix EGL")
       message(STATUS "Offscreen OpenGL Context - using Unix EGL")
       set(PLATFORM_SOURCES ${PLATFORM_SOURCES} src/glview/OffscreenContextEGL.cc)
-      target_compile_definitions(OpenSCAD PRIVATE GLEW_EGL)
+      if (NOT USE_GLAD)
+        target_compile_definitions(OpenSCAD PRIVATE GLEW_EGL)
+      endif()
       target_link_libraries(OpenSCAD PRIVATE OpenGL::EGL)
     else()
       set(OFFSCREEN_METHOD "Unix GLX on X11")

cmake/Modules/info.cmake

@@ -23,6 +23,12 @@ message(STATUS "Experimental Features: ${EXPERIMENTAL}")
 message(STATUS "Snapshot build:        ${SNAPSHOT}")
 message(STATUS "Headless build:        ${HEADLESS}")
 message(STATUS "NULLGL build:          ${NULLGL}")
+if (USE_GLAD)
+  set(WRANGLER "GLAD")
+else()
+  set(WRANGLER "glew")
+endif()
+message(STATUS "OpenGL wrangler:       ${WRANGLER}")
 message(STATUS "Profiling/coverage:    ${PROFILE}")
 message(STATUS "Use mimalloc:          ${USE_MIMALLOC}")
 message(STATUS "CSG node id-prefix:    ${IDPREFIX}")

src/glview/GLView.cc

@@ -197,7 +197,13 @@ void glCompileCheck(GLuint shader) {
 void GLView::enable_opencsg_shaders()
 {
   // All OpenGL 2 contexts are OpenCSG capable
-  if (GLEW_VERSION_2_0) {
+#ifdef USE_GLEW
+	const bool hasOpenGL2_0 = GLEW_VERSION_2_0;
+#endif
+#ifdef USE_GLAD
+	const bool hasOpenGL2_0 = GLAD_GL_VERSION_2_0;
+#endif
+  if (hasOpenGL2_0) {
 		this->is_opencsg_capable = true;
 		this->has_shaders = true;
   }

src/glview/NULLGL.cc

@@ -15,7 +15,7 @@ void GLView::setColorScheme(const std::string& cs) {assert(false && "not impleme
 #include "system-gl.h"
 
 double gl_version() { return -1; }
-std::string glew_dump() { return std::string("GL Renderer: NULLGL Glew\n"); }
-std::string glew_extensions_dump() { return std::string("NULLGL Glew Extensions"); }
+std::string gl_dump() { return std::string("GL Renderer: NULLGL\n"); }
+std::string gl_extensions_dump() { return std::string("NULLGL Extensions"); }
 bool report_glerror(const char *function) { return false; }
 

src/glview/OffscreenContextAll.hpp

@@ -57,11 +57,25 @@ bool save_framebuffer_common(const OffscreenContext *ctx, std::ostream& output)
 OffscreenContext *create_offscreen_context_common(OffscreenContext *ctx)
 {
   if (!ctx) return nullptr;
+
+#ifdef USE_GLEW
   GLenum err = glewInit(); // must come after Context creation and before FBO c$
   if (GLEW_OK != err) {
     std::cerr << "Unable to init GLEW: " << glewGetErrorString(err) << "\n";
     return nullptr;
   }
+#endif
+#ifdef USE_GLAD
+	// FIXME: We could ask for gladLoaderLoadGLES2() here instead
+	const auto version = gladLoaderLoadGL();
+	if (version == 0) {
+		// FIXME: Can we figure out why?
+    std::cerr << "Unable to init GLAD" << std::endl;
+    return nullptr;
+  }
+	// FIXME: Only if verbose
+	std::cout << "GLAD: Loaded OpenGL " << GLAD_VERSION_MAJOR(version) << "." <<  GLAD_VERSION_MINOR(version) << std::endl;
+#endif
 
   ctx->fbo = fbo_new();
   if (!fbo_init(ctx->fbo, ctx->width, ctx->height)) {

src/glview/OffscreenView.cc

@@ -39,5 +39,5 @@ bool OffscreenView::save(std::ostream& output) const
 
 std::string OffscreenView::getRendererInfo() const
 {
-  return STR(glew_dump(), offscreen_context_getinfo(this->ctx));
+  return STR(gl_dump(), offscreen_context_getinfo(this->ctx));
 }

src/glview/fbo.cc

@@ -18,7 +18,7 @@ fbo_t *fbo_new()
 bool use_ext()
 {
   // do we need to use the EXT or ARB version?
-  if (!glewIsSupported("GL_ARB_framebuffer_object") && glewIsSupported("GL_EXT_framebuffer_object")) {
+  if (!hasGLExtension(GL_ARB_framebuffer_object) && hasGLExtension(GL_EXT_framebuffer_object)) {
     return true;
   } else {
     return false;
@@ -90,7 +90,7 @@ bool fbo_ext_init(fbo_t *fbo, size_t width, size_t height)
     return false;
   }
 
-  if (glewIsSupported("GL_EXT_packed_depth_stencil")) {
+  if (hasGLExtension(GL_EXT_packed_depth_stencil)) {
     glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,
                                  GL_RENDERBUFFER_EXT, fbo->depthbuf_id);
     if (report_glerror("specifying depth render buffer EXT")) return false;
@@ -174,7 +174,7 @@ bool fbo_init(fbo_t *fbo, size_t width, size_t height)
    */
 
   auto result = false;
-  if (glewIsSupported("GL_ARB_framebuffer_object")) {
+  if (hasGLExtension(GL_ARB_framebuffer_object)) {
     result = fbo_arb_init(fbo, width, height);
   } else if (use_ext()) {
     result = fbo_ext_init(fbo, width, height);
@@ -188,7 +188,7 @@ bool fbo_resize(fbo_t *fbo, size_t width, size_t height)
 {
   if (use_ext()) {
     glBindRenderbufferEXT(GL_RENDERBUFFER, fbo->depthbuf_id);
-    if (glewIsSupported("GL_EXT_packed_depth_stencil")) {
+    if (hasGLExtension(GL_EXT_packed_depth_stencil)) {
       glRenderbufferStorageEXT(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, width, height);
       if (report_glerror("creating EXT depth stencil render buffer")) return false;
     } else {