use GLAD to link OpenGL

BUILDING-cmake.md

@@ -11,7 +11,6 @@ Required tools and dependencies:
 - CMake 3.21 or higher.
 - A working toolchain, e.g. Visual Studio on Windows or the `build-essentials` package on Ubuntu Linux.
 - Main OpenGL libraries and development files.
-- The `GLEW` Library on Windows.
 
 To use the library in other projects, it is required to install it. Use `CMAKE_INSTALL_PREFIX` to specify the
 installation directory.

BUILDING.md

@@ -100,11 +100,6 @@ development files. To build projectM, both binaries and development files need t
   library dependencies and/or using CMake to configure the build. Mainly used on Windows, but also works for Linux and
   macOS.
 
-### Only relevant for Windows:
-
-* [**GLEW**](http://glew.sourceforge.net/): The OpenGL Extension Wrangler Library. Only required if using CMake to
-  configure the build, the pre-created solutions use a bundled copy of GLEW.
-
 ## Building on Linux and macOS
 
 ### Installing dependencies

CMakeLists.txt

@@ -183,19 +183,6 @@ else()
         message(STATUS "Building for OpenGL Core Profile")
         find_package(OpenGL REQUIRED)
         set(PROJECTM_OPENGL_LIBRARIES OpenGL::GL)
-        # GLX is required by SOIL2 on platforms with the X Window System (e.g. most Linux distributions)
-        if(TARGET OpenGL::GLX)
-            list(APPEND PROJECTM_OPENGL_LIBRARIES OpenGL::GLX)
-        endif()
-        if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
-            find_package(GLEW REQUIRED)
-            # Prefer shared, but check for static lib if shared is not available.
-            if(TARGET GLEW::glew)
-                list(APPEND PROJECTM_OPENGL_LIBRARIES GLEW::glew)
-            elseif(TARGET GLEW::glew_s)
-                list(APPEND PROJECTM_OPENGL_LIBRARIES GLEW::glew_s)
-            endif()
-        endif()
     endif()
 endif()
 

docs/building.rst

@@ -138,9 +138,6 @@ Only relevant for Windows:
    library dependencies and/or using CMake to configure the build.
 -  `NuGet <https://www.nuget.org/>`__: Dependency manager for .NET.
    Required to build the EyeTune app.
--  `GLEW <http://glew.sourceforge.net/>`__: The OpenGL Extension
-   Wrangler Library. Only required if using CMake to configure the
-   build, the pre-created solutions use a bundled copy of GLEW.
 
 Building on Linux and macOS
 ---------------------------

src/api/include/projectM-4/core.h

@@ -44,6 +44,20 @@ extern "C" {
  */
 PROJECTM_EXPORT projectm_handle projectm_create();
 
+
+/**
+ * @brief Creates a new projectM instance using the given function to resolve GL api functions.
+ *
+ * The load_proc function accepts a function name and a user data pointer.
+ * If this function returns NULL, in most cases the OpenGL context is not initialized, not made
+ * current or insufficient to render projectM visuals.
+ *
+ * @return A projectM handle for the newly created instance that must be used in subsequent API calls.
+ *         NULL if the instance could not be created successfully.
+ * @since 4.2.0
+ */
+PROJECTM_EXPORT projectm_handle projectm_create_with_opengl_load_proc(void* (*load_proc)(const char*, void*), void* user_data);
+
 /**
  * @brief Destroys the given instance and frees the resources.
  *

src/libprojectM/CMakeLists.txt

@@ -6,11 +6,21 @@ add_compile_definitions(
         $<IF:$<PLATFORM_ID:Windows>,STBI_NO_DDS,>
         )
 
+include_directories(
+        "${PROJECTM_SOURCE_DIR}/vendor/glad/include"
+        )
+
 add_subdirectory(Audio)
 add_subdirectory(MilkdropPreset)
 add_subdirectory(Renderer)
 add_subdirectory(UserSprites)
 
+set(PROJECTM_LINK_GL_LIBS "")
+if (WIN32)
+    # windows libs need to link to opengl32.dll
+    set(PROJECTM_LINK_GL_LIBS "${PROJECTM_OPENGL_LIBRARIES}")
+endif()
+
 add_library(projectM_main OBJECT
         "${PROJECTM_EXPORT_HEADER}"
         Logging.cpp
@@ -70,6 +80,7 @@ add_library(projectM
         $<TARGET_OBJECTS:SOIL2>
         $<TARGET_OBJECTS:projectM_main>
         $<TARGET_OBJECTS:projectM::Eval>
+        $<TARGET_OBJECTS:glad_obj>
         )
 
 target_include_directories(projectM
@@ -79,9 +90,9 @@ target_include_directories(projectM
 
 target_link_libraries(projectM
         PUBLIC
-        ${PROJECTM_OPENGL_LIBRARIES}
         libprojectM::API
         ${PROJECTM_FILESYSTEM_LIBRARY}
+        ${PROJECTM_LINK_GL_LIBS}
         )
 
 if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
@@ -107,6 +118,7 @@ if(BUILD_SHARED_LIBS)
     target_link_libraries(projectM
             PUBLIC
             ${CMAKE_DL_LIBS}
+            ${PROJECTM_LINK_GL_LIBS}
             )
 else()
     target_compile_definitions(projectM_main

src/libprojectM/MilkdropPreset/CMakeLists.txt

@@ -140,7 +140,6 @@ target_link_libraries(MilkdropPreset
         PUBLIC
         hlslparser
         GLM::GLM
-        ${PROJECTM_OPENGL_LIBRARIES}
         )
 
 if(NOT BUILD_SHARED_LIBS)

src/libprojectM/ProjectMCWrapper.cpp

@@ -6,6 +6,10 @@
 
 #include <Audio/AudioConstants.hpp>
 
+#include <Renderer/CrossGlLoader.hpp>
+#include <SOIL2/soil2_gl_bridge.h>
+#include <SOIL2/SOIL2.h>
+
 #include <projectM-4/parameters.h>
 #include <projectM-4/render_opengl.h>
 
@@ -67,10 +71,27 @@ void projectm_free_string(const char* str)
 }
 
 projectm_handle projectm_create()
+{
+    return projectm_create_with_opengl_load_proc(nullptr, nullptr);
+}
+
+projectm_handle projectm_create_with_opengl_load_proc(void* (*load_proc)(const char*, void*), void* user_data)
 {
     try
     {
-        auto projectMInstance = new libprojectM::projectMWrapper();
+        // invoke loader to discover gl function pointer and init glad
+        auto success = libprojectM::Renderer::CrossGlLoader::Instance().Initialize(load_proc, user_data);
+        if (!success)
+        {
+            return nullptr;
+        }
+
+        // init SOIL2 gl functions
+        soil2_set_gl_resolver(&libprojectM::Renderer::CrossGlLoader::GladResolverThunk);
+        SOIL_init();
+
+        // create projectM
+        auto* projectMInstance = new libprojectM::projectMWrapper();
         return reinterpret_cast<projectm_handle>(projectMInstance);
     }
     catch (...)
@@ -83,6 +104,7 @@ void projectm_destroy(projectm_handle instance)
 {
     auto projectMInstance = handle_to_instance(instance);
     delete projectMInstance;
+    libprojectM::Renderer::CrossGlLoader::Instance().Shutdown();
 }
 
 void projectm_load_preset_file(projectm_handle instance, const char* filename,

src/libprojectM/Renderer/CMakeLists.txt

@@ -22,6 +22,8 @@ add_library(Renderer OBJECT
         Color.hpp
         CopyTexture.cpp
         CopyTexture.hpp
+        CrossGlLoader.cpp
+        CrossGlLoader.hpp
         FileScanner.cpp
         FileScanner.hpp
         Framebuffer.cpp
@@ -32,6 +34,7 @@ add_library(Renderer OBJECT
         MilkdropNoise.cpp
         MilkdropNoise.hpp
         OpenGL.h
+        PlatformLoader.h
         Point.hpp
         PresetTransition.cpp
         PresetTransition.hpp
@@ -76,6 +79,7 @@ target_link_libraries(Renderer
         GLM::GLM
         hlslparser
         SOIL2
+        glad
         )
 
 set_target_properties(Renderer PROPERTIES