OpenGL：ImGUI在GLFW库和GLAD/GLEW库的环境下使用

步骤1：修改examples/imgui_impl_opengl3.h中的默认OpenGL3 loader

此处我使用的是GLAD库，使用GLEW库的话可以改成IMGUI_IMPL_OPENGL_LOADER_GLEW

// Set default OpenGL3 loader to be gl3w
#if !defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)     \
 && !defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)     \
 && !defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)     \
 && !defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
#define IMGUI_IMPL_OPENGL_LOADER_GLAD//IMGUI_IMPL_OPENGL_LOADER_GL3W //****修改这里****
#endif

步骤2：

将examples/中的imgui_impl_glfw.h、imgui_impl_glfw.cpp、imgui_impl_opengl3.h（修改后）、imgui_impl_opengl3.cpp添加到项目中
步骤3：调用顺序

这里是examples/example_glfw_opengl3中的main.cpp中的内容的简化版
 

 // Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO(); (void)io;

// Setup Dear ImGui style
ImGui::StyleColorsDark();
//ImGui::StyleColorsClassic();

// Setup Platform/Renderer bindings
ImGui_ImplGlfw_InitForOpenGL(window, true);
ImGui_ImplOpenGL3_Init(glsl_version); //glsl_version可以使用字符串"#version 150"替代

bool show_demo_window = true;
bool show_another_window = false;
ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

// Main loop
while (!glfwWindowShouldClose(window))
{
    glfwPollEvents();

    // Start the Dear ImGui frame
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplGlfw_NewFrame();
    ImGui::NewFrame();

    // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
    if (show_demo_window)
        ImGui::ShowDemoWindow(&show_demo_window);

    // 2. Show a simple window that we create ourselves. We use a Begin/End pair to created a named window.
    {
        static float f = 0.0f;
        static int counter = 0;

        ImGui::Begin("Hello, world!");                          // Create a window called "Hello, world!" and append into it.

        ImGui::Text("This is some useful text.");               // Display some text (you can use a format strings too)
        ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
        ImGui::Checkbox("Another Window", &show_another_window);

        ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
        ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color

        if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
            counter++;
        ImGui::SameLine();
        ImGui::Text("counter = %d", counter);

        ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
        ImGui::End();
    }

    // 3. Show another simple window.
    if (show_another_window)
    {
        ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
        ImGui::Text("Hello from another window!");
        if (ImGui::Button("Close Me"))
            show_another_window = false;
        ImGui::End();
    }

    // Rendering
    ImGui::Render();
    int display_w, display_h;
    glfwMakeContextCurrent(window);
    glfwGetFramebufferSize(window, &display_w, &display_h);
    glViewport(0, 0, display_w, display_h);
    glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
    glClear(GL_COLOR_BUFFER_BIT);
    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

    glfwMakeContextCurrent(window);
    glfwSwapBuffers(window);
}

// Cleanup
ImGui_ImplOpenGL3_Shutdown();
ImGui_ImplGlfw_Shutdown();
ImGui::DestroyContext();