Dear ImGui结合CMake实现基于GLFW和OpenGL3的入门级hello world代码

如需转载请标明出处：https://blog.csdn.net/itas109
技术交流：129518033

环境：

OS: windows 10 / Ubuntu 22.04
imgui: 1.89.5
glw: 3.3.8

前言

Dear ImGui 是一个用于C ++的无膨胀图形用户界面库。它输出优化的顶点缓冲区，您可以随时在启用3D管线的应用程序中进行渲染。它快速，可移植，与渲染器无关并且是独立的（无外部依赖性）。

Dear Imgui是一个非常轻量级的库，没有额外的外部依赖，支持跨平台，很适合用于游戏引擎。

官方网站：https://github.com/ocornut/imgui

官方维护的后端：

渲染器：DirectX9，DirectX10，DirectX11，DirectX12，OpenGL，OpenGL3/ES/ES2，Vulkan，Metal
平台：GLFW，SDL2，Win32，Glut，OSX
框架：Emscripten，Allegro5，Marmalade

1. 下载ImGui代码及其依赖

这里我们使用GLFW3和OpenGL3进行渲染。

ImGui 1.89.5

https://github.com/ocornut/imgui/archive/refs/tags/v1.89.5.tar.gz

glw 3.3.8

https://github.com/glfw/glfw/archive/refs/tags/3.3.8.tar.gz

2. hello world代码

目录结构

imgui-1.89.5
$ tree
.
|-- CMakeLists.txt # my
|-- glfw-3.3.8.tar.gz # my
|-- main.cpp # my
...
|-- imconfig.h
|-- imgui.cpp
|-- imgui.h
|-- imgui.ini
|-- imgui_demo.cpp
|-- imgui_draw.cpp
|-- imgui_internal.h
|-- imgui_tables.cpp
|-- imgui_widgets.cpp
|-- imstb_rectpack.h
|-- imstb_textedit.h
|-- imstb_truetype.h
...

main.cpp

// Dear ImGui: standalone example application for GLFW + OpenGL3

#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_opengl3.h"

#include <GLFW/glfw3.h> // Will drag system OpenGL headers

// Main code
int main(int, char**)
{
    if (!glfwInit())
        return 1;

    // GL 3.0 + GLSL 130
    const char* glsl_version = "#version 130";

    // Create window with graphics context
    GLFWwindow* window = glfwCreateWindow(1280, 720, "Dear ImGui GLFW+OpenGL3", nullptr, nullptr);
    if (window == nullptr)
        return 1;
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1); // Enable vsync

    // Setup Dear ImGui context
    ImGui::CreateContext();

    // Setup Platform/Renderer backends
    ImGui_ImplGlfw_InitForOpenGL(window, true);
    ImGui_ImplOpenGL3_Init(glsl_version);

    // Main loop
    while (!glfwWindowShouldClose(window))
    {
        // Poll and handle events (inputs, window resize, etc.)
        glfwPollEvents();

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

        // ************ GUI **************
        ImGui::Begin("hello world");
        ImGui::Text("hello world");
        ImGui::End();
        // ************ GUI **************

        // Rendering
        ImGui::Render();
        int display_w, display_h;
        glfwGetFramebufferSize(window, &display_w, &display_h);
        glViewport(0, 0, display_w, display_h);

        static ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
        glClearColor(clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
        glClear(GL_COLOR_BUFFER_BIT);
        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

        glfwSwapBuffers(window);
    }

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

    glfwDestroyWindow(window);
    glfwTerminate();

    return 0;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.11.0)

project(main)

include_directories(.)
include_directories(backends)

set(IMGUI_FILES 
imgui.cpp 
imgui_draw.cpp 
imgui_tables.cpp 
imgui_widgets.cpp 
backends/imgui_impl_glfw.cpp # platform
backends/imgui_impl_opengl3.cpp # render
)

include(FetchContent)
# cmake 3.11 above
FetchContent_Declare(glfw URL ${CMAKE_CURRENT_SOURCE_DIR}/glfw-3.3.8.tar.gz)
FetchContent_GetProperties(glfw)
if(NOT glfw_POPULATED)
  # Fetch the content using previously declared details
  FetchContent_Populate(glfw)
  
  # Set custom variables
  set(BUILD_SHARED_LIBS OFF)
  set(GLFW_BUILD_EXAMPLES OFF)
  set(GLFW_BUILD_TESTS OFF)
  set(GLFW_BUILD_DOCS OFF)
  set(GLFW_INSTALL OFF)
  set(GLFW_VULKAN_STATIC OFF)

  # Bring the populated content into the build
  add_subdirectory(${glfw_SOURCE_DIR} ${glfw_BINARY_DIR})
endif()

add_executable(${PROJECT_NAME} main.cpp ${IMGUI_FILES})

if(WIN32)
target_link_libraries(${PROJECT_NAME} opengl32 glfw)
else()
target_link_libraries(${PROJECT_NAME} GL glfw)
endif()