戻る

imguiの導入

July 15, 2020

GLFWはUIの機能を提供しないとても軽量なパッケージのため, UIは自前で実装するかライブラリを使う必要があるが, imguiライブラリはとても有名で広く使われている. しかしこれもまた導入の説明が不親切なため, またMac向けに解説する.

imguiプロジェクト全体をダウンロードするのは無駄が多いので気が引けるが, imguiのソースコードがレポジトリのあちこちにあるため結局全部インストールして必要なものを抽出するのが手っ取り早い. https://github.com/ocornut/imgui/tree/master/examples/example_glfw_opengl3 imguiのexamplesでglfw, opengl3以降のものに対応したサンプルプロジェクトをビルドするのが一つの目標. そのままmakeでビルドできると思うが, 実際に自分のプロジェクトのビルドの時もすぐに対応できるようにはMakefileを覗いて何のソースに依存しているかを見て行く必要がある.

Makefileの必要な部分だけ抜粋する. このサンプルプログラムはimguiレポジトリ全体をダウンロードすることを前提とした構造となっている. 仕方ないかもしれないが. しかしいずれ自分のプロジェクトでもビルドできるようにはしたいので, 改変してみる.



#CXX = g++
#CXX = clang++

EXE = example_glfw_opengl3
SOURCES = main.cpp
SOURCES += imgui_impl_glfw.cpp imgui_impl_opengl3.cpp imgui.cpp imgui_demo.cpp imgui_draw.cpp imgui_widgets.cpp
OBJS = $(addsuffix .o, $(basename $(notdir $(SOURCES))))
UNAME_S := $(shell uname -s)

CXXFLAGS += -g -Wall -Wformat
LIBS =

# Using OpenGL loader: glad
SOURCES += glad.c
CXXFLAGS += -DIMGUI_IMPL_OPENGL_LOADER_GLAD

ifeq ($(UNAME_S), Darwin) #APPLE
	ECHO_MESSAGE = "Mac OS X"
	LIBS += -framework OpenGL -framework Cocoa -framework IOKit -framework CoreVideo
	LIBS += -lglfw

	CXXFLAGS += -I/usr/local/include -I/opt/local/include
	CFLAGS = $(CXXFLAGS)
endif

%.o:%.cpp
	$(CXX) $(CXXFLAGS) -c -o $@ $<


all: $(EXE)
	@echo Build complete for $(ECHO_MESSAGE)

$(EXE): $(OBJS)
	$(CXX) -o $@ $^ $(CXXFLAGS) $(LIBS)

clean:
	rm -f $(EXE) $(OBJS)

次のファイルをプロジェクトに加えなくてはならない. 結局, imguiレポジトリのトップの.h,.cppファイル全てとexamples内のimgui_impl_~の4つを導入すれば良い.

これで, makeでビルドできるはず.

main.cpp

inguiのgithubを見てみると, imguiのまともなドキュメントがどこにもない. FAQを見てみると, Q: Where is the documentation? This library is poorly documented at the moment and expects of the user to be acquainted with C/C++. 回答としては, imgui_demo.cpp, imgui.cpp, imgui.h を見れば良いとある. examplesのコードで十分だという.

gladを使っているため他のローダーなど関係ない部分は取り除いて簡潔にした. それでもgl3wなど他のローダーのコードを少し残したのはMakefileのフラグをどのように使っているのか見るため.


#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_opengl3.h"
#include <stdio.h>

#if defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
#include <GL/gl3w.h>            // Initialize with gl3wInit()
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
#include <GL/glew.h>            // Initialize with glewInit()
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
#include <glad/glad.h>          // Initialize with gladLoadGL()
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
#include <glad/gl.h>            // Initialize with gladLoadGL(...) or gladLoaderLoadGL()
#else
#include IMGUI_IMPL_OPENGL_LOADER_CUSTOM
#endif

// Include glfw3.h after our OpenGL definitions
#include <GLFW/glfw3.h>


static void glfw_error_callback(int error, const char* description)
{
    fprintf(stderr, "Glfw Error %d: %s\n", error, description);
}

int main(int, char**)
{
    // Setup window
    glfwSetErrorCallback(glfw_error_callback);
    if (!glfwInit())
        return 1;

    // Decide GL+GLSL versions
#if __APPLE__
    // GL 3.2 + GLSL 150
    const char* glsl_version = "#version 150";
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);  // 3.2+ only
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);            // Required on Mac
#else
    // GL 3.0 + GLSL 130
    const char* glsl_version = "#version 130";
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    //glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);  // 3.2+ only
    //glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);            // 3.0+ only
#endif

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

    // Initialize OpenGL loader
#if defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
    bool err = gl3wInit() != 0;
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
    bool err = glewInit() != GLEW_OK;
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
    bool err = gladLoadGL() == 0;
#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
    bool err = gladLoadGL(glfwGetProcAddress) == 0; // glad2 recommend using the windowing library loader instead of the (optionally) bundled one.
#else
    bool err = false; // If you use IMGUI_IMPL_OPENGL_LOADER_CUSTOM, your loader is likely to requires some form of initialization.
#endif
    if (err)
    {
        fprintf(stderr, "Failed to initialize OpenGL loader!\n");
        return 1;
    }

    // Setup Dear ImGui context
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;
    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls

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

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

    // Load Fonts
    // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
    // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
    // - If the file cannot be loaded, the function will return NULL. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
    // - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
    // - Read 'docs/FONTS.md' for more instructions and details.
    // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
    //io.Fonts->AddFontDefault();
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 15.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/ProggyTiny.ttf", 10.0f);
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
    //IM_ASSERT(font != NULL);

    // Our state
    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))
    {
        // Poll and handle events (inputs, window resize, etc.)
        // You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
        // - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application.
        // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application.
        // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
        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;
        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());

        glfwSwapBuffers(window);
    }

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

    glfwDestroyWindow(window);
    glfwTerminate();

    return 0;
}

glfwの機能は別のところで解説するので, ここではimguiに焦点を絞って解説する. 以下のコードはglfwの初期化処理後からwhile(!glfwWindowShouldClose(window)) メインループ前までのimguiの部分を抽出したものだ.


    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;
    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls

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

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

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

メインループ. 次の3天セットはつきもの. 基本的に, renderer(opengl), platform(glfw), imguiと3つが協調して動かなくてはならない.


ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplGlfw_NewFrame();
ImGui::NewFrame();

実行するとわかるが, コードの量の割に複雑なGUIが生成されている. ImGui::ShowDemoWindow一行で丸々生成できてしまう.


if (show_demo_window)
    ImGui::ShowDemoWindow(&show_demo_window);

メインのウィンドウ. ImGui::Begin("Hello, world!") でHello, World! というタイトルのウィンドウ生成. ImGui::End()でこのウィンドウの生成を完了する.


{
    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つ目のwindow. 正直これが一番簡単なので最初に解説しても良かったが. 解説することがない状態が望ましいのかもしれない.



        // 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;
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());

glfwSwapBuffers(window);

メインループ終了後は次の3つ.


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