imgui/examples/example_android_opengl3/main.cpp

// dear imgui: standalone example application for Android + OpenGL ES 3
// If you are new to dear imgui, see examples/README.txt and documentation at the top of imgui.cpp.

#include "imgui.h"
#include "imgui_impl_android.h"
#include "imgui_impl_opengl3.h"
#include <android/log.h>
#include <android_native_app_glue.h>
#include <android/asset_manager.h>
#include <EGL/egl.h>
#include <GLES3/gl3.h>

static EGLDisplay           g_EglDisplay = EGL_NO_DISPLAY;
static EGLSurface           g_EglSurface = EGL_NO_SURFACE;
static EGLContext           g_EglContext = EGL_NO_CONTEXT;
static struct android_app*  g_App = NULL;
static bool                 g_Initialized = false;
static char                 g_LogTag[] = "ImguiExample";

// Unfortunately, there is no way to show the on-screen input from native code.
// Therefore, we call showSoftInput() of the main activity implemented in MainActivity.kt via JNI.
static int showSoftInput()
{
    JavaVM* java_vm = g_App->activity->vm;
    JNIEnv* java_env = NULL;

    jint jni_return = java_vm->GetEnv((void**)&java_env, JNI_VERSION_1_6);
    if (jni_return == JNI_ERR)
        return -1;

    jni_return = java_vm->AttachCurrentThread(&java_env, NULL);
    if (jni_return != JNI_OK)
        return -2;

    jclass native_activity_clazz = java_env->GetObjectClass(g_App->activity->clazz);
    if (native_activity_clazz == NULL)
        return -3;

    jmethodID method_id = java_env->GetMethodID(native_activity_clazz, "showSoftInput", "()V");
    if (method_id == NULL)
        return -4;

    java_env->CallVoidMethod(g_App->activity->clazz, method_id);

    jni_return = java_vm->DetachCurrentThread();
    if (jni_return != JNI_OK)
        return -5;

    return 0;
}

// Unfortunately, the native KeyEvent implementation has no getUnicodeChar() function.
// Therefore, we implement the processing of KeyEvents in MainActivity.kt and poll
// the resulting Unicode characters here via JNI and send them to Dear ImGui.
static int pollUnicodeChars()
{
    JavaVM* java_vm = g_App->activity->vm;
    JNIEnv* java_env = NULL;

    jint jni_return = java_vm->GetEnv((void**)&java_env, JNI_VERSION_1_6);
    if (jni_return == JNI_ERR)
        return -1;

    jni_return = java_vm->AttachCurrentThread(&java_env, NULL);
    if (jni_return != JNI_OK)
        return -2;

    jclass native_activity_clazz = java_env->GetObjectClass(g_App->activity->clazz);
    if (native_activity_clazz == NULL)
        return -3;

    jmethodID method_id = java_env->GetMethodID(native_activity_clazz, "pollUnicodeChar", "()I");
    if (method_id == NULL)
        return -4;

    // Send the actual characters to Dear ImGui
    ImGuiIO& io = ImGui::GetIO();
    jint unicode_character;
    while ((unicode_character = java_env->CallIntMethod(g_App->activity->clazz, method_id)) != 0)
    {
        io.AddInputCharacter(unicode_character);
    }

    jni_return = java_vm->DetachCurrentThread();
    if (jni_return != JNI_OK)
        return -5;

    return 0;
}

static int GetAssetData(const char* filename, void** outData)
{
    int num_bytes = 0;
    AAsset* asset_descriptor = AAssetManager_open(g_App->activity->assetManager, filename, AASSET_MODE_BUFFER);
    if(asset_descriptor)
    {
        num_bytes = AAsset_getLength(asset_descriptor);
        *outData = IM_ALLOC(num_bytes);
        int64_t num_bytes_read = AAsset_read(asset_descriptor, *outData, num_bytes);
        AAsset_close(asset_descriptor);
        IM_ASSERT(num_bytes_read == num_bytes);
    }
    return num_bytes;
}

void init(struct android_app* app)
{
    if (g_Initialized)
        return;

    g_App = app;
    ANativeWindow_acquire(g_App->window);

    // Initialize EGL
    // This is mostly boilerplate code for EGL...
    g_EglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);

    if (g_EglDisplay == EGL_NO_DISPLAY)
        __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglGetDisplay(EGL_DEFAULT_DISPLAY) returned EGL_NO_DISPLAY");

    if (eglInitialize(g_EglDisplay, 0, 0) != EGL_TRUE)
        __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglInitialize(..) returned with an error");

    const EGLint egl_attributes[] = {
        EGL_BLUE_SIZE, 8,
        EGL_GREEN_SIZE, 8,
        EGL_RED_SIZE, 8,
        EGL_DEPTH_SIZE, 24,
        EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
        EGL_NONE};

    EGLint num_configs = 0;
    if (eglChooseConfig(g_EglDisplay, egl_attributes, nullptr, 0, &num_configs) != EGL_TRUE)
        __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglChooseConfig(..) returned with an error");

    if (num_configs == 0)
        __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglChooseConfig(..) returned 0 matching configs");

    // Get the (first) matching config
    EGLConfig egl_config;
    eglChooseConfig(g_EglDisplay, egl_attributes, &egl_config, 1, &num_configs);
    EGLint egl_format;
    eglGetConfigAttrib(g_EglDisplay, egl_config, EGL_NATIVE_VISUAL_ID, &egl_format);
    ANativeWindow_setBuffersGeometry(g_App->window, 0, 0, egl_format);

    const EGLint egl_context_attributes[] = {EGL_CONTEXT_CLIENT_VERSION, 3, EGL_NONE};
    g_EglContext = eglCreateContext(g_EglDisplay, egl_config, EGL_NO_CONTEXT, egl_context_attributes);

    if (g_EglContext == EGL_NO_CONTEXT)
        __android_log_print(ANDROID_LOG_ERROR, g_LogTag, "%s", "eglCreateContext(..) returned EGL_NO_CONTEXT");

    g_EglSurface = eglCreateWindowSurface(g_EglDisplay, egl_config, g_App->window, NULL);
    eglMakeCurrent(g_EglDisplay, g_EglSurface, g_EglSurface, g_EglContext);

    // Dear Imgui
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO();
    io.IniFilename = NULL;
    ImGui::StyleColorsDark();
    ImGui_ImplAndroid_Init(g_App->window);
    ImGui_ImplOpenGL3_Init("#version 300 es");

    // 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.
    // - add_font_from_assets_ttf() 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 \\ !
    // - The TTF files have to be placed into the assets/ directory (android/app/src/main/assets).

    // We load the default font with increased size to improve readability on many devices with "high" DPI.
    // FIXME: Put some effort into DPI awareness
    ImFontConfig font_cfg;
    font_cfg.SizePixels = 22.0f;
    io.Fonts->AddFontDefault(&font_cfg);
    //void* font_data;
    //int font_data_size;
    //ImFont* font;
    //font_data_size = GetAssetData("Roboto-Medium.ttf", &font_data);
    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 16.0f); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
    //IM_ASSERT(font != NULL);
    //font_data_size = GetAssetData("Cousine-Regular.ttf", &font_data);
    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 15.0f); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
    //IM_ASSERT(font != NULL);
    //font_data_size = GetAssetData("DroidSans.ttf", &font_data);
    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 16.0f); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
    //IM_ASSERT(font != NULL);
    //font_data_size = GetAssetData("ProggyTiny.ttf", &font_data);
    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 10.0f); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
    //IM_ASSERT(font != NULL);
    //font_data_size = GetAssetData("ArialUni.ttf", &font_data);
    //font = io.Fonts->AddFontFromMemoryTTF(font_data, font_data_size, 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese()); // Ownership of font_data is transfered to ImGui. Deletion is handled by ImGui.
    //IM_ASSERT(font != NULL);

    // Arbitrary scale-up
    // FIXME: Put some effort into DPI awareness
    ImGui::GetStyle().ScaleAllSizes(3.0f);

    g_Initialized = true;
}

void tick()
{
    // Our state (Dear Imgui)
    static bool show_demo_window = true;
    static bool show_another_window = false;
    static ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    if (g_EglDisplay != EGL_NO_DISPLAY)
    {
        ImGuiIO& io = ImGui::GetIO();

        // Poll Unicode characters via JNI
        // FIXME: do not call this every frame because of JNI overhead
        pollUnicodeChars();

        // Open on-screen (soft) input if demanded by Dear ImGui
        static bool WantTextInputLast = false;
        if (io.WantTextInput && !WantTextInputLast)
            showSoftInput();
        WantTextInputLast = io.WantTextInput;

        // Start the Dear ImGui frame
        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplAndroid_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();
        glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
        glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
        glClear(GL_COLOR_BUFFER_BIT);
        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
        eglSwapBuffers(g_EglDisplay, g_EglSurface);
    }
}

void shutdown()
{
    if (!g_Initialized)
        return;

    // Cleanup (Dear Imgui)
    ImGui_ImplOpenGL3_Shutdown();
    ImGui_ImplAndroid_Shutdown();
    ImGui::DestroyContext();

    if (g_EglDisplay != EGL_NO_DISPLAY)
    {
        eglMakeCurrent(g_EglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);

        if (g_EglContext != EGL_NO_CONTEXT)
            eglDestroyContext(g_EglDisplay, g_EglContext);

        if (g_EglSurface != EGL_NO_SURFACE)
            eglDestroySurface(g_EglDisplay, g_EglSurface);

        eglTerminate(g_EglDisplay);
    }

    g_EglDisplay = EGL_NO_DISPLAY;
    g_EglContext = EGL_NO_CONTEXT;
    g_EglSurface = EGL_NO_SURFACE;
    ANativeWindow_release(g_App->window);

    g_Initialized = false;
}

static void handleAppCmd(struct android_app* app, int32_t appCmd)
{
    switch (appCmd)
    {
    case APP_CMD_SAVE_STATE:
        break;
    case APP_CMD_INIT_WINDOW:
        init(app);
        break;
    case APP_CMD_TERM_WINDOW:
        shutdown();
        break;
    case APP_CMD_GAINED_FOCUS:
        break;
    case APP_CMD_LOST_FOCUS:
        break;
    }
}

static int32_t handleInputEvent(struct android_app* app, AInputEvent* inputEvent)
{
    return ImGui_ImplAndroid_HandleInputEvent(inputEvent);
}

void android_main(struct android_app* app)
{
    app->onAppCmd = handleAppCmd;
    app->onInputEvent = handleInputEvent;

    while (true)
    {
        int out_events;
        struct android_poll_source* out_data;

        // Poll all events. If the app is not visible, this loop blocks until g_Initialized == true.
        while (ALooper_pollAll(g_Initialized ? 0 : -1, NULL, &out_events, (void**)&out_data) >= 0)
        {
            // Process one event
            if (out_data != NULL)
                out_data->process(app, out_data);

            // Exit the app by returning from within the infinite loop
            if (app->destroyRequested != 0)
            {
                // shutdown() should have been called already while processing the
                // app command APP_CMD_TERM_WINDOW. But we play save here
                if (!g_Initialized)
                    shutdown();

                return;
            }
        }

        // Initiate a new frame
        tick();
    }
}