main.cpp

// dear imgui: standalone example application for Emscripten, using SDL2 + OpenGL3
// This is mostly the same code as the SDL2 + OpenGL3 example, simply with the modifications needed to run on Emscripten.
// It is possible to combine both code into a single source file that will compile properly on Desktop and using Emscripten.
// See https://github.com/ocornut/imgui/pull/2492 as an example on how to do just that.
//
// If you are new to dear imgui, see examples/README.txt and documentation at the top of imgui.cpp.
// (Emscripten is a C++-to-javascript compiler, used to publish executables for the web. See https://emscripten.org/)

#include "imgui.h"
#include "imgui_impl_emscripten.h"
#include "imgui_impl_opengl3.h"
#include <stdio.h>
#include <emscripten.h>
#include <emscripten/html5.h>
#include <GLES2/gl2.h>

// For clarity, our main loop code is declared at the end.
EM_BOOL main_loop(double time, void* userData);

int main(int, char**)
{
    // setup WebGL context and input handlers
    if (!ImGui_ImplEmsc_Init("#canvas")) {
        printf("Error: couldn't setup WebGL context\n");
        return -1;
    }

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

    // For an Emscripten build we are disabling file-system access, so let's not attempt to do a fopen() of the imgui.ini file.
    // You may manually call LoadIniSettingsFromMemory() to load settings from your own storage.
    io.IniFilename = NULL;

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

    // Setup Platform/Renderer bindings
    ImGui_ImplEmsc_InitInput();
    ImGui_ImplOpenGL3_Init("#version 100");

    // 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 'misc/fonts/README.txt' 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);

    // This function call won't return, will engage in an infinite loop, processing events from the browser, and dispatching them.
    emscripten_request_animation_frame_loop(main_loop, 0);
    return 0;
}

EM_BOOL main_loop(double /*time*/, void* /*userData*/)
{
    ImGuiIO& io = ImGui::GetIO();

    // Our state (make them static = more or less global) as a convenience to keep the example terse.
    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);

    // Start the Dear ImGui frame
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplEmsc_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());

    return EM_TRUE;
}