Tutorial_202_Viewer_imgui/main.cpp

This example shows how to enhance the default Easy3D viewer with menus using ImGui.

The header file of the viewer class:

/********************************************************************
 * Copyright (C) 2015 Liangliang Nan <liangliang.nan@gmail.com>
 * https://3d.bk.tudelft.nl/liangliang/
 *
 * This file is part of Easy3D. If it is useful in your research/work,
 * I would be grateful if you show your appreciation by citing it:
 * ------------------------------------------------------------------
 *      Liangliang Nan.
 *      Easy3D: a lightweight, easy-to-use, and efficient C++ library
 *      for processing and rendering 3D data.
 *      Journal of Open Source Software, 6(64), 3255, 2021.
 * ------------------------------------------------------------------
 *
 * Easy3D is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License Version 3
 * as published by the Free Software Foundation.
 *
 * Easy3D is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 ********************************************************************/
 
#ifndef EASY3D_TUTORIAL_VIEWER_IMGUI_H
#define EASY3D_TUTORIAL_VIEWER_IMGUI_H
 
 
#include <easy3d/viewer/viewer.h>
 
 
 
// A very good tutorial for imgui:
// https://eliasdaler.github.io/using-imgui-with-sfml-pt1/
// https://eliasdaler.github.io/using-imgui-with-sfml-pt2/
 
 
struct ImGuiContext;
 
 
namespace easy3d {
 
    class ViewerImGui : public Viewer
    {
    public:
        explicit ViewerImGui(
            const std::string& title = "Easy3D ViewerImGui",
            int samples = 4,
            int gl_major = 3,   // must >= 3
            int gl_minor = 2,   // must >= 2
            bool full_screen = false,
            bool resizable = true,
            int depth_bits = 24,
            int stencil_bits = 8,
            int width = 800,
            int height = 600
        );

        ~ViewerImGui() override;
 
    protected:
 
        // imgui plugins
        void init() override;
 
        // draw the widgets
        void pre_draw() override;
 
        //  the widgets
        void post_draw() override;
 
        void post_resize(int w, int h) override;
 
        bool callback_event_cursor_pos(double x, double y) override;
        bool callback_event_mouse_button(int button, int action, int modifiers) override;
        bool callback_event_keyboard(int key, int action, int modifiers) override;
        bool callback_event_character(unsigned int codepoint) override;
        bool callback_event_scroll(double dx, double dy) override;
 
        void draw_menu_file();
        void draw_menu_view();
 
    protected:
        // Ratio between the framebuffer size and the window size.
        // May be different from the DPI scaling!
        float pixel_ratio();
 
        float widget_scaling() { return dpi_scaling() / pixel_ratio(); }
 
        // We don't need a per-window font. So this function is static
        void  reload_font(int font_size = 16);
 
    protected:
        // Single global context by default, but can be overridden by the user
        static ImGuiContext *   context_;
 
        float menu_height_;
    };
 
}
 
#endif  // EASY3D_TUTORIAL_VIEWER_IMGUI_H

The source file of viewer class:

/********************************************************************
 * Copyright (C) 2015 Liangliang Nan <liangliang.nan@gmail.com>
 * https://3d.bk.tudelft.nl/liangliang/
 *
 * This file is part of Easy3D. If it is useful in your research/work,
 * I would be grateful if you show your appreciation by citing it:
 * ------------------------------------------------------------------
 *      Liangliang Nan.
 *      Easy3D: a lightweight, easy-to-use, and efficient C++ library
 *      for processing and rendering 3D data.
 *      Journal of Open Source Software, 6(64), 3255, 2021.
 * ------------------------------------------------------------------
 *
 * Easy3D is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License Version 3
 * as published by the Free Software Foundation.
 *
 * Easy3D is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 ********************************************************************/
 
#include "viewer.h"
 
#include <easy3d/util/file_system.h>
#include <easy3d/core/point_cloud.h>
#include <easy3d/core/surface_mesh.h>
#include <easy3d/renderer/text_renderer.h>
#include <easy3d/renderer/camera.h>
 
#include <3rd_party/glfw/include/GLFW/glfw3.h>  // for glfw functions
 
#include <3rd_party/imgui/misc/fonts/imgui_fonts_droid_sans.h>
#include <3rd_party/imgui/imgui.h>
#include <3rd_party/imgui/backends/imgui_impl_glfw.h>
#include <3rd_party/imgui/backends/imgui_impl_opengl3.h>
 
 
namespace easy3d {
 
    // \cond
 
    ImGuiContext* ViewerImGui::context_ = nullptr;
 
    ViewerImGui::ViewerImGui(
        const std::string& title /* = "Easy3D ImGui Viewer" */,
        int samples /* = 4 */,
        int gl_major /* = 3 */,
        int gl_minor /* = 2 */,
        bool full_screen /* = false */,
        bool resizable /* = true */,
        int depth_bits /* = 24 */,
        int stencil_bits /* = 8 */,
        int width /* = 960 */,
        int height /* = 800 */
    ) : Viewer(title, samples, gl_major, gl_minor, full_screen, resizable, depth_bits, stencil_bits, width, height)
    {
#if defined(_WIN32) && defined(_MSC_VER)
        // Liangliang: the internal glfw won't be shared across dll boundaries (But seems ok on macOS. That is weird!)
        // see https://github.com/LiangliangNan/Easy3D/issues/178
        glfwInit();
#endif
    }
 
 
    ViewerImGui::~ViewerImGui() {
        ImGui_ImplOpenGL3_Shutdown();
        ImGui_ImplGlfw_Shutdown();
 
        ImGui::DestroyContext(context_);
 
        // Not needed: it will be called in the destructor of the base class
        //Viewer::cleanup();
    }
 
 
    void ViewerImGui::init() {
        Viewer::init();
 
        if (!context_) {
            // Setup ImGui binding
            IMGUI_CHECKVERSION();
 
            context_ = ImGui::CreateContext();
 
            const char* glsl_version = "#version 150";
            ImGui_ImplGlfw_InitForOpenGL(window_, true);
            ImGui_ImplOpenGL3_Init(glsl_version);
            ImGuiIO& io = ImGui::GetIO();
            io.WantCaptureKeyboard = true;
            io.WantTextInput = true;
            io.IniFilename = nullptr;
            ImGui::StyleColorsLight();
            ImGuiStyle& style = ImGui::GetStyle();
            style.FrameRounding = 5.0f;
 
            // load font
            reload_font();
        }
    }
 
 
    float ViewerImGui::pixel_ratio() {
        // Computes pixel ratio for hidpi devices
        int fw = framebuffer_width();
        int vw = width();
        return static_cast<float>(fw) / static_cast<float>(vw);
    }
 
 
    void ViewerImGui::reload_font(int font_size)
    {
        ImGuiIO& io = ImGui::GetIO();
        io.Fonts->Clear();
        io.Fonts->AddFontFromMemoryCompressedTTF(droid_sans_compressed_data, droid_sans_compressed_size, static_cast<float>(font_size) * dpi_scaling());
        io.FontGlobalScale = 1.0f / pixel_ratio();
        ImGui_ImplOpenGL3_DestroyDeviceObjects();
    }
 
 
    void ViewerImGui::post_resize(int w, int h) {
        Viewer::post_resize(w, h);
        if (context_) {
            ImGui::GetIO().DisplaySize.x = float(w);
            ImGui::GetIO().DisplaySize.y = float(h);
        }
    }
 
 
    bool ViewerImGui::callback_event_cursor_pos(double x, double y) {
        if (ImGui::GetIO().WantCaptureMouse)
            return true;
        return Viewer::callback_event_cursor_pos(x, y);
    }
 
 
    bool ViewerImGui::callback_event_mouse_button(int button, int action, int modifiers) {
        if (ImGui::GetIO().WantCaptureMouse)
            return true;
        return Viewer::callback_event_mouse_button(button, action, modifiers);
    }
 
 
    bool ViewerImGui::callback_event_keyboard(int key, int action, int modifiers) {
        if (ImGui::GetIO().WantCaptureKeyboard)
            return true;
        return Viewer::callback_event_keyboard(key, action, modifiers);
    }
 
 
    bool ViewerImGui::callback_event_character(unsigned int codepoint) {
        if (ImGui::GetIO().WantCaptureKeyboard)
            return true;
        return Viewer::callback_event_character(codepoint);
    }
 
 
    bool ViewerImGui::callback_event_scroll(double dx, double dy) {
        if (ImGui::GetIO().WantCaptureMouse)
            return true;
        return Viewer::callback_event_scroll(dx, dy);
    }
 
 
    void ViewerImGui::pre_draw() {
        ImGui_ImplGlfw_NewFrame();
        ImGui_ImplOpenGL3_NewFrame();
        ImGui::NewFrame();   
 
        Viewer::pre_draw(); 
    }
 
 
    void ViewerImGui::post_draw() {
        static bool show_about = false;
        if (show_about) {
            ImGui::SetNextWindowPos(ImVec2(static_cast<float>(width()) * 0.5f, static_cast<float>(height()) * 0.5f), ImGuiCond_Appearing, ImVec2(0.5f, 0.5f));
            ImGui::Begin("About Easy3D ImGui Viewer", &show_about, ImGuiWindowFlags_NoResize);
            ImGui::Text("This viewer shows how to use ImGui for GUI creation and event handling");
            ImGui::Separator();
            ImGui::Text(
                "\n"
                "Liangliang Nan\n"
                "liangliang.nan@gmail.com\n"
                "https://3d.bk.tudelft.nl/liangliang/\n"
            );
            ImGui::End();
        }
 
        ImGui::PushStyleVar(ImGuiStyleVar_FramePadding, ImVec2(5, 8));
        if (ImGui::BeginMainMenuBar())
        {
            draw_menu_file();
            draw_menu_view();
 
            if (ImGui::BeginMenu("Help")) {
                ImGui::MenuItem("About", nullptr, &show_about);
                ImGui::EndMenu();
            }
            menu_height_ = ImGui::GetWindowHeight();
            ImGui::EndMainMenuBar();
        }
        ImGui::PopStyleVar();
 
        ImGui::Render();
        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData()); 
 
        // workaround to draw the Easy3D logo and framerate at a different location (due to the menu bar)
        auto show_logo = show_easy3d_logo_;
        auto show_fps = show_frame_rate_;
        show_easy3d_logo_ = false;
        show_frame_rate_ = false;
        Viewer::post_draw();
        show_easy3d_logo_ = show_logo;
        show_frame_rate_ = show_fps;
 
        // draw Easy3D logo (on the right side)
        if (texter_) {
            const float font_size = 15.0f;
            const float offset_x = (width() - texter_->string_width("Easy3D", font_size) - 50.0f) * dpi_scaling();
            if (show_easy3d_logo_) {
                const float offset_y = (20.0f + menu_height_) * dpi_scaling();
                texter_->draw("Easy3D", offset_x, offset_y, font_size, 0);
            }
 
            // draw the framerate
            if (show_frame_rate_) {
                const float offset_y = (50.0f + menu_height_) * dpi_scaling();
                texter_->draw(framerate_, offset_x, offset_y, font_size, 1);
            }
        }
    }
 
 
    void ViewerImGui::draw_menu_file() {
        if (ImGui::BeginMenu("File"))
        {
            if (ImGui::MenuItem("Open", "Ctrl+O"))
                open();
            if (ImGui::MenuItem("Save As...", "Ctrl+S"))
                save();
 
            ImGui::Separator();
            if (ImGui::MenuItem("Quit", "Alt+F4"))
                glfwSetWindowShouldClose(window_, GLFW_TRUE);
 
            ImGui::EndMenu();
        }
    }
 
 
    void ViewerImGui::draw_menu_view() {
        if (ImGui::BeginMenu("View"))
        {
            if (ImGui::MenuItem("Snapshot", nullptr))
                snapshot();
 
            ImGui::EndMenu();
        }
    }
 
    // \endcond
 
}

/********************************************************************
 * Copyright (C) 2015 Liangliang Nan <liangliang.nan@gmail.com>
 * https://3d.bk.tudelft.nl/liangliang/
 *
 * This file is part of Easy3D. If it is useful in your research/work,
 * I would be grateful if you show your appreciation by citing it:
 * ------------------------------------------------------------------
 *      Liangliang Nan.
 *      Easy3D: a lightweight, easy-to-use, and efficient C++ library
 *      for processing and rendering 3D data.
 *      Journal of Open Source Software, 6(64), 3255, 2021.
 * ------------------------------------------------------------------
 *
 * Easy3D is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License Version 3
 * as published by the Free Software Foundation.
 *
 * Easy3D is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 ********************************************************************/
 
#include <easy3d/renderer/camera.h>
#include <easy3d/util/resource.h>
#include <easy3d/util/initializer.h>
 
#include "viewer.h"

 
 
using namespace easy3d;
 
int main(int argc, char** argv) {
    // initialize Easy3D.
    initialize();
 
    const std::string file_name = resource::directory() + "/data/easy3d.ply";
    ViewerImGui viewer(EXAMPLE_TITLE);
    viewer.camera()->setViewDirection(vec3(0, 0, -1));
    viewer.camera()->setUpVector(vec3(0, 1, 0));
 
    if (!viewer.add_model(file_name)) {
        LOG(ERROR) << "failed to load model. Please make sure the file exists and format is correct.";
        return EXIT_FAILURE;
    }
 
    return viewer.run();
}