Building imgui with cmake, vcpkg.json and glfw(linking error)

Question

I have been trying to build imgui and glfw for my application using vcpkg and cmake. I am following an example available with sdl2 and imgui, I am getting linking errors when I follow the exact steps given this tutorial. I have already tried the existing solutions for linking glfw and imgui, using vcpkg minus the cmake preset part this. I modified the code around for glfw and imgui as it is my requirement.

Previously I was installing globally using vcpkg but I need to make a local build.

I am getting the following linking errors:

main.obj : error LNK2019: unresolved external symbol __imp_glClear referenced in function main [C:\Users\gopik\OneDrive\Desktop\my-project\bin\MY_PROJECT.vcxproj]
main.obj : error LNK2019: unresolved external symbol __imp_glClearColor referenced in function main [C:\Users\gopik\OneDrive\Desktop\my-project\bin\MY_PROJECT.vcxproj]
main.obj : error LNK2019: unresolved external symbol __imp_glViewport referenced in function main [C:\Users\gopik\OneDrive\Desktop\my-project\bin\MY_PROJECT.vcxproj]
C:\Users\gopik\OneDrive\Desktop\my-project\bin\Debug\MY_PROJECT.exe : fatal error LNK1120: 3 unresolved externals [C:\Users\gopik\OneDrive\Desktop\my-project\bin\MY_PROJECT.vcxproj]

and this:

-- Running vcpkg install
Detecting compiler hash for triplet x64-windows...
All requested packages are currently installed.
Total install time: 200 ns
freetype is compatible with built-in CMake targets:

    find_package(Freetype REQUIRED)
    target_link_libraries(main PRIVATE Freetype::Freetype) # since CMake 3.10

glad provides CMake targets:

    # this is heuristically generated, and may not be correct
    find_package(glad CONFIG REQUIRED)
    target_link_libraries(main PRIVATE glad::glad)

glfw3 provides CMake targets:

    # this is heuristically generated, and may not be correct
    find_package(glfw3 CONFIG REQUIRED)
    target_link_libraries(main PRIVATE glfw)

glm provides CMake targets:

    find_package(glm CONFIG REQUIRED)
    target_link_libraries(main PRIVATE glm::glm)

imgui provides CMake targets:

    # this is heuristically generated, and may not be correct
    find_package(imgui CONFIG REQUIRED)
    target_link_libraries(main PRIVATE imgui::imgui)

-- Running vcpkg install - done
CMake Warning (dev) at C:/Program Files/CMake/share/cmake-3.27/Modules/FindPackageHandleStandardArgs.cmake:438 (message):
  The package name passed to `find_package_handle_standard_args` (Freetype)
  does not match the name of the calling package (freetype).  This can lead
  to problems in calling code that expects `find_package` result variables
  (e.g., `_FOUND`) to follow a certain pattern.
Call Stack (most recent call first):
  C:/Program Files/CMake/share/cmake-3.27/Modules/FindFreetype.cmake:162 (find_package_handle_standard_args)
  bin/vcpkg_installed/x64-windows/share/freetype/vcpkg-cmake-wrapper.cmake:5 (_find_package)
  vcpkg/scripts/buildsystems/vcpkg.cmake:813 (include)
  CMakeLists.txt:24 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

-- Configuring done (2.3s)
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
IMGUI_LIBRARY
    linked by target "MY_PROJECT" in directory C:/Users/gopik/OneDrive/Desktop/my-project

-- Generating done (0.1s)
CMake Generate step failed.  Build files cannot be regenerated correctly.

My project structure:

my-project
|-cmake
  |- Vcpkg.cmake
|-src
  |- main.cpp
|-vcpkg
|-CMakeLists.txt
|-bin

My CMakeLists.txt:

cmake_minimum_required(VERSION 3.16 FATAL_ERROR)

include(cmake/Vcpkg.cmake) # needs to happen before project()

project(
    "MY_PROJECT" # replace this with the name of your executable
    VERSION 0.1.0
    LANGUAGES CXX
)

# add all headers (.h, .hpp) to this
set(PRJ_HEADERS )
# add all source files (.cpp) to this, except the one with main()
set(PRJ_SOURCES )
# set the source file containing main()
set(PRJ_MAIN src/main.cpp)

# add library targets here
set(PRJ_LIBRARIES 
freetype
glfw
glad::glad
glm::glm
imgui::imgui
)

# add dependency find_package calls and similar here
find_package(glfw3 REQUIRED)
find_package(glad REQUIRED)
find_package(glm REQUIRED)
find_package(freetype REQUIRED)
find_package(imgui REQUIRED)

add_executable(${PROJECT_NAME} ${PRJ_HEADERS} ${PRJ_SOURCES} ${PRJ_MAIN})
target_link_libraries(${PROJECT_NAME} PRIVATE ${PRJ_LIBRARIES})

vcpkg.json

{
    "name": "my-project",
    "version-string": "0.1.0",
    "dependencies": [
        "glfw3",
        "glad",
        "glm",
        "freetype",
      { 
        "name": "imgui", 
        "features": [
          "opengl3-binding", 
          "glfw-binding",
          "freetype"
        ] 
      }
    ]
  }

my main.cpp which is an example:

// Dear ImGui: standalone example application for GLFW + OpenGL 3, using programmable pipeline
// (GLFW is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan/Metal graphics context creation, etc.)
// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
// Read online: https://github.com/ocornut/imgui/tree/master/docs

#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_opengl3.h"
#include <stdio.h>
#define GL_SILENCE_DEPRECATION
#if defined(IMGUI_IMPL_OPENGL_ES2)
#include <GLES2/gl2.h>
#endif
#include <GLFW/glfw3.h> // Will drag system OpenGL headers

// [Win32] Our example includes a copy of glfw3.lib pre-compiled with VS2010 to maximize ease of testing and compatibility with old VS compilers.
// To link with VS2010-era libraries, VS2015+ requires linking with legacy_stdio_definitions.lib, which we do using this pragma.
// Your own project should not be affected, as you are likely to link with a newer binary of GLFW that is adequate for your version of Visual Studio.
#if defined(_MSC_VER) && (_MSC_VER >= 1900) && !defined(IMGUI_DISABLE_WIN32_FUNCTIONS)
#pragma comment(lib, "legacy_stdio_definitions")
#endif

// This example can also compile and run with Emscripten! See 'Makefile.emscripten' for details.
#ifdef __EMSCRIPTEN__
#include "../libs/emscripten/emscripten_mainloop_stub.h"
#endif

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

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

    // Decide GL+GLSL versions
#if defined(IMGUI_IMPL_OPENGL_ES2)
    // GL ES 2.0 + GLSL 100
    const char* glsl_version = "#version 100";
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_ES_API);
#elif defined(__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", nullptr, nullptr);
    if (window == nullptr)
        return 1;
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1); // Enable vsync

    // 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::StyleColorsLight();

    // Setup Platform/Renderer backends
    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 a nullptr. 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.
    // - Use '#define IMGUI_ENABLE_FREETYPE' in your imconfig file to use Freetype for higher quality font rendering.
    // - 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 \\ !
    // - Our Emscripten build process allows embedding fonts to be accessible at runtime from the "fonts/" folder. See Makefile.emscripten for details.
    //io.Fonts->AddFontDefault();
    //io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\segoeui.ttf", 18.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 15.0f);
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 18.0f, nullptr, io.Fonts->GetGlyphRangesJapanese());
    //IM_ASSERT(font != nullptr);

    // 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
#ifdef __EMSCRIPTEN__
    // 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 = nullptr;
    EMSCRIPTEN_MAINLOOP_BEGIN
#else
    while (!glfwWindowShouldClose(window))
#endif
    {
        // 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, or clear/overwrite your copy of the mouse data.
        // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application, or clear/overwrite your copy of the keyboard data.
        // 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 create 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 / io.Framerate, io.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.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);
    }
#ifdef __EMSCRIPTEN__
    EMSCRIPTEN_MAINLOOP_END;
#endif

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

    glfwDestroyWindow(window);
    glfwTerminate();

    return 0;
}

I am able to install imgui globally and use it in visual studio but that is not the aim of this exercise. Any help will be appreciated.

Answer 1

You need to #include "glad/glad.h" before loading glfw. See the documentation

Concretely, the glad.h header includes #defines like so:

typedef void (APIENTRYP PFNGLVIEWPORTPROC)(GLint x, GLint y, GLsizei width, GLsizei height);
GLAPI PFNGLVIEWPORTPROC glad_glViewport;
#define glViewport glad_glViewport

which enables the core gladLoadGLLoader function to look up all these functions at runtime and fill in the glad_glViewport function pointer (and others), which your OpenGL-using application knows nothing about.

You will also need to define the IMGUI_IMPL_OPENGL_LOADER_CUSTOM symbol to prevent Imgui from using its own loader.