英文:

How to fix memory access violation with OpenGL glViewport?

问题

我正在尝试使用C++、ImGUI、OpenGL和GLFW构建一个应用程序。

但是，当我尝试运行我的程序时，我得到一个白屏，然后崩溃并给我一个错误代码-1073741819。

这是我创建窗口的类，其中许多内容我从ImGUI opengl3示例中复制：

#include <imgui_impl_glfw.h>
#include <imgui_impl_opengl3.h>
#include <imgui_internal.h>
#include "imgui.h"
#include "AppWindow.h"

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

AppWindow::AppWindow(const char* title, int width, int height)
{
    glfwSetErrorCallback(glfw_error_callback);
    if (!glfwInit())
        return ;

    // 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
    window = glfwCreateWindow(width, height, title, nullptr, nullptr);
    if (window == nullptr)
        return ;
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1); // Enable vsync

    // Setup Dear ImGui context
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    io = ImGui::GetIO(); (void)io;
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
    //io.ConfigViewportsNoAutoMerge = true;
    //io.ConfigViewportsNoTaskBarIcon = true;

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

    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
    ImGuiStyle& style = ImGui::GetStyle();
    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
    {
        style.WindowRounding = 0.0f;
        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
    }

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

    // Our state
    bool show_demo_window = true;
    bool show_another_window = false;


}

AppWindow::~AppWindow()
{

#ifdef __EMSCRIPTEN__
    EMSCRIPTEN_MAINLOOP_END;
#endif

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

    glfwDestroyWindow(window);
    glfwTerminate();

    return;
}

void AppWindow::setUpdateFunction(void (*function)())
{
    updateFunction = function;
}

void AppWindow::update()
{
    if (updateFunction != nullptr)
        updateFunction();
}

void AppWindow::run()
{
#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();

        update();

        // Rendering
        ImGui::Render();
        int display_w, display_h;
        glfwGetFramebufferSize(window, &display_w, &display_h);
        glViewport(0, 0, 1280, 720);
        glClearColor(0.5f, 0.5f, 0.5f, 0.5f);
        glClear(GL_COLOR_BUFFER_BIT);
        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

        // Update and Render additional Platform Windows
        // (Platform functions may change the current OpenGL context, so we save/restore it to make it easier to paste this code elsewhere.
        //  For this specific demo app we could also call glfwMakeContextCurrent(window) directly)
        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
        {
            GLFWwindow* backup_current_context = glfwGetCurrentContext();
            ImGui::UpdatePlatformWindows();
            ImGui::RenderPlatformWindowsDefault();
            glfwMakeContextCurrent(backup_current_context);
        }

        glfwSwapBuffers(window);
    }


}

void AppWindow::addMouseCallBack(GLFWmousebuttonfun action)
{
    glfwSetMouseButtonCallback(window, action);
}

void AppWindow::addKeyCallBack(GLFWkeyfun action)
{
    glfwSetKeyCallback(window, action);
}

我的主方法：

int main(int ,  char**) {
    AppWindow window("My app", 1280, 720);

    window.run();

    return 0;
}

AppWindow.h：

#pragma once
#include <glad/glad.h>
#include <

<details>
<summary>英文:</summary>

I am trying to build an application in C++ with ImGUI, OpenGL and GLFW.

However, when i try to run my program, i get a white screen that then crashes and gives me an error code of -1073741819.

Here is my Class for creating a window, alot of the stuff i copied from the ImGUI opengl3 example:

#include <imgui_impl_glfw.h>
#include <imgui_impl_opengl3.h>
#include <imgui_internal.h>
#include "imgui.h"
#include "AppWindow.h"

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

AppWindow::AppWindow(const char* title, int width, int height)
{
glfwSetErrorCallback(glfw_error_callback);
if (!glfwInit())
return ;

// 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
window = glfwCreateWindow(width, height, title, nullptr, nullptr);
if (window == nullptr)
return ;
glfwMakeContextCurrent(window);
glfwSwapInterval(1); // Enable vsync
// Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
io = ImGui::GetIO(); (void)io;
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
//io.ConfigViewportsNoAutoMerge = true;
//io.ConfigViewportsNoTaskBarIcon = true;
// Setup Dear ImGui style
ImGui::StyleColorsDark();
//ImGui::StyleColorsLight();
// When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
ImGuiStyle& style = ImGui::GetStyle();
if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
{
style.WindowRounding = 0.0f;
style.Colors[ImGuiCol_WindowBg].w = 1.0f;
}
// Setup Platform/Renderer backends
ImGui_ImplGlfw_InitForOpenGL(window, true);
ImGui_ImplOpenGL3_Init(glsl_version);
// Our state
bool show_demo_window = true;
bool show_another_window = false;

}

AppWindow::~AppWindow()
{

#ifdef EMSCRIPTEN
EMSCRIPTEN_MAINLOOP_END;
#endif

// Cleanup
ImGui_ImplOpenGL3_Shutdown();
ImGui_ImplGlfw_Shutdown();
ImGui::DestroyContext();
glfwDestroyWindow(window);
glfwTerminate();
return;

}

void AppWindow::setUpdateFunction(void (*function)())
{
updateFunction = function;
}

void AppWindow::update()
{
if (updateFunction != nullptr)
updateFunction();
}

void AppWindow::run()
{
#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();
update();
// Rendering
ImGui::Render();
int display_w, display_h;
glfwGetFramebufferSize(window, &display_w, &display_h);
glViewport(0, 0, 1280, 720);
glClearColor(0.5f,0.5f, 0.5f, 0.5f);
glClear(GL_COLOR_BUFFER_BIT);
ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
// Update and Render additional Platform Windows
// (Platform functions may change the current OpenGL context, so we save/restore it to make it easier to paste this code elsewhere.
//  For this specific demo app we could also call glfwMakeContextCurrent(window) directly)
if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
{
GLFWwindow* backup_current_context = glfwGetCurrentContext();
ImGui::UpdatePlatformWindows();
ImGui::RenderPlatformWindowsDefault();
glfwMakeContextCurrent(backup_current_context);
}
glfwSwapBuffers(window);
}

}

void AppWindow::addMouseCallBack(GLFWmousebuttonfun action)
{
glfwSetMouseButtonCallback(window, action);
}

void AppWindow::addKeyCallBack(GLFWkeyfun action)
{
glfwSetKeyCallback(window, action);
}

my main method:
int main(int ,  char**) {
AppWindow window("My app", 1280, 720);
window.run();
return 0;
}
AppWindow.h:

#pragma once
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include "imgui.h"

class AppWindow
{
public:
ImVec4 BgColour = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
ImGuiIO io;
GLFWwindow* window;
void (*updateFunction)() = nullptr;

AppWindow(const char* title, int width, int height);
~AppWindow();
void setUpdateFunction(void (*updateFunction)());
void update();
void run();
void addMouseCallBack(GLFWmousebuttonfun action);
void addKeyCallBack(GLFWkeyfun action);

here is an image of my folder structure:
[my folder structure](https://i.stack.imgur.com/zonFu.png)
here is the imgui files I copied over:
[imgui files](https://i.stack.imgur.com/X6n5s.png)
my include directory contains:
Desktop\\ImgGUIApps\\LearningImGUI\\ImGUIwithOpenGL\\imguiDependencies
Desktop\\ImgGUIApps\\LearningImGUI\\ImGUIwithOpenGL\\Libraries\\include
my library directory:
Desktop\\ImgGUIApps\\LearningImGUI\\ImGUIwithOpenGL\\Libraries\\lib
additonal dependencies:
glfw3.lib
I figured out that this occurs due to a memory access violation in this portion of code as it runs:

glViewport(0, 0, 1280, 720);
glClearColor(0.5f,0.5f, 0.5f, 0.5f);
glClear(GL_COLOR_BUFFER_BIT);

commenting that out just gives me a non-crashing black screen.
I suspect that this may be due to me installing opengl and glfw and imgui incorrectly.
I also don't think that it is because my window variable is being freed, as i declared it in the class declaration.
</details>
# 答案1
**得分**: 0
在以下代码之后，只需简单地写入：
gladLoadGL();
在
glfwMakeContextCurrent(window);
之后。我不记得在教程中看到过这一点，或者可能是我没有注意到。不管怎样，感谢 @G.M. 将解决方案解释得很清楚。
<details>
<summary>英文:</summary>
Okay, so i had to simply write:
gladLoadGL();
after
glfwMakeContextCurrent(window);
I don&#39;t remember seeing it in tutorials, or maybe I wasn&#39;t paying attention. Anyhow, thanks to @G.M. for making the solution clear to me.
</details>