调整GLFW窗口大小时如何绘制？

Question

每当我调整GLFW窗口大小时，在调整窗口大小时都不会绘制。我调整窗口大小后，才可以绘制窗口新暴露的部分。您可以在下面的图片中自己看到它：

这是我的应用程序的代码。我在Visual Studio 2015上运行Windows 10

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);
void get_resolution(int* window_width, int* window_height);
void initGlfwSettings();
GLFWwindow* initGlfwWindow();
void initGlad();

// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

int main()
{
    initGlfwSettings();

    GLFWwindow* window = initGlfwWindow();

    initGlad();

    // glad: load all OpenGL function pointers
    // ---------------------------------------


    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        int width, height;
        glfwGetWindowSize(window, &width, &height);


        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
        // input
        // -----
        processInput(window);

        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
    glfwTerminate();
    return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    // make sure the viewport matches the new window dimensions; note that width and 
    // height will be significantly larger than specified on retina displays.
    glViewport(0, 0, width, height);
}

void get_resolution(int* window_width, int* window_height) {
    const GLFWvidmode * mode = glfwGetVideoMode(glfwGetPrimaryMonitor());

    *window_width = mode->width;
    *window_height = mode->height;
}

void initGlfwSettings()
{
    // glfw: initialize and configure
    // ------------------------------
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);


    #ifdef __APPLE__
        glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
    #endif
}

GLFWwindow* initGlfwWindow()
{
    /*GLFWmonitor* monitor = glfwGetPrimaryMonitor();
    int width;
    int height;

    get_resolution(&width, &height);*/



    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "learning opengl", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        exit(1);
    }

    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
    glfwSwapInterval(1);

    return window;
}

void initGlad()
{
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        exit(1);
    }
}

解释此问题的所有解决方案。

Answer 1

glfwPollEvents每当调整窗口大小时，事件处理 ( ) 就会停止，但在这样做时，它会不断发出调整大小事件，这些事件由您已经使用的调整大小回调即时处理。您可以从那里重绘场景并调用glfwSwapBuffers渲染，即使在glfwPollEvents. 实际上，这可以通过以下代码实现：

void draw()
{
    // Rendering code goes here
    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    glfwSwapBuffers(window);
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    // make sure the viewport matches the new window dimensions; note that width and 
    // height will be significantly larger than specified on retina displays.
    glViewport(0, 0, width, height);
    // Re-render the scene because the current frame was drawn for the old resolution
    draw();
}

并将渲染（glClearColor,glClear和glfwSwapBuffers）从主循环移动到draw. draw在主循环中调用并创建window一个全局变量或draw在调用它时将其传递给，否则它将超出 in 的范围draw，而glfwSwapBuffers.

这仅在用户按住鼠标移动鼠标时才有效- 只需按住左键单击调整大小窗口部分仍然会停止。要解决这个问题，除此之外，您还需要在单独的线程中进行渲染。（不，没有线程你不能这样做。对不起，这就是 GLFW 的工作方式，除了他们没有人可以改变它。）

Answer 2

这是 Windows 事件处理程序未将控制权返回给主线程。Windows 就是这样工作的，你无法改变它。

但是，您可以将所有渲染和 glfw 命令移动到不同的线程，该线程不会被窗口停止。