How to use GLFW callbacks.mp4

 

GLFW (Graphics Library Framework) provides a set of callback functions to handle various events in a windowing application. Here's a step-by-step guide on how to use GLFW callbacks:

1. Initialize GLFW

Before setting up callbacks, initialize GLFW and create a window:

cpp
#include <GLFW/glfw3.h>

int main() {
    if (!glfwInit()) {
        return -1;
    }

    GLFWwindow* window = glfwCreateWindow(640, 480, "GLFW Callbacks", NULL, NULL);
    if (!window) {
        glfwTerminate();
        return -1;
    }

    glfwMakeContextCurrent(window);
    
    // Set up callbacks here...

    while (!glfwWindowShouldClose(window)) {
        // Rendering code...

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glfwDestroyWindow(window);
    glfwTerminate();
    return 0;
}

2. Define Callback Functions

Define the callback functions you want to use. GLFW provides callbacks for events like keyboard input, mouse movement, window resizing, etc.

Example of a keyboard callback function:

cpp
void keyCallback(GLFWwindow* window, int key, int scancode, int action, int mods) {
    if (action == GLFW_PRESS) {
        if (key == GLFW_KEY_ESCAPE) {
            glfwSetWindowShouldClose(window, GLFW_TRUE);
        }
    }
}

3. Set Callbacks

Use glfwSetKeyCallback, glfwSetMouseButtonCallback, glfwSetCursorPosCallback, and other relevant functions to register your callbacks.

cpp
int main() {
    if (!glfwInit()) {
        return -1;
    }

    GLFWwindow* window = glfwCreateWindow(640, 480, "GLFW Callbacks", NULL, NULL);
    if (!window) {
        glfwTerminate();
        return -1;
    }

    glfwMakeContextCurrent(window);

    // Set the key callback function
    glfwSetKeyCallback(window, keyCallback);

    // Set other callbacks as needed
    // glfwSetMouseButtonCallback(window, mouseButtonCallback);
    // glfwSetCursorPosCallback(window, cursorPosCallback);

    while (!glfwWindowShouldClose(window)) {
        // Rendering code...

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glfwDestroyWindow(window);
    glfwTerminate();
    return 0;
}

4. Implement Additional Callbacks

Other common callbacks you might want to implement include:

• Mouse Button Callback:

  cpp
  void mouseButtonCallback(GLFWwindow* window, int button, int action, int mods) {
      if (button == GLFW_MOUSE_BUTTON_LEFT && action == GLFW_PRESS) {
          // Handle left mouse button press
      }
  }
  

• Cursor Position Callback:

  cpp
  void cursorPosCallback(GLFWwindow* window, double xpos, double ypos) {
      // Handle cursor movement
  }
  

• Window Resize Callback:

  cpp
  void framebufferSizeCallback(GLFWwindow* window, int width, int height) {
      glViewport(0, 0, width, height);
  }
  

Make sure to call glfwSetFramebufferSizeCallback(window, framebufferSizeCallback); to register the window resize callback.

5. Handle Events in the Main Loop

Call glfwPollEvents() in your main loop to ensure that callbacks are processed.

By following these steps, you can handle various user interactions and system events in your GLFW-based application.

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