Why does glfwGetMouseButton() miss button presses

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1

I poll events with GLFW 60 times per second. Which as I understand means that glfwGetMouseButton() should detect any mouse button press with the duration over ca 0.016 seconds. If I press and release a button quicker than that it will get the GLFW_RELEASE state. I don’t think it is physically possible to press and release a mouse button quicker than that. So how come most of my mouse clicks are missed when I use this function?

Of course using callback for this purpose works. But could someone explain to me why it works if I do this:

bool clickedLeft, clickedRight;
void MyClickCallback(GLFWwindow* window, int button, int action, int mods) {
    if (button == GLFW_MOUSE_BUTTON_LEFT && action == 1) {
        clickedLeft = (clickedLeft) ? false : true;
    }

    else if (button == GLFW_MOUSE_BUTTON_RIGHT && action == 1) {
        clickedRight = (clickedRight) ? false : true;
    }
}

void UpdateFrame() {
    if (clickedLeft)
        cout << "Clicked Left" << endl;
    if (clickedRight)
        cout << "Clicked Right" << endl;
}

In this example the boolean clickedLeft may be updated multiple times per frame if I click and release a button faster than the duration of a frame. But on frame update we get the final state of the clickedLeft. So how come glfw detects the button press correctly with this approach when it does not with glfwGetMouseButton()?

2

As you note glfwGetMouseButton() can miss events whereas a callback won’t.

Your code looks like it will toggle the state of your bool variables every time a button is pressed. I would instead use something like:

bool clickedLeft = false;
bool clickedRight = false;
void MyClickCallback(GLFWwindow* window, int button, int action, int mods) {
    if (button == GLFW_MOUSE_BUTTON_LEFT && action == 1) {
        clickedLeft = true;
    }

    else if (button == GLFW_MOUSE_BUTTON_RIGHT && action == 1) {
        clickedRight = true;
    }
}

void UpdateFrame() {
    if (clickedLeft)
        cout << "Clicked Left" << endl;
    if (clickedRight)
        cout << "Clicked Right" << endl;

    // reset every frame
    clickedLeft  = false;
    clickedRight = false;
}
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