GLFW switching boolean toggle - c++

Question

I am using GLFW for keyboard input but the processing happens too quick thus my boolean switch on a single press gets changed like 10 times, as input is processed every frame. All I need that for a single press of space bar it would switch the state. My current code is below:
if (glfwGetKey(window, GLFW_KEY_SPACE) == GLFW_PRESS)
{
show = !show;
}
Is there a better way of doing this?

Answer 1

Yes. glfwGetKey is meant to be used for continuous key input. GLFW manual lists glfwSetKeyCallback as a better alternative if you want one-time notification about key press.
Thus, for your case it'd be something like this:
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if (key == GLFW_KEY_SPACE && action == GLFW_PRESS)
show = !show;
}
If you don't want to use this method for whatever reason, you can always implement a similar thing yourself. You'll need a boolean value (or array of values) representing the key state. Then, in your input handling, you must only react on the change of the button state, like so:
bool spacePressed;
// in handling
bool spaceCurrentlyPressed = glfwGetKey(window, GLFW_KEY_SPACE) == GLFW_PRESS;
if (!spacePressed && spaceCurrentlyPressed) { // wasn't before, is now
show = !show;
}
spacePressed = spaceCurrentlyPressed;

Answer 2

I reccommend using GLFWs key callbacks instead of getting the key state yourself every frame. This way you will only receive one keypress and one keyrelease event per key.
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if(action == GLFW_RELEASE) return; //only handle press events
if(key == GLFW_KEY_SPACE) show = !show;
}
//in main or init
glfwSetKeyCallback(window, key_callback);