Handling Specific Key Presses like Escape in SDL2
How do I handle specific key presses, like the Escape key, to quit?
To handle specific key presses, like using the Escape key to quit the application, you need to expand your event handling logic to check for keyboard events and then identify which specific key was pressed.
Checking for Keyboard Events
First, within your event loop (while(SDL_PollEvent(...))
), you need to check if the type
of the event is SDL_KEYDOWN
. This event is generated when a key is initially pressed down. (There's also SDL_KEYUP
for when it's released).
Identifying the Specific Key
If the event type is SDL_KEYDOWN
, the SDL_Event
structure contains information about the key press within its key
member. Specifically, Event.key.keysym.sym
holds a value representing the specific key that was pressed.
SDL provides predefined constants for these keys, such as SDLK_ESCAPE
for the Escape key, SDLK_SPACE
for the spacebar, SDLK_a
for the 'A' key, and so on.
Example Implementation
Here's how you can modify the event loop to quit when the Escape key is pressed:
#include <SDL.h>
#include "Window.h" // Assume this includes our Window class
int main(int argc, char** argv) {
SDL_Init(SDL_INIT_VIDEO);
Window GameWindow;
bool shouldContinue{true};
SDL_Event Event;
while (shouldContinue) {
while (SDL_PollEvent(&Event)) {
// Check for the standard quit event (closing the window)
if (Event.type == SDL_QUIT) {
shouldContinue = false;
}
// Check for key presses
else if (Event.type == SDL_KEYDOWN) {
// Check if the key pressed was Escape
if (Event.key.keysym.sym == SDLK_ESCAPE) {
std::cout << "Escape key pressed - Quitting.\\n";
shouldContinue = false; // Set flag to end the loop
}
// You could add checks for other keys here
// else if (Event.key.keysym.sym == SDLK_SPACE) {
// std::cout << "Space bar pressed!\\n";
// }
}
// ... handle other event types if needed ...
}
// ... Update logic ...
// ... Render logic ...
SDL_Delay(16); // Example delay
}
SDL_Quit();
return 0;
}
Now, when you run this application, pressing the Escape key will print a message to the console and cause the shouldContinue
flag to become false
, gracefully ending the application loop, just like clicking the window's close button.
Implementing an Application Loop
Step-by-step guide on creating the SDL2 application and event loops for interactive games