Handling Specific Key Presses like Escape in SDL2

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:

1#include <SDL.h>
2#include "Window.h" // Assume this includes our Window class
3
4int main(int argc, char** argv) {
5  SDL_Init(SDL_INIT_VIDEO);
6  Window GameWindow;
7
8  bool shouldContinue{true};
9  SDL_Event Event;
10
11  while (shouldContinue) {
12    while (SDL_PollEvent(&Event)) {
13      // Check for the standard quit event (closing the window)
14      if (Event.type == SDL_QUIT) {
15        shouldContinue = false;
16      }
17      // Check for key presses
18      else if (Event.type == SDL_KEYDOWN) { 
19        // Check if the key pressed was Escape
20        if (Event.key.keysym.sym == SDLK_ESCAPE) { 
21          std::cout << "Escape key pressed - Quitting.\\n";
22          shouldContinue = false; // Set flag to end the loop
23        }
24        // You could add checks for other keys here
25        // else if (Event.key.keysym.sym == SDLK_SPACE) {
26        //   std::cout << "Space bar pressed!\\n";
27        // }
28      }
29      // ... handle other event types if needed ...
30    }
31
32    // ... Update logic ...
33    // ... Render logic ...
34
35    SDL_Delay(16); // Example delay
36  }
37
38  SDL_Quit();
39  return 0;
40}

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.