Resolving inconsistent SDL2 key press detection? - c++

Question

I am trying to detect when a key is pressed down using the SDL_Event system.
I am using this code to detect the key presses:
void GameLoop::update(SDL_Event eventHandler, Camera &camera){
Vector2 move = Vector2();
if (eventHandler.type == SDL_KEYDOWN){
switch (eventHandler.key.keysym.sym){
case SDLK_w:
move = Vector2(0, -1);
break;
case SDLK_s:
move = Vector2(0, 1);
break;
case SDLK_a:
move = Vector2(-1, 0);
break;
case SDLK_d:
move = Vector2(1, 0);
break;
}
}
camera.translateCamera(move);
}
If I switch out 'WASD' inputs to 'UP DOWN LEFT RIGHT' The system works and if I remove the line:
if (eventHandler.type == SDL_KEYDOWN){
It works due to the SDL_KEYUP type, using 'WASD' or 'UP DOWN LEFT RIGHT'
What is causing this behaviour and how to fix it?

Answer 1

SDL literally checks IF the keyboard is pressed, it just so happens that the program reads faster than the actual press which will result in numerous presses, I'm not sure about your up, down, left, right buttons, maybe they are meant to be read by SDL but their physical connection might not be the same with the letters in the keyboard.
Now if you change KEYDOWN to KEYUP, all it would read is IF it is up, this isn't really good.
What you would want to do is use booleans and ticks
if (eventHandler.type == SDL_KEYDOWN && !clicked){
ticking2 = SDL_GetTicks();
switch (eventHandler.key.keysym.sym){
case SDLK_w:
clicked = true;
break;
case SDLK_s:
clicked = true;
break;
}
}
if (eventHandler.type == SDL_KEYUP && clicked){
ticking = SDL_GetTicks();
switch (eventHandler.key.keysym.sym){
case SDLK_w:
if(ticking-ticking2 >= 3000)
{
move = Vector2(0, -1);
clicked = false;
}
break;
case SDLK_s:
if(ticking-ticking2 >= 3000)
{
move = Vector2(0, 1);
clicked = false;
}
break;
}
}
Upon pressing a button, it gets the time and pushes it into ticking2 but then after upon a click, it turns the bool clicked into true which then makes it stop reading the loop, thus, freezing the value of ticking 2.
Upon releasing a button, it checks if clicked is true so that the actions will only be made IF the button was actually pressed.
It gets the time and pushes it into ticking, ticking-ticking2 should equal to something around 0, I made those to ensure that effects won't be instant since it might cause some glitches.