Keyboard input question

Game Development
1

Hi every1.
Here’s my task:
I need to know exactly what key was pushed down/released up during the exact current frame. So that on the next frame keys that being held won’t generate duplicate events/messages.
Still, I want to get repeated key events.

My current solution is:

	const Uint8* curKeys = SDL_GetKeyboardState( 0 );
		const Uint8* newKeys = curKeys;
		Uint8 downKeys[ 512 ];
		Uint8 upKeys[ 512 ];
	// main loop start
	while( running ) {
		// ...
		// TODO: update input
			SDL_PumpEvents();
			newKeys = SDL_GetKeyboardState( 0 );
			for ( int i = 0; i < 512; i++ ) {
				downKeys[ i ] = 0;
				upKeys[ i ] = 0;
				if ( !curKeys[ i ] && newKeys[ i ] )
					downKeys[ i ] = 1;
				if ( curKeys[ i ] && !newKeys[ i ] )
					upKeys[ i ] = 1;
			}
			curKeys = newKeys;

			if ( curKeys [ SDL_SCANCODE_F ] )
				std::cerr << "'f' is pressed\n";
			if ( downKeys [ SDL_SCANCODE_F ] )
				std::cerr << "'f' is down\n";
			if ( upKeys [ SDL_SCANCODE_F ] )
				std::cerr << "'f' is up\n";
		//...
	}

The problem is that downKeys and upKeys are not functional - I’m getting response only from curKeys.
What am I doing wrong ? Somebody? :slight_smile:

2

So yeah…
The solution is pretty simple.
So there is how to implement basic SDL2 ‘buffered/unbuffered’ keyboard input class.

#define INPUT_NUM_SCANCODES 512

// -- basic input-handling class
class Input {
	public:
				Input		();
				~Input		();
		void 	Update		();
		bool	GetKey		( const int );
		bool	GetKeyDown	( const int );
		bool	GetKeyUp	( const int );
	public:
		bool 	textMode;

	private:

		bool 		currentKeys[ INPUT_NUM_SCANCODES ];
		bool 		downKeys[ INPUT_NUM_SCANCODES ];
		bool 		upKeys[ INPUT_NUM_SCANCODES ];
		SDL_Event 	event;
};

// -- implementation


Input::Input() {
	textMode = false;
}

Input::~Input() {
}

void Input::Update(){
	for ( int i = 0; i < INPUT_NUM_SCANCODES; i++ ) {
		downKeys[ i ] = false;
		upKeys[ i ] = false;
	}
	while( SDL_PollEvent( &event ) ) {
		if ( SDL_KEYDOWN == event.type ) {
			int value = event.key.keysym.scancode;
			if ( !currentKeys[ value ] && !textMode )
				downKeys[ value ] = true;
			else if ( textMode )
				downKeys[ value ] = true;
			currentKeys[ value ] = true;
		}
		if ( SDL_KEYUP == event.type ) {
			int value = event.key.keysym.scancode;
			upKeys[ value ] = true;
			currentKeys[ value ] = false;
		}
	}

}

bool Input::GetKey( const int key ) {
	return currentKeys[ key ];
}

bool Input::GetKeyDown( const int key ) {
	return downKeys[ key ];
}

bool Input::GetKeyUp( const int key ) {
	return upKeys[ key ];
}

Maybe it’s a bit of SDL internals reimplementation, but it’s a bit more intuitive, I think. And it works :slight_smile:

Thanks to everyone, again.