Hi all !
I'm writing a simple 2d game using SDL. I would like my game has got a changeable input from user. For the example: left arrow on the keyboard moves sth to the left. User change it, now Joystick axis motion moves sth to the left. I have no idea how do that. Can anybody help me ?
Changeable Input
Exact details depend on what programming language you are using, but there are a number of ways to do this. One way is to create a map or associative array of event objects to function pointers or function objects. Then in each event handling block invoke the functor for the received events. Alternately you can use a map of events to tokens and then have your input handling functionality dispatch tokens to game state objects.
I'm using C++, could you explain it a little more with short code example ?
typdef void (*action)(Player&);
void Action1(Player &p) {
code
}
void Action2(Player &p) {
code
}
...
...
...
...
std::map<int,action> actions = new std::map<int,action>();
actions[SDLK_SPACE] = Action1;
actions[SDLK_LEFT] = Action2;
(Assigning and reassigning can be done however you want)
....
then you just read input and call:
actions[keyThatWasPressed](playerobject);
i might have messed up the function pointer syntax somewhere but you should get the general idea.
Author
Thanks, but how can I do it for SDL_Event structure ?
I'd like to use joystick too, it seems that is for keyboard only.
Could you write how to use a map of events ? I tried it myself but it doesn't work.
I'd like to use joystick too, it seems that is for keyboard only.
Exact details depend on what programming language you are using, but there are a number of ways to do this. One way is to create a map or associative array of event objects to function pointers or function objects. Then in each event handling block invoke the functor for the received events. Alternately you can use a map of events to tokens and then have your input handling functionality dispatch tokens to game state objects.
Could you write how to use a map of events ? I tried it myself but it doesn't work.
Thanks, but how can I do it for SDL_Event structure ?
I'd like to use joystick too, it seems that is for keyboard only.
[quote name='SiCrane' timestamp='1326554293' post='4902658']
Exact details depend on what programming language you are using, but there are a number of ways to do this. One way is to create a map or associative array of event objects to function pointers or function objects. Then in each event handling block invoke the functor for the received events. Alternately you can use a map of events to tokens and then have your input handling functionality dispatch tokens to game state objects.
Could you write how to use a map of events ? I tried it myself but it doesn't work.
[/quote]
The key part of the map has to have a comparison operator defined (the < operator in this case) which SDL_Event doesn't have, You could write your own EventKey(ok, maybe not the best name) class that stores the necessary information and which overloads the < operator or you can pass a comparison function to the map.
You can use event.key.keysym.sym as the lookup key for key events:
Having a general event mapping system is a little more difficult. For most games, you might want to map key presses or releases, and mouse clicks. Mapping complicated, stateful actions like mouse dragging will take a bit more thought.
// Somewhere handy for inclusion
typedef void (*KeyFunction)(Player &player);
typedef void (*MouseFunction)(Player &player, int x, int y);
typedef std::map<SDL_KeySym, KeyFunction> KeyMap;
typedef std::map<Uint8, MouseFunction> MouseMap;
// Later, during setup in main().
KeyMap keyMap;
keyMap[SDLK_UP] = &playerForward;
keyMap[SDLK_DOWN] = &playerBackward;
keyMap[SDLK_LEFT] = &playerLeft;
keyMap[SDLK_RIGHT] = &playerRight;
MouseMap mouseMap;
mouseMap[SDL_BUTTON(1)] = &playerShoot;
// Later again, during game loop...
bool running = true;
while(running)
{
SDL_Event event;
while(SDL_PollEvent(&event))
{
if(event.type == SDL_QUIT)
{
running = false;
}
else if(event.type == SDL_KEYDOWN)
{
KeyMap::iterator i = keyMap.find(event.key.keysym.sym);
if(i != keyMap.end())
{
KeyFunction action = i->second;
action(player);
}
}
else if(event.type == SDL_MOUSEBUTTONDOWN)
{
MouseMap::iterator i = mouseMap.find(event.button.button);
if(i != mouseMap.end())
{
MouseFunction action = i->second;
action(player, event.button.x, event.button.y);
}
}
}
// ...
}
Having a general event mapping system is a little more difficult. For most games, you might want to map key presses or releases, and mouse clicks. Mapping complicated, stateful actions like mouse dragging will take a bit more thought.
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