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Kotorez

SDL Keyboard input

7 posts in this topic

Basically the problem in my program is when I move my character for example North/East and I hold W and D at the same time my character goes it a correct direction but when I let go W and continue holding D my character moves in D direction but it only plays the first frame of W animation for 1-2 seconds before switching to the W animation. Also when I was trying to "debug" the program I wrote some couts for which animation gets called (ACTIVE/IDLE) and I noticed that when I press move my active animation sometimes gets called 5 times but when ever I release the button the Idle animation gets called about 20-30 times. Can somebody please explain to me this behavior and also is there "industry standard" on setting up keyboard input? I was following lazyfoo's tutorials but those dont explain much in details.

[source]
void Game::GameLoop()
{

while (!quit && sdl_setup->GetMainEvent()->type != SDL_QUIT)
{
sdl_setup->Begin();
walkingGround->Draw();

player->Draw();

//float angle = atan2(Follow_Point_Y - player->GetY(), Follow_PointX - player->GetX());
//angle = angle * (180/3.14);

if(sdl_setup->GetMainEvent()->type == SDL_KEYDOWN)
{
switch(sdl_setup->GetMainEvent()->key.keysym.sym)
{
case SDLK_w:
moveUp = true;
break;
case SDLK_s:
moveDown = true;
break;
case SDLK_a:
moveLeft = true;
break;
case SDLK_d:
moveRight = true;
break;
default:
break;
}
}
if(sdl_setup->GetMainEvent()->type == SDL_KEYUP)
{
switch(sdl_setup->GetMainEvent()->key.keysym.sym )
{
case SDLK_w:
std::cout GetX() + 1);
// moveRight = false;
}
}
sdl_setup->End();
}
}
[/source]
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The site crops my source code for some reason. Here is full source code pastebin.com/NHCNTsG4
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You're only handling one event per frame. There can be anywhere from 0 to a few hundred of events per frame. If you only process one event per frame, then a keyboard or mouse event could take up to several seconds before it is processed.

A typical game loop looks something like this:
while running:
  event e
  while nextEvent(&e):
    processEvent(e)

  update()
  render()
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Also, it does not appear your Play_annimatedSprite routine doesn't have the ability to be interrupted. If Play_animatedSprite were called for an animation such as (1 3 1 125), then (1 3 2 125) cannot be used until "animationDelay + speed < SDL_GetTicks()" is true
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Thanks for response! Your suggestion did fix my problem however now I am getting a weird bug when if I just simply move character it works fine and then suddenly it just keeps going into random direction as if SDL did not notice that I release the button (SDL_KEYUP). In order to interrupt my character from moving uncontrollably I have to tap the button twice for sdl to register the SDL_KEYUP. At first I thought my keyboard was glitched so I rebind-ed the buttons. Same thing. I checked everywhere but I think I am doing something totally wrong with event handling. Any suggestions? pastebin.com/mGv4ZLmJ (updated)
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Thanks for response! Your suggestion did fix my problem however now I am getting a weird bug when if I just simply move character it works fine and then suddenly it just keeps going into random direction as if SDL did not notice that I release the button (SDL_KEYUP). In order to interrupt my character from moving uncontrollably I have to tap the button twice for sdl to register the SDL_KEYUP. At first I thought my keyboard was glitched so I rebind-ed the buttons. Same thing. I checked everywhere but I think I am doing something totally wrong with event handling. Any suggestions? pastebin.com/mGv4ZLmJ (updated)

 

If you are using this code: https://github.com/gratholio/sdlscroller as your base: please don't. it is making a huge mess of things.

the sdl_setup::begin method gets a single event from the queue and stores it as mainevent (which is then returned by all calls to GetMainEvent) and clears the renderer(big wtf), it also discards the return value from SDL_PollEvent, there is no way to use that wrapper correctly since the wrapper itself is completely broken.

 

Just use standard SDL instead.

 

[source]

 

while(!quit) {

    SDL_Event event;

    while(SDL_PollEvent(&event) != 0) {

        quit = event.type == SDL_QUIT;

        //handle the rest of the events here       

    }

    update();

    render();

}

 

Thanks a lot! Now it works perfect. I was actually following "Lets Make an RPG C++/SDL" tutorials on youtube but it appears that the code is exactly the same as the link you provided. Can you suggest a good resource to learn from or I should just stick to lazyfoo?

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Thanks for response! Your suggestion did fix my problem however now I am getting a weird bug when if I just simply move character it works fine and then suddenly it just keeps going into random direction as if SDL did not notice that I release the button (SDL_KEYUP). In order to interrupt my character from moving uncontrollably I have to tap the button twice for sdl to register the SDL_KEYUP. At first I thought my keyboard was glitched so I rebind-ed the buttons. Same thing. I checked everywhere but I think I am doing something totally wrong with event handling. Any suggestions? pastebin.com/mGv4ZLmJ (updated)

 

If you are using this code: https://github.com/gratholio/sdlscroller as your base: please don't. it is making a huge mess of things.

the sdl_setup::begin method gets a single event from the queue and stores it as mainevent (which is then returned by all calls to GetMainEvent) and clears the renderer(big wtf), it also discards the return value from SDL_PollEvent, there is no way to use that wrapper correctly since the wrapper itself is completely broken.

 

Just use standard SDL instead.

 

[source]

 

while(!quit) {

    SDL_Event event;

    while(SDL_PollEvent(&event) != 0) {

        quit = event.type == SDL_QUIT;

        //handle the rest of the events here       

    }

    update();

    render();

}

 

Thanks a lot! Now it works perfect. I was actually following "Lets Make an RPG C++/SDL" tutorials on youtube but it appears that the code is exactly the same as the link you provided. Can you suggest a good resource to learn from or I should just stick to lazyfoo?

 

 

The Lazyfoo tutorials are fairly high quality so they would be a good choice, i would recommend avoiding video tutorials (videos are a bad format for tutorials).

 

Video lectures however work great, these are worth watching(Not game specific):

http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-00-introduction-to-computer-science-and-programming-fall-2008/video-lectures/

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