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Funky keys

Started by Yamian Nov 22, 2004 at 12:45 PM 12 replies 2.8k views

Original Post

Nov 22, 2004 at 12:45 PM

In the following program how come if you are pushing up and down at the same time and then just one immediately after, it won't move?


#include <stdlib.h>

#include <SDL\SDL.h>
#include <SDL\SDL_gfxPrimitives.h>


void Slock(SDL_Surface *screen)
{
    if ( SDL_MUSTLOCK(screen) )
    {
        if ( SDL_LockSurface(screen) < 0 )
        {
            return;
        }
    }
}

void Sulock(SDL_Surface *screen)
{
    if ( SDL_MUSTLOCK(screen) )
    {
        SDL_UnlockSurface(screen);
    }
}


int main(int argc, char *argv[])
{
    SDL_Init(SDL_INIT_VIDEO);
    SDL_Surface *screen = SDL_SetVideoMode(640,480,32,SDL_HWSURFACE|SDL_DOUBLEBUF);
    atexit(SDL_Quit);
    SDL_WM_SetCaption("Phlong",NULL);
    
    int y=0;
    
    bool done = false;
    while(done == false)
    {
        SDL_Event event;
        while ( SDL_PollEvent(&event) )
        {
            if ( event.type == SDL_QUIT )  {  done = true;  }
            if ( event.type == SDL_KEYDOWN )
            {
                if ( event.key.keysym.sym == SDLK_ESCAPE ) { done = 1; }
            }
        }
        SDL_FillRect(screen,NULL,SDL_MapRGB(screen->format,0,0,0));
        Slock(screen);
            
            if ( event.type == SDL_KEYDOWN )
            {
                if ( event.key.keysym.sym == SDLK_UP   ) y-=5 ;
                if ( event.key.keysym.sym == SDLK_DOWN ) y+=5 ;    
            }       
            
            boxRGBA(screen, 5, y, 25, y+80, 255,255,255,255);
        
        Sulock(screen);
        SDL_Flip(screen);
    }
}

P.S what are the code tabs again?

edited by evolutional: The code tabs are [ source ][ /source ] (without spaces). See the FAQ for more information [smile] [Edited by - evolutional on November 22, 2004 1:55:22 PM]

Feidias

Nov 24, 2004 at 12:24 PM

Checking SDL_KEYDOWN is not the fast way to read the keyboard and it doesn't even have keyrepeat enabled by default. Also, you don't need to check it twice.

Rob Loach

Nov 24, 2004 at 12:40 PM

Try using the following:

Uint8 *keys = SDL_GetKeyState(NULL);if(keys[SDLK_UP]){    // Up is being pushed} else if(keys[SDLK_DOWN]){    // Down is being pushed}

Yamian

Nov 25, 2004 at 10:38 AM

I still don't quite getr it but thank you very much.

Yamian

Nov 25, 2004 at 10:53 AM

Now I have another problem. How come two paddles don't show up in this program?

#include <stdlib.h>#include <SDL\SDL.h>#include <SDL\SDL_gfxPrimitives.h>void Slock(SDL_Surface *screen){    if ( SDL_MUSTLOCK(screen) )    {        if ( SDL_LockSurface(screen) < 0 )        {            return;        }    }}void Sulock(SDL_Surface *screen){    if ( SDL_MUSTLOCK(screen) )    {        SDL_UnlockSurface(screen);    }}int main(int argc, char *argv[]){    SDL_Init(SDL_INIT_VIDEO);    SDL_Surface *screen = SDL_SetVideoMode(640,480,32,SDL_HWSURFACE|SDL_DOUBLEBUF);    atexit(SDL_Quit);    SDL_WM_SetCaption("Phlong",NULL);        bool done = false;    while(done == false)    {        SDL_Event event;                while ( SDL_PollEvent(&event) )        {            if ( event.type == SDL_QUIT )  {  done = true;  }            if ( event.type == SDL_KEYDOWN )            {                if ( event.key.keysym.sym == SDLK_ESCAPE ) { done = 1; }            }        }        SDL_FillRect(screen,NULL,SDL_MapRGB(screen->format,0,0,0));        Slock(screen);        Uint8 *keys = SDL_GetKeyState(NULL);            int ly;            if     (keys[SDLK_LSHIFT])ly-=3;            else if(keys[SDLK_LCTRL] )ly+=3;                        int ry;            if     (keys[SDLK_UP]  )ry-=3;            else if(keys[SDLK_DOWN])ry+=3;                        boxRGBA(screen,     5, ly,     25, ly+80, 255,255,255,255);            boxRGBA(screen, 640-5, ry, 640-25, ry+80, 255,255,255,255);                Sulock(screen);        SDL_Flip(screen);    }}

Squirm

Nov 26, 2004 at 4:57 AM

because your screen is 640x480 and you draw the second paddle at 640x640

Yamian

Nov 26, 2004 at 9:33 AM

No that's not it. The 640-25 is the second x coordinate. I actually replaced ry with ly in the actual drawing stage and the one affected by shift and ctrl shows on the right.

Yamian

Nov 26, 2004 at 9:53 AM

bizaare. If you switch around the order and make the right paddle checked on the top then only the right one shows up

Yamian

Nov 26, 2004 at 3:40 PM

I also switch around the variables int h drawing. Maybe theer is something bad about calling the keys array multiple time or something.

Nairb

Nov 26, 2004 at 4:14 PM

It doesn't look like you're initializing ly and ry, which means you don't know what they're going to be.

I would advise moving int ly and int ry out of your main loop and initializing them both to zero.

Cheers,
--Brian

Yamian

Nov 26, 2004 at 5:00 PM

Okay that worked, but why does the first one I initialized work but not the second?

coderx04

Nov 28, 2004 at 9:30 AM

How to check if there is any key being pressed??

Rob Loach

Nov 28, 2004 at 11:46 AM

Quote:
Original post by coderx04
How to check if there is any key being pressed??

SDL_Event event;while ( SDL_PollEvent(&event) ){	if ( event.type == SDL_QUIT )  {  done = true;  }	if ( event.type == SDL_KEYDOWN ){		// User is pressing the "Any" key :-P	}}

coderx04

Nov 28, 2004 at 4:52 PM

ooww thank you, Im giving funny question yeah? :P..
Thankss..

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