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7.6

SDL Keyboard Input Problems (Multiple Key Presses, Hardware).

Asked by maeve100 in Game Programming, Game Programming User Interface, C++ Programming Language

Tags: SDL Keyboard Key Presses Press Multiple Many Hardware

Hello,

I have been using SDL for the first time, attempting to write a simple game in C++ (MVC++ 2008). Everything has been going great except now I've run into a problem with my keyboard input.

At this point the goal of the program is to allow two balls to be moved around the screen independently and simultaneously, with a held key resulting in continued movement. There are plenty of examples online and fundamentally the code works. I can move both balls independently just fine. I can also move the both simultaneously left/right/up/down without trouble.

The Problem: Very specific key combinations result in one of the two balls not being able to move.

IE: Pressing the down arrow key and the right arrow key together (Moving ball #2 diagonally) makes it so ball #1 cannot be moved at all.

Other key combinations either work fine or generate their own non-functioning directions.

The combinations are not random and have stayed the same through out my troubleshooting.

What I've Tried: I've tried two different methods for reading the keyboard and storing the information (Both present in the code provided, with one commented out). Both seem to run exactly the same, with the same problems arising. I also tried switching from the arrow keys to jikl. This configuration has the same type of problems, however the problematic directional combinations have changed.

Speculation: I currently think that this is due to my keyboard's physical hardware. IE when I enter notepad and hold the down and right arrows, I am similarly unable to use asdw. I have read online that this can be a problem.

Question: If this is the problem, how do I get around it (in a keyboard independent manner)? How do commercial games deal with this issue? If this isn't the problem, did I miss something stupid? I am still a little shaky on sdl events.

Thank you.

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             SDL_Event keyevent;    //The SDL event that we will poll to get events.
 
//Variables for the first method I tried.
/*	
int running = 1;
int left = 0;
int right = 0;
int up = 0;
int down = 0;
int lefta = 0;
int rightd = 0;
int upw = 0;
int downs = 0;
*/
 
// Variables for the second method I tried.
int running = 1;
Uint8* keystates;
keystates = SDL_GetKeyState(0);  // or SDL_GetKeyState(NULL)
 
while (running)
{
	
        //Second Method
        while(SDL_PollEvent(&keyevent))
	{
	   if(keyevent.type == SDL_KEYDOWN)
	   {
			keystates[keyevent.key.keysym.sym] = true;
	   }
	   else if(keyevent.type == SDL_KEYUP)
	   {
	        keystates[keyevent.key.keysym.sym] = false;
	   }
	}
	
// ...
        //First method.
	/*
	while (SDL_PollEvent(&keyevent))   //Poll our SDL key event for any keystrokes.
	{
		if (keyevent.type == SDL_KEYDOWN)
		{
			switch(keyevent.key.keysym.sym)
			{
				case SDLK_LEFT:
					left = 1;
				  break;
				case SDLK_RIGHT:
					right = 1;
				  break;
				case SDLK_UP:
					up = 1;
				  break;
				case SDLK_DOWN:
					down = 1;
				  break;
				case SDLK_a:
					lefta = 1;
				  break;
				case SDLK_d:
					rightd = 1;
				  break;
				case SDLK_w:
					upw = 1;
				  break;
				case SDLK_s:
					downs = 1;
				  break;
				case SDLK_ESCAPE:
					running = 0;
				  break;
				default:
				  break;
			}
		}
		if (keyevent.type == SDL_KEYUP)
		{
			switch(keyevent.key.keysym.sym)
			{
				case SDLK_LEFT:
					left = 0;
				  break;
				case SDLK_RIGHT:
					right = 0;
				  break;
				case SDLK_UP:
					up = 0;
				  break;
				case SDLK_DOWN:
					down = 0;
				  break;
				 case SDLK_a:
					lefta = 0;
				  break;
				case SDLK_d:
					rightd = 0;
				  break;
				case SDLK_w:
					upw = 0;
				  break;
				case SDLK_s:
					downs = 0;
				  break;
				case SDLK_ESCAPE:
					running = 0;
				  break;
				default:
				  break;
			}
		}
	}*/
	
	if(keystates[SDLK_a] && (dest.x > 0)){dest.x = (dest.x - 1);}
	if(keystates[SDLK_d] && (dest.x < 780)){dest.x = (dest.x + 1);}
	if(keystates[SDLK_w] && (dest.y > 50)){dest.y = (dest.y - 1);}
	if(keystates[SDLK_s] && (dest.y < 530)){dest.y = (dest.y + 1);}
 
	if(keystates[SDLK_j] && (dest2.x > 0)){dest2.x = (dest2.x - 1);}
	if(keystates[SDLK_l] && (dest2.x < 780)){dest2.x = (dest2.x + 1);}
	if(keystates[SDLK_i] && (dest2.y > 50)){dest2.y = (dest2.y - 1);}
	if(keystates[SDLK_k] && (dest2.y < 530)){dest2.y = (dest2.y + 1);}
	
	if(keystates[SDLK_ESCAPE]) running = 0;
}

           
         

20091111-EE-VQP-89 - Hierarchy / EE_QW_3_20080625

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SDL Keyboard Input Problems (Multiple Key Presses, Hardware).

Asked by maeve100 in Game Programming, Game Programming User Interface, C++ Programming Language

Tags: SDL Keyboard Key Presses Press Multiple Many Hardware

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