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[SDL] Strange Key blocking


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#1 XeraNox   Members   -  Reputation: 105

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Posted 09 September 2012 - 05:27 AM

Hello Forum Posted Image
I started working on programming a small 2D platformer with the SDL and had a strange bug in a specific method.

What this method does is first checking for the arrow keys wether they are pressed or not, then for the WASD keys.

Three states are currently used:
The Left/Right keys move the Player two the specified direction.

The combination of the Up-key and the S-key let the Player Jump.

The problem I have now is that the player can't jump and move left at the same time, but he can actually move to the right while jumping.
I've done some testing and found that my program doesn't register the left key while the Up-Key and the S-key are pressed.

The relevant code:

void CPlayer::ProcessMovement ()
{
if (g_pFramework->KeyDown(SDLK_UP))
{
  if (g_pFramework->KeyDown(SDLK_w))
  {
   cout << "Direction: 1, Action: 1" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_d))
  {
   cout << "Direction: 1, Action: 2" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_s)) //The section for triggering the jump method
  {
   cout << "Direction: 1, Action: 3" << endl;
   if (m_bJumpAllow == 1)
   {
    cout << "Jump" << endl;
    Jump ();
   }
   m_bKeyPressed = true;
  }
  if (g_pFramework->KeyDown(SDLK_a))
  {
   cout << "Direction: 1, Action: 4" << endl;
  }
}
if (g_pFramework->KeyDown(SDLK_LEFT))
{
  if (g_pFramework->KeyDown(SDLK_w))
  {
  
  }
  if (g_pFramework->KeyDown(SDLK_d))
  {
   cout << "Direction: 4, Action: 2" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_s))
  {
   cout << "Direction: 4, Action: 3" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_a))
  {
   cout << "Direction: 4, Action: 4" << endl;
  }
}
if (g_pFramework->KeyDown(SDLK_RIGHT))
{
  if (g_pFramework->KeyDown(SDLK_w))
  {
   cout << "Direction: 2, Action: 1" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_d))
  {
   cout << "Direction: 2, Action: 2" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_s))
  {
   cout << "Direction: 2, Action: 3" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_a))
  {
   cout << "Direction: 2, Action: 4" << endl;
  }
}
if (g_pFramework->KeyDown(SDLK_LEFT)) //Checking for movement to the left
  Run (0);
if (g_pFramework->KeyDown(SDLK_RIGHT)) //Same as above for the right
  Run (1);
if (!(g_pFramework->KeyDown(SDLK_LEFT)) && !(g_pFramework->KeyDown(SDLK_RIGHT)))
  CancelRun (); //This method Stops all horizontal movement if neither left or right is pressed
if (g_pFramework->KeyDown(SDLK_DOWN))
{
  if (g_pFramework->KeyDown(SDLK_w))
  {
   cout << "Direction: 3, Action: 1" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_d))
  {
   cout << "Direction: 3, Action: 2" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_s))
  {
   cout << "Direction: 3, Action: 3" << endl;
  }
  if (g_pFramework->KeyDown(SDLK_a))
  {
   cout << "Direction: 3, Action: 4" << endl;
  }
}
CheckJump ();
if (m_bKeyPressed == false)
{
  CancelJump();
}
else
{
  m_bKeyPressed = false;
}
}/
I hope you can help me with this problem, thanks in advance for that Posted Image

Edited by XeraNox, 09 September 2012 - 05:32 AM.


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#2 Bacterius   Crossbones+   -  Reputation: 8658

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Posted 09 September 2012 - 06:52 AM

This is, uh, an unfortunate keyboard limitation. Some complex key combinations simply do not work while others will - it has nothing to do with your code and cannot really be worked around as it is a hardware issue. Most keyboard designs, especially gaming ones, will do an honest effort keeping the leftmost region of the keyboard relatively usable for complex key combinations - the same cannot be said of the arrow keys, unfortunately.

This might shed some more light on the issue.

The slowsort algorithm is a perfect illustration of the multiply and surrender paradigm, which is perhaps the single most important paradigm in the development of reluctant algorithms. The basic multiply and surrender strategy consists in replacing the problem at hand by two or more subproblems, each slightly simpler than the original, and continue multiplying subproblems and subsubproblems recursively in this fashion as long as possible. At some point the subproblems will all become so simple that their solution can no longer be postponed, and we will have to surrender. Experience shows that, in most cases, by the time this point is reached the total work will be substantially higher than what could have been wasted by a more direct approach.

 

- Pessimal Algorithms and Simplexity Analysis


#3 XeraNox   Members   -  Reputation: 105

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Posted 10 September 2012 - 09:58 AM

Ah, that is unfortunate :( Guess I'll have to change my game idea a bit :D
So anyway, thanks for your replay :)




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