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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: 7009

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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 best comment is a deleted comment."


#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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