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wm_timer

Posted on 1999-01-22
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Last Modified: 2010-04-02
i have some problem with the timer.
dun quite understand how it works???
when did i start the timer?how do i stop? quite confused!
let say when i want to rotate the object by 3 degree
everytime i pressed the arrow key...
how do i do it?
or is there other ways to do it?
like using a flag to indicate as shown in the code below:

void CDhView::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags)
{      
switch(nChar) {
                        
      case VK_LEFT:
                  z_angle -= 3.0f;
                  if (z_angle <=0.0f);
                        z_angle = 359.0f;
                  cameramode = ROTATE;
                  Invalidate();
                  break;



On_Draw()

      if (cameramode == ROTATE)
      {      
            
            glRotatef(z_angle, 0.0f, 1.0f, 0.0f);      
            cameramode == STOP;            
      }

so once i rotate the z_angle by 3 degree, then the object
should stop rotating until i press arrow key again.
but it keep on rotating...why??
thanks
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Question by:at75
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6 Comments
 
LVL 22

Accepted Solution

by:
nietod earned 60 total points
ID: 1184881
SetTimer() starts the timer and KillTimer() destroys (stops) it.  In between that you will get periodic WM_TIMER notifications messages as long as you are running a "message pump".
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LVL 22

Expert Comment

by:nietod
ID: 1184882
>>.let say when i want to rotate the object by 3 degree
>>  everytime i pressed the arrow key...
>>   how do i do it?
That doesn't have anything to do with a timer.  Handle the WM_KEYDOWN message to determine when the arrow key is pressed.  Then adjust whatver variables you are using that records the current camera angle and then invalidate the window.  Then return  when the window is redrawn (shortly) it will be redrawn at the new angle.

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LVL 22

Expert Comment

by:nietod
ID: 1184883
>>so once i rotate the z_angle by 3 degree, then the object
>>   should stop rotating until i press arrow key again.
>>   but it keep on rotating...why??
Do you mean it continues to rotate more and more?  it doesn't look like it should from the code.  Do you mean it stays rotated?  Like do you want it to appear unrotated again?

what does glRotatef()  do?
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LVL 1

Expert Comment

by:dvest
ID: 1184884


   void CDhView::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags)
   {
   switch(nChar) {

   case VK_LEFT:
   if(nRepCnt != 0)  // if this isn't the initial keypress
   {return;}
   z_angle -= 3.0f;
   if (z_angle <=0.0f);
   z_angle = 359.0f;
   cameramode = ROTATE;
   Invalidate();
   break;

I didn't get to test this, but by the name of the variable I'd think it would start off at zero.  If this
doesn't work, try using one.
David
0
 

Author Comment

by:at75
ID: 1184885
dvest : thanks.i tried using your method. It continues to rotate!!
any idea how to stop it???

Thanks.
0
 
LVL 22

Expert Comment

by:nietod
ID: 1184886
That code is fine (as is what I suggested).  It cannot make it continue to rotate.  I think you must have other code somewhere that is the culprit.  Look for other occurances of code that alters z_angle.

I still don't see where WM_TIMER comes into this.  That sounds suspicious.
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