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AmiDARK
exit from a function defined for glutMainLoop() possible ?
Posted on: 2009/3/23 19:59    #1
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Hi All,

in fact, I'd like to know if I can do something like this :


My display function :
void MyDisplayFunction( void ){
  If ( MyChecking == TRUE ){
    Exit(0);
   }
 }


Define the display function from setup :
glutDisplayFunc( MyDisplayFunction );


And the glut start :
...
... (some code);
...
glutMainLoop();
...
... (some code part 2);
...


In fact, I'd like to replace Exit(0) with something that will quit the program from glutMainLoop() and continue just after (at some code part 2 place)...
is it possible ?
All we have to decide is what to do with the time that is given to us.
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salass00
Re: exit from a function defined for glutMainLoop() possible ?
Posted on: 2009/3/23 20:14    #2
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@freddix

This is from a program of mine:
#include <setjmp.h>

static jmp_buf jmpbuf;
static int jmp_set = FALSE;

void enter_main_loop () {
    if (!setjmp(jmpbuf)) {
        jmp_set = TRUE;
        glutMainLoop();
    }
    jmp_set = FALSE;
}

void leave_main_loop () {
    if (jmp_set) longjmp(jmpbuf, 1);
}

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AmiDARK
Re: exit from a function defined for glutMainLoop() possible ?
Posted on: 2009/3/23 21:04    #3
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@Salass00:
If I'm not wrong, I should do something like this :

At the beginning of my source code :
#include <setjmp.h>
static jmp_buf jmpbuf;


Display function :
void MyDisplayFunction( void ){
  ... all my display function here
  if (jmp_set) longjmp(jmpbuf, 1);
   }
 }


Define the display function from setup :
glutDisplayFunc( MyDisplayFunction );


And the glut start :
...
... (some code);
...
if (!setjmp(jmpbuf)){
  jmp_set = TRUE;
  glutMainLoop();
 }
jmp_set = FALSE;
... (some code part 2);
...


Is that correct ?
All we have to decide is what to do with the time that is given to us.
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salass00
Re: exit from a function defined for glutMainLoop() possible ?
Posted on: 2009/3/23 23:27    #4
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@freddix

If I were you I would just use the functions I posted as is, i.e. replace glutMainLoop() in your code with enter_main_loop() and add leave_main_loop() where you want to leave the loop. If you don't like the function names you can always rename them.

Some GLUT implementations have a glutLeaveMainLoop() function but apparently this function isn't implemented in MiniGL.
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AmiDARK
Re: exit from a function defined for glutMainLoop() possible ?
Posted on: 2009/3/23 23:29    #5
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@Salass00:
Thank you :)
Your system work perfectly.
It allow me to use glut and to control the sync sequencially without having it to loop with the glutDisplayFunc() defined :p
All we have to decide is what to do with the time that is given to us.
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Hans
Re: exit from a function defined for glutMainLoop() possible ?
Posted on: 2009/3/24 1:26    #6
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@freddix

No need to make things so complicated. The C std lib allows you to define an exit hook using atexit(). For example, my code usually looks something like this:

Quote:

void cleanup();

int main(int argc, const char* argv[])
{
// ----- Insert code to Parse args, etc. -----

atexit(cleanup);

// ----- Code to init GLUT, create objects, etc. ----

exit(0);
}

void cleanup()
{
// ----- Code to cleanup ----
}



This allows you to call exit() anywhere, and still have it execute your cleanup code.

MiniGL's glut also has the ability to set a hook for when someone clicks on the close window button:
glCloseFunc();

Or, you could tell GLUT to exit the main loop when someone clicks on the close button by using glutSet() to set:
GLUT_ACTION_ON_WINDOW_CLOSE
to:
GLUT_ACTION_GLUTMAINLOOP_RETURNS

Unfortunately there is no glutLeaveMainLoop() though, although it could be added in a future version, if people really needed it.

Hans
http://hdrlab.org.nz/ - Amiga OS 4 projects, programming articles and more.
https://keasigmadelta.com/ - more of my work
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AmiDARK
Re: exit from a function defined for glutMainLoop() possible ?
Posted on: 2009/3/24 10:18    #7
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@Hans
In fact, my problem is not to quit the app, but simply quit the glutMainLoop...
And after quitting it it can recall it again ...
it's because I want glutMainLoop to act as single step function and not as a loop.
With Salass00 informations, I can do that now :)

Thank you all.
All we have to decide is what to do with the time that is given to us.
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Hans
Re: exit from a function defined for glutMainLoop() possible ?
Posted on: 2009/3/24 23:07    #8
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@freddix

That kind of defeats the purpose of a mainloop now doesn't it? I would have simply had a static flag that indicates when to do the next step, e.g., :

Quote:
static BOOL nextStep = FALSE;

// -----------

if ( MyChecking == TRUE ){
nextStep = TRUE;
}

// -----------

if(nextStep)
{
doNextStep();
nextStep = FALSE;
}



IMHO, this is simpler than trying to get GLUT to do something that it's not designed for.

Hans
http://hdrlab.org.nz/ - Amiga OS 4 projects, programming articles and more.
https://keasigmadelta.com/ - more of my work
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AmiDARK
Re: exit from a function defined for glutMainLoop() possible ?
Posted on: 2009/3/25 0:38    #9
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@Hans
The principle is quite simple. Having something act like an engine/ or a basic language (engine is only the first step ... language will be the second one).

For exemple, here is my demo source code for stars in its actual state :

#include "AmiDARKEngine.c"

void DarkLoop( void ){
  int XLoop = 0;
  int SColor = 0;
  float XSpeed = 0.0;

  for( XLoop = 0; XLoop<=(StaticAmount -1); XLoop++){
    Stars[ XLoop ].XPos = (float)DERnd( 640 );
    Stars[ XLoop ].YPos = (float)DERnd( 479 );
   }

  DESetDisplayMode( 640, 480, 32 );
  DESyncOff();
  DEInk( DERgb( 255, 255, 255 ), 0 );

  while( !DELoop() ){
    DECls();
    for( XLoop = 0; XLoop<=(StaticAmount -1); XLoop++){
      XSpeed = (float)(XLoop+1) * 0.0025 ;
      Stars[ XLoop ].XPos = Stars[ XLoop ].XPos - XSpeed;
      if( Stars[ XLoop ].XPos < 0.0 ){
        Stars[ XLoop ].XPos = Stars[ XLoop ].XPos + 640.0;
       }
      SColor = XLoop * 2.5 ;
      DEDotEx( (int)Stars[ XLoop ].XPos, (int)Stars[ XLoop ].YPos, DERgb( SColor, SColor, SColor ) );
     }
    DESync();
   }
 }

This is what developer makes to use my engine and doing star scroll.
in background, my system uses GLUT.

The functions-sets constructors are defined like this :
void CORE_Constructor( void ){
  IsSyncOn = FALSE;
  glutDisplayFunc( MyDisplayFunc );
  glutIdleFunc( MyDisplayFunc );
 }

For example, in this one I set the display one ... it's what interest us ..

and now, MyDisplayFunc :
void MyDisplayFunc(){
  // Automatically clear the backdrop is active
  if( BasicCamera.Backdrop == 1 ){
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
   }
  UpdateLights(); // Update all true 3D lighting.
  UpdateWorld(); // Update all Basic 3D
  UpdateCamera(); // Update all camera 3D
  glutSwapBuffers();
  if (jmp_set) longjmp( jmpbuf, 1);
  // Until the function glutLeaveMainLoop() is added to MiniGL.
 }

The end of the function forces to quit glutMainLoop...

Now, if you look the 1st code, you'll see 2 interesting function : DELoop() ...
It work like a QUIT function detecting specific entries that can lead to quit the application.
For example escape key.

Look for example, the keyboard, mouse and specials functions are defined as follow :
MyMouseFunc( int MButtons, int State, int XP, int YP ){
  DBMouse.LeftButton = FALSE;
  DBMouse.RightButton = FALSE;
  DBMouse.MiddleButton = FALSE;
  DBMouse.OldXPos = DBMouse.XPos;
  DBMouse.OldYPos = DBMouse.YPos;
  DBMouse.XPos = XP;
  DBMouse.YPos = YP;
  if (State == GLUT_DOWN ){
    switch( MButtons ){
      case GLUT_LEFT_BUTTON:
        DBMouse.LeftButton = TRUE;
        break;
      case GLUT_RIGHT_BUTTON:
        DBMouse.RightButton = TRUE;
        break;
     }
   }
 }

MyKeyboardFunc( unsigned char k, int x, int y ){
  // Reset Special Keys
  DBKey.Escape = FALSE;
  switch (k){
    // Get Escape Key
    case 27:
      DBKey.Escape = TRUE;
      break;
    default:
      return;
   }
 }

MySpecialFunc( void ){

 }
MyEntryFunc( void ){
 }


INPUT_Constructor( void ){
  glutKeyboardFunc( MyKeyboardFunc );
  glutMouseFunc( MyMouseFunc );
  glutEntryFunc( MyEntryFunc );
  glutSpecialFunc( MySpecialFunc );
  DBMouse.XPos = 0;
  DBMouse.YPos = 0;
  DBMouse.OldXPos = 0;
  DBMouse.OldYPos = 0;
  DBMouse.LeftButton = 0;
  DBMouse.RightButton = 0;
  DBMouse.MiddleButton = 0;
 }

I can then store all infos and make them available in my entire program ..
With that, my DELoop() function is simple :
BOOL DELoop(){    
  int done = DBKey.Escape;
  return done;
 }

I will add support for window close gadget caption.

Do you know understand the principle ?

At the end of this,
When developer call DESync() function it do this :
/* Rafraichir l'affichage */
void DESync(){
  if ( !setjmp( jmpbuf)){
    jmp_set = TRUE;
    glutMainLoop();
   }
  Basic2D.IsOrthoActive = FALSE;
 }

It setup the longjmp, call glutMainLoop() that'll execute all GLUT defined functions I've made (key, mouse, special, and at the end display or idle and then quit glutMainLoop() .. glutMainLoop() do what it is supposed to ... provide a full set of functionalities and then it quit it ... I get these informaitons and then can use them in my full program ...

Here is the explanation on why I needed this ...
All we have to decide is what to do with the time that is given to us.
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