force FLTK to redraw without event Handles - c++

Question

I'm using Fltk to render openGL graphs. currently I'm debugging a global array which is sorted by a heapsort function. My purpose is to see after each swap of elements in the heapsort function a graphical swap of elements. but I don't want to catch an event from FLTK event_handle for every time i need to redraw after I swapped and waiting at breakpoint. (the heapsort function and the opengl render part are running in 2 different threads (if that doesn't has to go without saying)).
So the first try I had was to use:
Fl::add_timeout(1.0, MyRedrawCallback, (void *)&myWindow);
Fl::run();
void MyRedrawCallback(void *myWindow)
{
MyWindow *pMyWindow;
pMyWindow = (MyWindow *) myWindow;
pMyWindow->redraw();
Fl::repeat_timeout(1.0, MyRedrawCallback, (void *)&pMyWindow);
}
But every Time the callback is called the 2nd time i get an "Access violation reading"
I'm suggesting that FL::run starts a different thread so maybe the first time is still in same thread so the address of redraw is still usable but after that I'm in a different thread and the function at address is not that what I'm expecting?!
But I already took a different way because I wasn't sure i cant even use the timeout on this way.
So i was looking for a way to get an event that's eq to "set amount of time passed" or "nothing is happening for..." but there isn't such a handle I'm right?
Finally is there a way to let FLTK execute commands even outside the eventloop? or is there another way to solve my problem?

Answer 1

Please take a look at the following example, taken from here: http://seriss.com/people/erco/fltk/#OpenGlInterp
#include <FL/Fl.H>
#include <FL/Fl_Gl_Window.H>
#include <FL/gl.h>
#include <math.h>
//
// Demonstrate interpolating shapes
// erco 06/10/05
//
class Playback : public Fl_Gl_Window {
int frame;
// Linear interpolation between two values based on 'frac' (0.0=a, 1.0=b)
float Linterp(float frac, float a, float b) {
return( a + ( frac * (b - a) ));
}
// Sinusoidal easein/easeout interpolation between two values based on 'frac' (0.0=a, 1.0=b)
float SinInterp(float frac, float a, float b) {
float pi = 3.14159;
frac = (sin(pi/2 + frac*pi ) + 1.0 ) / 2.0; // 0 ~ 1 -> 0 ~ 1
return(Linterp(frac,a,b));
}
// DRAW SIMPLE SHAPE INTERPOLATION
// Interpolation is based on the current frame number
//
void DrawShape(int frame) {
// Calculate a fraction that represents the frame# being shown
float frac = ( frame % 48 ) / 48.0 * 2;
if ( frac > 1.0 ) frac = 2.0-frac; // saw tooth wave: "/\/\/\"
static float a_xy[9][2] = {
{ -.5, -1. }, { 0.0, -.5 }, { -.5, -1. }, { 0.0, -.5 },
{ 0.0, 0.0 },
{ 0.0, -.5 }, { +.5, -1. }, { 0.0, -.5 }, { +.5, -1. },
};
static float b_xy[9][2] = {
{ -.25, -1. }, { -.50, -.75 }, { -.75, -1.0 }, { -.50, -.75 },
{ 0.0, 0.0 },
{ +.50, -.75 }, { +.75, -1.0 }, { +.50, -.75 }, { +.25, -1.0 }
};
// Linterp a and b to form new shape c
float c_xy[9][2];
for ( int i=0; i<9; i++ )
for ( int xy=0; xy<2; xy++ )
c_xy[i][xy] = SinInterp(frac, a_xy[i][xy], b_xy[i][xy]);
// Draw shape
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_LINE_STRIP);
for ( int i=0; i<9; i++ )
glVertex2f(c_xy[i][0], c_xy[i][1]);
glEnd();
}
// DRAW THE WIDGET
// Each time we're called, assume
//
void draw() {
if (!valid()) {
valid(1);
glLoadIdentity();
glViewport(0,0,w(),h());
}
glClear(GL_COLOR_BUFFER_BIT);
// Draw shape 4x, rotated at 90 degree positions
glPushMatrix();
DrawShape(frame); glRotatef(90.0, 0, 0, 1);
DrawShape(frame); glRotatef(90.0, 0, 0, 1);
DrawShape(frame); glRotatef(90.0, 0, 0, 1);
DrawShape(frame);
glPopMatrix();
// Advance frame counter
++frame;
}
// 24 FPS TIMER CALLBACK
// Called 24x per second to redraw the widget
//
static void Timer_CB(void *userdata) {
Playback *pb = (Playback*)userdata;
pb->redraw();
Fl::repeat_timeout(1.0/24.0, Timer_CB, userdata);
}
public:
// Constructor
Playback(int X,int Y,int W,int H,const char*L=0) : Fl_Gl_Window(X,Y,W,H,L) {
frame = 0;
Fl::add_timeout(1.0/24.0, Timer_CB, (void*)this); // 24fps timer
end();
}
};
int main() {
Fl_Window win(500, 500);
Playback playback(10, 10, win.w()-20, win.h()-20);
win.resizable(&playback);
win.show();
return(Fl::run());
}
This example more/less does exactly what you want. Greg Ercolano has more FLTK examples on his web-site. I recommend taking a look at http://seriss.com/people/erco/fltk/ .