The screen do not refresh although I use glFlush() unless I press ALT+TAB twice please tell me whats wroung This is my simple program /*--------------------------------------------------------------- header file for clipping project ----------------------------------------------------------------*/ //SCREEN SIZE const SCREEEN_X = 600; const SCREEEN_Y = 600; //global variables bool IsQuadPainted = false;//after 2 clicks of left mouse click becomes true bool IsLinePainted = false;//after 2 clicks of right mouse click becomes true // struct for represent point in the screen struct sPoint { float x, y; }; // node in list of lines struct sLine { sPoint p1, p2; sLine *NextLine; }; sPoint corner1,corner2 ;//rectangle ''s values float Line_x1,Line_y1;//line''s values sLine *lines; // list of lines float Rleft , Rright , Rtop ,Rbottom;//the rectanle''s values with meaning int RightClickCounter = 0;//Right Click Counter int LeftClickCounter = 0;//Left Click Counter //calculets the code of given point char CalcCode(float X,float Y); // convert value of int to float. float convertVal(int xyVal,bool isX); // draw a blue rectangle void PaintQuad(); // draw clipped line void PaintLine(sPoint p1,sPoint p2); // set borders of rectangle using for the clipping algorithm void SetBorders(); void myDisplay(); void myMouse(int btn,int st, int x ,int y); void myKey(unsigned char key, int x, int y); void myInit(); // free list of lines. void FreeLines(sLine *line); #include #include "clipping.h" #include // CalcCode : calculets the code of given point // Parameters : x,y - value of given point. // Returns : the code for this point. char CalcCode(float X,float Y) { char result=0; if (!IsQuadPainted) return result; if (X < Rleft) result = result | 1; else result = result & 14; if (Y > Rtop) result = result | 2; else result = result & 13; if (X > Rright) result = result | 4; else result = result & 11; if (Y < Rbottom) result = result | 8; else result = result & 7; return result; } // convertVal : converts integer position on screen to float position // Parameters : xyVal - value in integer // isX - if we have x value of point (x,y) // Returns : float position float convertVal(int xyVal,bool isX) { if (isX) return ((float)(xyVal)/SCREEEN_X); else return ((float)(SCREEEN_Y - xyVal)/SCREEEN_Y); } // PaintQuad : paints rectangle on screen // Parameters : Global void PaintQuad() { glColor3f(0.0f,0.0f,1.0f);//blue glRectf(corner1.x,corner1.y,corner2.x,corner2.y); //glFlush(); } // PaintLine : paints the line on screen with the right colors // parameters : p1 , p2 - two points on screen which represent line to be drawn void PaintLine(sPoint p1 ,sPoint p2) { float tmpX1,tmpX2,tmpY1,tmpY2; do { if(CalcCode(p1.x,p1.y) & CalcCode(p2.x,p2.y)) { // outside the rect in the same zone glColor3f(1.0f,0.0f,0.0f); // red glBegin(GL_LINES); glVertex2f(p1.x, p1.y); glVertex2f(p2.x, p2.y); glEnd(); //glFlush(); return; } if(!(CalcCode(p1.x,p1.y) | CalcCode(p2.x,p2.y))) { // inside the rect glColor3f(0.0f,1.0f,0.0f);//green glEnable(GL_LINE_STIPPLE); glLineStipple(1,0x5555);//as asked for glBegin(GL_LINES); glVertex2f(p1.x,p1.y); glVertex2f(p2.x,p2.y); glEnd(); glDisable(GL_LINE_STIPPLE); //glFlush(); return; } tmpX1 = p1.x; tmpX2 = p2.x; tmpY1 = p1.y; tmpY2 = p2.y; if (p1.xRright) { p1.y+=(((p2.y-p1.y)/(p1.x-p2.x))*(p1.x-Rright)); p1.x=Rright; } else if (p2.x>Rright) { p2.y+=(((p1.y-p2.y)/(p2.x-p1.x))*(p2.x-Rright)); p2.x=Rright; } if (p1.yRtop) { p1.x+=(((p2.x-p1.x)/(p1.y-p2.y))*(p1.y-Rtop)); p1.y=Rtop; } else if (p2.y>Rtop) { p2.x+=(((p1.x-p2.x)/(p2.y-p1.y))*(p2.y-Rtop)); p2.y=Rtop; } glColor3f(1.0f,0.0f,0.0f);//red glBegin(GL_LINES); glVertex2f(tmpX1,tmpY1); glVertex2f(p1.x,p1.y); glVertex2f(p2.x,p2.y); glVertex2f(tmpX2,tmpY2); glEnd(); //glFlush(); glColor3f(0.0f,1.0f,0.0f);//green glEnable(GL_LINE_STIPPLE); glLineStipple(1,0x5555); glBegin(GL_LINES); glVertex2f(p1.x,p1.y); glVertex2f(p2.x,p2.y); glEnd(); glDisable(GL_LINE_STIPPLE); //glFlush(); return; } while(1); } // SetBorders : sets the rect values to know the borders // Parameters : none. void SetBorders() { if (corner1.x < corner2.x) { Rleft = corner1.x; Rright = corner2.x; } else { Rleft = corner2.x; Rright = corner1.x; } if (corner1.y < corner2.y) { Rbottom = corner1.y; Rtop = corner2.y; } else { Rbottom = corner2.y; Rtop = corner1.y; } } // FreeLines : free allocated memory for all lines // Parameters : line - pointer to a list of lines. void FreeLines(sLine *line) { if (line != NULL) { FreeLines(line->NextLine); delete line; line = NULL; } } // myDisplay : function that draw all things that we have in the window // void myDisplay() { sLine *line; glClear(GL_COLOR_BUFFER_BIT); glColor3f(0.6f,0.8f,0.0f); if (IsQuadPainted) { PaintQuad(); SetBorders(); } if (IsLinePainted) { line = lines; while(line) { PaintLine(line->p1, line->p2); line = line->NextLine; }; } glFlush(); } void myMouse(int btn,int st, int x ,int y) { sLine *CurrentLine; switch(btn) { case GLUT_MIDDLE_BUTTON: if (st == GLUT_DOWN) { FreeLines(lines); exit(0); } break; case GLUT_LEFT_BUTTON: if (IsQuadPainted) if (st == GLUT_DOWN) { switch(LeftClickCounter%2) { case 0: Line_x1=convertVal(x,true); Line_y1=convertVal(y,false); IsLinePainted = false; break; case 1: if(lines == NULL) { CurrentLine = new sLine; lines = CurrentLine; } else { CurrentLine = lines; while(CurrentLine->NextLine) CurrentLine = CurrentLine->NextLine; CurrentLine->NextLine = new sLine; CurrentLine = CurrentLine->NextLine; }; CurrentLine->NextLine = NULL; CurrentLine->p1.x = Line_x1; CurrentLine->p1.y = Line_y1; CurrentLine->p2.x = convertVal(x,true); CurrentLine->p2.y = convertVal(y,false); IsLinePainted = true; break; } LeftClickCounter++; } break; case GLUT_RIGHT_BUTTON: if (!IsQuadPainted) if (st == GLUT_UP) { switch(RightClickCounter) { case 0: corner1.x=convertVal(x,true); corner1.y=convertVal(y,false); break; case 1: corner2.x=convertVal(x,true); corner2.y=convertVal(y,false); IsQuadPainted = true; break; } RightClickCounter++; } break; } } void myKey(unsigned char key, int x, int y) { switch(key) { case ''q'': FreeLines(lines); exit(0); } } void myInit() { glClearColor(1.0f,1.0f,0.0f,0.0f); glMatrixMode(GL_PROJECTION); glLoadIdentity(); lines = NULL; glOrtho(0.0,1.0,0.0,1.0,-1.0,1.0); } int main(int argc, char **argv) { glutInit(&argc, argv); glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB ); glutInitWindowSize(SCREEEN_X, SCREEEN_Y); glutCreateWindow("ILan Rozen and Yaniv Cohen - Targil No 1"); myInit(); glutMouseFunc(myMouse); glutKeyboardFunc(myKey); glutDisplayFunc(myDisplay); glutMainLoop(); return 0; }

Why don''t you try making your own loop in the main function

I don''t use glut so i can barely read that but don''t you need to swap the buffers in your program? If you don''t swap the buffers it won''t redraw anything to the best of my knowledge. Like i said though i don''t use glut so i don''t know if glut does it for you or not. If you don''t know how to swap the buffers it is OS specific.
I only know windows which is:
SwapBuffers( HDC );
where HDC is you handle for the device context(now that i think about it glut probably does it for you since it sets up the window and you don''t even have to worry about the device context)

"Those who want it, but can''''t get it, will complain about it.

At the end of your myDisplay() function, after glFlush(), add this line:

glutSwapBuffer();

That should do it

Keep in mind that if you had an idle function, that you would declare with glutIdleFunc(), you would also have to call glutPostRedisplay(void) within the idle function every time you wanted to redraw the window. Otherwise, all you need is the line above after your drawing code.

Good luck

man... he''s lucky... whenever I forget to swap the buffers my computer then procedes to puke, crash, and sqeak at me until I reboot....

*** After glancing at the code ***

wait, he''s using single buffered mode.. he shouldnt need to swap them... just place a glutPostRedisplay(); at the end of the display function.. this tells it to draw again... Really though, if you want fast graphics... then I''d suggest using GLUT_DOUBLE, for double buffering, and using glutSwapBuffers(); as mentioned earlier...