Problem with creating a class for drawing....

Myles Evans · 2013-01-18T00:35:30

class QuadDrawing { private: float QuadoffX; float QuadoffY; public: QuadDrawing(float, float); void Draw(); }; QuadDrawing::QuadDrawing( float Xoff, float Yoff) { Xoff = QuadoffX; Yoff = QuadoffY; } void QuadDrawing::Draw() { glPushMatrix(); glTranslatef(QuadOffX,QuadoffY,0.0f); glBegin(GL_QUADS); //Set color glColor4f(1.0,0.0,0.0,0.0); glVertex2f(90.0,50); glVertex2f(90.0,-80); glVertex2f(0.0,-80); glVertex2f(0.0,50); glEnd(); glPopMatrix(); } int main( int argc, char *argv[] ) { //Quit flag bool quit = false; //Initialize if( init() == false ) { return 1; } //The frame rate regulator Timer fps; Drawing Square1(300.0, 300.0); int x = 0, y = 0; //Wait for user exit while( quit == false ) { //Start the frame timer fps.start(); //While there are events to handle while( SDL_PollEvent( &event ) ) { if( event.type == SDL_QUIT ) { quit = true; } else if( event.type == SDL_KEYDOWN ) { //Handle keypress with current mouse position SDL_GetMouseState( &x, &y ); handleKeys (event.key.keysym.unicode. x. y); } } MenuState(); Square1.Draw(); update(); //Cap the frame rate if( fps.get_ticks() < 1000 / FRAMES_PER_SECOND ) { SDL_Delay( ( 1000 / FRAMES_PER_SECOND ) - fps.get_ticks() ); } } //Clean up clean_up(); return 0; } The problem is I want to draw a square to test the class I made which should just take two floating point numbers and draw a square at those points, but the square is never drawn...instead the window comes up but stays completely blank. The window was even clear (no clear color) so I thought that was the problem and added glClear( GL_COLOR_BUFFER_BIT ); to the Draw function in the class making it... void QuadDrawing::Draw() { glClear( GL_COLOR_BUFFER_BIT); glPushMatrix(); glTranslatef(QuadOffX,QuadoffY,0.0f); glBegin(GL_QUADS); //Set color glColor4f(1.0,0.0,0.0,0.0); glVertex2f(90.0,50); glVertex2f(90.0,-80); glVertex2f(0.0,-80); glVertex2f(0.0,50); glEnd(); glPopMatrix(); } Still didn't work and the window come up clear/blank (not even the clear color). But the thing is if I just make it a function and not a class and pass the floating X/Y to draw the square there it works fine. So its a problem with the class.

For Beginners

Started by MylesEvans January 15, 2013 09:43 PM

10 comments, last by MylesEvans 11 years, 3 months ago

MylesEvans

151

Author

January 17, 2013 10:24 PM

One kind of obvious thing that jumps at me is your constructor. Take a good look at it and if you don't notice it, describe to me in detail what it does ,-)

Trienco that looks like it might be why it doesn't work.

GDsnakes you should make all function inputs const unless you have to modify it.

I changed it to this. Still the exact same same issues.


QuadDrawing::QuadDrawing( float Xoff, float Yoff)
{
QuadoffX = Xoff;
QuadoffY = Yoff;
}

MylesEvans

151

Author

January 18, 2013 12:35 AM

Fixed it. Needed to Swap Buffers.

Problem with creating a class for drawing....

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Problem with creating a class for drawing....

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