OpenGL Mouse, how it works..

[fpsasm]

Hi, I know that there are a lot of webpages devoted in telling me how the OpenGL mouse function works, but I still don't understand.

What I need to know, when my:

void processMouse( int button, int state, int x, int y){
...
}

Returns x,y. What does x,y look like? as in:
Are the values of X Y the pixel location on the screen (where the resolution is 800x600, for example, so XY could be (400,300))

Does X = 0 , and Y = 0 at the bottom left side of the screen?

If the values of X Y relate to the location of the mouse on the screen, how do i get the position of the mouse in the window?

I know you probably read this before, please don't link sites, I wouldn't ask this on this forum if I understood the sites :)

Thanks alot,
Matthew

[sfuo]

The values that get passed into that function will be pixel coordinates then the functions would call gluPickMatrix((GLdouble) x, (GLdouble) (viewport[3] -y), 1.0, 1.0, viewport); where 1.0 and 1.0 is the size I chose of the selection region.

Not sure if you know anything about selecting objects in OpenGL but I managed to make this from looking around at websites and using the Red and Blue books.

This is the code I have for selection.

//in my windows message area
case WM_LBUTTONDOWN:
	MouseFunc(SF_LEFT_BUTTON, SF_DOWN, LOWORD(lParam), HIWORD(lParam));
	break;

//functions
void MouseFunc( int button, int state, int x, int y )
{
	if( button == SF_LEFT_BUTTON && state == SF_UP )
		leftMouseDown = false;

	if( button == SF_RIGHT_BUTTON && state == SF_UP )
		rightMouseDown = false;

	if( button == SF_LEFT_BUTTON && state == SF_DOWN )
		leftMouseDown = true;

	if( !leftMouseDown || rightMouseDown )
		return;

	GLuint BUFSIZE = 512;
	GLuint selectBuf[BUFSIZE];
	GLint hits;
	GLint viewport[4];

	glGetIntegerv(GL_VIEWPORT, viewport);

	glSelectBuffer(BUFSIZE, selectBuf);

	glMatrixMode(GL_PROJECTION);
	glPushMatrix();

		glRenderMode(GL_SELECT);
		glInitNames();
		glPushName(0);

		glLoadIdentity();

		gluPickMatrix((GLdouble) x, (GLdouble) (viewport[3] -y), 1.0, 1.0, viewport);

		ORTHO_WIDTH = ORTHO_HEIGHT*((GLdouble)WINDOW_WIDTH/(GLdouble)WINDOW_HEIGHT);

		glOrtho(0, ORTHO_WIDTH, 0, ORTHO_HEIGHT, -1, 20);

		glMatrixMode(GL_MODELVIEW);

		glPushMatrix();

			//DrawFunc(GL_SELECT);

			hits = glRenderMode(GL_RENDER);

		glPopMatrix();

		glMatrixMode(GL_PROJECTION);

	glPopMatrix();

	glMatrixMode(GL_MODELVIEW);

	glFlush();

	objectSelected = ProcessHits(hits, selectBuf);
	if( objectSelected >= 0 )
		cout << "selected object: " << objectSelected << endl;
}

GLint ProcessHits(GLint hits, GLuint buffer[])
{
	if( hits == 0 )
		return -1;

	GLuint lowestDepth = buffer[1];
	GLint selectedObject = buffer[3];

	for( sui i = 1; i < hits; i++ )
	{
		if(buffer[(i*4)+1] < lowestDepth)
		{
			lowestDepth = buffer[(i*4)+1];
			selectedObject = buffer[(i*4)+3];
		}
	}
	return selectedObject;
}