Hello people!
First, I have done some research, but I’m unfortunately unable to apply what I’ve seen to the problem I’m currently having.
A GLUT window will open, and the user can click and draw some simple lines, but if the window is stretched or moved, the coordinates for drawing the lines becomes skewed. I know that I have to adjust the window and the coordinates to that of the window being moved or resized, but I’m unsure how.
The following is my code:
//#include <windows.h>
#define _USE_MATH_DEFINES //provides access to math constants like M_PI
#include <math.h>
#include <iostream>
#include <string.h>
#include <vector>
#include "glut.h" //glut.h includes gl.h and glu.h
using namespace std;
/******************************************
GLUT Bitmap Fonts
0 GLUT_BITMAP_8_BY_13
1 GLUT_BITMAP_9_BY_15
3 GLUT_BITMAP_TIMES_ROMAN_10
4 GLUT_BITMAP_TIMES_ROMAN_24
5 GLUT_BITMAP_HELVETICA_10
6 GLUT_BITMAP_HELVETICA_12
7 GLUT_BITMAP_HELVETICA_18
GLUT Basic Color RGB Values
0 black 0.0, 0.0, 0.0
1 light grey 0.75, 0.75, 0.75
2 dark grey 0.5, 0.5, 0.5
3 maroon 0.5, 0.0, 0.0
4 red 1.0, 0.0, 0.0
5 purple 0.5, 0.0, 0.5
6 fuchsia 1.0, 0.0, 1.0
7 green 0.0, 0.5, 0.0
8 lime 0.0, 1.0, 0.0
9 olive 0.5, 0.5, 0.0
10 yellow 1.0, 1.0, 0.0
11 navy 0.0, 0.0, 0.5
12 blue 0.0, 0.0, 1.0
13 teal 0.0, 0.5, 0.5
14 aqua 0.0, 1.0, 1.0
15 white 1.0, 1.0, 1.0
******************************************/
const int screenWidth = 600; // width of screen window in pixels
const int screenHeight = 600; // height of screen window in pixels
const int screenLeft = 200; // left edge of screen window in pixels
const int screenTop = 50; // top edge of screen window in pixels
struct point {
int x;
int y;
};
// program specific variables
vector<point> points;
vector<vector <point>> lines;
bool mouseClicked;
//World coordinates
int leftSide = - screenWidth/2, rightSide = screenWidth/2;
int bottomSide = - screenHeight/2, topSide = screenHeight/2;
int nearSide = (screenWidth < screenHeight) ? - screenWidth/2 : -screenHeight/2;
int farSide = (screenWidth < screenHeight) ? screenWidth/2 : screenHeight/2;
//Bitmap font print
void bitmap_text(float x, float y, char *string, void *font)
{
int len, i;
glRasterPos2f(x, y);
len = (int) strlen(string);
for (i = 0; i < len; i++)
{
glutBitmapCharacter(font, string[i]);
}
}
//Initialize window
void init(void)
{
//Clear color
glClearColor(0.0, 0.0, 0.0, 0.0);
//Specify Projection view transformation matrix
glMatrixMode(GL_PROJECTION);
//Load identity matrix
glLoadIdentity();
//Viewing volume
//2D version
gluOrtho2D(leftSide, rightSide, bottomSide, topSide);
//3D version
//glOrtho(leftSide, rightSide, bottomSide, topSide, nearSide, farSide);
}
//Display callback function
void display(void)
{
//Clear window
glClear(GL_COLOR_BUFFER_BIT);
//Specify Model view transfromation matrix
glMatrixMode( GL_MODELVIEW );
//Load identity matrix
glLoadIdentity();
//Flush GL buffer = force OpenGL commands to execute
glFlush();
}
void idleDisplay(void)
{
//Clear window
glClear(GL_COLOR_BUFFER_BIT);
//Specify Model view transfromation matrix
glMatrixMode( GL_MODELVIEW );
//Load identity matrix
glLoadIdentity();
glColor3f( 0.0, 1.0, 0.0 ); //green
glBegin(GL_LINE_STRIP);
for (int i = 0; i < (int)points.size(); i++)
{
glVertex2f(points.at(i).x - screenWidth/2, -(points.at(i).y - screenHeight/2));
}
glEnd();
for (int i = 0; i < (int)lines.size(); i++)
{
glBegin(GL_LINE_STRIP);
for (int j = 0; j < (int)lines.at(i).size(); j++)
{
glVertex2f(lines.at(i).at(j).x - screenWidth/2, -(lines.at(i).at(j).y - screenHeight/2));
}
glEnd();
}
glFlush();
}
void mouse(int button, int state, int x, int y) {
if (state == 0 && button == 0) {
mouseClicked = true;
cout << x << ", " << y << endl;
cout << "button #: " << button << endl;
cout << "button state: " << state << endl;
point newPoint;
newPoint.x = x;
newPoint.y = y;
points.push_back(newPoint);
vector<point> newPoints;
lines.push_back(newPoints);
}
if (state == 1 && button == 0)
mouseClicked = false;
display();
}
void mouseMove(int x, int y)
{
if (mouseClicked == true)
{
point point;
point.x = x;
point.y = y;
lines.at(lines.size() - 1).push_back(point);
}
}
void reshape(int width, int height)
{
}
int main(int argc, char** argv)
{
cout << "
***************************************";
cout << "
Simple Drawing Program" << endl;
cout << " Hit 'q' to exit." << endl << endl;
cout << " ***************************************";
//Initialize GLUT
glutInit(&argc,argv);
//set color and buffering modes
//glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );
//set intial window size
glutInitWindowSize(screenWidth,screenHeight);
//set intial window position
glutInitWindowPosition(screenLeft, screenTop);
//Create window
glutCreateWindow(" OpenGL Visualization");
//Initialize window
init();
//Reshaping window function
glutReshapeFunc(NULL);
//Specify display callback
glutDisplayFunc(display);
//Specify idle display
glutIdleFunc(idleDisplay);
//register mouse click callback
glutMouseFunc(mouse);
//register mouse motion callback
glutMotionFunc(mouseMove);
//Start even processing loop
glutMainLoop();
return 0;
}
If anyone has any hints or tips, please inform. I’m trying to learn, so make me think a little. 
Thank you for your time.