world_of_cow/mmn_17.c

#include <GL/freeglut.h>
#include <GL/freeglut_std.h>
#include <GL/gl.h>
#include <GL/glext.h>
#include <GL/glu.h>
#include <stdio.h>
#include <math.h>
#include "ui.h"

void testButtonClick();


// Ui stuff
ui_button buttons[] = {
    { 
            /* pos */ { { 0.5, 0.5, 0.0 }, { -50.0, -25.0, 0.0 } },
            /* size */ { 100.0, 50.0, 0.0 },
            /* onclick */ testButtonClick,
            /* text */ "Test :)"
        }
};
ui_slider sliders[] = {
    {
        /* pos */ { { 0.5, 0.7, 0.0 }, {-50.0, -5.0, 0.0 } },
        /* size */ { 100.0, 10.0, 10.0 },
        0.1
    }
};

void testButtonClick() {
    printf("Clicked!\n");
    sliders[0].value = 0.5;
    glutPostRedisplay();
}

void drawUi(void) {
    glDisable(GL_LIGHTING);
    
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    // set ui camera
    int wWidth = glutGet(GLUT_WINDOW_WIDTH);
    int wHeight = glutGet(GLUT_WINDOW_HEIGHT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, wWidth, 0.0, wHeight);
    
    // Draw buttons
    for(ui_button* b = buttons; b < buttons + sizeof buttons / sizeof(ui_button); b += 1) {
        ui_button_draw(b);
    }
    for(ui_slider* s = sliders; s < sliders + sizeof sliders / sizeof(ui_slider); s += 1) {
        ui_slider_draw(s);
    }
    
    int err = glGetError();
    if(err != 0) {
        printf("opengl error %d: %s\n", err, gluErrorString(err));
    }
}

void drawWorld(void) {
    // set perspective camera
    GLdouble wWidth = (GLdouble) glutGet(GLUT_WINDOW_WIDTH);
    GLdouble wHeight = (GLdouble) glutGet(GLUT_WINDOW_HEIGHT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(0.0, 10.0, 20.0, (0.5 - sliders[0].value) * 10.0, 0.0, 0.0, 0.0, 1.0, 0.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(90, wWidth / wHeight  , 1.0, 100.0);
    // Lights
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    GLfloat light1[] = { 0.0, 1.0, 0.0, 0.0 };
    glLightfv(GL_LIGHT0, GL_POSITION, light1);
    // World
    glBegin(GL_QUADS);
        glColor3f(1.0, 1.0, 0.0);
        glNormal3f(0.0, 1.0, 0.0);
        glVertex3f(-50.0, 0.0, -50.0);
        glVertex3f(50.0, 0.0, -50.0);
        glVertex3f(50.0, 0.0, 50.0);
        glVertex3f(-50.0, 0.0, 50.0);
    glEnd();
}

void display(void) {
    // Clear screen
    glClearColor(0.0, 0.0, 0.0, 1.0); // Dark theme :)
    glClear(GL_COLOR_BUFFER_BIT);

    drawWorld();
    drawUi();

    glutSwapBuffers();
    glFlush();
}

void mouseEvent(int button, int state, int x, int y) {
    if(state == 0) {
        for(ui_button* b = buttons; b < buttons + sizeof buttons / sizeof(ui_button); b += 1) {
            if(ui_button_mouse_over(b, x, y) && b->onClick != NULL) {
                b->onClick();
                return;
            }
        }
    }
    for(ui_slider* s = sliders; s < sliders + sizeof sliders / sizeof(ui_slider); s += 1) {
        if(ui_slider_mouse_over(s, x, y)) {
            ui_slider_onclick(s, x, y, button, state);
        }
    }
}

void mouseWheelEvent(int wheel, int dir, int x, int y) {
    for(ui_slider* s = sliders; s < sliders + sizeof sliders / sizeof(ui_slider); s += 1) {
        if(ui_slider_mouse_over(s, x, y)) {
            s->value += dir * 0.05;
            if(s->value < 0.0) s->value = 0.0;
            if(s->value > 1.0) s->value = 1.0;
            printf("Updated %p value to %f\n", s, s->value);
        }
    }
    glutPostRedisplay();
}

void keyboardEvent(unsigned char c, int x, int y) {
    if(c == '\e') {
        glutLeaveMainLoop();
        exit(0);
    }
    if(c == 'a') {
        glutPostRedisplay();
    }
}

int main(int argc, char** argv) {
    /* initialize glut and window */
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(800, 500);
    glutInitWindowPosition(450, 450);
    /* create window and set callbacks */
    glutCreateWindow("World of Cow");
    glutDisplayFunc(display);
    glutMouseFunc(mouseEvent);
    glutKeyboardFunc(keyboardEvent);
    glutMouseWheelFunc(mouseWheelEvent);
    
    /* set projection and camera */
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, 800.0, 0.0, 500.0);
    
    glutMainLoop();
    
    return 0;
}