erc-c/src/vm_screen.c

/*
 * vm_screen.c
 *
 * Functions here support drawing to the virtual machine's "screen";
 * exactly how that is done is an abstraction to the rest of the
 * program, which only knows to call the functions here.
 */

#include <stdbool.h>
#include <stdlib.h>

#include "log.h"
#include "vm_screen.h"

/*
 * Something to help us remember if we've already initialized glew or
 * not.
 */
static bool init_glew = false;

/*
 * Initialize the glew library, if it is needed -- it may not be.
 */
static void
glew_init()
{
    if (!init_glew) {
        glewExperimental = GL_TRUE;
        glewInit();

        init_glew = true;
    }
}

int
vm_screen_init()
{
    if (!glfwInit()) {
        return ERR_GFXINIT;
    }

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

    return OK;
}

void
vm_screen_finish()
{
    glfwTerminate();
}

/*
 * Return a new screen. We also set the color to black.
 */
vm_screen *
vm_screen_create()
{
    vm_screen *screen;

    screen = (vm_screen *)malloc(sizeof(vm_screen));
    if (screen == NULL) {
        log_critical("Failed to allocate vm_screen");
        exit(1);
    }

    vm_screen_set_color(screen, 0, 0, 0, 0);
    return screen;
}

int
vm_screen_add_window(vm_screen *screen)
{
    screen->window = glfwCreateWindow(VM_SCREEN_DEFWIDTH, 
                                      VM_SCREEN_DEFHEIGHT,
                                      "erc", NULL, NULL);

    if (screen->window == NULL) {
        log_critical("Could not create a window");
        return ERR_GFXINIT;
    }

    glfwMakeContextCurrent(screen->window);

    // glew can only be initialized _after_ the window is built; if you
    // do so beforehand, you will be rudely presented with a segfault.
    glew_init();

    return OK;
}

/*
 * Free the contents of a screen.
 */
void
vm_screen_free(vm_screen *screen)
{
    free(screen);
}

bool
vm_screen_active(vm_screen *screen)
{
    return !glfwWindowShouldClose(screen->window);
}

void
vm_screen_refresh(vm_screen *screen)
{
    glClear(GL_COLOR_BUFFER_BIT);

    glfwSwapBuffers(screen->window);

    glfwPollEvents();
}

/*
 * Set the color of a screen screen to a given RGBA value.
 */
void
vm_screen_set_color(vm_screen *screen,
                    int red,
                    int green,
                    int blue,
                    int alpha)
{
    screen->color_red = red;
    screen->color_green = green;
    screen->color_blue = blue;
    screen->color_alpha = alpha;
}

/*
 * Draw a rectangle on the screen at a given x/y position, with a given
 * set of x/y dimensions, with a given screen.
 */
void
vm_screen_draw_rect(vm_screen *screen,
                    int xpos,
                    int ypos,
                    int xsize,
                    int ysize)
{
    // FIXME: NOOP
}