spacebox/src/Display.cpp

/*       /\         +--------------------------------------------------------------+ 
    ____/  \____   /| - zlib/MIT/Unlicenced game framework licensed to freely use, |
    \          /  / |   copy, and modify without restriction                       |
  +--\ ^__^   /--+  |                                                              |
  | ~/        \~ |  | - originally created at [http://nugget.fun]                  |
  | ~~~~~~~~~~~~ |  +--------------------------------------------------------------+
  | SPACE ~~~~~  | /
  |  ~~~~~~~ BOX |/
  +-------------*/

#include "Display.hpp"

/* Create a Display instance and subscribe to commands */
sb::Display::Display(Node* parent) : Node(parent)
{
    get_delegate().subscribe(&Display::respond, this);
}

/* Return the (x, y) size in pixels of the window as an integer vector */
glm::ivec2 sb::Display::window_size() const
{
    glm::ivec2 size;
    SDL_GetWindowSize(const_cast<SDL_Window*>(window()), &size.x, &size.y);
    return size;
}

/* Return the window dimensions in pixels as a Box object. If invert_y is set, the lower left will be (0, 0).
 * Otherwise, the top left will be (0, 0). Setting invert will cause the values to be compatible with
 * glViewport. */
Box sb::Display::window_box(bool invert_y) const
{
    return Box(glm::vec2(0, 0), window_size(), invert_y);
}

/* Return a box object with NDC coordinates of the window subsection. The subsection should be specified in
 * pixel coordinates. */
Box sb::Display::ndc_subsection(const Box& subsection) const
{
    Box ndc_subsection = ndc;
    Box window = window_box(subsection.inverted_y());
    ndc_subsection.move({(subsection.x - window.x) / window.width() * 2.0f, (subsection.y - window.y) / window.height() * 2.0f});
    ndc_subsection.size({subsection.width() / window.width() * 2.0f, subsection.height() / window.height() * 2.0f});
    return ndc_subsection;
}

/* Convert a NDC area of the screen to a box object containing measurements in pixels that are based on the
 * screen resolution. */
Box sb::Display::ndc_to_pixel(const Box& ndc) const
{
    Box pixel_subsection = window_box();
    /* The NDC size is double the ratio of the pixel size */
    pixel_subsection.size(0.5f * ndc.size() * window_box().size(), true);
    /* The NDC center is offset by double the ratio of the size of window in pixels, with the Y-axis inverted */
    pixel_subsection.move(glm::vec2({0.5f, -0.5f}) * ndc.center() * window_box().size());
    return pixel_subsection;
}

/* Get the pixel format of display at specified index (defaults to index 0) */
Uint32 sb::Display::pixel_format(int display_index) const
{
    SDL_DisplayMode display_mode;
    if (SDL_GetCurrentDisplayMode(display_index, &display_mode) != 0)
    {
        std::ostringstream message;
        message << "could not get display mode for index " << display_index;
        sb::Log::sdl_error(message.str());
        return SDL_PIXELFORMAT_UNKNOWN;
    }
    else
    {
        return display_mode.format;
    }
}

/* Fill the supplied, pre-allocated buffer with 32-bit pixels (8 bits per component) from the GL
 * read buffer if in GL context or from the SDL renderer if in SDL context */
void sb::Display::screen_pixels(unsigned char* pixels, int w, int h, int x, int y) const
{
    if (get_root()->is_gl_context)
    {
        GLenum format;
        if constexpr (SDL_BYTEORDER == SDL_BIG_ENDIAN)
        {
            format = GL_BGRA;
        }
        else
        {
            format = GL_RGBA;
        }
        glReadBuffer(GL_FRONT);
        glReadPixels(x, y, w, h, format, GL_UNSIGNED_BYTE, pixels);
        /* Debug statement showing the framebuffer status and first pixel read */
        std::ostringstream message;
        message << "read framebuffer status: " << glCheckFramebufferStatus(GL_READ_FRAMEBUFFER) <<
            ", draw framebuffer status: " << glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER) <<
            ", upper left screen pixel value read: " << pixels[0] << " " << pixels[1] << " " << pixels[2] << " " << pixels[3];
        sb::Log::log(message, sb::Log::DEBUG);
    }
    else
    {
        SDL_Renderer* renderer = const_cast<SDL_Renderer*>(get_renderer());
        SDL_SetRenderTarget(renderer, nullptr);
        SDL_RenderPresent(renderer);
        SDL_RenderReadPixels(renderer, nullptr, SDL_PIXELFORMAT_RGBA32, pixels, bpp / 8 * w);
    }
}

SDL_Surface* sb::Display::screen_surface() const
{
    glm::ivec2 size = window_size();
    unsigned char* pixels = new unsigned char[bpp / 8 * size.x * size.y];
    screen_pixels(pixels, size.x, size.y);
    SDL_Surface* surface = screen_surface_from_pixels(pixels, get_root()->is_gl_context);
    delete[] pixels;
    return surface;
}

SDL_Surface* sb::Display::screen_surface_from_pixels(unsigned char* pixels, bool flip) const
{
    glm::ivec2 size = window_size();
    SDL_Surface* surface;
    Uint32 rmask, gmask, bmask, amask;
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
    rmask = 0xff000000;
    gmask = 0x00ff0000;
    bmask = 0x0000ff00;
    amask = 0x000000ff;
#else
    rmask = 0x000000ff;
    gmask = 0x0000ff00;
    bmask = 0x00ff0000;
    amask = 0xff000000;
#endif
    if (flip)
    {
        SDL_Surface* pixel_surface = SDL_CreateRGBSurfaceFrom(
            pixels, size.x, size.y, bpp, bpp / 8 * size.x, rmask, gmask, bmask, amask);
        surface = zoomSurface(pixel_surface, 1, -1, SMOOTHING_OFF);
        SDL_FreeSurface(pixel_surface);
    }
    else
    {
        surface = SDL_CreateRGBSurface(0, size.x, size.y, bpp, rmask, gmask, bmask, amask);
        std::memcpy(surface->pixels, pixels, bpp / 8 * size.x * size.y);
    }
    return surface;
}

/* Handle fullscreen request */
void sb::Display::respond(SDL_Event& event)
{
    if (get_delegate().compare(event, "fullscreen"))
    {
        toggle_fullscreen();
    }
}

/* Use SDL window flags to determine if fullscreen is on or off and use SDL fullscreen
 * function to toggle the fullscreen state */
void sb::Display::toggle_fullscreen() const
{
    if (SDL_GetWindowFlags(const_cast<SDL_Window*>(window())) & SDL_WINDOW_FULLSCREEN)
    {
        sb::Log::log("fullscreen requested");
        SDL_SetWindowFullscreen(const_cast<SDL_Window*>(window()), 0);
    }
    else
    {
        sb::Log::log("exit fullscreen requested");
        SDL_SetWindowFullscreen(const_cast<SDL_Window*>(window()), SDL_WINDOW_FULLSCREEN);
    }
}