SDL/src/video/offscreen/SDL_offscreenvideo.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "SDL_internal.h"

#ifdef SDL_VIDEO_DRIVER_OFFSCREEN

/* Offscreen video driver is similar to dummy driver, however its purpose
 * is enabling applications to use some of the SDL video functionality
 * (notably context creation) while not requiring a display output.
 *
 * An example would be running a graphical program on a headless box
 * for automated testing.
 */

#include "SDL_offscreenvideo.h"
#include "SDL_offscreenevents_c.h"
#include "SDL_offscreenframebuffer_c.h"
#include "SDL_offscreenopengles.h"
#include "SDL_offscreenvulkan.h"
#include "SDL_offscreenwindow.h"

#define OFFSCREENVID_DRIVER_NAME "offscreen"

// Initialization/Query functions
static bool OFFSCREEN_VideoInit(SDL_VideoDevice *_this);
static bool OFFSCREEN_SetDisplayMode(SDL_VideoDevice *_this, SDL_VideoDisplay *display, SDL_DisplayMode *mode);
static void OFFSCREEN_VideoQuit(SDL_VideoDevice *_this);

// OFFSCREEN driver bootstrap functions

static void OFFSCREEN_DeleteDevice(SDL_VideoDevice *device)
{
    SDL_free(device);
}

static bool OFFSCREEN_Available(const char *drivername)
{
    const char *hint = SDL_GetHint(SDL_HINT_VIDEO_DRIVER);
    if (hint && SDL_strstr(hint, drivername) != NULL) {
        return true;
    }
    return false;
}

static SDL_VideoDevice *OFFSCREEN_CreateDevice(void)
{
    SDL_VideoDevice *device;

    if (!OFFSCREEN_Available(OFFSCREENVID_DRIVER_NAME)) {
        return NULL;
    }

    // Initialize all variables that we clean on shutdown
    device = (SDL_VideoDevice *)SDL_calloc(1, sizeof(SDL_VideoDevice));
    if (!device) {
        return NULL;
    }

    // General video
    device->VideoInit = OFFSCREEN_VideoInit;
    device->VideoQuit = OFFSCREEN_VideoQuit;
    device->SetDisplayMode = OFFSCREEN_SetDisplayMode;
    device->PumpEvents = OFFSCREEN_PumpEvents;
    device->CreateWindowFramebuffer = SDL_OFFSCREEN_CreateWindowFramebuffer;
    device->UpdateWindowFramebuffer = SDL_OFFSCREEN_UpdateWindowFramebuffer;
    device->DestroyWindowFramebuffer = SDL_OFFSCREEN_DestroyWindowFramebuffer;
    device->free = OFFSCREEN_DeleteDevice;

#ifdef SDL_VIDEO_OPENGL_EGL
    // GL context
    device->GL_SwapWindow = OFFSCREEN_GLES_SwapWindow;
    device->GL_MakeCurrent = OFFSCREEN_GLES_MakeCurrent;
    device->GL_CreateContext = OFFSCREEN_GLES_CreateContext;
    device->GL_DestroyContext = OFFSCREEN_GLES_DestroyContext;
    device->GL_LoadLibrary = OFFSCREEN_GLES_LoadLibrary;
    device->GL_UnloadLibrary = OFFSCREEN_GLES_UnloadLibrary;
    device->GL_GetProcAddress = OFFSCREEN_GLES_GetProcAddress;
    device->GL_GetSwapInterval = OFFSCREEN_GLES_GetSwapInterval;
    device->GL_SetSwapInterval = OFFSCREEN_GLES_SetSwapInterval;
#endif

#ifdef SDL_VIDEO_VULKAN
    device->Vulkan_LoadLibrary = OFFSCREEN_Vulkan_LoadLibrary;
    device->Vulkan_UnloadLibrary = OFFSCREEN_Vulkan_UnloadLibrary;
    device->Vulkan_GetInstanceExtensions = OFFSCREEN_Vulkan_GetInstanceExtensions;
    device->Vulkan_CreateSurface = OFFSCREEN_Vulkan_CreateSurface;
    device->Vulkan_DestroySurface = OFFSCREEN_Vulkan_DestroySurface;
#endif

    // "Window"
    device->CreateSDLWindow = OFFSCREEN_CreateWindow;
    device->DestroyWindow = OFFSCREEN_DestroyWindow;
    device->SetWindowSize = OFFSCREEN_SetWindowSize;

    return device;
}

VideoBootStrap OFFSCREEN_bootstrap = {
    OFFSCREENVID_DRIVER_NAME, "SDL offscreen video driver",
    OFFSCREEN_CreateDevice,
    NULL, // no ShowMessageBox implementation
    false
};

static bool OFFSCREEN_VideoInit(SDL_VideoDevice *_this)
{
    SDL_DisplayMode mode;

    // Use a fake 32-bpp desktop mode
    SDL_zero(mode);
    mode.format = SDL_PIXELFORMAT_XRGB8888;
    mode.w = 1024;
    mode.h = 768;
    if (SDL_AddBasicVideoDisplay(&mode) == 0) {
        return false;
    }

    // We're done!
    return true;
}

static bool OFFSCREEN_SetDisplayMode(SDL_VideoDevice *_this, SDL_VideoDisplay *display, SDL_DisplayMode *mode)
{
    return true;
}

void OFFSCREEN_VideoQuit(SDL_VideoDevice *_this)
{
}

#endif // SDL_VIDEO_DRIVER_OFFSCREEN