src/render/software/SDL_render_sw.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2016 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"

#if !SDL_RENDER_DISABLED

#include "../SDL_sysrender.h"
#include "SDL_render_sw_c.h"
#include "SDL_hints.h"

#include "SDL_draw.h"
#include "SDL_blendfillrect.h"
#include "SDL_blendline.h"
#include "SDL_blendpoint.h"
#include "SDL_drawline.h"
#include "SDL_drawpoint.h"
#include "SDL_rotate.h"

/* SDL surface based renderer implementation */

static SDL_Renderer *SW_CreateRenderer(SDL_Window * window, Uint32 flags);
static void SW_WindowEvent(SDL_Renderer * renderer,
                           const SDL_WindowEvent *event);
static int SW_GetOutputSize(SDL_Renderer * renderer, int *w, int *h);
static int SW_CreateTexture(SDL_Renderer * renderer, SDL_Texture * texture);
static int SW_SetTextureColorMod(SDL_Renderer * renderer,
                                 SDL_Texture * texture);
static int SW_SetTextureAlphaMod(SDL_Renderer * renderer,
                                 SDL_Texture * texture);
static int SW_SetTextureBlendMode(SDL_Renderer * renderer,
                                  SDL_Texture * texture);
static int SW_UpdateTexture(SDL_Renderer * renderer, SDL_Texture * texture,
                            const SDL_Rect * rect, const void *pixels,
                            int pitch);
static int SW_LockTexture(SDL_Renderer * renderer, SDL_Texture * texture,
                          const SDL_Rect * rect, void **pixels, int *pitch);
static void SW_UnlockTexture(SDL_Renderer * renderer, SDL_Texture * texture);
static int SW_SetRenderTarget(SDL_Renderer * renderer, SDL_Texture * texture);
static int SW_UpdateViewport(SDL_Renderer * renderer);
static int SW_UpdateClipRect(SDL_Renderer * renderer);
static int SW_RenderClear(SDL_Renderer * renderer);
static int SW_RenderDrawPoints(SDL_Renderer * renderer,
                               const SDL_FPoint * points, int count);
static int SW_RenderDrawLines(SDL_Renderer * renderer,
                              const SDL_FPoint * points, int count);
static int SW_RenderFillRects(SDL_Renderer * renderer,
                              const SDL_FRect * rects, int count);
static int SW_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
                         const SDL_Rect * srcrect, const SDL_FRect * dstrect);
static int SW_RenderCopyEx(SDL_Renderer * renderer, SDL_Texture * texture,
                          const SDL_Rect * srcrect, const SDL_FRect * dstrect,
                          const double angle, const SDL_FPoint * center, const SDL_RendererFlip flip);
static int SW_RenderReadPixels(SDL_Renderer * renderer, const SDL_Rect * rect,
                               Uint32 format, void * pixels, int pitch);
static void SW_RenderPresent(SDL_Renderer * renderer);
static void SW_DestroyTexture(SDL_Renderer * renderer, SDL_Texture * texture);
static void SW_DestroyRenderer(SDL_Renderer * renderer);


SDL_RenderDriver SW_RenderDriver = {
    SW_CreateRenderer,
    {
     "software",
     SDL_RENDERER_SOFTWARE | SDL_RENDERER_TARGETTEXTURE,
     8,
     {
      SDL_PIXELFORMAT_ARGB8888,
      SDL_PIXELFORMAT_ABGR8888,
      SDL_PIXELFORMAT_RGBA8888,
      SDL_PIXELFORMAT_BGRA8888,
      SDL_PIXELFORMAT_RGB888,
      SDL_PIXELFORMAT_BGR888,
      SDL_PIXELFORMAT_RGB565,
      SDL_PIXELFORMAT_RGB555
     },
     0,
     0}
};

typedef struct
{
    SDL_Surface *surface;
    SDL_Surface *window;
} SW_RenderData;


static SDL_Surface *
SW_ActivateRenderer(SDL_Renderer * renderer)
{
    SW_RenderData *data = (SW_RenderData *) renderer->driverdata;

    if (!data->surface) {
        data->surface = data->window;
    }
    if (!data->surface) {
        SDL_Surface *surface = SDL_GetWindowSurface(renderer->window);
        if (surface) {
            data->surface = data->window = surface;

            SW_UpdateViewport(renderer);
            SW_UpdateClipRect(renderer);
        }
    }
    return data->surface;
}

SDL_Renderer *
SW_CreateRendererForSurface(SDL_Surface * surface)
{
    SDL_Renderer *renderer;
    SW_RenderData *data;

    if (!surface) {
        SDL_SetError("Can't create renderer for NULL surface");
        return NULL;
    }

    renderer = (SDL_Renderer *) SDL_calloc(1, sizeof(*renderer));
    if (!renderer) {
        SDL_OutOfMemory();
        return NULL;
    }

    data = (SW_RenderData *) SDL_calloc(1, sizeof(*data));
    if (!data) {
        SW_DestroyRenderer(renderer);
        SDL_OutOfMemory();
        return NULL;
    }
    data->surface = surface;
    data->window = surface;

    renderer->WindowEvent = SW_WindowEvent;
    renderer->GetOutputSize = SW_GetOutputSize;
    renderer->CreateTexture = SW_CreateTexture;
    renderer->SetTextureColorMod = SW_SetTextureColorMod;
    renderer->SetTextureAlphaMod = SW_SetTextureAlphaMod;
    renderer->SetTextureBlendMode = SW_SetTextureBlendMode;
    renderer->UpdateTexture = SW_UpdateTexture;
    renderer->LockTexture = SW_LockTexture;
    renderer->UnlockTexture = SW_UnlockTexture;
    renderer->SetRenderTarget = SW_SetRenderTarget;
    renderer->UpdateViewport = SW_UpdateViewport;
    renderer->UpdateClipRect = SW_UpdateClipRect;
    renderer->RenderClear = SW_RenderClear;
    renderer->RenderDrawPoints = SW_RenderDrawPoints;
    renderer->RenderDrawLines = SW_RenderDrawLines;
    renderer->RenderFillRects = SW_RenderFillRects;
    renderer->RenderCopy = SW_RenderCopy;
    renderer->RenderCopyEx = SW_RenderCopyEx;
    renderer->RenderReadPixels = SW_RenderReadPixels;
    renderer->RenderPresent = SW_RenderPresent;
    renderer->DestroyTexture = SW_DestroyTexture;
    renderer->DestroyRenderer = SW_DestroyRenderer;
    renderer->info = SW_RenderDriver.info;
    renderer->driverdata = data;

    SW_ActivateRenderer(renderer);

    return renderer;
}

SDL_Renderer *
SW_CreateRenderer(SDL_Window * window, Uint32 flags)
{
    SDL_Surface *surface;

    surface = SDL_GetWindowSurface(window);
    if (!surface) {
        return NULL;
    }
    return SW_CreateRendererForSurface(surface);
}

static void
SW_WindowEvent(SDL_Renderer * renderer, const SDL_WindowEvent *event)
{
    SW_RenderData *data = (SW_RenderData *) renderer->driverdata;

    if (event->event == SDL_WINDOWEVENT_SIZE_CHANGED) {
        data->surface = NULL;
        data->window = NULL;
    }
}

static int
SW_GetOutputSize(SDL_Renderer * renderer, int *w, int *h)
{
    SDL_Surface *surface = SW_ActivateRenderer(renderer);

    if (surface) {
        if (w) {
            *w = surface->w;
        }
        if (h) {
            *h = surface->h;
        }
        return 0;
    } else {
        SDL_SetError("Software renderer doesn't have an output surface");
        return -1;
    }
}

static int
SW_CreateTexture(SDL_Renderer * renderer, SDL_Texture * texture)
{
    int bpp;
    Uint32 Rmask, Gmask, Bmask, Amask;

    if (!SDL_PixelFormatEnumToMasks
        (texture->format, &bpp, &Rmask, &Gmask, &Bmask, &Amask)) {
        return SDL_SetError("Unknown texture format");
    }

    texture->driverdata =
        SDL_CreateRGBSurface(0, texture->w, texture->h, bpp, Rmask, Gmask,
                             Bmask, Amask);
    SDL_SetSurfaceColorMod(texture->driverdata, texture->r, texture->g,
                           texture->b);
    SDL_SetSurfaceAlphaMod(texture->driverdata, texture->a);
    SDL_SetSurfaceBlendMode(texture->driverdata, texture->blendMode);

    if (texture->access == SDL_TEXTUREACCESS_STATIC) {
        SDL_SetSurfaceRLE(texture->driverdata, 1);
    }

    if (!texture->driverdata) {
        return -1;
    }
    return 0;
}

static int
SW_SetTextureColorMod(SDL_Renderer * renderer, SDL_Texture * texture)
{
    SDL_Surface *surface = (SDL_Surface *) texture->driverdata;
    /* If the color mod is ever enabled (non-white), permanently disable RLE (which doesn't support
     * color mod) to avoid potentially frequent RLE encoding/decoding.
     */
    if ((texture->r & texture->g & texture->b) != 255) {
        SDL_SetSurfaceRLE(surface, 0);
    }
    return SDL_SetSurfaceColorMod(surface, texture->r, texture->g,
                                  texture->b);
}

static int
SW_SetTextureAlphaMod(SDL_Renderer * renderer, SDL_Texture * texture)
{
    SDL_Surface *surface = (SDL_Surface *) texture->driverdata;
    /* If the texture ever has multiple alpha values (surface alpha plus alpha channel), permanently
     * disable RLE (which doesn't support this) to avoid potentially frequent RLE encoding/decoding.
     */
    if (texture->a != 255 && surface->format->Amask) {
        SDL_SetSurfaceRLE(surface, 0);
    }
    return SDL_SetSurfaceAlphaMod(surface, texture->a);
}

static int
SW_SetTextureBlendMode(SDL_Renderer * renderer, SDL_Texture * texture)
{
    SDL_Surface *surface = (SDL_Surface *) texture->driverdata;
    /* If add or mod blending are ever enabled, permanently disable RLE (which doesn't support
     * them) to avoid potentially frequent RLE encoding/decoding.
     */
    if ((texture->blendMode == SDL_BLENDMODE_ADD || texture->blendMode == SDL_BLENDMODE_MOD)) {
        SDL_SetSurfaceRLE(surface, 0);
    }
    return SDL_SetSurfaceBlendMode(surface, texture->blendMode);
}

static int
SW_UpdateTexture(SDL_Renderer * renderer, SDL_Texture * texture,
                 const SDL_Rect * rect, const void *pixels, int pitch)
{
    SDL_Surface *surface = (SDL_Surface *) texture->driverdata;
    Uint8 *src, *dst;
    int row;
    size_t length;

    if(SDL_MUSTLOCK(surface))
        SDL_LockSurface(surface);
    src = (Uint8 *) pixels;
    dst = (Uint8 *) surface->pixels +
                        rect->y * surface->pitch +
                        rect->x * surface->format->BytesPerPixel;
    length = rect->w * surface->format->BytesPerPixel;
    for (row = 0; row < rect->h; ++row) {
        SDL_memcpy(dst, src, length);
        src += pitch;
        dst += surface->pitch;
    }
    if(SDL_MUSTLOCK(surface))
        SDL_UnlockSurface(surface);
    return 0;
}

static int
SW_LockTexture(SDL_Renderer * renderer, SDL_Texture * texture,
               const SDL_Rect * rect, void **pixels, int *pitch)
{
    SDL_Surface *surface = (SDL_Surface *) texture->driverdata;

    *pixels =
        (void *) ((Uint8 *) surface->pixels + rect->y * surface->pitch +
                  rect->x * surface->format->BytesPerPixel);
    *pitch = surface->pitch;
    return 0;
}

static void
SW_UnlockTexture(SDL_Renderer * renderer, SDL_Texture * texture)
{
}

static int
SW_SetRenderTarget(SDL_Renderer * renderer, SDL_Texture * texture)
{
    SW_RenderData *data = (SW_RenderData *) renderer->driverdata;

    if (texture ) {
        data->surface = (SDL_Surface *) texture->driverdata;
    } else {
        data->surface = data->window;
    }
    return 0;
}

static int
SW_UpdateViewport(SDL_Renderer * renderer)
{
    SW_RenderData *data = (SW_RenderData *) renderer->driverdata;
    SDL_Surface *surface = data->surface;

    if (!surface) {
        /* We'll update the viewport after we recreate the surface */
        return 0;
    }

    SDL_SetClipRect(data->surface, &renderer->viewport);
    return 0;
}

static int
SW_UpdateClipRect(SDL_Renderer * renderer)
{
    SW_RenderData *data = (SW_RenderData *) renderer->driverdata;
    SDL_Surface *surface = data->surface;
    if (surface) {
        if (renderer->clipping_enabled) {
            SDL_SetClipRect(surface, &renderer->clip_rect);
        } else {
            SDL_SetClipRect(surface, NULL);
        }
    }
    return 0;
}

static int
SW_RenderClear(SDL_Renderer * renderer)
{
    SDL_Surface *surface = SW_ActivateRenderer(renderer);
    Uint32 color;
    SDL_Rect clip_rect;

    if (!surface) {
        return -1;
    }

    color = SDL_MapRGBA(surface->format,
                        renderer->r, renderer->g, renderer->b, renderer->a);

    /* By definition the clear ignores the clip rect */
    clip_rect = surface->clip_rect;
    SDL_SetClipRect(surface, NULL);
    SDL_FillRect(surface, NULL, color);
    SDL_SetClipRect(surface, &clip_rect);
    return 0;
}

static int
SW_RenderDrawPoints(SDL_Renderer * renderer, const SDL_FPoint * points,
                    int count)
{
    SDL_Surface *surface = SW_ActivateRenderer(renderer);
    SDL_Point *final_points;
    int i, status;

    if (!surface) {
        return -1;
    }

    final_points = SDL_stack_alloc(SDL_Point, count);
    if (!final_points) {
        return SDL_OutOfMemory();
    }
    if (renderer->viewport.x || renderer->viewport.y) {
        int x = renderer->viewport.x;
        int y = renderer->viewport.y;

        for (i = 0; i < count; ++i) {
            final_points[i].x = (int)(x + points[i].x);
            final_points[i].y = (int)(y + points[i].y);
        }
    } else {
        for (i = 0; i < count; ++i) {
            final_points[i].x = (int)points[i].x;
            final_points[i].y = (int)points[i].y;
        }
    }

    /* Draw the points! */
    if (renderer->blendMode == SDL_BLENDMODE_NONE) {
        Uint32 color = SDL_MapRGBA(surface->format,
                                   renderer->r, renderer->g, renderer->b,
                                   renderer->a);

        status = SDL_DrawPoints(surface, final_points, count, color);
    } else {
        status = SDL_BlendPoints(surface, final_points, count,
                                renderer->blendMode,
                                renderer->r, renderer->g, renderer->b,
                                renderer->a);
    }
    SDL_stack_free(final_points);

    return status;
}

static int
SW_RenderDrawLines(SDL_Renderer * renderer, const SDL_FPoint * points,
                   int count)
{
    SDL_Surface *surface = SW_ActivateRenderer(renderer);
    SDL_Point *final_points;
    int i, status;

    if (!surface) {
        return -1;
    }

    final_points = SDL_stack_alloc(SDL_Point, count);
    if (!final_points) {
        return SDL_OutOfMemory();
    }
    if (renderer->viewport.x || renderer->viewport.y) {
        int x = renderer->viewport.x;
        int y = renderer->viewport.y;

        for (i = 0; i < count; ++i) {
            final_points[i].x = (int)(x + points[i].x);
            final_points[i].y = (int)(y + points[i].y);
        }
    } else {
        for (i = 0; i < count; ++i) {
            final_points[i].x = (int)points[i].x;
            final_points[i].y = (int)points[i].y;
        }
    }

    /* Draw the lines! */
    if (renderer->blendMode == SDL_BLENDMODE_NONE) {
        Uint32 color = SDL_MapRGBA(surface->format,
                                   renderer->r, renderer->g, renderer->b,
                                   renderer->a);

        status = SDL_DrawLines(surface, final_points, count, color);
    } else {
        status = SDL_BlendLines(surface, final_points, count,
                                renderer->blendMode,
                                renderer->r, renderer->g, renderer->b,
                                renderer->a);
    }
    SDL_stack_free(final_points);

    return status;
}

static int
SW_RenderFillRects(SDL_Renderer * renderer, const SDL_FRect * rects, int count)
{
    SDL_Surface *surface = SW_ActivateRenderer(renderer);
    SDL_Rect *final_rects;
    int i, status;

    if (!surface) {
        return -1;
    }

    final_rects = SDL_stack_alloc(SDL_Rect, count);
    if (!final_rects) {
        return SDL_OutOfMemory();
    }
    if (renderer->viewport.x || renderer->viewport.y) {
        int x = renderer->viewport.x;
        int y = renderer->viewport.y;

        for (i = 0; i < count; ++i) {
            final_rects[i].x = (int)(x + rects[i].x);
            final_rects[i].y = (int)(y + rects[i].y);
            final_rects[i].w = SDL_max((int)rects[i].w, 1);
            final_rects[i].h = SDL_max((int)rects[i].h, 1);
        }
    } else {
        for (i = 0; i < count; ++i) {
            final_rects[i].x = (int)rects[i].x;
            final_rects[i].y = (int)rects[i].y;
            final_rects[i].w = SDL_max((int)rects[i].w, 1);
            final_rects[i].h = SDL_max((int)rects[i].h, 1);
        }
    }

    if (renderer->blendMode == SDL_BLENDMODE_NONE) {
        Uint32 color = SDL_MapRGBA(surface->format,
                                   renderer->r, renderer->g, renderer->b,
                                   renderer->a);
        status = SDL_FillRects(surface, final_rects, count, color);
    } else {
        status = SDL_BlendFillRects(surface, final_rects, count,
                                    renderer->blendMode,
                                    renderer->r, renderer->g, renderer->b,
                                    renderer->a);
    }
    SDL_stack_free(final_rects);

    return status;
}

static int
SW_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
              const SDL_Rect * srcrect, const SDL_FRect * dstrect)
{
    SDL_Surface *surface = SW_ActivateRenderer(renderer);
    SDL_Surface *src = (SDL_Surface *) texture->driverdata;
    SDL_Rect final_rect;

    if (!surface) {
        return -1;
    }

    if (renderer->viewport.x || renderer->viewport.y) {
        final_rect.x = (int)(renderer->viewport.x + dstrect->x);
        final_rect.y = (int)(renderer->viewport.y + dstrect->y);
    } else {
        final_rect.x = (int)dstrect->x;
        final_rect.y = (int)dstrect->y;
    }
    final_rect.w = (int)dstrect->w;
    final_rect.h = (int)dstrect->h;

    if ( srcrect->w == final_rect.w && srcrect->h == final_rect.h ) {
        return SDL_BlitSurface(src, srcrect, surface, &final_rect);
    } else {
        /* If scaling is ever done, permanently disable RLE (which doesn't support scaling)
         * to avoid potentially frequent RLE encoding/decoding.
         */
        SDL_SetSurfaceRLE(surface, 0);
        return SDL_BlitScaled(src, srcrect, surface, &final_rect);
    }
}

static int
GetScaleQuality(void)
{
    const char *hint = SDL_GetHint(SDL_HINT_RENDER_SCALE_QUALITY);

    if (!hint || *hint == '0' || SDL_strcasecmp(hint, "nearest") == 0) {
        return 0;
    } else {
        return 1;
    }
}

static int
SW_RenderCopyEx(SDL_Renderer * renderer, SDL_Texture * texture,
                const SDL_Rect * srcrect, const SDL_FRect * dstrect,
                const double angle, const SDL_FPoint * center, const SDL_RendererFlip flip)
{
    SDL_Surface *surface = SW_ActivateRenderer(renderer);
    SDL_Surface *src = (SDL_Surface *) texture->driverdata;
    SDL_Rect final_rect, tmp_rect;
    SDL_Surface *surface_rotated, *surface_scaled;
    int retval, dstwidth, dstheight, abscenterx, abscentery;
    double cangle, sangle, px, py, p1x, p1y, p2x, p2y, p3x, p3y, p4x, p4y;

    if (!surface) {
        return -1;
    }

    if (renderer->viewport.x || renderer->viewport.y) {
        final_rect.x = (int)(renderer->viewport.x + dstrect->x);
        final_rect.y = (int)(renderer->viewport.y + dstrect->y);
    } else {
        final_rect.x = (int)dstrect->x;
        final_rect.y = (int)dstrect->y;
    }
    final_rect.w = (int)dstrect->w;
    final_rect.h = (int)dstrect->h;

    /* SDLgfx_rotateSurface doesn't accept a source rectangle, so crop and scale if we need to */
    tmp_rect = final_rect;
    tmp_rect.x = 0;
    tmp_rect.y = 0;
    if (srcrect->w == final_rect.w && srcrect->h == final_rect.h && srcrect->x == 0 && srcrect->y == 0) {
        surface_scaled = src; /* but if we don't need to, just use the original */
        retval = 0;
    } else {
        SDL_Surface *blit_src = src;
        Uint32 colorkey;
        SDL_BlendMode blendMode;
        Uint8 alphaMod, r, g, b;
        SDL_bool cloneSource = SDL_FALSE;

        surface_scaled = SDL_CreateRGBSurface(SDL_SWSURFACE, final_rect.w, final_rect.h, src->format->BitsPerPixel,
                                              src->format->Rmask, src->format->Gmask,
                                              src->format->Bmask, src->format->Amask );
        if (!surface_scaled) {
            return -1;
        }

        /* copy the color key, alpha mod, blend mode, and color mod so the scaled surface behaves like the source */
        if (SDL_GetColorKey(src, &colorkey) == 0) {
            SDL_SetColorKey(surface_scaled, SDL_TRUE, colorkey);
            cloneSource = SDL_TRUE;
        }
        SDL_GetSurfaceAlphaMod(src, &alphaMod); /* these will be copied to surface_scaled below if necessary */
        SDL_GetSurfaceBlendMode(src, &blendMode);
        SDL_GetSurfaceColorMod(src, &r, &g, &b);

        /* now we need to blit the src into surface_scaled. since we want to copy the colors from the source to
         * surface_scaled rather than blend them, etc. we'll need to disable the blend mode, alpha mod, etc.
         * but we don't want to modify src (in case it's being used on other threads), so we'll need to clone it
         * before changing the blend options
         */
        cloneSource |= blendMode != SDL_BLENDMODE_NONE || (alphaMod & r & g & b) != 255;
        if (cloneSource) {
            blit_src = SDL_ConvertSurface(src, src->format, src->flags); /* clone src */
            if (!blit_src) {
                SDL_FreeSurface(surface_scaled);
                return -1;
            }
            SDL_SetSurfaceAlphaMod(blit_src, 255); /* disable all blending options in blit_src */
            SDL_SetSurfaceBlendMode(blit_src, SDL_BLENDMODE_NONE);
            SDL_SetColorKey(blit_src, 0, 0);
            SDL_SetSurfaceColorMod(blit_src, 255, 255, 255);
            SDL_SetSurfaceRLE(blit_src, 0); /* don't RLE encode a surface we'll only use once */

            SDL_SetSurfaceAlphaMod(surface_scaled, alphaMod); /* copy blending options to surface_scaled */
            SDL_SetSurfaceBlendMode(surface_scaled, blendMode);
            SDL_SetSurfaceColorMod(surface_scaled, r, g, b);
        }

        retval = SDL_BlitScaled(blit_src, srcrect, surface_scaled, &tmp_rect);
        if (blit_src != src) {
            SDL_FreeSurface(blit_src);
        }
    }

    if (!retval) {
        SDLgfx_rotozoomSurfaceSizeTrig(tmp_rect.w, tmp_rect.h, -angle, &dstwidth, &dstheight, &cangle, &sangle);
        surface_rotated = SDLgfx_rotateSurface(surface_scaled, -angle, dstwidth/2, dstheight/2, GetScaleQuality(), flip & SDL_FLIP_HORIZONTAL, flip & SDL_FLIP_VERTICAL, dstwidth, dstheight, cangle, sangle);
        if(surface_rotated) {
            /* Find out where the new origin is by rotating the four final_rect points around the center and then taking the extremes */
            abscenterx = final_rect.x + (int)center->x;
            abscentery = final_rect.y + (int)center->y;
            /* Compensate the angle inversion to match the behaviour of the other backends */
            sangle = -sangle;

            /* Top Left */
            px = final_rect.x - abscenterx;
            py = final_rect.y - abscentery;
            p1x = px * cangle - py * sangle + abscenterx;
            p1y = px * sangle + py * cangle + abscentery;

            /* Top Right */
            px = final_rect.x + final_rect.w - abscenterx;
            py = final_rect.y - abscentery;
            p2x = px * cangle - py * sangle + abscenterx;
            p2y = px * sangle + py * cangle + abscentery;

            /* Bottom Left */
            px = final_rect.x - abscenterx;
            py = final_rect.y + final_rect.h - abscentery;
            p3x = px * cangle - py * sangle + abscenterx;
            p3y = px * sangle + py * cangle + abscentery;

            /* Bottom Right */
            px = final_rect.x + final_rect.w - abscenterx;
            py = final_rect.y + final_rect.h - abscentery;
            p4x = px * cangle - py * sangle + abscenterx;
            p4y = px * sangle + py * cangle + abscentery;

            tmp_rect.x = (int)MIN(MIN(p1x, p2x), MIN(p3x, p4x));
            tmp_rect.y = (int)MIN(MIN(p1y, p2y), MIN(p3y, p4y));
            tmp_rect.w = dstwidth;
            tmp_rect.h = dstheight;

            retval = SDL_BlitSurface(surface_rotated, NULL, surface, &tmp_rect);
            SDL_FreeSurface(surface_rotated);
        }
    }

    if (surface_scaled != src) {
        SDL_FreeSurface(surface_scaled);
    }
    return retval;
}

static int
SW_RenderReadPixels(SDL_Renderer * renderer, const SDL_Rect * rect,
                    Uint32 format, void * pixels, int pitch)
{
    SDL_Surface *surface = SW_ActivateRenderer(renderer);
    Uint32 src_format;
    void *src_pixels;
    SDL_Rect final_rect;

    if (!surface) {
        return -1;
    }

    if (renderer->viewport.x || renderer->viewport.y) {
        final_rect.x = renderer->viewport.x + rect->x;
        final_rect.y = renderer->viewport.y + rect->y;
        final_rect.w = rect->w;
        final_rect.h = rect->h;
        rect = &final_rect;
    }

    if (rect->x < 0 || rect->x+rect->w > surface->w ||
        rect->y < 0 || rect->y+rect->h > surface->h) {
        return SDL_SetError("Tried to read outside of surface bounds");
    }

    src_format = surface->format->format;
    src_pixels = (void*)((Uint8 *) surface->pixels +
                    rect->y * surface->pitch +
                    rect->x * surface->format->BytesPerPixel);

    return SDL_ConvertPixels(rect->w, rect->h,
                             src_format, src_pixels, surface->pitch,
                             format, pixels, pitch);
}

static void
SW_RenderPresent(SDL_Renderer * renderer)
{
    SDL_Window *window = renderer->window;

    if (window) {
        SDL_UpdateWindowSurface(window);
    }
}

static void
SW_DestroyTexture(SDL_Renderer * renderer, SDL_Texture * texture)
{
    SDL_Surface *surface = (SDL_Surface *) texture->driverdata;

    SDL_FreeSurface(surface);
}

static void
SW_DestroyRenderer(SDL_Renderer * renderer)
{
    SW_RenderData *data = (SW_RenderData *) renderer->driverdata;

    SDL_free(data);
    SDL_free(renderer);
}

#endif /* !SDL_RENDER_DISABLED */

/* vi: set ts=4 sw=4 expandtab: */