SDL-mirror/src/render/software/SDL_drawline.c

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2010 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

#include "SDL_draw.h"
#include "SDL_drawline.h"
#include "SDL_drawpoint.h"


static void
SDL_DrawLine1(SDL_Surface * dst, int x1, int y1, int x2, int y2, Uint32 color,
              SDL_bool draw_end)
{
    if (y1 == y2) {
        //HLINE(Uint8, DRAW_FASTSETPIXEL1, draw_end);
        int length;
        int pitch = (dst->pitch / dst->format->BytesPerPixel);
        Uint8 *pixel;
        if (x1 <= x2) {
            pixel = (Uint8 *)dst->pixels + y1 * pitch + x1;
            length = draw_end ? (x2-x1+1) : (x2-x1);
        } else {
            pixel = (Uint8 *)dst->pixels + y1 * pitch + x2;
            if (!draw_end) {
                ++pixel;
            }
            length = draw_end ? (x1-x2+1) : (x1-x2);
        }
        SDL_memset(pixel, color, length);
    } else if (x1 == x2) {
        VLINE(Uint8, DRAW_FASTSETPIXEL1, draw_end);
    } else if (ABS(x1 - x2) == ABS(y1 - y2)) {
        DLINE(Uint8, DRAW_FASTSETPIXEL1, draw_end);
    } else {
        BLINE(x1, y1, x2, y2, DRAW_FASTSETPIXELXY1, draw_end);
    }
}

static void
SDL_DrawLine2(SDL_Surface * dst, int x1, int y1, int x2, int y2, Uint32 color,
              SDL_bool draw_end)
{
    if (y1 == y2) {
        HLINE(Uint16, DRAW_FASTSETPIXEL2, draw_end);
    } else if (x1 == x2) {
        VLINE(Uint16, DRAW_FASTSETPIXEL2, draw_end);
    } else if (ABS(x1 - x2) == ABS(y1 - y2)) {
        DLINE(Uint16, DRAW_FASTSETPIXEL2, draw_end);
    } else {
        Uint8 _r, _g, _b, _a;
        const SDL_PixelFormat * fmt = dst->format;
        SDL_GetRGBA(color, fmt, &_r, &_g, &_b, &_a);
        if (fmt->Rmask == 0x7C00) {
            AALINE(x1, y1, x2, y2,
                   DRAW_FASTSETPIXELXY2, DRAW_SETPIXELXY_BLEND_RGB555,
                   draw_end);
        } else if (fmt->Rmask == 0xF800) {
            AALINE(x1, y1, x2, y2,
                   DRAW_FASTSETPIXELXY2, DRAW_SETPIXELXY_BLEND_RGB565,
                   draw_end);
        } else {
            AALINE(x1, y1, x2, y2,
                   DRAW_FASTSETPIXELXY2, DRAW_SETPIXELXY2_BLEND_RGB,
                   draw_end);
        }
    }
}

static void
SDL_DrawLine4(SDL_Surface * dst, int x1, int y1, int x2, int y2, Uint32 color,
              SDL_bool draw_end)
{
    if (y1 == y2) {
        HLINE(Uint32, DRAW_FASTSETPIXEL4, draw_end);
    } else if (x1 == x2) {
        VLINE(Uint32, DRAW_FASTSETPIXEL4, draw_end);
    } else if (ABS(x1 - x2) == ABS(y1 - y2)) {
        DLINE(Uint32, DRAW_FASTSETPIXEL4, draw_end);
    } else {
        Uint8 _r, _g, _b, _a;
        const SDL_PixelFormat * fmt = dst->format;
        SDL_GetRGBA(color, fmt, &_r, &_g, &_b, &_a);
        if (fmt->Rmask == 0x00FF0000) {
            if (!fmt->Amask) {
                AALINE(x1, y1, x2, y2,
                       DRAW_FASTSETPIXELXY4, DRAW_SETPIXELXY_BLEND_RGB888,
                       draw_end);
            } else {
                AALINE(x1, y1, x2, y2,
                       DRAW_FASTSETPIXELXY4, DRAW_SETPIXELXY_BLEND_ARGB8888,
                       draw_end);
            }
        } else {
            AALINE(x1, y1, x2, y2,
                   DRAW_FASTSETPIXELXY4, DRAW_SETPIXELXY4_BLEND_RGB,
                   draw_end);
        }
    }
}

typedef void (*DrawLineFunc) (SDL_Surface * dst,
                              int x1, int y1, int x2, int y2,
                              Uint32 color, SDL_bool draw_end);

static DrawLineFunc
SDL_CalculateDrawLineFunc(const SDL_PixelFormat * fmt)
{
    switch (fmt->BytesPerPixel) {
    case 1:
        if (fmt->BitsPerPixel < 8) {
            break;
        }
        return SDL_DrawLine1;
    case 2:
        return SDL_DrawLine2;
    case 4:
        return SDL_DrawLine4;
    }
    return NULL;
}

int
SDL_DrawLine(SDL_Surface * dst, int x1, int y1, int x2, int y2, Uint32 color)
{
    DrawLineFunc func;

    if (!dst) {
        SDL_SetError("SDL_DrawLine(): Passed NULL destination surface");
        return -1;
    }

    func = SDL_CalculateDrawLineFunc(dst->format);
    if (!func) {
        SDL_SetError("SDL_DrawLine(): Unsupported surface format");
        return -1;
    }

    /* Perform clipping */
    /* FIXME: We don't actually want to clip, as it may change line slope */
    if (!SDL_IntersectRectAndLine(&dst->clip_rect, &x1, &y1, &x2, &y2)) {
        return 0;
    }

    func(dst, x1, y1, x2, y2, color, SDL_TRUE);
    return 0;
}

int
SDL_DrawLines(SDL_Surface * dst, const SDL_Point * points, int count,
              Uint32 color)
{
    int i;
    int x1, y1;
    int x2, y2;
    SDL_bool draw_end;
    DrawLineFunc func;

    if (!dst) {
        SDL_SetError("SDL_DrawLines(): Passed NULL destination surface");
        return -1;
    }

    func = SDL_CalculateDrawLineFunc(dst->format);
    if (!func) {
        SDL_SetError("SDL_DrawLines(): Unsupported surface format");
        return -1;
    }

    for (i = 1; i < count; ++i) {
        x1 = points[i-1].x;
        y1 = points[i-1].y;
        x2 = points[i].x;
        y2 = points[i].y;

        /* Perform clipping */
        /* FIXME: We don't actually want to clip, as it may change line slope */
        if (!SDL_IntersectRectAndLine(&dst->clip_rect, &x1, &y1, &x2, &y2)) {
            continue;
        }

        /* Draw the end if it was clipped */
        draw_end = (x2 != points[i].x || y2 != points[i].y);

        func(dst, x1, y1, x2, y2, color, draw_end);
    }
    if (points[0].x != points[count-1].x || points[0].y != points[count-1].y) {
        SDL_DrawPoint(dst, points[count-1].x, points[count-1].y, color);
    }
    return 0;
}

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