view src/video/SDL_rect.c @ 5157:fb424691cfc7

Moved the rendering code out to a separate directory in the hope that it can someday be completely decoupled from the rest of the library and be expanded to an awesome 2D on 3D library.
author Sam Lantinga <slouken@libsdl.org>
date Wed, 02 Feb 2011 14:34:54 -0800
parents 0a5dbe96c3be
children 307ccc9c135e
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/*
    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_rect.h"

SDL_bool
SDL_HasIntersection(const SDL_Rect * A, const SDL_Rect * B)
{
    int Amin, Amax, Bmin, Bmax;

    /* Horizontal intersection */
    Amin = A->x;
    Amax = Amin + A->w;
    Bmin = B->x;
    Bmax = Bmin + B->w;
    if (Bmin > Amin)
        Amin = Bmin;
    if (Bmax < Amax)
        Amax = Bmax;
    if (Amax <= Amin)
        return SDL_FALSE;

    /* Vertical intersection */
    Amin = A->y;
    Amax = Amin + A->h;
    Bmin = B->y;
    Bmax = Bmin + B->h;
    if (Bmin > Amin)
        Amin = Bmin;
    if (Bmax < Amax)
        Amax = Bmax;
    if (Amax <= Amin)
        return SDL_FALSE;

    return SDL_TRUE;
}

SDL_bool
SDL_IntersectRect(const SDL_Rect * A, const SDL_Rect * B, SDL_Rect * result)
{
    int Amin, Amax, Bmin, Bmax;

    /* Horizontal intersection */
    Amin = A->x;
    Amax = Amin + A->w;
    Bmin = B->x;
    Bmax = Bmin + B->w;
    if (Bmin > Amin)
        Amin = Bmin;
    result->x = Amin;
    if (Bmax < Amax)
        Amax = Bmax;
    result->w = Amax - Amin;

    /* Vertical intersection */
    Amin = A->y;
    Amax = Amin + A->h;
    Bmin = B->y;
    Bmax = Bmin + B->h;
    if (Bmin > Amin)
        Amin = Bmin;
    result->y = Amin;
    if (Bmax < Amax)
        Amax = Bmax;
    result->h = Amax - Amin;

    return !SDL_RectEmpty(result);
}

void
SDL_UnionRect(const SDL_Rect * A, const SDL_Rect * B, SDL_Rect * result)
{
    int Amin, Amax, Bmin, Bmax;

    /* Horizontal union */
    Amin = A->x;
    Amax = Amin + A->w;
    Bmin = B->x;
    Bmax = Bmin + B->w;
    if (Bmin < Amin)
        Amin = Bmin;
    result->x = Amin;
    if (Bmax > Amax)
        Amax = Bmax;
    result->w = Amax - Amin;

    /* Vertical intersection */
    Amin = A->y;
    Amax = Amin + A->h;
    Bmin = B->y;
    Bmax = Bmin + B->h;
    if (Bmin < Amin)
        Amin = Bmin;
    result->y = Amin;
    if (Bmax > Amax)
        Amax = Bmax;
    result->h = Amax - Amin;
}

SDL_bool
SDL_EnclosePoints(const SDL_Point * points, int count, const SDL_Rect * clip,
                  SDL_Rect * result)
{
    int minx = 0;
    int miny = 0;
    int maxx = 0;
    int maxy = 0;
    int x, y, i;

    if (count < 1) {
        return SDL_FALSE;
    }

    if (clip) {
        SDL_bool added = SDL_FALSE;
        int clip_minx = clip->x;
        int clip_miny = clip->y;
        int clip_maxx = clip->x+clip->w-1;
        int clip_maxy = clip->y+clip->h-1;

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

            if (x < clip_minx || x > clip_maxx ||
                y < clip_miny || y > clip_maxy) {
                continue;
            }
            if (!added) {
                minx = maxx = x;
                miny = maxy = y;
                added = SDL_TRUE;
                continue;
            }
            if (x < minx) {
                minx = x;
            } else if (x > maxx) {
                maxx = x;
            }
            if (y < miny) {
                miny = y;
            } else if (y > maxy) {
                maxy = y;
            }
        }
        if (!added) {
            return SDL_FALSE;
        }
    } else {
        /* No clipping, always add the first point */
        minx = maxx = points[0].x;
        miny = maxy = points[0].y;

        for (i = 1; i < count; ++i) {
            x = points[i].x;
            y = points[i].y;

            if (x < minx) {
                minx = x;
            } else if (x > maxx) {
                maxx = x;
            }
            if (y < miny) {
                miny = y;
            } else if (y > maxy) {
                maxy = y;
            }
        }
    }

    if (result) {
        result->x = minx;
        result->y = miny;
        result->w = (maxx-minx)+1;
        result->h = (maxy-miny)+1;
    }
    return SDL_TRUE;
}

/* Use the Cohen-Sutherland algorithm for line clipping */
#define CODE_BOTTOM 1
#define CODE_TOP    2
#define CODE_LEFT   4
#define CODE_RIGHT  8

static int ComputeOutCode(const SDL_Rect * rect, int x, int y)
{
    int code = 0;
    if (y < 0) {
        code |= CODE_TOP;
    } else if (y >= rect->y + rect->h) {
        code |= CODE_BOTTOM;
    }
    if (x < 0) {
        code |= CODE_LEFT;
    } else if (x >= rect->x + rect->w) {
        code |= CODE_RIGHT;
    }
    return code;
}

SDL_bool
SDL_IntersectRectAndLine(const SDL_Rect * rect, int *X1, int *Y1, int *X2,
                         int *Y2)
{
    int x = 0;
    int y = 0;
    int x1, y1;
    int x2, y2;
    int rectx1;
    int recty1;
    int rectx2;
    int recty2;
    int outcode1, outcode2;

    if (!rect || !X1 || !Y1 || !X2 || !Y2) {
        return SDL_FALSE;
    }

    x1 = *X1;
    y1 = *Y1;
    x2 = *X2;
    y2 = *Y2;
    rectx1 = rect->x;
    recty1 = rect->y;
    rectx2 = rect->x + rect->w - 1;
    recty2 = rect->y + rect->h - 1;

    /* Check to see if entire line is inside rect */
    if (x1 >= rectx1 && x1 <= rectx2 && x2 >= rectx1 && x2 <= rectx2 &&
        y1 >= recty1 && y1 <= recty2 && y2 >= recty1 && y2 <= recty2) {
        return SDL_TRUE;
    }

    /* Check to see if entire line is to one side of rect */
    if ((x1 < rectx1 && x2 < rectx1) || (x1 > rectx2 && x2 > rectx2) ||
        (y1 < recty1 && y2 < recty1) || (y1 > recty2 && y2 > recty2)) {
        return SDL_FALSE;
    }

    if (y1 == y2) {
        /* Horizontal line, easy to clip */
        if (x1 < rectx1) {
            *X1 = rectx1;
        } else if (x1 > rectx2) {
            *X1 = rectx2;
        }
        if (x2 < rectx1) {
            *X2 = rectx1;
        } else if (x2 > rectx2) {
            *X2 = rectx2;
        }
        return SDL_TRUE;
    }

    if (x1 == x2) {
        /* Vertical line, easy to clip */
        if (y1 < recty1) {
            *Y1 = recty1;
        } else if (y1 > recty2) {
            *Y1 = recty2;
        }
        if (y2 < recty1) {
            *Y2 = recty1;
        } else if (y2 > recty2) {
            *Y2 = recty2;
        }
        return SDL_TRUE;
    }

    /* More complicated Cohen-Sutherland algorithm */
    outcode1 = ComputeOutCode(rect, x1, y1);
    outcode2 = ComputeOutCode(rect, x2, y2);
    while (outcode1 || outcode2) {
        if (outcode1 & outcode2) {
            return SDL_FALSE;
        }

        if (outcode1) {
            if (outcode1 & CODE_TOP) {
                y = recty1;
                x = x1 + ((x2 - x1) * (y - y1)) / (y2 - y1);
            } else if (outcode1 & CODE_BOTTOM) {
                y = recty2;
                x = x1 + ((x2 - x1) * (y - y1)) / (y2 - y1);
            } else if (outcode1 & CODE_LEFT) {
                x = rectx1;
                y = y1 + ((y2 - y1) * (x - x1)) / (x2 - x1);
            } else if (outcode1 & CODE_RIGHT) {
                x = rectx2;
                y = y1 + ((y2 - y1) * (x - x1)) / (x2 - x1);
            }
            x1 = x;
            y1 = y;
            outcode1 = ComputeOutCode(rect, x, y);
        } else {
            if (outcode2 & CODE_TOP) {
                y = recty1;
                x = x1 + ((x2 - x1) * (y - y1)) / (y2 - y1);
            } else if (outcode2 & CODE_BOTTOM) {
                y = recty2;
                x = x1 + ((x2 - x1) * (y - y1)) / (y2 - y1);
            } else if (outcode2 & CODE_LEFT) {
                x = rectx1;
                y = y1 + ((y2 - y1) * (x - x1)) / (x2 - x1);
            } else if (outcode2 & CODE_RIGHT) {
                x = rectx2;
                y = y1 + ((y2 - y1) * (x - x1)) / (x2 - x1);
            }
            x2 = x;
            y2 = y;
            outcode2 = ComputeOutCode(rect, x, y);
        }
    }
    *X1 = x1;
    *Y1 = y1;
    *X2 = x2;
    *Y2 = y2;
    return SDL_TRUE;
}

void
SDL_AddDirtyRect(SDL_DirtyRectList * list, const SDL_Rect * rect)
{
    SDL_DirtyRect *dirty;

    /* FIXME: At what point is this optimization too expensive? */
    for (dirty = list->list; dirty; dirty = dirty->next) {
        if (SDL_HasIntersection(&dirty->rect, rect)) {
            SDL_UnionRect(&dirty->rect, rect, &dirty->rect);
            return;
        }
    }

    if (list->free) {
        dirty = list->free;
        list->free = dirty->next;
    } else {
        dirty = (SDL_DirtyRect *) SDL_malloc(sizeof(*dirty));
        if (!dirty) {
            return;
        }
    }
    dirty->rect = *rect;
    dirty->next = list->list;
    list->list = dirty;
}

void
SDL_ClearDirtyRects(SDL_DirtyRectList * list)
{
    SDL_DirtyRect *prev, *curr;

    /* Skip to the end of the free list */
    prev = NULL;
    for (curr = list->free; curr; curr = curr->next) {
        prev = curr;
    }

    /* Add the list entries to the end */
    if (prev) {
        prev->next = list->list;
    } else {
        list->free = list->list;
    }
    list->list = NULL;
}

void
SDL_FreeDirtyRects(SDL_DirtyRectList * list)
{
    while (list->list) {
        SDL_DirtyRect *elem = list->list;
        list->list = elem->next;
        SDL_free(elem);
    }
    while (list->free) {
        SDL_DirtyRect *elem = list->free;
        list->free = elem->next;
        SDL_free(elem);
    }
}

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