Mercurial > hg > dmlib
view dmlineclip.h @ 510:43ea59887c69
Start work on making C64 formats encoding possible by changing DMDecodeOps
to DMEncDecOps and adding fields and op enums for custom encode functions, renaming,
etc. Split generic op sanity checking into a separate function in
preparation for its use in generic encoding function.
author | Matti Hamalainen <ccr@tnsp.org> |
---|---|
date | Mon, 19 Nov 2012 15:06:01 +0200 |
parents | 4ad2b9739c4a |
children |
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/* Clip line coordinates. Return value: * = 0 : No clipping needed. * > 0 : Clipped. Line partially inside the clipping area. * < 0 : Line completely outside the clipping area. */ #ifndef DM_HEADER #define DM_CLIP_BITS(QB, QX, QY) \ do { \ QB = 0; \ if (QX < clipX0) QB |= CLIP_LEFT; \ else \ if (QX > clipX1) QB |= CLIP_RIGHT; \ \ if (QY < clipY0) QB |= CLIP_TOP; \ else \ if (QY > clipY1) QB |= CLIP_BOTTOM; \ } while (0) #define xA (fx0) #define xB (fx1) #define yA (fy0) #define yB (fy1) #endif #ifdef DM_CLIP_DEBUG #define CLIPDEB(fmt, ...) fprintf(stderr, fmt, __VA_ARGS__) #else #define CLIPDEB(fmt, ...) #endif int DM_CLIP_FUNC (SDL_Surface *screen, DM_COORD_TYPE *x0, DM_COORD_TYPE *y0, DM_COORD_TYPE *x1, DM_COORD_TYPE *y1) #ifdef DM_HEADER ; #else { const DM_COORD_TYPE clipX0 = screen->clip_rect.x, clipY0 = screen->clip_rect.y, clipX1 = clipX0 + screen->clip_rect.w - 1, clipY1 = clipY0 + screen->clip_rect.h - 1; double fx0 = *x0, fy0 = *y0, fx1 = *x1, fy1 = *y1; int clipA, clipB; DM_CLIP_BITS(clipA, xA, yA); DM_CLIP_BITS(clipB, xB, yB); CLIPDEB("-- clip [%1.3f, %1.3f - %1.3f, %1.3f] --\n", xA, yA, xB, yB); #if 1 // Cohen-Sutherland clipping method do { const int c = clipA ? clipA : clipB; DM_COORD_TYPE x, y; // The segment is inside? if ((clipA | clipB) == 0) { *x0 = fx0; *y0 = fy0; *x1 = fx1; *y1 = fy1; return 0; } // The line segment is outside of the clip region if (clipA & clipB) return -1; #ifdef DM_CLIP_DEBUG CLIPDEB "CLIP : "); if (c == clipA) CLIPDEB("A [%1.3f, %1.3f]\n", xA, yA); else CLIPDEB("B [%1.3f, %1.3f]\n", xB, yB); #endif if (c & CLIP_TOP) { if (yB - yA != 0) x = xA + ((clipY0 - yA) * (xB - xA)) / (yB - yA); else x = xA; y = clipY0; CLIPDEB("TOP : %1.3f, %1.3f\n", x, y); } else if (c & CLIP_BOTTOM) { if (yB - yA != 0) x = xA + ((clipY1 - yA) * (xB - xA)) / (yB - yA); else x = xA; y = clipY1; CLIPDEB("BOTTOM : %1.3f, %1.3f\n", x, y); } else if (c & CLIP_RIGHT) { if (xB - xA != 0) y = yA + ((clipX1 - xA) * (yB - yA)) / (xB - xA); else y = yA; x = clipX1; CLIPDEB("RIGHT : %1.3f, %1.3f\n", x, y); } else { if (xB - xA != 0) y = yA + ((clipX0 - xA) * (yB - yA)) / (xB - xA); else y = yA; x = clipX0; CLIPDEB("LEFT : %1.3f, %1.3f\n", x, y); } if (c == clipA) { xA = x; yA = y; DM_CLIP_BITS(clipA, xA, yA); } else { xB = x; yB = y; DM_CLIP_BITS(clipB, xB, yB); } } while (1); #else // Buyu-Skala clipping method const DM_COORD_TYPE dx = xB - xA; const DM_COORD_TYPE dy = yB - yA; float k, m; int z; switch (clipA + clipB) { case 1: if (clipA == 1) { xA = clipX0; yA = (clipX0 - xB) * dy / dx + yB; } else { xB = clipX0; yB = (clipX0 - xA) * dy / dx + yA; } break; case 3: k = dy / dx; yA = (clipX0 - xA) * k + yA; xA = clipX0; yB = (clipX1 - xB) * k + yB; xB = clipX1; break; case 5: k = dy / dx; z = (clipX0 - xA) * k + yA; if (z < clipY0) { switch (clipA) { case 0: xB = xB + (clipY0 - yB) / k; yB = clipY0; break; case 5: xA = xA + (clipY0 - yA) / k; yA = clipY0; break; default: return -1; /* the line segment is outside */ } } else { switch (clipA) { case 0: xB = clipX0; yB = z; break; case 1: xB = xB + (clipY0 - yB) / k; yB = clipY0; xA = clipX0; yA = z; break; case 4: xA = xA + (clipY0 - yA) / k; yA = clipY0; xB = clipX0; yB = z; break; case 5: xA = clipX0; yA = z; break; } } break; case 7: switch (clipA) { case 1: k = dy / dx; yA = (clipX0 - xB) * k + yB; if (yA < clipY0) return -1; /* the line segment is outside */ xA = clipX0; yB = (clipX1 - clipX0) * k + yA; if (yB < clipY0) { xB = (clipY0 - yB) / k + clipX1; yB = clipY0; } else xB = clipX1; break; /* similarly for cases clipA == 2, 5, 6 */ } case 15: switch (clipA) { case 5: if (dy * (clipX1 - clipX0) < dx * (clipY1 - clipY0)) { k = dy / dx; yA = (clipX0 - xB) * k + yB; if (yA > clipY1) return -1; /* the line segment is outside */ yB = (clipX1 - clipX0) * k + yA; if (yB < clipY0) return -1; /* the line segment is outside */ if (yA < clipY0) { xA = (clipY0 - yA) / k + clipX0; yA = clipY0; xB = clipX1; } else { xA = clipX0; if (yB > clipY1) { xB = (clipY1 - yB) / k + clipX1; yB = clipY1; } else xB = clipX1; } } else { m = dx / dy; xA = (clipY0 - yB) * m + xB; if (xA > clipX1) return -1; /* the line segment is outside */ xB = (clipY1 - clipY0) * m + xA; if (xB < clipX0) return -1; /* the line segment is outside */ if (xA < clipX0) { yA = (clipX0 - xA) / m + clipY0; xA = clipX0; yB = clipY1; } else { yA = clipY0; if (xB > clipX1) { yB = (clipX1 - xB) / m + clipY1; xB = clipX1; } else yB = clipY1; } } /* similarly for cases clipA == 6, 9, 10 */ } /* cases 2, 4, 8 are similar as case 1, cases 6, 9, 10 are similar as case 5 */ /* cases 11, 13, 14 are similar as case 7, case 12 is similar case 3 */ } /* of case clipA + clipB */ #endif return 1; } #undef DM_CLIP_BITS #undef xA #undef xB #undef yA #undef yB #undef CLIPDEB #endif #undef DM_CLIP_FUNC #undef DM_COORD_TYPE