Mercurial > hg > dmlib
annotate dmdrawline.h @ 96:6bf5220fa47e
Urgh .. use memset to silence some bogus GCC warnings about using
potentially uninitialized values, while that will not actually be possible.
In any case, it is annoying.
| author | Matti Hamalainen <ccr@tnsp.org> |
|---|---|
| date | Tue, 02 Oct 2012 18:52:28 +0300 |
| parents | 997e26f17946 |
| children | 92cc5e1fa180 |
| rev | line source |
|---|---|
| 0 | 1 |
|
22
997e26f17946
Initial fixes for getting the line drawing functions "working".
Matti Hamalainen <ccr@tnsp.org>
parents:
0
diff
changeset
|
2 static int DM_DRAWLINE_NAME (SDL_Surface *screen, int x0, int y0, int x1, int y1, const Uint32 col) |
| 0 | 3 { |
| 4 int dx, dy, xstep, ystep; | |
| 5 const int qpitch = screen->pitch / DM_DRAWLINE_DST_BYTES; | |
| 6 | |
| 7 // Clipping | |
| 8 if (dmClipLineCoords(&x0, &y0, &x1, &y1, screen)) | |
| 9 return -1; | |
| 10 | |
| 11 // Compute initial deltas | |
| 12 dx = (x1 - x0) * 2; | |
| 13 dy = (y1 - y0) * 2; | |
| 14 | |
| 15 if (dx < 0) | |
| 16 { | |
| 17 dx = -dx; | |
| 18 xstep = -1; | |
| 19 } | |
| 20 else | |
| 21 xstep = 1; | |
| 22 | |
| 23 if (dy < 0) | |
| 24 { | |
| 25 dy = -dy; | |
| 26 ystep = -qpitch; | |
| 27 } | |
| 28 else | |
| 29 ystep = qpitch; | |
| 30 | |
| 31 // Compute offsets | |
| 32 y0 *= qpitch; | |
| 33 y1 *= qpitch; | |
| 34 | |
| 35 DM_DRAWLINE_DST_TYPE *pix = screen->pixels; | |
| 36 | |
| 37 // Continue based on which delta is larger | |
| 38 if (dx > dy) | |
| 39 { | |
| 40 int afrac = dy - (dx / 2); | |
| 41 while (x0 != x1) | |
| 42 { | |
| 43 if (afrac >= 0) | |
| 44 { | |
| 45 y0 += ystep; | |
| 46 afrac -= dx; | |
| 47 } | |
| 48 | |
| 49 x0 += xstep; | |
| 50 afrac += dy; | |
| 51 | |
| 52 DM_DRAWLINE_INNER | |
| 53 } | |
| 54 } | |
| 55 else | |
| 56 { | |
| 57 int afrac = dx - (dy / 2); | |
| 58 while (y0 != y1) | |
| 59 { | |
| 60 if (afrac >= 0) | |
| 61 { | |
| 62 x0 += xstep; | |
| 63 afrac -= dy; | |
| 64 } | |
| 65 | |
| 66 y0 += ystep; | |
| 67 afrac += dx; | |
| 68 | |
| 69 DM_DRAWLINE_INNER | |
| 70 } | |
| 71 } | |
| 72 | |
| 73 return 0; | |
| 74 } | |
| 75 | |
| 76 #undef DM_DRAWLINE_NAME | |
| 77 #undef DM_DRAWLINE_DST_BYTES | |
| 78 #undef DM_DRAWLINE_DST_TYPE |