Attachment 109340 Details for Bug 86200 – test case

test case

t.c (text/plain), 2.13 KB, created by André Draszik on 2014-11-12 14:16:55 UTC

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Creator: André Draszik

Created: 2014-11-12 14:16:55 UTC

Size: 2.13 KB

patch

obsolete

>#include <cairo.h>
>#include <math.h>
>#include <float.h>
>#include <stdio.h>
>
>#undef MAX
>#define MAX(a, b) ((a) > (b) ? (a) : (b))
>
>static cairo_matrix_t m1 = {
>  .xx = -38.835274957135283,
>  .yx = -5.9002831204844393,
>  .xy = 310.8899410274783,
>  .yy = 43.796450025375023,
>  .x0 = -266.44259062779747,
>  .y0 = 242.52585686041357,
>};
>int x_offset1 = 0;
>int y_offset1 = 0;
>
>int *x_offset = &x_offset1, *y_offset = &y_offset1;
>cairo_matrix_t *matrix = &m1;
>
>int main (int argc, char *argv[])
>{
>  cairo_matrix_t m;
>
>  m = *matrix;
>  cairo_matrix_translate (&m, *x_offset, *y_offset);
>
>  printf ("DBL_EPSILON: %g\n", DBL_EPSILON);
>
>    if (m.x0 != 0.0 || m.y0 != 0.0) {
>        double tx, ty, norm;
>        int i, j;
>
>        /* pixman also limits the [xy]_offset to 16 bits so evenly
>         * spread the bits between the two.
>         *
>         * To do this, find the solutions of:
>         *   |x| = |x*m.xx + y*m.xy + m.x0|
>         *   |y| = |x*m.yx + y*m.yy + m.y0|
>         *
>         * and select the one whose maximum norm is smallest.
>         */
>        tx = m.x0;
>        ty = m.y0;
>        norm = MAX (fabs (tx), fabs (ty));
>
>	for (i = -1; i < 2; i+=2) {
>	    for (j = -1; j < 2; j+=2) {
>		double x, y, den, new_norm;
>
>		den = (m.xx - i) * (m.yy - j) - m.xy * m.yx;
>		if (fabs (den) < DBL_EPSILON)
>		    continue;
>
>		x = m.y0 * m.xy - m.x0 * (m.yy - j);
>		y = m.x0 * m.yx - m.y0 * (m.xx - i);
>
>		den = 1 / den;
>		x *= den;
>		y *= den;
>
>		new_norm = MAX (fabs (x), fabs (y));
>		if (norm > new_norm) {
>		    norm = new_norm;
>		    tx = x;
>		    ty = y;
>		}
>	    }
>	}
>
>	tx = floor (tx);
>	ty = floor (ty);
>	*x_offset = -tx;
>	*y_offset = -ty;
>	cairo_matrix_translate (&m, tx, ty);
>    } else {
>	*x_offset = 0;
>	*y_offset = 0;
>    }
>
>    printf("matrix orig: xx/yx/xy/yy/x0/y0 %f %f %f %f %f %f\n",
>           fabs (matrix->xx), fabs (matrix->yx), fabs (matrix->xy),
>           fabs (matrix->yy), fabs (matrix->x0), fabs (matrix->y0));
>    printf("matrix new : xx/yx/xy/yy/x0/y0 %f %f %f %f %f %f\n",
>           fabs (m.xx), fabs (m.yx), fabs (m.xy),
>           fabs (m.yy), fabs (m.x0), fabs (m.y0));
>    printf("offset x/y: %d/%d\n", *x_offset, *y_offset);
>
>  return 0;
>}

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