404      *      sqrt(1/(slope*slope+1.0))  ------>\ \   \ /  in _glamor_create_linear_gradient_program()
414      *        slope = (p2.y - p1.y) /       |           /     p2d   /  in _glamor_create_linear_gradient_program()
430      *      step 1: compute the distance of p, pt1 and pt2 in the slope direction.  in _glamor_create_linear_gradient_program()
432      *              get the value on slope direction(pd, p1d and p2d represent the  in _glamor_create_linear_gradient_program()
1122     float slope;  in glamor_generate_linear_gradient_picture()  local
1396         /* The slope need to compute here. In shader, the viewport set will change  in glamor_generate_linear_gradient_picture()
1397            the original slope and the slope which is vertical to it will not be correct. */  in glamor_generate_linear_gradient_picture()
1398         slope = -(float) (src_picture->pSourcePict->linear.p2.x  in glamor_generate_linear_gradient_picture()
1402         slope = slope * yscale / xscale;  in glamor_generate_linear_gradient_picture()
1403         glUniform1f(pt_slope_uniform_location, slope);  in glamor_generate_linear_gradient_picture()
1406         cos_val = sqrt(1.0 / (slope * slope + 1.0));  in glamor_generate_linear_gradient_picture()
1409         p1_distance = (pt1[1] - pt1[0] * slope) * cos_val;  in glamor_generate_linear_gradient_picture()
1410         pt_distance = (pt2[1] - pt2[0] * slope) * cos_val - p1_distance;  in glamor_generate_linear_gradient_picture()