/* * Copyright © 2012 Intel Corporation * * Permission is hereby granted, free of charge, to any person obtaining * a copy of this software and associated documentation files (the * "Software"), to deal in the Software without restriction, including * without limitation the rights to use, copy, modify, merge, publish, * distribute, sublicense, and/or sell copies of the Software, and to * permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice (including the * next paragraph) shall be included in all copies or substantial * portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ #include #include #include #include "shared/helpers.h" #include "vertex-clipping.h" WESTON_EXPORT_FOR_TESTS float float_difference(float a, float b) { /* http://www.altdevblogaday.com/2012/02/22/comparing-floating-point-numbers-2012-edition/ */ static const float max_diff = 4.0f * FLT_MIN; static const float max_rel_diff = 4.0e-5; float diff = a - b; float adiff = fabsf(diff); if (adiff <= max_diff) return 0.0f; a = fabsf(a); b = fabsf(b); if (adiff <= (a > b ? a : b) * max_rel_diff) return 0.0f; return diff; } /* A line segment (p1x, p1y)-(p2x, p2y) intersects the line x = x_arg. * Compute the y coordinate of the intersection. */ static float clip_intersect_y(float p1x, float p1y, float p2x, float p2y, float x_arg) { float a; float diff = float_difference(p1x, p2x); /* Practically vertical line segment, yet the end points have already * been determined to be on different sides of the line. Therefore * the line segment is part of the line and intersects everywhere. * Return the end point, so we use the whole line segment. */ if (diff == 0.0f) return p2y; a = (x_arg - p2x) / diff; return p2y + (p1y - p2y) * a; } /* A line segment (p1x, p1y)-(p2x, p2y) intersects the line y = y_arg. * Compute the x coordinate of the intersection. */ static float clip_intersect_x(float p1x, float p1y, float p2x, float p2y, float y_arg) { float a; float diff = float_difference(p1y, p2y); /* Practically horizontal line segment, yet the end points have already * been determined to be on different sides of the line. Therefore * the line segment is part of the line and intersects everywhere. * Return the end point, so we use the whole line segment. */ if (diff == 0.0f) return p2x; a = (y_arg - p2y) / diff; return p2x + (p1x - p2x) * a; } enum path_transition { PATH_TRANSITION_OUT_TO_OUT = 0, PATH_TRANSITION_OUT_TO_IN = 1, PATH_TRANSITION_IN_TO_OUT = 2, PATH_TRANSITION_IN_TO_IN = 3, }; static void clip_append_vertex(struct clip_context *ctx, float x, float y) { *ctx->vertices.x++ = x; *ctx->vertices.y++ = y; } static enum path_transition path_transition_left_edge(struct clip_context *ctx, float x, float y) { return ((ctx->prev.x >= ctx->clip.x1) << 1) | (x >= ctx->clip.x1); } static enum path_transition path_transition_right_edge(struct clip_context *ctx, float x, float y) { return ((ctx->prev.x < ctx->clip.x2) << 1) | (x < ctx->clip.x2); } static enum path_transition path_transition_top_edge(struct clip_context *ctx, float x, float y) { return ((ctx->prev.y >= ctx->clip.y1) << 1) | (y >= ctx->clip.y1); } static enum path_transition path_transition_bottom_edge(struct clip_context *ctx, float x, float y) { return ((ctx->prev.y < ctx->clip.y2) << 1) | (y < ctx->clip.y2); } static void clip_polygon_leftright(struct clip_context *ctx, enum path_transition transition, float x, float y, float clip_x) { float yi; switch (transition) { case PATH_TRANSITION_IN_TO_IN: clip_append_vertex(ctx, x, y); break; case PATH_TRANSITION_IN_TO_OUT: yi = clip_intersect_y(ctx->prev.x, ctx->prev.y, x, y, clip_x); clip_append_vertex(ctx, clip_x, yi); break; case PATH_TRANSITION_OUT_TO_IN: yi = clip_intersect_y(ctx->prev.x, ctx->prev.y, x, y, clip_x); clip_append_vertex(ctx, clip_x, yi); clip_append_vertex(ctx, x, y); break; case PATH_TRANSITION_OUT_TO_OUT: /* nothing */ break; default: assert(0 && "bad enum path_transition"); } ctx->prev.x = x; ctx->prev.y = y; } static void clip_polygon_topbottom(struct clip_context *ctx, enum path_transition transition, float x, float y, float clip_y) { float xi; switch (transition) { case PATH_TRANSITION_IN_TO_IN: clip_append_vertex(ctx, x, y); break; case PATH_TRANSITION_IN_TO_OUT: xi = clip_intersect_x(ctx->prev.x, ctx->prev.y, x, y, clip_y); clip_append_vertex(ctx, xi, clip_y); break; case PATH_TRANSITION_OUT_TO_IN: xi = clip_intersect_x(ctx->prev.x, ctx->prev.y, x, y, clip_y); clip_append_vertex(ctx, xi, clip_y); clip_append_vertex(ctx, x, y); break; case PATH_TRANSITION_OUT_TO_OUT: /* nothing */ break; default: assert(0 && "bad enum path_transition"); } ctx->prev.x = x; ctx->prev.y = y; } static void clip_context_prepare(struct clip_context *ctx, const struct polygon8 *src, float *dst_x, float *dst_y) { ctx->prev.x = src->x[src->n - 1]; ctx->prev.y = src->y[src->n - 1]; ctx->vertices.x = dst_x; ctx->vertices.y = dst_y; } static int clip_polygon_left(struct clip_context *ctx, const struct polygon8 *src, float *dst_x, float *dst_y) { enum path_transition trans; int i; if (src->n < 2) return 0; clip_context_prepare(ctx, src, dst_x, dst_y); for (i = 0; i < src->n; i++) { trans = path_transition_left_edge(ctx, src->x[i], src->y[i]); clip_polygon_leftright(ctx, trans, src->x[i], src->y[i], ctx->clip.x1); } return ctx->vertices.x - dst_x; } static int clip_polygon_right(struct clip_context *ctx, const struct polygon8 *src, float *dst_x, float *dst_y) { enum path_transition trans; int i; if (src->n < 2) return 0; clip_context_prepare(ctx, src, dst_x, dst_y); for (i = 0; i < src->n; i++) { trans = path_transition_right_edge(ctx, src->x[i], src->y[i]); clip_polygon_leftright(ctx, trans, src->x[i], src->y[i], ctx->clip.x2); } return ctx->vertices.x - dst_x; } static int clip_polygon_top(struct clip_context *ctx, const struct polygon8 *src, float *dst_x, float *dst_y) { enum path_transition trans; int i; if (src->n < 2) return 0; clip_context_prepare(ctx, src, dst_x, dst_y); for (i = 0; i < src->n; i++) { trans = path_transition_top_edge(ctx, src->x[i], src->y[i]); clip_polygon_topbottom(ctx, trans, src->x[i], src->y[i], ctx->clip.y1); } return ctx->vertices.x - dst_x; } static int clip_polygon_bottom(struct clip_context *ctx, const struct polygon8 *src, float *dst_x, float *dst_y) { enum path_transition trans; int i; if (src->n < 2) return 0; clip_context_prepare(ctx, src, dst_x, dst_y); for (i = 0; i < src->n; i++) { trans = path_transition_bottom_edge(ctx, src->x[i], src->y[i]); clip_polygon_topbottom(ctx, trans, src->x[i], src->y[i], ctx->clip.y2); } return ctx->vertices.x - dst_x; } WESTON_EXPORT_FOR_TESTS int clip_simple(struct clip_context *ctx, struct polygon8 *surf, float *ex, float *ey) { int i; for (i = 0; i < surf->n; i++) { ex[i] = CLIP(surf->x[i], ctx->clip.x1, ctx->clip.x2); ey[i] = CLIP(surf->y[i], ctx->clip.y1, ctx->clip.y2); } return surf->n; } WESTON_EXPORT_FOR_TESTS int clip_transformed(struct clip_context *ctx, struct polygon8 *surf, float *ex, float *ey) { struct polygon8 polygon; int i, n; polygon.n = clip_polygon_left(ctx, surf, polygon.x, polygon.y); surf->n = clip_polygon_right(ctx, &polygon, surf->x, surf->y); polygon.n = clip_polygon_top(ctx, surf, polygon.x, polygon.y); surf->n = clip_polygon_bottom(ctx, &polygon, surf->x, surf->y); /* Get rid of duplicate vertices */ ex[0] = surf->x[0]; ey[0] = surf->y[0]; n = 1; for (i = 1; i < surf->n; i++) { if (float_difference(ex[n - 1], surf->x[i]) == 0.0f && float_difference(ey[n - 1], surf->y[i]) == 0.0f) continue; ex[n] = surf->x[i]; ey[n] = surf->y[i]; n++; } if (float_difference(ex[n - 1], surf->x[0]) == 0.0f && float_difference(ey[n - 1], surf->y[0]) == 0.0f) n--; return n; }