On Fri, Sep 13, 2013 at 10:01:21AM +0800, Sam Spilsbury wrote:
> ---
> src/Makefile.am | 4 +-
> src/gl-renderer.c | 292 +---------------------------------------------
> src/vertex-clipping.c | 317
> ++++++++++++++++++++++++++++++++++++++++++++++++++
> src/vertex-clipping.h | 65 +++++++++++
> 4 files changed, 389 insertions(+), 289 deletions(-)
> create mode 100644 src/vertex-clipping.c
> create mode 100644 src/vertex-clipping.h
Wouldn't it be nicer to make calculate_edges() the entry point into
the clipping code? As it is, too many internal details spill into the
header and much of the clipping logic is still in calculate_edges().
The only problem I see is that calculate_edges() calls
weston_surface_to_global_float(), but we can stub that out.
Kristian
> diff --git a/src/Makefile.am b/src/Makefile.am
> index 3710be6..92426b0 100644
> --- a/src/Makefile.am
> +++ b/src/Makefile.am
> @@ -52,7 +52,9 @@ weston_SOURCES = \
>
> if ENABLE_EGL
> weston_SOURCES += \
> - gl-renderer.c
> + gl-renderer.c \
> + vertex-clipping.c \
> + vertex-clipping.h
> endif
>
> git-version.h : .FORCE
> diff --git a/src/gl-renderer.c b/src/gl-renderer.c
> index 4381a2e..6999121 100644
> --- a/src/gl-renderer.c
> +++ b/src/gl-renderer.c
> @@ -33,6 +33,7 @@
> #include <linux/input.h>
>
> #include "gl-renderer.h"
> +#include "vertex-clipping.h"
>
> #include <EGL/eglext.h>
> #include "weston-egl-ext.h"
> @@ -179,270 +180,8 @@ gl_renderer_print_egl_error_state(void)
> egl_error_string(code), (long)code);
> }
>
> -struct polygon8 {
> - GLfloat x[8];
> - GLfloat y[8];
> - int n;
> -};
> -
> -struct clip_context {
> - struct {
> - GLfloat x;
> - GLfloat y;
> - } prev;
> -
> - struct {
> - GLfloat x1, y1;
> - GLfloat x2, y2;
> - } clip;
> -
> - struct {
> - GLfloat *x;
> - GLfloat *y;
> - } vertices;
> -};
> -
> -static GLfloat
> -float_difference(GLfloat a, GLfloat b)
> -{
> - /*
> http://www.altdevblogaday.com/2012/02/22/comparing-floating-point-numbers-2012-edition/
> */
> - static const GLfloat max_diff = 4.0f * FLT_MIN;
> - static const GLfloat max_rel_diff = 4.0e-5;
> - GLfloat diff = a - b;
> - GLfloat 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 GLfloat
> -clip_intersect_y(GLfloat p1x, GLfloat p1y, GLfloat p2x, GLfloat p2y,
> - GLfloat x_arg)
> -{
> - GLfloat a;
> - GLfloat 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 GLfloat
> -clip_intersect_x(GLfloat p1x, GLfloat p1y, GLfloat p2x, GLfloat p2y,
> - GLfloat y_arg)
> -{
> - GLfloat a;
> - GLfloat 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, GLfloat x, GLfloat y)
> -{
> - *ctx->vertices.x++ = x;
> - *ctx->vertices.y++ = y;
> -}
> -
> -static enum path_transition
> -path_transition_left_edge(struct clip_context *ctx, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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,
> - GLfloat x, GLfloat y, GLfloat clip_x)
> -{
> - GLfloat 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,
> - GLfloat x, GLfloat y, GLfloat clip_y)
> -{
> - GLfloat 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,
> - GLfloat *dst_x, GLfloat *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,
> - GLfloat *dst_x, GLfloat *dst_y)
> -{
> - enum path_transition trans;
> - int i;
> -
> - 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,
> - GLfloat *dst_x, GLfloat *dst_y)
> -{
> - enum path_transition trans;
> - int i;
> -
> - 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,
> - GLfloat *dst_x, GLfloat *dst_y)
> -{
> - enum path_transition trans;
> - int i;
> -
> - 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,
> - GLfloat *dst_x, GLfloat *dst_y)
> -{
> - enum path_transition trans;
> - int i;
> -
> - 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;
> -}
> -
> #define max(a, b) (((a) > (b)) ? (a) : (b))
> #define min(a, b) (((a) > (b)) ? (b) : (a))
> -#define clip(x, a, b) min(max(x, a), b)
>
> /*
> * Compute the boundary vertices of the intersection of the global coordinate
> @@ -457,7 +196,7 @@ static int
> calculate_edges(struct weston_surface *es, pixman_box32_t *rect,
> pixman_box32_t *surf_rect, GLfloat *ex, GLfloat *ey)
> {
> - struct polygon8 polygon;
> +
> struct clip_context ctx;
> int i, n;
> GLfloat min_x, max_x, min_y, max_y;
> @@ -500,11 +239,7 @@ calculate_edges(struct weston_surface *es,
> pixman_box32_t *rect,
> * vertices to the clip rect bounds:
> */
> if (!es->transform.enabled) {
> - 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;
> + return clip_simple(&ctx, &surf, ex, ey);
> }
>
> /* Transformed case: use a general polygon clipping algorithm to
> @@ -513,26 +248,7 @@ calculate_edges(struct weston_surface *es,
> pixman_box32_t *rect,
> *
> http://www.codeguru.com/cpp/misc/misc/graphics/article.php/c8965/Polygon-Clipping.htm
> * but without looking at any of that code.
> */
> - 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--;
> + n = clip_transformed(&ctx, &surf, ex, ey);
>
> if (n < 3)
> return 0;
> diff --git a/src/vertex-clipping.c b/src/vertex-clipping.c
> new file mode 100644
> index 0000000..603ce6f
> --- /dev/null
> +++ b/src/vertex-clipping.c
> @@ -0,0 +1,317 @@
> +/*
> + * Copyright © 2012 Intel Corporation
> + *
> + * Permission to use, copy, modify, distribute, and sell this software and
> + * its documentation for any purpose is hereby granted without fee, provided
> + * that the above copyright notice appear in all copies and that both that
> + * copyright notice and this permission notice appear in supporting
> + * documentation, and that the name of the copyright holders not be used in
> + * advertising or publicity pertaining to distribution of the software
> + * without specific, written prior permission. The copyright holders make
> + * no representations about the suitability of this software for any
> + * purpose. It is provided "as is" without express or implied warranty.
> + *
> + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
> + * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
> + * FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
> + * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
> + * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
> + * CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
> + * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
> + */
> +#include <assert.h>
> +#include <float.h>
> +#include <math.h>
> +
> +#include <GLES2/gl2.h>
> +
> +#include "vertex-clipping.h"
> +
> +GLfloat
> +float_difference(GLfloat a, GLfloat b)
> +{
> + /*
> http://www.altdevblogaday.com/2012/02/22/comparing-floating-point-numbers-2012-edition/
> */
> + static const GLfloat max_diff = 4.0f * FLT_MIN;
> + static const GLfloat max_rel_diff = 4.0e-5;
> + GLfloat diff = a - b;
> + GLfloat 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 GLfloat
> +clip_intersect_y(GLfloat p1x, GLfloat p1y, GLfloat p2x, GLfloat p2y,
> + GLfloat x_arg)
> +{
> + GLfloat a;
> + GLfloat 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 GLfloat
> +clip_intersect_x(GLfloat p1x, GLfloat p1y, GLfloat p2x, GLfloat p2y,
> + GLfloat y_arg)
> +{
> + GLfloat a;
> + GLfloat 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, GLfloat x, GLfloat y)
> +{
> + *ctx->vertices.x++ = x;
> + *ctx->vertices.y++ = y;
> +}
> +
> +static enum path_transition
> +path_transition_left_edge(struct clip_context *ctx, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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, GLfloat x, GLfloat 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,
> + GLfloat x, GLfloat y, GLfloat clip_x)
> +{
> + GLfloat 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,
> + GLfloat x, GLfloat y, GLfloat clip_y)
> +{
> + GLfloat 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,
> + GLfloat *dst_x, GLfloat *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,
> + GLfloat *dst_x, GLfloat *dst_y)
> +{
> + enum path_transition trans;
> + int i;
> +
> + 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,
> + GLfloat *dst_x, GLfloat *dst_y)
> +{
> + enum path_transition trans;
> + int i;
> +
> + 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,
> + GLfloat *dst_x, GLfloat *dst_y)
> +{
> + enum path_transition trans;
> + int i;
> +
> + 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,
> + GLfloat *dst_x, GLfloat *dst_y)
> +{
> + enum path_transition trans;
> + int i;
> +
> + 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;
> +}
> +
> +#define max(a, b) (((a) > (b)) ? (a) : (b))
> +#define min(a, b) (((a) > (b)) ? (b) : (a))
> +#define clip(x, a, b) min(max(x, a), b)
> +
> +int
> +clip_simple(struct clip_context *ctx,
> + struct polygon8 *surf,
> + GLfloat *ex,
> + GLfloat *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;
> +}
> +
> +int
> +clip_transformed(struct clip_context *ctx,
> + struct polygon8 *surf,
> + GLfloat *ex,
> + GLfloat *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;
> +}
> diff --git a/src/vertex-clipping.h b/src/vertex-clipping.h
> new file mode 100644
> index 0000000..a16b1df
> --- /dev/null
> +++ b/src/vertex-clipping.h
> @@ -0,0 +1,65 @@
> +/*
> + * Copyright © 2012 Intel Corporation
> + *
> + * Permission to use, copy, modify, distribute, and sell this software and
> + * its documentation for any purpose is hereby granted without fee, provided
> + * that the above copyright notice appear in all copies and that both that
> + * copyright notice and this permission notice appear in supporting
> + * documentation, and that the name of the copyright holders not be used in
> + * advertising or publicity pertaining to distribution of the software
> + * without specific, written prior permission. The copyright holders make
> + * no representations about the suitability of this software for any
> + * purpose. It is provided "as is" without express or implied warranty.
> + *
> + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
> + * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
> + * FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
> + * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
> + * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
> + * CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
> + * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
> + */
> +#ifndef _WESTON_VERTEX_CLIPPING_H
> +#define _WESTON_VERTEX_CLIPPING_H
> +
> +#include <GLES2/gl2.h>
> +
> +struct polygon8 {
> + GLfloat x[8];
> + GLfloat y[8];
> + int n;
> +};
> +
> +struct clip_context {
> + struct {
> + GLfloat x;
> + GLfloat y;
> + } prev;
> +
> + struct {
> + GLfloat x1, y1;
> + GLfloat x2, y2;
> + } clip;
> +
> + struct {
> + GLfloat *x;
> + GLfloat *y;
> + } vertices;
> +};
> +
> +GLfloat
> +float_difference(GLfloat a, GLfloat b);
> +
> +int
> +clip_simple(struct clip_context *ctx,
> + struct polygon8 *surf,
> + GLfloat *ex,
> + GLfloat *ey);
> +
> +int
> +clip_transformed(struct clip_context *ctx,
> + struct polygon8 *surf,
> + GLfloat *ex,
> + GLfloat *ey);\
> +
> +#endif
> --
> 1.8.3.2
>
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