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#include <stdbool.h>
#include "libnsfb.h"
#include "libnsfb_plot.h"
#include "libnsfb_plot_util.h"
#include "nsfb.h"
enum {
POINT_LEFTOF_REGION = 1,
POINT_RIGHTOF_REGION = 2,
POINT_ABOVE_REGION = 4,
POINT_BELOW_REGION = 8,
};
#define REGION(x,y,cx1,cx2,cy1,cy2) \
( ( (y) > (cy2) ? POINT_BELOW_REGION : 0) | \
( (y) < (cy1) ? POINT_ABOVE_REGION : 0) | \
( (x) > (cx2) ? POINT_RIGHTOF_REGION : 0) | \
( (x) < (cx1) ? POINT_LEFTOF_REGION : 0) )
#define SWAP(a, b) do { int t; t=(a); (a)=(b); (b)=t; } while(0)
/* clip a rectangle with another clipping rectangle.
*
* @param clip The rectangle to clip to.
* @param rect The rectangle to clip.
* @return false if the \a rect lies completely outside the \a clip rectangle,
* true if some of the \a rect is still visible.
*/
bool
nsfb_plot_clip(const nsfb_bbox_t * restrict clip, nsfb_bbox_t * restrict rect)
{
char region1;
char region2;
if (rect->x1 < rect->x0) SWAP(rect->x0, rect->x1);
if (rect->y1 < rect->y0) SWAP(rect->y0, rect->y1);
region1 = REGION(rect->x0, rect->y0, clip->x0, clip->x1 - 1, clip->y0, clip->y1 - 1);
region2 = REGION(rect->x1, rect->y1, clip->x0, clip->x1 - 1, clip->y0, clip->y1 - 1);
/* area lies entirely outside the clipping rectangle */
if ((region1 | region2) && (region1 & region2))
return false;
if (rect->x0 < clip->x0)
rect->x0 = clip->x0;
if (rect->x0 > clip->x1)
rect->x0 = clip->x1;
if (rect->x1 < clip->x0)
rect->x1 = clip->x0;
if (rect->x1 > clip->x1)
rect->x1 = clip->x1;
if (rect->y0 < clip->y0)
rect->y0 = clip->y0;
if (rect->y0 > clip->y1)
rect->y0 = clip->y1;
if (rect->y1 < clip->y0)
rect->y1 = clip->y0;
if (rect->y1 > clip->y1)
rect->y1 = clip->y1;
return true;
}
bool
nsfb_plot_clip_ctx(nsfb_t *nsfb, nsfb_bbox_t * restrict rect)
{
return nsfb_plot_clip(&nsfb->clip, rect);
}
/** Clip a line to a bounding box.
*/
bool nsfb_plot_clip_line(const nsfb_bbox_t *clip, nsfb_bbox_t * restrict line)
{
char region1;
char region2;
region1 = REGION(line->x0, line->y0, clip->x0, clip->x1 - 1, clip->y0, clip->y1 - 1);
region2 = REGION(line->x1, line->y1, clip->x0, clip->x1 - 1, clip->y0, clip->y1 - 1);
while (region1 | region2) {
if (region1 & region2) {
/* line lies entirely outside the clipping rectangle */
return false;
}
if (region1) {
/* first point */
if (region1 & POINT_BELOW_REGION) {
/* divide line at bottom */
line->x0 = (line->x0 + (line->x1 - line->x0) *
(clip->y1 - 1 - line->y0) / (line->y1 - line->y0));
line->y0 = clip->y1 - 1;
} else if (region1 & POINT_ABOVE_REGION) {
/* divide line at top */
line->x0 = (line->x0 + (line->x1 - line->x0) *
(clip->y0 - line->y0) / (line->y1 - line->y0));
line->y0 = clip->y0;
} else if (region1 & POINT_RIGHTOF_REGION) {
/* divide line at right */
line->y0 = (line->y0 + (line->y1 - line->y0) *
(clip->x1 - 1 - line->x0) / (line->x1 - line->x0));
line->x0 = clip->x1 - 1;
} else if (region1 & POINT_LEFTOF_REGION) {
/* divide line at right */
line->y0 = (line->y0 + (line->y1 - line->y0) *
(clip->x0 - line->x0) / (line->x1 - line->x0));
line->x0 = clip->x0;
}
region1 = REGION(line->x0, line->y0, clip->x0, clip->x1 - 1, clip->y0, clip->y1 - 1);
} else {
/* second point */
if (region2 & POINT_BELOW_REGION) {
/* divide line at bottom*/
line->x1 = (line->x0 + (line->x1 - line->x0) *
(clip->y1 - 1 - line->y0) / (line->y1 - line->y0));
line->y1 = clip->y1 - 1;
} else if (region2 & POINT_ABOVE_REGION) {
/* divide line at top*/
line->x1 = (line->x0 + (line->x1 - line->x0) *
(clip->y0 - line->y0) / (line->y1 - line->y0));
line->y1 = clip->y0;
} else if (region2 & POINT_RIGHTOF_REGION) {
/* divide line at right*/
line->y1 = (line->y0 + (line->y1 - line->y0) *
(clip->x1 - 1 - line->x0) / (line->x1 - line->x0));
line->x1 = clip->x1 - 1;
} else if (region2 & POINT_LEFTOF_REGION) {
/* divide line at right*/
line->y1 = (line->y0 + (line->y1 - line->y0) *
(clip->x0 - line->x0) / (line->x1 - line->x0));
line->x1 = clip->x0;
}
region2 = REGION(line->x1, line->y1, clip->x0, clip->x1 - 1, clip->y0, clip->y1 - 1);
}
}
return true;
}
bool nsfb_plot_clip_line_ctx(nsfb_t *nsfb, nsfb_bbox_t * restrict line)
{
return nsfb_plot_clip_line(&nsfb->clip, line);
}
/* documented in libnsfb_plot_util.h */
bool
nsfb_plot_add_rect(const nsfb_bbox_t *box1, const nsfb_bbox_t *box2, nsfb_bbox_t *result)
{
/* lower x coordinate */
if (box1->x0 < box2->x0)
result->x0 = box1->x0;
else
result->x0 = box2->x0;
/* lower y coordinate */
if (box1->y0 < box2->y0)
result->y0 = box1->y0;
else
result->y0 = box2->y0;
/* upper x coordinate */
if (box1->x1 > box2->x1)
result->x1 = box1->x1;
else
result->x1 = box2->x1;
/* upper y coordinate */
if (box1->y1 > box2->y1)
result->y1 = box1->y1;
else
result->y1 = box2->y1;
return true;
}
bool nsfb_plot_bbox_intersect(const nsfb_bbox_t *box1, const nsfb_bbox_t *box2)
{
if (box2->x1 < box1->x0)
return false;
if (box2->y1 < box1->y0)
return false;
if (box2->x0 > box1->x1)
return false;
if (box2->y0 > box1->y1)
return false;
return true;
}
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