polygons: rasterizer demo
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K. Lange
parent
e60de1aed3
commit
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/**
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* @brief Draw filled polygons from line segments.
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*/
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#include <stdio.h>
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#include <sys/fswait.h>
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#include <toaru/yutani.h>
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#include <toaru/graphics.h>
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#define min(a,b) ((a) < (b) ? (a) : (b))
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static int left, top, width, height;
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static yutani_t * yctx;
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static yutani_window_t * wina;
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static gfx_context_t * ctx;
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static int should_exit = 0;
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struct coord {
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float x;
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float y;
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};
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struct edge {
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struct coord start;
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struct coord end;
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};
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struct contour {
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size_t edgeCount;
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size_t nextAlloc;
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struct edge edges[];
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};
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struct intersection {
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float x;
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int affect;
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};
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struct contour * shape = NULL;
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int edge_sorter_high_scanline(const void * a, const void * b) {
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const struct edge * left = a;
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const struct edge * right = b;
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float left_lowest = min(left->start.y, left->end.y);
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float right_lowest = min(right->start.y, right->end.y);
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if (left_lowest < right_lowest) return -1;
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if (left_lowest > right_lowest) return 1;
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return 0;
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}
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void sort_edges(size_t edgeCount, struct edge edges[edgeCount]) {
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qsort(edges, edgeCount, sizeof(struct edge), edge_sorter_high_scanline);
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}
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int intersection_sorter(const void * a, const void * b) {
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const struct intersection * left = a;
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const struct intersection * right = b;
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if (left->x < right->x) return -1;
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if (left->x > right->x) return 1;
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return 0;
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}
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void sort_intersections(size_t cnt, struct intersection intersections[cnt]) {
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qsort(intersections, cnt, sizeof(struct intersection), intersection_sorter);
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}
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size_t prune_edges(size_t edgeCount, float y, struct edge edges[edgeCount], struct edge into[edgeCount]) {
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size_t outWriter = 0;
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for (size_t i = 0; i < edgeCount; ++i) {
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if (y > edges[i].start.y && y > edges[i].end.y) continue;
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if (y <= edges[i].start.y && y <= edges[i].end.y) break;
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into[outWriter++] = edges[i];
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}
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return outWriter;
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}
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float edge_at(float y, struct edge * edge) {
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float u = (y - edge->start.y) / (edge->end.y - edge->start.y);
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return edge->start.x + u * (edge->end.x - edge->start.x);
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}
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int was_moving = 0;
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size_t last_start = 0;
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static void move_to(float x, float y);
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static void add_point(float x, float y) {
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if (!shape) {
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move_to(x,y);
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} else if (was_moving) {
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shape->edges[shape->edgeCount].end.x = x;
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shape->edges[shape->edgeCount].end.y = y;
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shape->edgeCount++;
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was_moving = 0;
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} else {
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if (shape->edgeCount + 1 == shape->nextAlloc) {
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shape->nextAlloc *= 2;
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shape = realloc(shape, sizeof(struct contour) + sizeof(struct edge) * (shape->nextAlloc));
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}
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shape->edges[shape->edgeCount].start.x = shape->edges[shape->edgeCount-1].end.x;
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shape->edges[shape->edgeCount].start.y = shape->edges[shape->edgeCount-1].end.y;
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shape->edges[shape->edgeCount].end.x = x;
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shape->edges[shape->edgeCount].end.y = y;
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shape->edgeCount++;
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was_moving = 0;
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}
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}
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static void move_to(float x, float y) {
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if (!shape) {
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shape = malloc(sizeof(struct contour) + sizeof(struct edge) * 2);
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shape->edgeCount = 0;
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shape->nextAlloc = 2;
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} else if (!was_moving && shape->edgeCount) {
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add_point(shape->edges[last_start].start.x, shape->edges[last_start].start.y);
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}
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if (shape->edgeCount + 1 == shape->nextAlloc) {
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shape->nextAlloc *= 2;
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shape = realloc(shape, sizeof(struct contour) + sizeof(struct edge) * (shape->nextAlloc));
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}
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shape->edges[shape->edgeCount].start.x = x;
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shape->edges[shape->edgeCount].start.y = y;
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last_start = shape->edgeCount;
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was_moving = 1;
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}
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static void draw(void) {
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draw_fill(ctx, rgb(0,0,0));
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if (shape) {
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if (last_start + 1 == shape->edgeCount) {
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draw_line(ctx, shape->edges[last_start].start.x, shape->edges[last_start].end.x, shape->edges[last_start].start.y, shape->edges[last_start].end.y, rgb(255,255,255));
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}
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if (shape->edgeCount > 1) {
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/* Oh boy */
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size_t size = shape->edgeCount + 1;
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struct edge * tmp = malloc(sizeof(struct edge) * size);
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memcpy(tmp, shape->edges, sizeof(struct edge) * shape->edgeCount);
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if (was_moving) {
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size--;
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} else {
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tmp[shape->edgeCount].start.x = shape->edges[shape->edgeCount-1].end.x;
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tmp[shape->edgeCount].start.y = shape->edges[shape->edgeCount-1].end.y;
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tmp[shape->edgeCount].end.x = shape->edges[last_start].start.x;
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tmp[shape->edgeCount].end.y = shape->edges[last_start].start.y;
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}
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sort_edges(size, tmp);
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struct edge * intersects = malloc(sizeof(struct edge) * size);
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struct intersection * crosses = malloc(sizeof(struct intersection) * size);
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float * subsamples = malloc(sizeof(float) * width);
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memset(subsamples, 0, sizeof(float) * width);
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/* We have sorted by the scanline at which the line becomes active, so we should be able to do this... */
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int start_y = (int)min(tmp[0].start.y, tmp[0].end.y);
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int yres = 4;
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for (int y = start_y; y < height; ++y) {
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/* Figure out which ones fit here */
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float _y = (float)y;
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for (int l = 0; l < yres; ++l) {
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size_t cnt = prune_edges(size, _y, tmp, intersects);
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if (cnt) {
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int wind = 0;
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/* Get intersections */
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for (size_t j = 0; j < cnt; ++j) {
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crosses[j].x = edge_at(_y,&intersects[j]);
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crosses[j].affect = (intersects[j].start.y < intersects[j].end.y) ? -1 : 1;
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}
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/* Now sort the intersections */
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sort_intersections(cnt, crosses);
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size_t j = 0;
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for (int x = 0; x < width; ++x) {
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while (j < cnt && x > crosses[j].x) {
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wind += crosses[j].affect;
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j++;
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}
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float last = x;
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while (j < cnt && (x+1) > crosses[j].x) {
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if (wind != 0) {
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subsamples[x] += crosses[j].x - last;
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}
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last = crosses[j].x;
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wind += crosses[j].affect;
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j++;
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}
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if (wind != 0) {
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subsamples[x] += (x+1) - last;
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}
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}
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}
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_y += 1.0/(float)yres;
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}
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for (int x = 0; x < width; ++x) {
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int c = subsamples[x] / (float)yres * 255;
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GFX(ctx,x,y) = rgb(c,c,c);
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subsamples[x] = 0;
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}
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}
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free(subsamples);
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free(crosses);
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free(intersects);
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free(tmp);
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}
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}
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}
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static void finish_draw(void) {
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flip(ctx);
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yutani_flip(yctx, wina);
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}
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int main (int argc, char ** argv) {
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left = 100;
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top = 100;
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width = 500;
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height = 500;
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yctx = yutani_init();
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if (!yctx) {
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fprintf(stderr, "%s: failed to connect to compositor\n", argv[0]);
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return 1;
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}
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wina = yutani_window_create(yctx, width, height);
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yutani_window_move(yctx, wina, left, top);
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yutani_window_advertise_icon(yctx, wina, "polygons", "polygons");
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ctx = init_graphics_yutani_double_buffer(wina);
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draw();
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finish_draw();
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while (!should_exit) {
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int fds[1] = {fileno(yctx->sock)};
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int index = fswait2(1,fds,20);
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if (index == 0) {
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yutani_msg_t * m = yutani_poll(yctx);
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while (m) {
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switch (m->type) {
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case YUTANI_MSG_KEY_EVENT:
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{
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struct yutani_msg_key_event * ke = (void*)m->data;
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if (ke->event.action == KEY_ACTION_DOWN && ke->event.keycode == 'q') {
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should_exit = 1;
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}
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}
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break;
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case YUTANI_MSG_WINDOW_MOUSE_EVENT:
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{
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struct yutani_msg_window_mouse_event * me = (void*)m->data;
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float x = (float)me->new_x;
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float y = (float)me->new_y;
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if (me->command == YUTANI_MOUSE_EVENT_DOWN && me->buttons & YUTANI_MOUSE_BUTTON_LEFT) {
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add_point(x, y);
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draw();
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finish_draw();
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} else if (me->buttons & YUTANI_MOUSE_BUTTON_RIGHT) {
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move_to(x, y);
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draw();
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finish_draw();
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} else if (shape && was_moving) {
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draw();
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draw_line(ctx,
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shape->edges[shape->edgeCount].start.x,
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x,
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shape->edges[shape->edgeCount].start.y,
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y,
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rgb(0,255,0));
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finish_draw();
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} else if (shape && !was_moving) {
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draw();
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draw_line(ctx,
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shape->edges[shape->edgeCount-1].end.x,
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x,
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shape->edges[shape->edgeCount-1].end.y,
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y,
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rgb(0,255,0));
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finish_draw();
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}
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}
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break;
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case YUTANI_MSG_WINDOW_CLOSE:
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case YUTANI_MSG_SESSION_END:
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should_exit = 1;
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break;
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default:
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break;
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}
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free(m);
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m = yutani_poll_async(yctx);
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}
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}
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}
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yutani_close(yctx, wina);
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return 0;
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}
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