pt2game/pinetab2_framework.cpp

#include <libdrm/drm.h>
#include <libdrm/drm_fourcc.h>
#include <errno.h>
#include <error.h>
#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/random.h>
#include <linux/input.h>
#include <math.h>
#include <sys/timerfd.h>
#include <sys/poll.h>
#include <inttypes.h>
#include "engine.h"
#include "compiled_structures.h"

#define PLAYFIELD_WIDTH 1280
#define PLAYFIELD_HEIGHT 800


static int touchscreen_fd;

static struct navmesh null_navmesh = {0};
struct navmesh *cur_navmesh = &null_navmesh;
struct object objects[MAX_GAME_OBJECTS];
struct script scripts[MAX_GAME_SCRIPTS];
bool need_rerender = false;



#define MAX_MT_SLOTS 16
static struct mtslot {
	int x, y, touch, lasttouch;
	int lastx, lasty;
} mtslots[MAX_MT_SLOTS] = {0};
static struct mtslot *curslot = &mtslots[0]; // TODO: query the current value of ABS_MT_SLOT

static void handle_tap(int x, int y); // x and y in landscape orientation
static void poll_touchscreen() {
	struct input_event buf[64];
	int nread;
retry_read:
	nread = read(touchscreen_fd, buf, sizeof buf);
	if(nread < 0) {
		if(errno == EINTR)
			goto retry_read;
		if(errno == EAGAIN)
			return;
		error(1, errno, "read touchscreen");
	}

	if(nread % sizeof(struct input_event))
		error(1, 0, "odd size read from touchscreen");

	for(int i = 0; i < nread; i += sizeof(struct input_event)) {
		struct input_event *evt = (struct input_event*)((char*)buf + i);
		//printf("type=%d code=%d value=%d\n", evt->type, evt->code, evt->value);
		if(evt->type == EV_SYN && evt->code == SYN_DROPPED) error(0, 0, "got SYN_DROPPED"); // TODO: resynchronize
		if(evt->type == EV_SYN && evt->code == SYN_REPORT) {
			for(int j = 0; j < MAX_MT_SLOTS; j++) {
				struct mtslot *s = &mtslots[j];
				if(s->touch) {
					//printf("slot %d x=%d y=%d\n", j, s->x, s->y);
					/*uint32_t col;
					switch(j & 3) {
						case 0: col = 0xFFFFFFFF; break;
						case 1: col = 0xFF0000FF; break;
						case 2: col = 0x00FF00FF; break;
						case 3: col = 0x0080FFFF; break;
					}

					int segs = s->lastx<0 ? 1 : (int)(0.9 + 2*sqrt((s->lastx-s->x)*(s->lastx-s->x) + (s->lasty-s->y)*(s->lasty-s->y)));
					if(segs<1) segs=1;
					for(int f = 0; f <= segs; f++) {
						int _x, _y;
						if(s->lastx != -1) {
							_x = (s->lastx + (s->x-s->lastx)*f/segs);
							_y = (s->lasty + (s->y-s->lasty)*f/segs);
						} else {
							_x = s->x;
							_y = s->y;
						}
						for(int dy = -5; dy <= 5; dy++) {
							for(int dx = -5; dx <= 5; dx++) {
								if(dx*dx + dy*dy <= 5*5) {
									int x = dx+_x, y = dy+_y;
									if(x >= 0 && y >= 0 && x < 800 && y < 1280) {
										*(uint32_t*)(fb + (y*800 + x)) = col;
									}
								}
							}
						}
					}*/
					if(!s->lasttouch) {
						handle_tap(s->y, 799-s->x);
					}
				}
				s->lasttouch = s->touch;
				s->lastx = s->x;
				s->lasty = s->y;
			}
		}
		if(evt->type == EV_ABS && evt->code == ABS_MT_SLOT) {
			if(evt->value >= 0 && evt->value < MAX_MT_SLOTS) curslot = &mtslots[evt->value];
			else curslot = NULL;
		}
		if(evt->type == EV_ABS && evt->code == ABS_MT_POSITION_X) {
			if(curslot) curslot->x = evt->value;
		}
		if(evt->type == EV_ABS && evt->code == ABS_MT_POSITION_Y) {
			if(curslot) curslot->y = evt->value;
		}
		if(evt->type == EV_ABS && evt->code == ABS_MT_TRACKING_ID) {
			if(curslot) {
				if(!curslot->touch) {
					curslot->lastx = curslot->lasty = -1;
				}
				curslot->touch = evt->value != -1;
			}
		}
	}
}

// Rendering is dumb, double-buffered with page flip, always redrawing the whole frame.
// It could be improved.

uint32_t current_animframe;

struct sprite {
	int width, height;
	uint32_t *pixels;
};

static uint32_t *curfb; // used during render cycle
static void blit(int x, int y, const struct sprite *spr) {
	uint32_t *inbase = spr->pixels;
	//printf("blit %dx%d at %d,%d\n", spr->width, spr->height, x, y);
	y = PLAYFIELD_HEIGHT - spr->height - y;
	if(y >= PLAYFIELD_HEIGHT || x >= PLAYFIELD_WIDTH || y <= -spr->height || x <= -spr->width) return;
	if(spr->height > PLAYFIELD_HEIGHT) error(1, 0, "sprite bigger than playfield not supported"); // would need to clip top and bottom simultaneously - not implemented for now

	uint32_t *outbase = curfb + x*PLAYFIELD_HEIGHT + y;
	for(int dx = 0; dx < spr->width; dx++, inbase += spr->height, outbase += PLAYFIELD_HEIGHT, x++) {
		if(x < 0) continue;
		if(x >= PLAYFIELD_WIDTH) break;

		if(y < 0) {
			// TODO: loop inversion would make sense
			int offset = -y;
			// must have at least one pixel to copy
			memcpy(outbase+offset, inbase+offset, (spr->height-offset)*4);
		} else {
			int ncopy = PLAYFIELD_HEIGHT-y;
			if(ncopy > spr->height) ncopy = spr->height;
			memcpy(outbase, inbase, ncopy*4);
		}
	}
}

void scene_set_navmesh(struct navmesh *navmesh) {
	cur_navmesh = navmesh;
}

static uint32_t scene_generation_count = 0;
static int curscene;
void transition_scene(int scene) {
	scene_generation_count++;
	curscene = scene;
	memset(objects, 0, sizeof objects);
	memset(scripts, 0, sizeof scripts); // script state is local to scene, so no cancel notification
	cur_navmesh = &null_navmesh;
	scene_setup(scene);
}

void scene_add_object(int id, int x, int y, int width, int height, const char *pixels) {
	if(id == 0) error(1, 0, "scene_add_object: id 0 is invalid");

	for(int i = 0; i < MAX_GAME_OBJECTS; i++) {
		if(objects[i].id == 0) {
			objects[i].id = id;
			objects[i].x = x;
			objects[i].y = y;
			objects[i].width = width;
			objects[i].height = height;
			objects[i].pixels = pixels;
			return;
		}
	}
	error(1, 0, "too many game objects");
}

struct object *find_object_by_id(int id) {
	for(int i = 0; i < MAX_GAME_OBJECTS; i++) {
		if(objects[i].id == id)
			return &objects[i];
	}
	return nullptr;
}
struct script *scene_add_script(int id, bool interrupt_existing) {
	for(int i = 0; i < MAX_GAME_SCRIPTS; i++) {
		if(scripts[i].id == id && interrupt_existing) {
			// interrupt existing script?
			// player walk script is safe to trivially cancel, at least
			scripts[i].id = 0;
			if(deliver_script_wakeup(SCRIPT_WAKEUP_OTHER_SCRIPT, id, SCRIPT_WAKEUP_OTHER_SCRIPT_INTERRUPTED, 0, 0, 0, 0))
				return NULL; // scene changed. this probably crashes the caller. should be tested or we need a better way to cancel all running operations on scene change.
		}
		if(scripts[i].id == 0) {
			memset(&scripts[i], 0, sizeof(scripts[i]));
			scripts[i].id = id;
			return &scripts[i];
		}
	}
	error(1, 0, "too many game scripts");
	__builtin_unreachable();
}

static void closest_point_inside_tri(int *x, int *y, const struct navmesh_tri *tri) {
	double fx = *x, fy = *y;
	int edgeHitMask = 0;

	// Moving a point outside of one half-plane can move it into another half-plane, so check again.
	// If this happens, we must be in a corner region.
	// Repeated normal-vector moves don't necessarily bring us to the corner, but we can just hardcode the corner.
	for(int j = 0; j < 2; j++) {
		for(int i = 0; i < tri->num_verts; i++) {
			double edgeval = fx*tri->edges[i].a + fy*tri->edges[i].b + tri->edges[i].c;
			if(edgeval <= 0) {
				// edge.a,b is normalized so that moving 1 unit of a and 1 unit of b changes edgeval by 1.
				fx -= tri->edges[i].a*edgeval;
				fy -= tri->edges[i].b*edgeval;
				edgeHitMask |= 1 << i;
			}
		}
	}

	for(int i = 0; i < tri->num_verts; i++) {
		int next = (i+1) % tri->num_verts;
		int mask = (1 << i) | (1 << next);
		if((edgeHitMask & mask) == mask) {
			*x = tri->points[next].x;
			*y = tri->points[next].y;
			return;
		}
	}
/*
	switch(edgeHitMask) {
	case 3: // hit edge 0-1 and 1-2
		*x = tri->points[1].x;
		*y = tri->points[1].y;
		return;
	case 5: // hit edge 0-1 and 2-0
		*x = tri->points[0].x;
		*y = tri->points[0].y;
		return;
	case 6: // hit edge 1-2 and 2-0
		*x = tri->points[2].x;
		*y = tri->points[2].y;
		return;
	}*/

	// may be slightly outside of triangle due to rounding errors, but good enough for us
	*x = (int)(fx + 0.5);
	*y = (int)(fy + 0.5);
}

static double point_to_point_dist(int x, int y, const struct navmesh_point *pt) {
	x -= pt->x;
	y -= pt->y;
	return sqrt(x*x + y*y);
}

// Returns distance from triangle, 0 if inside.
static double is_point_in_tri(int x, int y, const struct navmesh_tri *tri) {
	/*double edgedist[3]; // positive if outside
	for(int edge = 0; edge < 3; edge++)
		edgedist[edge] = -(x*tri->edges[edge].a + y*tri->edges[edge].b + tri->edges[edge].c);
	if(edgedist[0] < 0 && edgedist[1] < 0 && edgedist[2] < 0) return 0; // inside
	if(edgedist[0] >= 0 && edgedist[1] >= 0) return point_to_point_dist(x, y, &tri->points[0]); // are these correct? shouldn't it be points 1,2,0?
	if(edgedist[1] >= 0 && edgedist[2] >= 0) return point_to_point_dist(x, y, &tri->points[1]);
	if(edgedist[2] >= 0 && edgedist[0] >= 0) return point_to_point_dist(x, y, &tri->points[2]);
	if(edgedist[0] >= 0) return edgedist[0];
	if(edgedist[1] >= 0) return edgedist[1];
	if(edgedist[2] >= 0) return edgedist[2];*/

	double edgedist[tri->num_verts];
	bool all_inside = true;
	for(int edge = 0; edge < tri->num_verts; edge++) {
		edgedist[edge] = -(x*tri->edges[edge].a + y*tri->edges[edge].b + tri->edges[edge].c);
		if(edgedist[edge] > 0)
			all_inside = false;
	}
	if(all_inside) return 0;
	for(int edge = 0; edge < tri->num_verts; edge++) {
		int next = (edge+1)%tri->num_verts;
		if(edgedist[edge] >= 0 && edgedist[next] >= 0) return point_to_point_dist(x, y, &tri->points[next]);
	}
	for(int edge = 0; edge < tri->num_verts; edge++)
		if(edgedist[edge] >= 0)
			return edgedist[edge];

	return 0; // branch should be unreachable; maybe within epsilon of triangle border?
}
static int find_navmesh_tri(int x, int y, int tolerance) {
	int best_tri = -1;
	double best_dist = tolerance;
	for(int i = 0; i < cur_navmesh->num_tris; i++) {
		double dist = is_point_in_tri(x, y, &cur_navmesh->tris[i]);
		if(dist == 0)
			return i;
		if(dist < best_dist) {
			best_dist = dist;
			best_tri = i;
		}
	}
	return best_tri;
}

static void update_player_walk_script_on_frame(struct script *scr, int wakeupMode, int, int, int, int);

static uint32_t player_walk_generation = 0;
void start_player_walk_to_point(int targetX, int targetY) {
	player_walk_generation++;

	struct object *player = find_object_by_id(OBJID_PLAYER);
	if(!player) error(1, 0, "start_player_walk_to_point: no player object");

	int destTri = find_navmesh_tri(targetX, targetY, 999999);
	if(destTri == -1) error(1, 0, "start_player_walk_to_point: no navmesh");

	struct script_player_walk *player_walk_script = (struct script_player_walk *)scene_add_script(OBJID_PLAYER_WALK_SCRIPT, true);
	player_walk_script->targetX = targetX;
	player_walk_script->targetY = targetY;
	player_walk_script->targetNavmeshTri = destTri;
	player_walk_script->wakeupMode = SCRIPT_WAKEUP_VIDEO_FRAME;
	player_walk_script->wakeupFn = update_player_walk_script_on_frame;

	int sourceTri = find_navmesh_tri(player->x+player->width*2, player->y+player->height, 1000000);
	player_walk_script->currentNavmeshTri = sourceTri;
	printf("set course from triangle %d to %d\n", sourceTri, destTri);
}

void handle_tap(int x, int y) {
	uint32_t gencount = scene_generation_count;
	uint32_t walkgen = player_walk_generation;
	for(int i = 0; i < MAX_GAME_OBJECTS; i++) {
		if(objects[i].id && (unsigned int)(x - objects[i].x) < objects[i].width && (unsigned int)(y - objects[i].y) < objects[i].height) {
			onclick(curscene, objects[i].id);
			if(gencount != scene_generation_count) return; // early exit if scene changed, and don't walk the player either
		}
	}

	if(walkgen == player_walk_generation) { // no other handler moved the player
		struct object *player = find_object_by_id(OBJID_PLAYER);
		if(player) {
			int destTri = find_navmesh_tri(x, y, 50);
			if(destTri != -1) {
				int targetX = x, targetY = y;
				closest_point_inside_tri(&targetX, &targetY, &cur_navmesh->tris[destTri]);
				start_player_walk_to_point(targetX, targetY);
			}
		}
	}
}

static int move_towards(int cur, int target, int maxrate) {
	if(target > cur+maxrate) return cur+maxrate;
	if(target < cur-maxrate) return cur-maxrate;
	return target;
}

static void update_player_walk_script_on_frame(struct script *scr, int wakeupMode, int, int, int, int) {
	int script_id = scr->id;
	struct script_player_walk *player_walk_script = (struct script_player_walk *)scr;
	if(!player_walk_script) return;
	struct object *player = find_object_by_id(OBJID_PLAYER);
	if(!player) {
		player_walk_script->id = 0;
		deliver_script_wakeup(SCRIPT_WAKEUP_OTHER_SCRIPT, script_id, SCRIPT_WAKEUP_OTHER_SCRIPT_INTERRUPTED, 0, 0, 0, 0);
		return;
	}

	if(player_walk_script->currentNavmeshTri == -1) {
		// something weird happened. just teleport player and end movement.
		player->x = player_walk_script->targetX - player->width/2;
		player->y = player_walk_script->targetY - player->height;
		player_walk_script->id = 0;
		deliver_script_wakeup(SCRIPT_WAKEUP_OTHER_SCRIPT, script_id, SCRIPT_WAKEUP_OTHER_SCRIPT, 0, 0, 0, 0);
		need_rerender = true;
	} else {
		int x = player->x+player->width/2;
		int y = player->y+player->height;
		int nmtri = player_walk_script->currentNavmeshTri;
		int nextX;
		int nextY;
		int nextTri = -1;
		if(nmtri == player_walk_script->targetNavmeshTri) {
			nextX = player_walk_script->targetX;
			nextY = player_walk_script->targetY;
		} else {
			nextTri = cur_navmesh->pathfindgrid[player_walk_script->targetNavmeshTri * cur_navmesh->num_tris + nmtri];
			nextX = -1;
			for(int edge = 0; edge < cur_navmesh->tris[nmtri].num_verts; edge++) {
				if(cur_navmesh->tris[nmtri].edges[edge].other_tri == nextTri) {
					nextX = cur_navmesh->tris[nmtri].edges[edge].center.x;
					nextY = cur_navmesh->tris[nmtri].edges[edge].center.y;
					goto center_found;
				}
			}
			// shouldn't happen
			player_walk_script->id = 0;
			deliver_script_wakeup(SCRIPT_WAKEUP_OTHER_SCRIPT, script_id, SCRIPT_WAKEUP_OTHER_SCRIPT_INTERRUPTED, 0, 0, 0, 0);
			return;
		center_found:;
		}
		if(nextX == x && nextY == y) {
			printf("in triangle %d, next triangle %d\n", nmtri, nextTri);
			if(x == player_walk_script->targetX && y == player_walk_script->targetY) {
				player_walk_script->id = 0;
				deliver_script_wakeup(SCRIPT_WAKEUP_OTHER_SCRIPT, script_id, SCRIPT_WAKEUP_OTHER_SCRIPT, 0, 0, 0, 0);
			} else {
				player_walk_script->currentNavmeshTri = nextTri; // even if -1
			}
		} else {
			x = move_towards(x, nextX, 5);
			y = move_towards(y, nextY, 2);
			player->x = x - player->width/2;
			player->y = y - player->height;
		}
		need_rerender = true;
	}
}

bool deliver_script_wakeup(int wakeupMode, int wakeupArg1, int wakeupType, int arg1, int arg2, int arg3, int arg4) {
	uint32_t gen = scene_generation_count;
	for(int i = 0; i < MAX_GAME_SCRIPTS; i++) {
		if(scripts[i].id && scripts[i].wakeupMode == wakeupMode && scripts[i].wakeupArg1 == wakeupArg1) {
			scripts[i].wakeupFn(&scripts[i], wakeupType, arg1, arg2, arg3, arg4);
			if(scene_generation_count != gen) return true; // scene changed - abort early
		}
	}
	return false;
}


int main(int argc, char **argv) {

	if(getuid() != 0) {
		execlp("sudo", "sudo", argv[0], NULL);
		error(1, errno, "execlp");
		return 1;
	}

	int fd = open("/dev/dri/card0", O_RDWR | O_NONBLOCK);
	if(fd < 0) error(1, errno, "open display");
	touchscreen_fd = open("/dev/input/event1", O_RDONLY | O_NONBLOCK);
	if(touchscreen_fd < 0) error(1, errno, "open touchscreen");

	if(ioctl(fd, DRM_IOCTL_SET_MASTER, NULL) < 0) error(1, errno, "set master");

	// attach CRTC 51, connector 56, to a new framebuffer with a new dumbbuffer

	// create two buffers
	uint32_t *fbs[2];
	uint32_t fb_ids[2];
	for(int i = 0; i < 2; i++) {
		struct drm_mode_create_dumb createdumb = {
			.height = 1280,
			.width = 800,
			.bpp = 32,
			.flags = 0,
		};
		if(ioctl(fd, DRM_IOCTL_MODE_CREATE_DUMB, &createdumb) < 0) error(1, errno, "create dumb buffer");

		if(createdumb.pitch != 800*4 || createdumb.size != 1280*800*4)
			error(1, 0, "unexpected size for dumb buffer (pitch=%d size=%d)", (int)createdumb.pitch, (int)createdumb.size);

		struct drm_mode_fb_cmd2 addfb = {
			.width = 800,
			.height = 1280,
			.pixel_format = DRM_FORMAT_XRGB8888,
			.flags = 0,
			.handles = {createdumb.handle, 0, 0, 0},
			.pitches = {createdumb.pitch, 0, 0, 0},
			.offsets = {0, 0, 0, 0},
		};
		if(ioctl(fd, DRM_IOCTL_MODE_ADDFB2, &addfb) < 0) error(1, errno, "add framebuffer");

		struct drm_mode_map_dumb mapdumb = {
			.handle = createdumb.handle
		};
		if(ioctl(fd, DRM_IOCTL_MODE_MAP_DUMB, &mapdumb) < 0) error(1, errno, "map dumb buffer");

		fbs[i] = (uint32_t*)mmap(NULL, createdumb.size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, mapdumb.offset);
		if(!fbs[i]) error(1, errno, "mmap dumb buffer");
		fb_ids[i] = addfb.fb_id;

		memset(fbs[i], 0, createdumb.size);
	}

	uint32_t connectors[1] = {56};
	struct drm_mode_crtc crtc = {.crtc_id = 51};
	if(ioctl(fd, DRM_IOCTL_MODE_GETCRTC, &crtc) < 0) error(1, errno, "get crtc");
	//struct drm_mode_crtc oldcrtc = crtc;
	crtc.set_connectors_ptr = (uint64_t)connectors;
	crtc.count_connectors=1;
	crtc.fb_id = fb_ids[0];
	if(ioctl(fd, DRM_IOCTL_MODE_SETCRTC, &crtc) < 0) error(1, errno, "set crtc");

	int timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK | TFD_CLOEXEC);
	if(timerfd < 0) error(1, errno, "timerfd_create");
	{
		struct itimerspec tspec = {.it_interval = {.tv_nsec = 250000000}, .it_value = {.tv_nsec=250000000}};
		if(timerfd_settime(timerfd, 0, &tspec, NULL) < 0) error(1, errno, "timerfd_settime");
	}

	transition_scene(SCENE_LOBBY);

	int cur_buffer = 0;

	need_rerender = true;
	bool awaiting_vblank = false;
	for(;;) {
		struct pollfd polls[] = {
			{.fd = touchscreen_fd, .events = POLLIN},
			{.fd = timerfd, .events = POLLIN},
			{.fd = fd, .events = POLLIN},
		};
		const int NPOLLS = sizeof(polls)/sizeof(polls[0]);
		static const char *pollfd_labels[NPOLLS] = {"touchscreen", "animation timer", "display"};
		int npoll = poll(polls, NPOLLS, 0);
		if(npoll < 0) error(1, errno, "poll");

		// POLLERR, POLLHUP, POLLNVAL can always be returned
		for(int i = 0; i < NPOLLS; i++) {
			if(polls[i].revents & (POLLNVAL | POLLERR | POLLHUP)) {
				if(polls[i].revents & POLLNVAL) error(1, 0, "poll: got POLLNVAL (%s)", pollfd_labels[i]);
				if(polls[i].revents & POLLERR) error(1, 0, "poll: got POLLERR (%s)", pollfd_labels[i]);
				if(polls[i].revents & POLLHUP) error(1, 0, "poll: got POLLHUP (%s)", pollfd_labels[i]);
			}
		}
		if(polls[0].revents & POLLIN) {
			poll_touchscreen();
			need_rerender = true; // TODO not always
		}
		if(polls[1].revents & POLLIN) {
			uint64_t dummy; // don't care about expiration count
			if(read(timerfd, &dummy, sizeof dummy) < 0) error(1, errno, "read (timerfd)");
			current_animframe++;
			//printf("animation frame %u\n", (unsigned int)current_animframe);
			need_rerender = true;
		}
		if(polls[2].revents & POLLIN) {
			char buf[256];
			int nread = read(fd, buf, sizeof buf);
			if(nread < 0) error(1, errno, "read (display)");

			char *pos = buf;
			while(pos < buf + nread) {
				struct drm_event *evthdr = (struct drm_event*)pos;
				pos += evthdr->length;
				switch(evthdr->type) {
				case DRM_EVENT_FLIP_COMPLETE:
					awaiting_vblank = false;
					break;
				default:
					fprintf(stderr, "unknown DRM event type 0x%08" PRIx32, (unsigned int)evthdr->type);
					break;
				}
			}
		}

		if(!awaiting_vblank) {
			// return value ignored
			// What is this really doing? It's giving scripts the opportunity to trigger a video frame.
			// But if no script actually does, this can run over and over many times in the same video frame.
			// It's not saying a video frame happened, it's saying one can happen.
			deliver_script_wakeup(SCRIPT_WAKEUP_VIDEO_FRAME, 0, SCRIPT_WAKEUP_VIDEO_FRAME, 0, 0, 0, 0);
		}

		if(need_rerender && !awaiting_vblank) {
			cur_buffer = 1-cur_buffer; // for testing, just keep writing into the same buffer
			curfb = fbs[cur_buffer];

			for(int i = 0; i < MAX_GAME_OBJECTS; i++) {
				if(objects[i].id != 0 && objects[i].pixels) {
					struct sprite spr = {.width = objects[i].width, .height = objects[i].height, .pixels = (uint32_t*)objects[i].pixels};
					blit(objects[i].x, objects[i].y, &spr);
				}
			}

			struct drm_mode_crtc_page_flip flipcmd = {
				.crtc_id = crtc.crtc_id,
				.fb_id = fb_ids[cur_buffer],
				.flags = DRM_MODE_PAGE_FLIP_EVENT, // async flip doesn't work on pinetab
			};
			if(ioctl(fd, DRM_IOCTL_MODE_PAGE_FLIP, &flipcmd) < 0)
				error(1, errno, "DRM page flip");
			awaiting_vblank = true;
			need_rerender = false;
		}
	}

	//if(ioctl(fd, DRM_IOCTL_MODE_SETCRTC, &oldcrtc) < 0) error(1, errno, "restore crtc"); // doesn't work: EINVAL (maybe because framebuffer id is local to our connection)
}