triangle_group_limit_set/initcairo.c

#include <sys/stat.h>
#include <sys/time.h>
#include <math.h>
#include <cairo-xlib.h>

#include "initcairo.h"

#define ERROR(condition, msg, ...) if(condition){fprintf(stderr, msg, ##__VA_ARGS__); return 0;}

static Bool alwaysTruePredicate(Display *display, XEvent *event, XPointer arg)
{
	return true;
}

GraphicsInfo *initCairo(int screen, int mask, int width, int height, const char *name)
{
	GraphicsInfo *info = malloc(sizeof(GraphicsInfo));
	DimensionsInfo *dim = malloc(sizeof(DimensionsInfo));
	info->dim = dim;

	mask |= StructureNotifyMask | ExposureMask | KeyPressMask | ButtonPressMask | PointerMotionMask;

	info->display = XOpenDisplay(NULL);
	ERROR(!info->display, "Failed to open X display\n");

	Visual *visual = XDefaultVisual(info->display, screen);
	int depth = XDefaultDepth(info->display, screen);
	Window root = XRootWindow(info->display, screen);
	XSetWindowAttributes swa;
	info->cmap = XCreateColormap(info->display, root, visual, AllocNone);
	swa.colormap = info->cmap;
	swa.background_pixmap = None;
	swa.border_pixel = 0;
	swa.event_mask = mask;
	info->win = XCreateWindow(info->display, root, 0, 0, width, height, 0, depth, InputOutput, visual, CWBorderPixel|CWColormap|CWEventMask, &swa);
	ERROR(!info->win, "Failed to create window.\n");
	XStoreName(info->display, info->win, name);

	XMapWindow(info->display, info->win);

	// create xlib surface
	info->surface = cairo_xlib_surface_create(info->display, info->win, visual, width, height);
	cairo_xlib_surface_set_size(info->surface, width, height);
	info->front_context = cairo_create(info->surface);
	cairo_set_antialias(info->front_context, CAIRO_ANTIALIAS_NONE);

	// create backbuffer surface
	int stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, width);
	info->buffer = malloc(stride*height);
	info->buffer_surface = cairo_image_surface_create_for_data(info->buffer, CAIRO_FORMAT_ARGB32, width, height, stride);
	info->buffer_context = cairo_create(info->buffer_surface);
	cairo_matrix_init_identity(&info->dim->matrix);
	info->dim->width = width;
	info->dim->height = height;
	updateDimensions(info->dim);

	info->wm_delete_window = XInternAtom(info->display, "WM_DELETE_WINDOW", 0);
	info->wm_protocols = XInternAtom(info->display, "WM_PROTOCOLS", 0);
	XSetWMProtocols(info->display, info->win, &info->wm_delete_window, 1);

	XFlush(info->display);

	return info;
}

void destroyCairo(GraphicsInfo *info)
{
	cairo_destroy(info->buffer_context);
	cairo_destroy(info->front_context);
	cairo_surface_destroy(info->surface);
	cairo_surface_destroy(info->buffer_surface);
	free(info->buffer);
	XDestroyWindow(info->display, info->win);
	XFreeColormap(info->display, info->cmap);
	XCloseDisplay(info->display);
	free(info->dim);
	free(info);
}

void startTimer(GraphicsInfo *info)
{
	gettimeofday(&info->start_time, NULL);
	info->frames = 0;
}

void waitUpdateTimer(GraphicsInfo *info)
{
	struct timeval current_time;
	double new_elapsed;

	gettimeofday(&current_time, NULL);
	new_elapsed = current_time.tv_sec - info->start_time.tv_sec;
	new_elapsed += (current_time.tv_usec - info->start_time.tv_usec) * 1e-6;
	info->frametime = new_elapsed - info->elapsed;
	if(info->frametime < 0.01) {              // frames < 10ms are considered too short; sleep a while and then measure again
		usleep(10000 - info->frametime*1e6);
		gettimeofday(&current_time, NULL);
		new_elapsed = current_time.tv_sec - info->start_time.tv_sec;
		new_elapsed += (current_time.tv_usec - info->start_time.tv_usec) * 1e-6;
		info->frametime = new_elapsed - info->elapsed;
	}
	info->elapsed = new_elapsed;
	info->frames++;
}

int processStandardEvent(GraphicsInfo *info, XEvent *ev, void (*draw)(void *))
{
	int state;
	static int last_x, last_y;
	int stride;
	int status = STATUS_NOTHING;

	switch(ev->type) {

	case Expose:
		return STATUS_REDRAW;

	case ConfigureNotify:
		printf("ConfigureNotify Event, new dimensions: %d %d %d %d\n", ev->xconfigure.x, ev->xconfigure.y, ev->xconfigure.width, ev->xconfigure.height);
		info->dim->width = ev->xconfigure.width;
		info->dim->height = ev->xconfigure.height;
		updateDimensions(info->dim);
		cairo_xlib_surface_set_size(info->surface, info->dim->width, info->dim->height);

		cairo_destroy(info->buffer_context);
		cairo_surface_destroy(info->buffer_surface);
		free(info->buffer);
		stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, info->dim->width);
		info->buffer = malloc(stride*info->dim->height);
		info->buffer_surface = cairo_image_surface_create_for_data(info->buffer, CAIRO_FORMAT_ARGB32, info->dim->width, info->dim->height, stride);
		info->buffer_context = cairo_create(info->buffer_surface);

		return STATUS_REDRAW;

	case KeyPress:
		state = ev->xkey.state & (ShiftMask | LockMask | ControlMask);
		if(state == 0 && ev->xkey.keycode == 24)
			return STATUS_QUIT;
		return STATUS_NOTHING;

	case ButtonPress:
		if(ev->xbutton.button == 4) {
			cairo_matrix_t transform;
			cairo_matrix_init_identity(&transform);
			cairo_matrix_translate(&transform, ev->xbutton.x, ev->xbutton.y);
			cairo_matrix_scale(&transform, 5.0/4.0, 5.0/4.0);
			cairo_matrix_translate(&transform, -ev->xbutton.x, -ev->xbutton.y);
			cairo_matrix_multiply(&info->dim->matrix, &info->dim->matrix, &transform);
			status = STATUS_REDRAW;
		} else if(ev->xbutton.button == 5) {
			cairo_matrix_t transform;
			cairo_matrix_init_identity(&transform);
			cairo_matrix_translate(&transform, ev->xbutton.x, ev->xbutton.y);
			cairo_matrix_scale(&transform, 4.0/5.0, 4.0/5.0);
			cairo_matrix_translate(&transform, -ev->xbutton.x, -ev->xbutton.y);
			cairo_matrix_multiply(&info->dim->matrix, &info->dim->matrix, &transform);
			status = STATUS_REDRAW;
		}

		last_x = ev->xbutton.x;
		last_y = ev->xbutton.y;
		updateDimensions(info->dim);
		return status;

	case MotionNotify:
		if(ev->xmotion.state & Button1Mask && !(ev->xmotion.state & ShiftMask)) {
			int dx = ev->xmotion.x - last_x;
			int dy = ev->xmotion.y - last_y;

			cairo_matrix_t transform;
			cairo_matrix_init_identity(&transform);
			cairo_matrix_translate(&transform, dx, dy);
			cairo_matrix_multiply(&info->dim->matrix, &info->dim->matrix, &transform);
			status = STATUS_REDRAW;
		} else if(ev->xmotion.state & Button1Mask && ev->xmotion.state & ShiftMask) {
			double width = (double) cairo_xlib_surface_get_width(info->surface);
			double height = (double) cairo_xlib_surface_get_height(info->surface);

			double angle =
				atan2((double)ev->xmotion.y - height/2, (double)ev->xmotion.x - width/2)-
				atan2((double)last_y        - height/2, (double)last_x        - width/2);

			cairo_matrix_t transform;
			cairo_matrix_init_identity(&transform);
			cairo_matrix_translate(&transform, width/2, height/2);
			cairo_matrix_rotate(&transform, angle);
			cairo_matrix_translate(&transform, -width/2, -height/2);
			cairo_matrix_multiply(&info->dim->matrix, &info->dim->matrix, &transform);
			status = STATUS_REDRAW;
		}

		last_x = ev->xmotion.x;
		last_y = ev->xmotion.y;

		return status;

	case ClientMessage:
		if((Atom)ev->xclient.message_type == info->wm_protocols && (Atom)ev->xclient.data.l[0] == info->wm_delete_window) {
//			printf("Window closed\n");
			return STATUS_QUIT;
		}
		return STATUS_NOTHING;
	}

	return STATUS_NOTHING;
}

int checkEvents(GraphicsInfo *info, int (*process)(GraphicsInfo*, XEvent*), void (*draw)(void *)) // get any events from the queue and the server, process them if neccessary, quit if wanted
{
	XEvent ev;
	int x11_fd;
	fd_set fds;
	int status = STATUS_NOTHING, result;

	int x11_event = 0;

	if(XPending(info->display)) { // select() would miss events which are picked up already, so we have to catch them first
		x11_event = 1;
	} else {
		x11_fd = ConnectionNumber(info->display);
		FD_ZERO(&fds);
		FD_SET(x11_fd, &fds);

		select(x11_fd + 1, &fds, NULL, NULL, NULL);

		if(FD_ISSET(x11_fd, &fds))
			x11_event = 1;
	}

	if(x11_event) {
		while(XPending(info->display)) {
			XNextEvent(info->display, &ev);

			if(ev.xany.window != info->win)
				continue;

			result = processStandardEvent(info, &ev, draw);
			if(result == STATUS_QUIT)
				return STATUS_QUIT;
			else if(result == STATUS_REDRAW)
				status = STATUS_REDRAW;

			result = process(info, &ev);
			if(result == STATUS_QUIT)
				return STATUS_QUIT;
			else if(result == STATUS_REDRAW)
				status = STATUS_REDRAW;
		}
	}

	return status;
}

// this computes center, radius and scalefactor out of ctx->matrix
void updateDimensions(DimensionsInfo *dim)
{
	double det = dim->matrix.xx * dim->matrix.yy - dim->matrix.xy * dim->matrix.yx;
	double cx = (double)dim->width/2;
	double cy = (double)dim->height/2;
	double r = 2*sqrt((cx*cx + cy*cy)/det); // this is not safe anymore if we have non-uniform scaling

	// don't use cairo_device_to_user() since the matrix might not be our CTM yet
	cx -= dim->matrix.x0;
	cy -= dim->matrix.y0;
	dim->center_x = (  dim->matrix.yy * cx - dim->matrix.xy * cy) / det;
	dim->center_y = (- dim->matrix.yx * cx + dim->matrix.xx * cy) / det;
	dim->radius = r;
	dim->scalefactor = sqrt(det);
}