draw_brace.m

function h = draw_brace(start, stop, width, varargin)
% draw_brace   Draw curly brace on current figure
%	draw_brace([X1, Y1], [X2, Y2]) draws a curly brace from the point [X1,
%	Y1] to the point [X2, Y2]
%
%	draw_brace([X1,Y1], [X2,Y2], W) draws a brace using the brace width W.
%
%	draw_brace(..., 'Param1', 'Value1', 'Param2', 'Value2') draws a brace
%	using the LineSeries property values specified by 'Param1'/'Value1',
%	'Param2'/'Value2', ... .
%
%	h = draw_brace(...) returns the LineSeries handle to the brace.
%
%	Example:
%	   h = draw_brace([0 0], [1 1], 20, 'Color', 'k')

	% Get axis size
	pos = get(gca, 'Position');
	opos = get(gcf, 'Position');
	ylims = ylim;
	xlims = xlim;

	% Take logarithmic scale into account
	isxlog = strcmp(get(gca, 'XScale'), 'log');
	isylog = strcmp(get(gca, 'YScale'), 'log');

	if isxlog
		start(1) = log(start(1));
		stop(1) = log(stop(1));
		xlims = log(xlims);
	end

	if isylog
		start(2) = log(start(2));
		stop(2) = log(stop(2));
		ylims = log(ylims);
	end

	% Transform from axis to screen coordinates
	xscale = pos(3) * opos(3) / diff(xlims);
	yscale = pos(4) * opos(4) / diff(ylims);
	start = (start - [xlims(1) ylims(1)]) .* [xscale yscale];
	stop = (stop - [xlims(1) ylims(1)]) .* [xscale yscale];

	% Find standard width
	if nargin == 2
		width = norm(stop - start)/10;
	end

	% Find brace points
	th = atan2(stop(2)-start(2), stop(1)-start(1));
	c1 = start + width*[cos(th) sin(th)];
	c2 = 0.5*(start+stop) + 2*width*[-sin(th) cos(th)] - width*[cos(th) sin(th)];
	c3 = 0.5*(start+stop) + 2*width*[-sin(th) cos(th)] + width*[cos(th) sin(th)];
	c4 = stop - width*[cos(th) sin(th)];

	% Assemble brace coordinates
	q = linspace(0+th, pi/2+th, 50)';
	t = flipud(q);
	part1x = width*cos(t+pi/2) + c1(1);
	part1y = width*sin(t+pi/2) + c1(2);
	part2x = width*cos(q-pi/2) + c2(1);
	part2y = width*sin(q-pi/2) + c2(2);
	part3x = width*cos(q+pi) + c3(1);
	part3y = width*sin(q+pi) + c3(2);
	part4x = width*cos(t) + c4(1);
	part4y = width*sin(t) + c4(2);
	x = [part1x; part2x; part3x; part4x];
	y = [part1y; part2y; part3y; part4y];

	% Transform back to axis coordinates
	x = x / xscale + xlims(1);
	y = y / yscale + ylims(1);

	if isxlog
		x = exp(x)
	end

	if isylog
		y = exp(y)
	end

	% Plot brace
	h = line(x, y);

	for i = 1:2:numel(varargin)
		set(h, varargin{i}, varargin{i+1})
	end

end