Rectangle whose free corner follows the mouse cursor

mouse_rectangle.m

function mouse_rectangle
    % Make a rectangle that is anchored at one corner at the axis origin but follows
    % the mouse cursor at the other.
    %
    % Instructions
    % Run "mouse_rectangle" then move mouse cursor over the axes.
    %
    % Inputs
    % none
    %
    % Outputs
    % None


    % Build a pretty figure window
    hFig = figure(123324);
    clf(hFig)
    hAx = axes(hFig);

    set(hAx, ...
        'XLim', [-1,1], ...
        'YLim', [-1,1], ...
        'XTick', [-1:1], ...
        'YTick', [-1:1], ...
        'Box', 'On')


    % Set callback for mouse motion
    set(hFig, ...
        'MenuBar','none', ...
        'WindowButtonMotionFcn', @mouseMoved_Callback)



    % Indicate the axis origin with two intersecting lines
    hold on
    plot([-1,1],[0,0],'--k')
    plot([0,0],[-1,1],'--k')


    % Plot an invisible patch object that will follow the mouse cursor
    hPatch = patch([0,0,0,0], [0,0,0,0],1);
    set(hPatch, ...
        'EdgeColor', 'r', ...
        'FaceColor', [1,0.9,0.9]);


    %% Internal functions follow
    function mouseMoved_Callback(src,~)
        % This callback runs every time the mouse moves over the figure window
        ax = src.Children; % There is just one child, so don't index or check what it is
        mousePos = ax.CurrentPoint(1,1:2);

        % Bail out if the mouse is out of range
        if any(abs(mousePos)>1)
            return
        end

        % Get the properties of the rectangle and modify them
        mouseX   = mousePos(1);
        mouseY   = mousePos(2);
        hPatch = findobj(ax.Children,'Type','Patch');
        hPatch.XData(2:3) = mouseX;
        hPatch.YData(3:4) = mouseY;