how to stop while loop by right mouse button click

I would like to stop execution of the while loop by pressung right-click button. I wrote small function to pickup point from graph:

function y=graph_scan_ext (Name,Title,Xax,Yax,u,v)
Name=Name;
Tit=Title;
Xax=Xax;
Yax=Yax;
mainfg=figure();
mainax=axes();
htxt=uicontrol('Style','Text');

set(mainfg,'Name',Name,'NumberTitle','off');

x=u;
y=v;
plot(mainax,x,y);
title(Tit);
xlabel(Xax);
ylabel(Yax);
hold;
mark=0;
q=[];
while mark==0;
    c=ginput(1);
    scatter(c(1),c(2));
    q=[q;c];
  prompt = 'To continue press Enter; To stop, press any other key:';
  str=input(prompt,'s');

if isempty(str)==0
   mark=1;
   y=q;
end

end
---------------

I works, but every time you need to confirm that you want to continue by pressing Enter or stop by pressing any other key.

My goal is to replace "key" action with simply right click of mouse button to stop while execution and do nothing to continue. I tried to change "while loop" like this:

while mark==0;
    set(mainfg,'SelectionType','normal');
    c=ginput(1);
    scatter(c(1),c(2));
    q=[q;c]
  set(mainfg,'Selectiontype','alt');
set(mainfg,'WindowButtonDownFcn',@RightButDownFcn)
function click=RightButDownFcn(mainfg,event_data);
   break;
 end
y=q;
end

And got

Error: File: graph_scan_rc.m Line: 36 Column: 1
Function definition is misplaced or improperly nested.

Answer 1

[Walter Roberson]

ax = gca;
fig = ancestor(ax, 'figure');

q = [];
hold(ax, 'on');

while true
  c = ginput(1);
  sel = get(fig, 'SelectionType');
  if strcmpi(sel, 'alt'); break; end
  scatter(c(1),c(2));
  q=[q;c]
end

hold(ax, 'off')

[Sergey Lopatnikov]

Thank you, it works perfectly.

Answer 2

[Chad Greene]

From an old answer by Jose-Luis,

f = figure(1);
click_type=get(f,'SelectionType');
if strcmp(click_type,'normal') %right click
   %Do some stuff
elseif strcmp(click_type,'alt') %left click
   %Do some other stuff
end

[Sergey Lopatnikov]

It definitely does not work.