Matlab - Closing vision.VideoPlayer handler - computer-vision

Question

First of all, excusme for my bad English. I am working in it.
I am working in a computer vision application. I am using a webcam. The main loop is like this:
while true
get frame
process frame
show frame in figure
end while
And I want something like this:
while figure is open
get frame
process frame
show frame in figure
end while
I used to use figure and imshow for plot the frame, and I used handlers for knowing when the figure is closed by the user.
fig = figure;
set(fig,'KeyPressFcn','exit = true;');
set(fig,'CloseRequestFcn', 'exit = true; delete(gcf)');
But now I am using the vision.VideoPlayer from the Computer System Toolbox because is faster, and I can not find a way to do some similar. I don't want to use a GUI.
The code is this (from this other thread):
vid = videoinput('winvideo', 1, 'RGB24_320x240'); %select input device
hvpc = vision.VideoPlayer; %create video player object
src = getselectedsource(vid);
vid.FramesPerTrigger =1;
vid.TriggerRepeat = Inf;
vid.ReturnedColorspace = 'rgb';
src.FrameRate = '30';
start(vid)
%start main loop for image acquisition
for t=1:500
imgO=getdata(vid,1,'uint8'); %get image from camera
hvpc.step(imgO); %see current image in player
end
Some idea?

Answer 1

You can find the figure handle of vision.VideoPlayer object by turning on "ShowHiddenHandles".
set(0, 'ShowHiddenHandles', 'on') % Revert this back to off after you get the handle
After this gcf can give you the handle. But it is risky to change callbacks for hidden handles. They might already have many of their callbacks set for proper functioning of VideoPlayer object. You might want to check for their validity and visibility to detect whether it is open.
h = gcf;
...
ishandle(h)
get(h, 'Visible') % will return 'off' if the figure is not visible.