Update image representation and renderer

Hi all,

is there any way to update an image so MATLAB doesn't give the control back until those changes are represented in the screen by the renderer?

I know if I run:

tic
drawnow
toc

the drawnow function sends the renderer an update, but it returns the control when the renderer accepts the update, not when it has represented them.

Thanks in advance

Answer 1

[Image Analyst]

Try

% Change mouse pointer (cursor) to an hourglass.
% QUIRK: use 'watch' and you'll actually get an hourglass not a watch.
set(gcf,'Pointer','watch');
drawnow;  % Cursor won't change right away unless you do this.

When you want user to interact with the GUI again:

% Change mouse pointer (cursor) to an arrow.
set(gcf,'Pointer','arrow');
drawnow; % Cursor won't change right away unless you do this.

[Lask]

Sorry but I cannot see how could this help to answer my question. I just want to track the exact moment when the screen refreshes and shows a new frame.

[Image Analyst]

It basically takes control away from the user (or so the user thinks) and doesn't return control until you tell it to. But if that's not what you want, see Walter's response.

[Walter Roberson]

There is a blog entry that says that control is returned from drawnow() when the renderer portion has accepted the update request; that is not something the user can change to not return control until the frame update.

Answer 2

[Walter Roberson]

There is pretty much no point in trying to do this without using the free thrid-party PsychToolbox, which has been carefully designed to provide timings relative to the vertical refresh of when an image gets painted.