MATLAB Function Reference

drawnow - Flush event queue and update figure window

Syntax

drawnow
drawnow expose
drawnow update

Description

drawnow causes figure windows and their children to update and flushes the system event queue. Any callbacks generated by incoming events (e.g. mouse or key events) are dispatched before drawnow returns.

drawnow expose causes only graphics objects to refresh, if needed. It does not allow callbacks to execute and does not process other events in the queue.

drawnow update causes only non-graphics objects to refresh, if needed. It does not allow callbacks to execute and does not process other events in the queue.

You can combine the expose and update options to obtain both effects.

drawnow expose update

Other Events That Cause Event Queue Processing

Other events that cause MATLAB to flush the event queue and draw the figure includes:

• Returning to the MATLAB prompt

• Executing the following functions

  • figure

  • getframe

  • input

  • keyboard

  • pause

• Functions that wait for user input (i.e., waitforbuttonpress, waitfor, ginput)

• Any code that causes one of the above functions to be executed. For example, suppose h is the handle of an axes. Calling axes(h) causes its parent figure to be made the current figure and brought to the front of all displayed figures, which results in the event queue being flushed.

Examples

Using drawnow in a loop causes the display to update while the loop executes:

t = 0:pi/20:2*pi;
y = exp(sin(t));
h = plot(t,y,'YDataSource','y');
for k = 1:.1:10
	y = exp(sin(t.*k));
	refreshdata(h,'caller') % Evaluate y in the function workspace
	drawnow; pause(.1)
end

See Also

waitfor, waitforbuttonpress

Figure Windows for related functions

dragrect

dsearch