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Index › Programming Questions & Help › Syntax Questions › Forcing screen updates
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Forcing screen updates (Read 2542 times)
Bejoscha
Forcing screen updates
Jun 16th, 2010, 11:56pm  
I know from the helpfiles that the screen is only updated at the end of the draw() function, but is there actually a way of forcing a screen update at a particular time of the sketch, e.g. just before putting a delay?
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PhiLho 
Re: Forcing screen updates
Reply #1 - Jun 17th, 2010, 4:47am  
That's a FAQ.
Basically, just don't use delay()...
Use millis() instead.
I should really take time to write a full article on the topic for our brand new wiki.
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Bejoscha
Re: Forcing screen updates
Reply #2 - Jun 18th, 2010, 12:24am  
Yes, this sounds like a good idea.
However, I'm not sure how to use millis() correctly for my needs.
Keeping it in a loop until some time elapses? But how does this help me update the screen? I do not want to execute draw every x-th time only, but rather more complicated have some objects which on conditions draw something or not, and while in general this should be "as fast as possible" there are certain times I want the algorithm to "to freeze" after the incident. (mainly for debugging.)
Well, I maybe "could" make a boolean and exit all loops and then use the millis() and boolean in the main-draw functions, but it seem really not very elegant to me. In particular, as I want to "hack it in & out" at several positions mainly during debugging.
That's why I would need a "stop here. Update Screen. Then pause" kind of functionality. Suggestions?
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blindfish
Re: Forcing screen updates
Reply #3 - Jun 18th, 2010, 1:19am  
As PhiLho says, this is a FAQ, which might have prompted you to search the forum...

Entering into a loop within draw will cause the same problems as using delay(): all you'll see drawn to the screen is the result of the last iteration of the loop.

The answer is to use conditions within draw to determine what state something is in and change the result of these conditions using the value of millis() compared to a stored start time + some arbitrary threshold...
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Where is the what if the what is in why?
 
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