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Re: repeated use of TVRD() gives different results [message #93756 is a reply to message #93750]

Wed, 12 October 2016 20:11

wlandsman
Messages: 743
Registered: June 2000

Senior Member

Thanks. Interestingly, I don't find any other problems with using IDL_GR_X_RETAIN = 1 (the default value) on my MacBook. The backing store seems to work fine, and you only run into trouble when using TVRD().

It turns out that this has been a cause of a lot of mysterious color problems I've had when using Coyote graphics. The safe fix is to always set RETAIN=2 but I've also sent a pull request to https://github.com/idl-coyote/coyote to update CGCOLOR so that it never uses TVRD() on X windows when IDL_GR_X_RETAIN is less than 2. I've also put an updated CGCOLOR on
http://idlastro.gsfc.nasa.gov/ftp/pro/coyote/cgcolor.pro

--Wayne

On Wednesday, October 12, 2016 at 9:42:06 AM UTC-4, ri...@crd.ge.com wrote:
> There's a note in the documentation under TVRD about "unexpected results" unless IDL is providing the backing store (which I hadn't seen before). Ages ago, I found that TVRD() didn't work properly when the graphics window extended off the edge of the screen. (I solved it by copying the window's contents to a pixmap and calling TVRD on the pixmap.) The note explains why.
>
> --Wayne

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[Message index]

		repeated use of TVRD() gives different results By: wlandsman on Tue, 11 October 2016 11:44
		Re: repeated use of TVRD() gives different results By: Burch on Tue, 11 October 2016 12:55
		Re: repeated use of TVRD() gives different results By: wlandsman on Tue, 11 October 2016 20:29
		Re: repeated use of TVRD() gives different results By: Bill Nel on Wed, 12 October 2016 06:41
		Re: repeated use of TVRD() gives different results By: wlandsman on Wed, 12 October 2016 20:11
		Re: repeated use of TVRD() gives different results By: penteado on Fri, 28 October 2016 12:03
		Re: repeated use of TVRD() gives different results By: rawahranger on Sat, 15 October 2016 11:36

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