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I'm currently working on a paper for an ACM conference and they require me to use the sigplanconf.cls

I want to use subcaption, but if I add


then I get the following messages :

Package caption Warning: Unsupported document class (or package) detected,
(caption)                usage of the caption package is not recommended.
! Package caption Error: No float type 'copyrightbox' defined.

Anyone encounter that problem ? Is there a fix that doesn't require messing with the cls since I'm supposed to use it as is ?

Full MWE :





\conferenceinfo{XXX '13}{Date, Place.} 
\copyrightdata{[numbers] \copyright2013 IEEE}

\title{Title Text}
\subtitle{Subtitle Text, if any}




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I don't get any error when I load figures. About the warning message, ask them directly about the rules on using subfigures. – hpesoj626 Dec 12 '12 at 2:30
I get a warning but no no error. In general, it means that the given documentclass has its own way of defining the caption command – cmhughes Dec 12 '12 at 4:30
Is it possible taht it comes from my version of latex then ? – Lexiel Dec 13 '12 at 17:57

(CW from comments)

The package caption is incompatible with the sigplanconf class that implements its own method for captions.

If you need to use the class, there's no way to incorporate subcaption that relies on caption working.

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The same error occurs with the sig-alternate template, but is fixed there by using


This might work for you as well. Reference at: http://tug.org/pipermail/texhax/2010-September/015596.html

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A similar warning is produced when using the sig-alternate.cls style. The issue there is that ACM defined bold captions, so as suggested here, just load the caption package with the font option set to bold:


This way you can freely use the subcaption package with the ACM proceedings class, without affecting the (ugly) bold captions they require.

You can include also skip=\baselineskip as suggested in the linked answer, but note it will eat more of your paper's space.

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