Make it easier to open IHM files with .cif suffixes

[Tom Goddard]

Brinda Vallat asks if ChimeraX can make it easier to open IHM files with .cif file suffix.

Begin forwarded message:

From: Brinda Vallat
Subject: Re: ChimeraX support for IHMCIF
Date: November 25, 2025 at 5:56:39 AM PST
To: Tom Goddard
Cc: Ben Webb

Hello Tom,

I was wondering if you have thought about supporting IHM files without the "format ihm" argument.

We have received multiple "bug reports" from RCSB.org users about the downloaded mmCIF files not working with ChimeraX.

We have been telling users about the command line argument. However, it will be useful to have some kind of support.

Please let me know what you and other developers of ChimeraX think about this.

Thank you,
Brinda

[Tom Goddard]

Made some improvements which should help a little in opening IHM data. In ChimeraX 1.11 release candidate and daily builds Nov 25, 2025 and newer.

I added an Integrative Hybrid Models entry to Fetch By Id panel.

Added ".cif" file suffixs to allowed IHM file suffixes for open file dialog. This can help if the user has local IHM files.

Issue warning when opening a ".cif" file as mmCIF that contains "ihm_struct_assembly" table. Warning describes how to open it as IHM. The warning message is

"This mmCIF file contains IHM (integrative hybrid model) data. You may want to open it by choosing the Integrative Hybrid Models in the File / Fetch By ID dialog or in the File Type menu of the File / Open dialog or use a command like "open 8zze format ihm" to read additional IHM data."

Unfortunately if the IHM file has no atomic coordinates (e.g. 8zzc) then our C++ mmCIF reader returns no atomic models and no warning is issued, since the code needs an atomic model to see that the ihm_struct_assembly table is present.

Another problem is that the warning message is often buried in the log mixed with other warning messages about problems detected in the IHM file.