Vim's modeline support / tabulation settings per-file

[twasilczyk]

Vim have useful feature, to set indentation related configuration per-file. It's done by adding a comment to the source file (usually at the end), for example:

/* vim: set tabstop=8 softtabstop=4 shiftwidth=4 noexpandtab: */

The above config means in mc:

• Fake half tabs enabled
• Fill tabs with spaces disabled
• Tab spacing 8

I think having such feature in mc would be a nice step forward. I also think it should use the same namespace as vim, despite being totally distinct project.

[twasilczyk]

Added vim's modeline support - initial implementation

[twasilczyk]

I did initial implementation for this, however, it needs some work:

• mc_findinfile should be placed somewhere else (maybe vfs.h?) and maybe named somehow better
• vim's tabstop parameter isn't mapped to mc's tab spacing (it's easy to implement, I'll do it later)
• currently, only C comments are supported; we should discuss other comment types that should be supported (C++ //, Python's #, others?)
• I guess there should be some max size limit, to not look for config in 1MB+ files
• mc depends on glib (which version?) so the scan could take advantage of it (regexp?)
• there should be a warning in config file, if the global settings are overriden by local ones
• if using fake half tabs with no tab-to-space filling, there is a possibility to create "bad" indentations (<tab><4xspace><tab><tab><4xspace>) - they should be converted (when editing a specific indentation) to standard ones (<tab><tab><tab><4xspace>)

[andrew_b]

Replying to twasilczyk:

I did initial implementation for this, however, it needs some work:

Thanks!

Some remarks:

• this option should be optional

• I guess there should be some max size limit, to not look for config in 1MB+ files

• scanning modeline in editor buffer after (or even during) file load is better than scanning directly in file because we scan file only once. mcedit supports file of any size.

• mc depends on glib (which version?) so the scan could take advantage of it (regexp?)

• glib >= 2.12 is required, but mc already has own regexp-based search engine (see lib/search, lib/search.h)

[twasilczyk]

Replying to andrew_b:
If we scan for modeline during file load, there will be no necessity to omit 1MB+ files, as it won't affect performance.

[twasilczyk]

Added vim's modeline support - with "tabstop" mapped to tab spacing

[twasilczyk]

Small bugfix (backspace at line beginning created spaces)

[twasilczyk]

Various comment types supported

[angel_il]

so... scan_modeline try scan all file, potentially this could take a long time...
for example file size is 4gb, without '\n'

[twasilczyk]

As far, as I understand, file is scanned anyway (for example, to find out the number of lines). Thus, adding another check into that loop won't affect performance that much.

Am I right?

[angel_il]

i think, need scan first ~2000b

[ossi]

maybe also the last - some files have the modeline at the bottom.

there is also an entirely different approach to the matter: ​http://kate-editor.org/2006/02/09/kateconfig-files/