How to change in gvim GTK file browser the default file mask wildcard (glob)?

Question

In gvim the command :browse confirm e launches a GTK file browser. The default file mask in this window depends on the filetype from which the browse window is invoked. I would like to change that default file mask depending on the filetype. For example from .cpp file the mask is *.cpp *.c++ and I want to add *.hpp *.ipp there. From python file the mask is *.py I would like it to be *. And so on.

I use gvim version 8.1.141 on linux devuan beowulf.

(I could not find proper tags for this question, I tried to use tags: file browser, gtk, wildcard, glob, mask)

So far by grepping gvim sources I have found:

grep -E "\*\.cpp \*\.c++" . -r --color

./runtime/ftplugin/pyrex.vim:                   \ "C++ Source Files (*.cpp *.c++)\t*.cpp;*.c++\n" .
./runtime/ftplugin/c.vim:    let b:browsefilter = "C++ Source Files (*.cpp *.c++)\t*.cpp;*.c++\n" .
./runtime/ftplugin/c.vim:         \ "C++ Source Files (*.cpp *.c++)\t*.cpp;*.c++\n" .

So what is b:browsefilter and how to use it?

The :h browsefilter says that "You can override the filter setting on a per-buffer basis by setting the b:browsefilter variable.".

But I want to override it not per-buffer, but per-filetype from where the browse dialog was invoked.

Answer 1

The browsefilter variable is a convenient way to add custom glob like filters for the graphical :browse dialog and select only the relevant filetypes for display.

As you discovered, those are usually set in the filetype plugins. If you want to customize those filters, create a file in ~/.vim/after/ftplugin/<filetype>.vim (replace <filetype> by the wanted filetype, e.g. c and python) and add the following content (this example is for your c filetype):

if exists("b:browsefilter")
    let b:browsefilter = "My C Source Files (cpp,c++,hpp,ipp)\t*.cpp;*.c++;*.hpp;*.ipp\n". b:browsefilter
endif

It is important to place this in the after directory, as the default filetype needs to be run first to initialize the b:browsefilter variable that you can than customize further.