From WinMerge

Filtering one of areas WinMerge shines. And area we want to continue to improve in future.

Our filtering is based on Regular Expressions.

Contents 1 File Filtering 1.1 Storage 2 Line Filtering 2.1 Storage 3 Making File- and Line-filters to Work Together 3.1 Combined Storage 3.2 GUI 4 Todo

[edit] File Filtering

File filtering is for folder compare. File filtering goal is to avoid comparing files/folders user doesn't care (temp files etc).

Filtering happens after items are collected but before actual compare:

1. Collect items in folders to compare
   1. after we find new item we match that item against file filter. If the item matches, we include/exclude item based on filtering rules.
2. Compare items in list of collected items

[edit] Storage

File filters are stored in separate .flt files.

The .flt file format cannot be expanded in practice without breaking ability for older WinMerge versions to read those files. So we need totally new format with new filename extension.

[edit] Line Filtering

Line filtering is for file compare. Line filtering goal is to ignore changes user is not interested about.

File filtering is applied when:

1. files are compare in folder compare (only for full content compare, as quick compare does not necessarily read the whole file)
2. files are opened to file compare
3. files are rescanned in file compare

2.7.1.6 experimental and later releases have so-called "post-filtering", where filters are applied after the actual compare:

1. load files
2. compare files using diffutils engine
3. post-filter difference list returned by diffutils

[edit] Storage

Line filters are stored into registry (accessible using OptionsManager).

[edit] Making File- and Line-filters to Work Together

Currently (as of 2.8.0) line filters and file filters are independent in implementation and in compare results.

However, it would allow some very interesting use cases if we could combine their effects. Some ideas:

• determine applied line filter with file filter
  • have a file filter: \.cpp and have a line filter ^// to filter some comments from .cpp files.
  • negation could be useful too, applying line filter to all files, except...
• a lot easier filter selection for user, user only selects applied filter set, which includes line- and file-filters
• in same storage, editing easier
• speed, line filters only applied to files wanted, not all files

[edit] Combined Storage

Current file filter-file format is hard to expand, and even harder to add line filters to it. So we just should create a new storage.

• line filters must be also able to be stand-alone, without any file filters

[edit] GUI

This is a challenge. Filter selection must be a snap, click from dialog/dropdown. And handling of single filters/combinations shouldn't be too much work either.

[edit] Todo

• Combine file filters and line filter definitions to same file.
  • XML file
• Filter based on path, not just filename
• Apply linefilters to only certain files (determined by file filter rules?)
  • Apply different filters for different filesets