cdacamar/gap

Source: https://github.com/cdacamar/gap

gap - GUI Text Diff.

gap

This is a very simple text GUI diffing utility started during the Handmade Essentials 2026 Jam.

The goal of gap is to provide a very simple native utility which presents diffs in a way that you might see them on popular source control sites such as Github or Azure DevOps.

The secondary goal of gap is to serve as a proof-of-concept for implementing the linear variant of the Myers diff algorithm for use in fred.

Features

• Self-contained repo. There are no dependencies outside of a C++ compiler (some Linux caveats).
• Multiple options for viewing inner-diffs within similar blocks (word-based and character-based).
• Easily swap the order of diffs with a single button.
• Expand/collapse context window at the push of a button (anything below 0 indicates ‘infinite’ context, implying there is no window).
• Supports directory diffing where each file in the corresponding directory is matched to files in the opposite directory.
• Full configuration explorer just like in fred from which you can change settings such as viewing line numbers, changing colors, or disabling animations.
• Help panel which provides hotkey rebinding.
• Multiple renderer options on Windows (DX11 and OpenGL with DX11 being default).
• Supports subpixel font rendering (on by default).
• Supports both Windows and Linux (no OSX).

Usage

$ gap a.txt b.txt # file diffing.
$ gap .\A .\B     # directory diffing.

Or simply open gap and drag-and-drop files onto each panel side for diffing. You can overwrite a file by dragging and dropping a new file onto that panel. You can also open the directory diffing panel via the default of CTRL+O and drag directories onto each side for a directory comparison.

Another way of using gap is to tie it into git for viewing local diffs:

$ git config difftool.gap.path "D:/git_projects/gap/build/gap.exe"
$ git config difftool.gap.cmd "D:/git_projects/gap/build/gap.exe """$LOCAL""" """$REMOTE""""
$ git config diff.tool gap

Which you can then use git difftool instead of git diff to view diffs locally.

Additionally, you may want to consider invoking git difftool as git difftool -d to take advantage of the directory diffing in gap.

On Linux you would simply escape the quotes differently and alter paths.

Screenshots

Building

Windows:

1. Open up an VS2022 (or later) x64 Developer Command Prompt

$ build

Or for release:

$ build release

Linux:

1. Ensure you have a recent-ish version of gcc. I used 13.3.0.
2. Have the following system dependencies installed:
   • OpenGL (I used libglx-dev)
   • X11 (I used libx11-dev)
   • X11-ext (I used libxext-dev)
   • Xrandr (I used libxrandr-dev)

$ ./build.sh

Or for release:

$ ./build.sh release

License

MIT