Common Features
===============

.. module:: common.dialog
	:synopsis: Features common to many dialogs

These features are common to many TortoiseHg tools, so we document them
here just once.

Visual Diffs
------------

.. figure:: figures/visual-diff.jpg
	:alt: Visual Diff Window

	Visual Diff Window

In TortoiseHg 1.0, the visual (external) diff infrastructure was
refactored.  The new system uses tool descriptions in
:file:`mergetools.rc` to detect most common diff tools on your computer
(including KDiff3, which ships in our installer) and select the best
available tool.

If the user has selected a merge tool
(:menuselection:`TortoiseHg --> Three-way Merge Tool`), that tool will
also be used to perform visual diffs, bypassing the tool selection
process.  However the user can still select a separate tool
(:menuselection:`TortoiseHg --> Visual Diff Tool`) for visual diffs if
they chose.

The merge tool configuration file contains optimal command lines for
each tool, so no further configuration is required by the user.  They
only need to select the tools they wish use, or accept the defaults.

The visual diff system will use any existing extdiff configuration it
finds.  Since extdiff did not support three way diff arguments until
very recently and still does not support label arguments, you will
likely have a better experience by disabling or deleting any extdiff
configuration you may have.

The visual diff system will directly use the selected diff tool unless
the action you are attempting requires the use of the TortoiseHg visual
diff window.  The list of conditions includes:

1) The selection of files being compared require multiple tools
2) The selected tool forks detached background processes
3) The selected tool does not support the required directory diffs
4) The selected tool does not support three way comparisons
5) The file changes include renames or copies

When the visual diff window is used, the temporary files are cleaned up
when the dialog is closed.  Thus it should be left open until you close
all of your diff tool instances.  When your diff tool is launched
directly, the temporary files are deleted when your tool exits.

If your diff tool is launched directly to compare a working copy file,
it will directly diff against the working file so you may modify it from
within the diff tool.  If you are comparing multiple files, the visual
diff system will make a snapshot of the working copy files and track
their initial sizes and timestamps.  When your diff tool exits, the
system compares the sizes and timestamps and copies modified files back
over the original working copies.  In this way, you can still modify
your working copy files from your visual diff tool even when performing
directory comparisons.

When the visual diff window is used to compare working copy files, it
always directly diffs against the working copy files since it always
operates on a single file at a time.

.. deprecated:: 1.0
	The :menuselection:`TortoiseHg --> Skip Diff Window` configurable
	has been removed because it is now redundant.

Adding Tools
~~~~~~~~~~~~

If you have a visual diff tool installed that is not supported by
TortoiseHg, you can create a tool configuration for it in your user
:file:`Mercurial.ini` file.  See Mercurial's
`documentation <https://www.mercurial-scm.org/doc/hgrc.5.html#merge-tools>`_
on how to configure your tool for use in file merges.  When that is
complete, you can add the extra keys used by TortoiseHg for visual
diff::

	diffargs:  the arguments to use for two-way file comparisons
	diff3args: the arguments to use for three-way file comparisons
	dirdiff:   this tool supports two-way directory comparisons
	dir3diff:  this tool supports three-way directory comparisons

When building command line arguments, you can use the following
variables::

	$parent1:  the file or directory from the first parent revision
	$parent2:  the file or directory from the second parent revision
	$child:    the file or directory from the revision being compared
	$parent:   a synonym for $parent1

	$plabel1:  a symbolic name for the first parent revision
	$plabel2:  a symbolic name for the second parent revision
	$clabel:   a symbolic name for the revision being compared

Obviously, $parent2 and $ancestor are only meaningful when used in three
way diff arguments, for viewing merge changesets.  If your diff tool
cannot use the ancestor revision in any productive way, it is safe to
leave it out of the diff3args command line.

.. note::
	On Windows, the `executable` parameter can use environment variables
	using the syntax ${ProgramFiles}

If unconfigured, the default value of **diffargs** is '$parent $child'.
The default value of **diff3args** is "", indicating the visual diff
tool cannot perform three way comparisons.

If you create a new visual diff tool configuration, or improve upon an
existing configuration, please email it to our development mailing list
so it may be incorporated in a future release.


Word Diffs
~~~~~~~~~~

The TortoiseHg Windows installers now include TortoiseSVN's scripts for
comparing (and sometimes merging) many binary document formats.  These
are configured in the site-wide :file:`mergepatterns.rc` as handlers for
each binary format's common file extensions, so no user intervention is
required.

In order to support file extension based tool selection, TortoiseHg has
added support for a **[diff-patterns]** section equivalent to Mercurial's
`merge-patterns <https://www.mercurial-scm.org/doc/hgrc.5.html#merge-patterns>`_
section.

.. vim: noet ts=4
