*diffchar.txt*  Highlight the exact differences, based on characters and words
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Last Change:	2021/12/07
Version:	8.91
Author:		Rick Howe (Takumi Ohtani) <rdcxy754@ybb.ne.jp>
Copyright:	(c) 2014-2021 by Rick Howe

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INTRODUCTION                                           *diffchar*

This plugin has been developed in order to make diff mode more useful. Vim
highlights all the text in between the first and last different characters on
a changed line. But this plugin will find the exact differences between them,
character by character - so called DiffChar.

For example, in diff mode: ([|hl-DiffText|], <|hl-DiffAdd|>)
>
    (window A) The [quick brown fox jumps over the lazy] dog.
    (window B) The [lazy fox jumps over the quick brown] dog.
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this plugin will exactly show the changed and added units:
>
    (window A) The [quick] <brown >fox jumps over the [lazy] dog.
    (window B) The [lazy] fox jumps over the [quick] <brown >dog.
<
This plugin will synchronously show/reset the highlights of the exact
differences as soon as the diff mode begins/ends. And the exact differences
will be kept updated while editing.

This plugin shows the differences based on a |g:DiffUnit|. Its default is
'Word1' and it handles a \w\+ word and a \W character as a difference unit.
There are other types of word provided and you can also set 'Char' to compare
character by character.

In diff mode, the corresponding |hl-DiffChange| lines are compared between two
windows. You can set a number of matching colors to a |g:DiffColors| to make
it easy to find the corresponding units between two windows. As a default, all
the changed units are highlighted with |hl-DiffText|. In addition,
|hl-DiffAdd| is always used for the added units and both the previous and next
character of the deleted units are shown in bold/underline.

While showing the exact differences, when the cursor is moved on a difference
unit, you can see its corresponding unit highlighted with |hl-Cursor|,
|hl-TermCursor|, or similar one in another window, based on a
|g:DiffPairVisible|. If you change its default, the corresponding unit is
echoed in the command line or displayed in a popup/floating window just below
the cursor position or at the mouse position.

You can use `]b` or `]e` to jump cursor to start or end position of the next
difference unit, and `[b` or `[e` to the start or end position of the previous
unit. Those keymaps are configurable in your vimrc and so on.

Like line-based `:diffget`/`:diffput` and `do`/`dp` vim commands, you can use
`<Leader>g` and `<Leader>p` commands in normal mode to get and put each
difference unit, where the cursor is on, between 2 buffers and undo its
difference.

When the diff mode begins, this plugin locally checks the |hl-DiffChange|
lines in the limited range of the current visible and its upper/lower lines of
a window. And each time a cursor is moved on to a different range upon
scrolling or searching, the new |hl-DiffChange| lines will be incrementally
checked in that range. Which means, independently of the file size, the number
of lines to be checked and then the time consumed are always constant.

This plugin works on each tab page individually. You can use a tab page
variable (t:), instead of a global one (g:), to specify different options on
each tab page. Note that this plugin can not handle more than two diff mode
windows in a tab page. If it would happen, to prevent any trouble, all the
highlighted units are to be reset in the tab page.

To find the exact differences, this plugin uses "An O(NP) Sequence Comparison
Algorithm" developed by S.Wu, et al., which always finds an optimum sequence.
But it takes time to check a long and dissimilar line. To improve the
performance, if there are so many diff units included in a line or it has
taken much time in a diff session, this plugin tries to use the external diff
command together if available.

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OPTIONS                                                *diffchar-options*

|g:DiffUnit|, |t:DiffUnit|
    A type of difference unit
    'Char'   : any single character
    'Word1'  : \w\+ word and any \W single character (default)
    'Word2'  : non-space and space words
    'Word3'  : \< or \> character class boundaries
    'CSV(,)' : separated by characters such as ',', ';', and '\t'

|g:DiffColors|, |t:DiffColors|
    Matching colors for changed units
    0   : |hl-DiffText| (default)
    1   : |hl-DiffText| + up to 3 other highlights
    2   : |hl-DiffText| + up to 7 other highlights
    3   : |hl-DiffText| + up to 15 other highlights

|g:DiffPairVisible|, |t:DiffPairVisible|
    Visibility of corresponding diff units
    0 : disable
    1 : highlight with |hl-Cursor| (default)
    2 : highlight with |hl-Cursor| + echo in the command line
    3 : highlight with |hl-Cursor| + popup/floating window at cursor position
    4 : highlight with |hl-Cursor| + popup/floating window at mouse position

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KEYMAPS                                                *diffchar-keymaps*

<Plug>JumpDiffCharPrevStart (default: `[b`)
    Jump cursor to the start position of the previous difference unit

<Plug>JumpDiffCharNextStart (default: `]b`)
    Jump cursor to the start position of the next difference unit

<Plug>JumpDiffCharPrevEnd (default: `[e`)
    Jump cursor to the end position of the previous difference unit

<Plug>JumpDiffCharNextEnd (default: `]e`)
    Jump cursor to the end position of the next difference unit

<Plug>GetDiffCharPair (default: `<Leader>g`)
    Get a corresponding difference unit from another buffer to undo difference

<Plug>PutDiffCharPair (default: `<Leader>p`)
    Put a corresponding difference unit to another buffer to undo difference

-----------------------------------------------------------------------------
CHANGE HISTORY                                         *diffchar-history*

Update : 8.91
* Updated to check a new WinClosed event (patch-8.2.3591) to appropriately
  reset or repair the highlighted DiffChar units when a window is closed.

Update : 8.9
* Fixed not to overrule syntax highlighting.
* Fixed to successfully sync with diff mode even without patch-8.1.414.
* Changed the highlighting groups used in |g:DiffColors| option.

Update : 8.8
* Changed the highlighting groups used in |g:DiffColors| option, to completely
  highlight a changed diff unit and to make each unit more visible.
* Changed to use |hl-Cursor|, |hl-TermCursor|, or similar one, as appropriate,
  to highlight a corresponding diff unit, for |g:DiffPairVisible| option.
* Fixed to use proper |hl-Diff| highlighting groups even if they are linked.
* Optimized how to draw each unit and then improved performance.

Update : 8.7
* Enhanced |g:DiffPairVisible| option to show a corresponding diff unit as
  well in a floating window on nvim, if its value is 3, and show a popup (not
  a balloon) window at the mouse position, if its value is 4.
* Improved performance, use the external diff command together if available,
  if there are so many diff units included in a line or it has taken much time
  in a diff session.
* Removed |g:DiffMaxLines| option, and locally checks the limited number of
  the |hl-DiffChange| lines and incrementally checks them upon scrolling or
  searching.
* Removed |g:DiffModeSync| option, and always synchronize with the diff mode.
* `:SDChar`, `:RDChar`, `:TDChar`, and `:EDChar` commands are still available
  but deprecated.

Update : 8.6
* Enhanced |g:DiffPairVisible| option to show a corresponding diff unit as a
  popup-window just below the cursor position (available on patch-8.1.1391).
  And changed its default as 1 (diff unit highlighting only).
* Fixed not to stop monitoring the changes of text and 'diffopt' option,
  even if there is no |hl-DiffChange| line, when |g:DiffModeSync| option is
  enabled.

Update : 8.5
* Enhanced to show a balloon on GUI and display a corresponding diff unit,
  where the mouse is pointing, if |g:DiffPairVisible| option is enabled
  (patch-8.1.647 is required to correctly display multibyte characters).
* Fixed to correctly handle |hl-DiffChange| lines while editing.

Update : 8.4
* Extended |g:DiffMaxLines| option to allow a negative value as multiples of
  the window height and changed its default as -3.
* Fixed to reset all highlighted DiffChar units when more than two windows
  become diff mode in a tab page.
* Deleted |g:DiffSplitTime| option.

Update : 8.3
* Fixed not to detect more |hl-DiffChange| lines than |g:DiffMaxLines| option.

Update : 8.2
* Fixed to correctly update the highlighted DiffChar units while editing when
  a new internal diff is not specified in 'diffopt' option (patch-8.1.360).

Update : 8.1
* Fixed to properly detect |hl-DiffChange| lines even when all visible lines
  of current window are in a closed fold if a |g:DiffMaxLines| option is
  enabled.

Update : 8.0
* Introduced a |g:DiffMaxLines| option to dynamically detect a limited number
  of |hl-DiffChange| lines, when the diff mode begins and whenever a cursor is
  moved onto an undetected line. It enables to always take a minimum constant
  time, independently of the file size.
* Enhanced to check a new DiffUpdated event (patch-8.1.397) to follow diff
  updates and some changes of 'diffopt' option.
* Enhanced to support new iwhiteall and iwhiteeol of 'diffopt' option
  (patch-8.1.360).
* Removed |g:DiffUpdate| option and merged it into |g:DiffModeSync|.
* Removed keymap for <F7> and <F8>, which toggle to show/reset the highlights.
* Changed to work in diff mode, not in non-diff mode.
* Removed a support for vim version 7.x.
* Changed not to set 'diffexpr' option when a new internal diff is specified
  in 'diffopt' (patch-8.1.360).

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