NAME¶
Padre::Delta - A very simple diff object that can be applied to editors fast
SYNOPSIS¶
my $editor = Padre::Current->editor;
my $from = $editor->GetText;
my $to = transform_function($from);
Padre::Delta->from_scalars( \$from => \$to )->to_editor($editor);
DESCRIPTION¶
As a refactoring IDE many different modules and tools may wish to calculate
changes to a document in the background and then apply the changes in the
foreground.
Padre::Delta objects provide a mechanism for defining change to an
editor, with the representation stored in a way that is extremely well aligned
with the Padre::Wx::Editor and Wx::Scintilla APIs.
By doing as much preliminary calculations as possible in the background and
passing a Padre::Delta object back to the parent, the amount of time spent
blocking in the foreground is kept to an absolute minimum.
METHODS¶
# Alter a document by line range, in loose form
my $delta1 = Padre::Delta->new(
'line',
[ 1, 1, 'Content' ], # Insert a single line
[ 4, 3, '' ], # Remove a single line
[ 6, 9, 'Alternate' ], # Replace three lines with one
)->tidy;
# Alter a document by character range in tight form
my $delta2 = Padre::Delta->new(
'position',
[ 35, 37, 'fghjkl' ], # Replace two characters with six
[ 23, 27, '' ], # Remove four characters
[ 12, 12, 'abcd' ], # Insert four characters
);
The "new" constructor takes a replacement mode and a list of targets
and returns the delta object, which can then be applied to a
"SCALAR" reference of Padre::Wx::Editor object.
The first parameter should be the replacement mode. This will be either 'line'
for line range deltas as per the
diff program, or 'position' for
character position range deltas which operate at a lower level and directly on
top of the position system of Wx::Scintilla.
After the replacement mode, the constructor is provided with an arbitrarily
sized list of replacement targets.
Each replacement target should be an "ARRAY" reference containing
three elements which will be the start of the range to be removed, the end of
the range to be removed, and the text to replace the range with.
The start of the range must always be a lower value than the end of the range.
While providing a high to low range may incidentall work on some operating
systems, on others it can cause Wx::Scintilla to segfault.
Each replacement target will both remove existing content and replace it with
new content. To achieve a simple insert, both range positions should be set to
the same value at the position you wish to insert at. To achieve a simple
deletion the replacement string should be set to the null string.
The ordering of the replacement target is critically important. When the changes
applied they will always be made naively and in the same order as supplied to
the constructor.
Because a change early in the document will alter the positions of all content
after it, you should be very careful to ensure that your change makes sense if
applied in the supplied order.
If the positions of your replacement targets are not inherently precalculated to
adjust for content changes, you should supply your changes from the bottom of
the document upwards.
Returns the new Padre::Delta object.
mode¶
The "mode" accessor indicates if the replacement will be done using
line numbers or character positions.
Returns 'line' or 'position'.
null¶
The "null" method returns true if the delta contains zero changes to
the document and thus has no effect, or false if the delta contains any
changes to the document.
The ability to create null deltas allows refactoring to indicate a successful
transform resulting in no changes to the current document, as opposed to some
other response indicating a failure to apply the transform or similar
response.
from_diff¶
my $delta = Padre::Delta->from_diff(
Algorithm::Diff::diff( \@from => \@to )
);
The "from_diff" method takes a list of hunk structures as returned by
the Algorithm::Diff function "diff" and creates a new delta that
will apply that diff to a document.
Returns a new Padre::Delta object.
from_scalars¶
my $delta = Padre::Delta->from_scalars( \$from => \$to );
The "from_scalars" method takes a pair of documents "from"
and "to" and creates a Padre::Delta object that when applied to
document "from" will convert it into document "to".
The documents are provided as SCALAR references to avoid the need for
superfluous copies of what may be relatively large strings.
Returns a new Padre::Delta object.
tidy¶
Padre::Delta->new( line => @lines )->tidy->to_editor($editor);
The "tidy" method is provided as a convenience for situations where
the quality of the replacement targets passed to the constructor is imperfect.
To ensure that changes are applied quickly and editor objects are locked for the
shortest time possible, the replacement targets in the delta are considered to
have an inherent order and are always applied naively.
For situations where the replacement targets do
not have an inherent
order, applying them in the order provided will result in a corrupted
transform.
Calling tidy on a delta object will correct ranges that are not provided in low
to high order and sort them so changes are applied from the bottom of the
document upwards to avoid document corruption.
Returns the same Padre::Delta object as a convenience so that the tidy method
can be used in changed calls as demonstrated above.
to_editor¶
my $changes = $delta->to_editor($editor);
The "to_editor" method applies the changes in a delta object to a
Padre::Wx::Editor instance.
The changes are applied in the most simple and direct manner possible, wrapped
in a single Undo action for easy of reversion, and in an update locker for
speed.
Return the number of changes made to the text contained in the editor, which may
be zero in the case of a null delta.
COPYRIGHT & LICENSE¶
Copyright 2008-2012 The Padre development team as listed in Padre.pm.
This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included with this
module.