Scripting with JavaScript

Since Kate 3.4 in KDE 4.4 the Kate editor component is easily extensible by writing scripts. The scripting language is ECMAScript (widely known as JavaScript). Kate supports two kinds of scripts: indentation and command line scripts.

Indentation Scripts

Indentation scripts - also referred as indenters - automatically indent the source code while typing text. As example, after hitting the return-key code the indentation level often increases.

The following sections describe step by step how to create the skeleton for a simple indenter. As first step, create a new *.js file called e.g. javascript.js in the local home folder $KDEHOME/share/apps/katepart/script/indentation.

The Indentation Script Header

The header of the file javascript.js is embedded in a comment and is of the following form

/* kate-script
 * name: JavaScript
 * author: Example Name <example.name@some.address.org>
 * license: BSD
 * revision: 1
 * kate-version: 3.4
 * required-syntax-style: javascript
 * indent-languages: javascript
 * priority: 0
 * i18n-catalog: mycatalog
 *
 * A line without colon ':' stops header parsing. That is, you can add optional
 * text here such as a detailed license.
 */

Each entry is explained in detail now:

kate-script [required]: This text string has to appear in the first line of the *.js file, otherwise Kate skips the script.
name [required]: This is the indenter name that appears in the menu Tools → Indentation and in the configuration dialog.
author [optional]: The author's name and contact information.
license [optional]: Short form of the license, such as BSD or LGPLv3.
revision [required]: The revision of the script. This number should be increased whenever the script is modified.
kate-version [required]: Minimal required Kate version.
required-syntax-style [optional]: Comma separated list of required syntax highlighting styles. This is important for indenters that rely on specific highlight information in the document. If a required syntax style is specified, the indenter is available only when the appropriate highlighter is active. This prevents “undefined behavior” caused by using the indenter without the expected highlighting schema. For instance, the Ruby indenter makes use of this in the files ruby.js and ruby.xml.
indent-languages [optional]: Comma separated list of syntax styles the indenter can indent correctly, e.g.: c++, java.
priority [optional]: If several indenters are suited for a certain highlighted file, the priority decides which indenter is chosen as default indenter.
i18n-catalog [optional]: Additional message catalog (po file) loaded for translation of 3rd-party indenters.

Kate reads all pairs of the form “key:value” until it cannot find a colon anymore. This implies that the header can contain arbitrary text such as a license as shown in the example.

The Indenter Source Code

Having specified the header this section explains how the indentation scripting itself works. The basic skeleton of the body looks like this:

// required katepart js libraries, e.g. range.js if you use Range
require ("range.js");
  
triggerCharacters = "{}/:;";
function indent(line, indentWidth, ch)
{
    // called for each newline (ch == '\n') and all characters specified in
    // the global variable triggerCharacters. When calling Tools → Align
    // the variable ch is empty, i.e. ch == ''.
    //
    // see also: Scripting API
    return -2;
}

The function indent() has three parameters:

line: the line that has to be indented
indentWidth: the indentation width in amount of spaces
ch: either a newline character (ch == '\n'), the trigger character specified in triggerCharacters or empty if the user invoked the action Tools → Align.

The return value of the indent() function specifies how the line will be indented. If the return value is a simple integer number, it is interpreted as follows:

return value -2: do nothing
return value -1: keep indentation (searches for previous non-blank line)
return value 0: numbers >= 0 specify the indentation depth in spaces

Alternatively, an array of two elements can be returned:

return [ indent, align ];

In this case, the first element is the indentation depth like above with the same meaning of the special values. However, the second element is an absolute value representing a column for “alignment”. If this value is higher than the indent value, the difference represents a number of spaces to be added after the indentation of the first parameter. Otherwise, the second number is ignored. Using tabs and spaces for indentation is often referred to as “mixed mode”.

Consider the following example: Assume using tabs to indent, and tab width is set to 4. Here, <tab> represents a tab and '.' a space:

1: <tab><tab>foobar("hello",
2: <tab><tab>......."world");

When indenting line 2, the indent() function returns [8, 15]. As result, two tabs are inserted to indent to column 8, and 7 spaces are added to align the second parameter under the first, so that it stays aligned if the file is viewed with a different tab width.

A default KDE installation ships Kate with several indenters. The corresponding JavaScript source code can be found in $KDEDIR/share/apps/katepart/script/indentation.

Developing an indenter requires to reload the scripts to see whether the changes behave appropriately. Instead of restarting the application, simply switch to the command line and invoke the command reload-scripts.

If you develop useful scripts please consider contributing to the Kate Project by contacting the mailing list.

Command Line Scripts

As it is hard to satisfy everyone's needs, Kate supports little helper tools for quick text manipulation through the built-in command line. For instance, the command sort is implemented as script. This section explains how to create *.js files to extend Kate with arbitrary helper scripts.

Command line scripts are located in the same folder as indentation scripts. So as first step, create a new *.js file called myutils.js in the local home folder $KDEHOME/share/apps/katepart/script/commands.

The Command Line Script Header

The header of each command line script is embedded in a comment and is of the following form

/* kate-script
 * author: Example Name <example.name@some.address.org>
 * license: BSD
 * revision: 1
 * kate-version: 3.4
 * functions: sort, format-paragraph
 * i18n-catalog: mycatalog
 *
 * A line without colon ':' stops header parsing. That is, you can add optional
 * text here such as a detailed license.
 */

Each entry is explained in detail now:

kate-script [required]: This text string has to appear in the first line of the *.js file, otherwise Kate skips the script.
author [optional]: The author's name and contact information.
license [optional]: Short form of the license, such as BSD or LGPLv3.
revision [required]: The revision of the script. This number should be increased whenever the script is modified.
kate-version [required]: Minimal required Kate version.
functions [required]: Comma separated list of commands in the script.
i18n-catalog [optional]: Additional message catalog (po file) loaded for translation of 3rd-party scripts.

Kate reads all pairs of the form “key:value” until it cannot find a colon anymore. This implies that the header can contain arbitrary text such as a license as shown in the example. The value of the key functions is a comma separated list of command line commands. This means a single script contains an arbitrary amount of command line commands. Each function is available through Kate's built-in command line.

The Script Source Code

All functions specified in the header have to be implemented in the script. For instance, the script file from the example above needs to implement the two functions sort and format-paragraph. All functions have the following syntax:

// required katepart js libraries, e.g. range.js if you use Range
require ("range.js");

function <name>(arg1, arg2, ...)
{
    // ... implementation, see also: Scripting API
}

Arguments in the command line are passed to the function as arg1, arg2, etc. In order to provide documentation for each command, simply implement the 'help' function as follows:

function help(cmd)
{
    if (cmd == "sort") {
        return i18n("Sort the selected text.");
    } else if (cmd == "...") {
        // ...
    }
}

Executing help sort in the command line then calls this help function with the argument cmd set to the given command, i.e. cmd == "sort". Kate then presents the returned text as documentation to the user. Make sure to translate the strings.

Binding Shortcuts

In order to be able to assign shortcuts, the script needs to provide a function called action as follows:

function action(cmd)
{
    var a = new Object();
    if (cmd == "sort") {
        a.text = i18n("Sort Selected Text");
        a.icon = "";
        a.category = "";
        a.interactive = false;
        a.shortcut = "";
    } else if (cmd == "moveLinesDown") {
        // same for next action
    }
    return a;
}

The parameter cmd of the function specifies the command for which a shortcut is requested. There are several fields you have to specify in the returned javascript object:

a.text [required]: The text appears in the menu Tools → Scripts. Make sure to use i18n for translation.
a.icon [optional]: The icon appears next to the text in the menu. All KDE icon names can be used here.
a.category [optional]: If a category is specified, the script appears in a submenu. Make sure to use i18n for translation.
a.interactive [optional]: If the script needs user input, set this to true.
a.shortcut [optional]: The shortcut given here is the default shortcut. Example: Ctrl+Alt+t. See the Qt documentation for further details.

Developing a command line script requires to reload the scripts to see whether the changes behave appropriately. Instead of restarting the application, simply switch to the command line and invoke the command reload-scripts.

If you develop useful scripts please consider contributing to the Kate Project by contacting the mailing list.

Scripting API

The scripting API presented here is available in all scripts, i.e. indentation scripts and command line commands. The Cursor and Range are provided by library files in $KDEDIR/share/apps/katepart/libraries. If you want to use them in your script, which is required to use some of the Document or View functions, please include the needed library by using:

// required katepart js libraries, e.g. range.js if you use Range
require ("range.js");

To extend the standard scripting API with own functions and prototypes simply create a new file in the KDE's local configuration folder $KDEHOME/share/apps/katepart/libraries and include it into your script using:

require ("myscriptnamehere.js");

To extend existing prototypes like Cursor or Range, the recommended way is to not modify the global *.js files. Instead, change the Cursor prototype in JavaScript after the cursor.js is included into your script via require.

Cursors and Ranges

As Kate is a text editor, all the scripting API is based on cursors and ranges whenever possible. A Cursor is a simple (line, column) tuple representing a text position in the document. A Range spans text from a starting cursor position to an ending cursor position. The API is explained in detail in the next sections.

The Cursor Prototype

Cursor();

Constructor. Returns a Cursor at position (0, 0).

Example: var cursor = new Cursor();

Cursor(int line, int column);

Constructor. Returns a Cursor at position (line, column).

Example: var cursor = new Cursor(3, 42);

Cursor(Cursor other);

Copy constructor. Returns a copy of the cursor other.

Example: var copy = new Cursor(other);

Cursor Cursor.clone();

Returns a clone of the cursor.

Example: var clone = cursor.clone();

Cursor.setPosition(int line, int column);

Sets the cursor position to line and column.

Since: KDE 4.11

bool Cursor.isValid();

Check whether the cursor is valid. The cursor is invalid, if line and/or column are set to -1.

Example: var valid = cursor.isValid();

Cursor Cursor.invalid();

Returns an new invalid cursor located at (-1, -1).

Example: var invalidCursor = cursor.invalid();

int Cursor.compareTo(Cursor other);

Compares this cursor to the cursor other. Returns

-1, if this cursor is located before the cursor other,
0, if both cursors equal and
+1, if this cursor is located after the cursor other.

bool Cursor.equals(Cursor other);

Returns true, if this cursor and the cursor other are equal, otherwise false.

String Cursor.toString();

Returns the cursor as a string of the form “Cursor(line, column)”.

The Range Prototype

Range();

Constructor. Calling new Range() returns a Range at (0, 0) - (0, 0).

Range(Cursor start, Cursor end);

Constructor. Calling new Range(start, end) returns the Range (start, end).

Range(int startLine, int startColumn, int endLine, int endColumn);

Constructor. Calling new Range(startLine, startColumn, endLine, endColumn) returns the Range from (startLine, startColumn) to (endLine, endColumn).

Range(Range other);

Copy constructor. Returns a copy of Range other.

Range Range.clone();

Returns a clone of the range.

Example: var clone = range.clone();

bool Range.isEmpty();

Returns true, if the start and end cursors are equal.

Example: var empty = range.isEmpty();

Since: KDE 4.11

bool Range.isValid();

Returns true, if both start and end cursor are valid, otherwise false.

Example: var valid = range.isValid();

Range Range.invalid();

Returns the Range from (-1, -1) to (-1, -1).

bool Range.contains(Cursor cursor);

Returns true, if this range contains the cursor position, otherwise false.

bool Range.contains(Range other);

Returns true, if this range contains the Range other, otherwise false.

bool Range.containsColumn(int column);

Returns true, if column is in the half open interval [start.column, end.column), otherwise false.

bool Range.containsLine(int line);

Returns true, if line is in the half open interval [start.line, end.line), otherwise false.

bool Range.overlaps(Range other);

Returns true, if this range and the range other share a common region, otherwise false.

bool Range.overlapsLine(int line);

Returns true, if line is in the interval [start.line, end.line], otherwise false.

bool Range.overlapsColumn(int column);

Returns true, if column is in the interval [start.column, end.column], otherwise false.

bool Range.onSingleLine();

Returns true, if the range starts and ends at the same line, i.e. if Range.start.line == Range.end.line.

Since: KDE 4.9

bool Range.equals(Range other);

Returns true, if this range and the Range other are equal, otherwise false.

String Range.toString();

Returns the range as a string of the form “Range(Cursor(line, column), Cursor(line, column))”.

Global Functions

This section lists all global functions.

Reading & Including Files

String read(String file);: Will search the given file relative to the katepart/script/files directory and return its content as a string.

void require(String file);

Will search the given file relative to the katepart/script/libraries directory and evaluate it. require is internally guarded against multiple inclusions of the same file.

Since: KDE 4.10

Debugging

void debug(String text);: Prints text to stdout in the console launching the application.

Translation

In order to support full localization, there are several functions to translate strings in scripts, namely i18n, i18nc, i18np and i18ncp. These functions behave exactly like KDE's translation functions.

The translation functions translate the wrapped strings through KDE's translation system to the language used in the application. Strings in scripts being developed in the official Kate sources are automatically extracted and translatable. In other words, as a Kate developer you do not have to bother with message extraction and translation. However, for 3rd-party scripts developed outside of KDE, you have to extract and translate the messages yourself. Along with your scripts you have to also distribute a translation catalog, that includes all translated strings. Further, your script header then must explicitly state the catalog to load by specifying i18n-catalog.

void i18n(String text, arg1, ...);: Translates text into the language used by the application. The arguments arg1, ..., are optional and used to replace the placeholders %1, %2, etc.
void i18nc(String context, String text, arg1, ...);: Translates text into the language used by the application. Additionally, the string context is visible to translators so they can provide a better translation. The arguments arg1, ..., are optional and used to replace the placeholders %1, %2, etc.
void i18np(String singular, String plural, int number, arg1, ...);: Translates either singular or plural into the language used by the application, depending on the given number. The arguments arg1, ..., are optional and used to replace the placeholders %1, %2, etc.
void i18ncp(String context, String singular, String plural, int number, arg1, ...);: Translates either singular or plural into the language used by the application, depending on the given number. Additionally, the string context is visible to translators so they can provide a better translation. The arguments arg1, ..., are optional and used to replace the placeholders %1, %2, etc.

The View API

Whenever a script is being executed, there is a global variable “view” representing the current active editor view. The following is a list of all available View functions.

Cursor view.cursorPosition(): Returns the current cursor position in the view.
void view.setCursorPosition(int line, int column); void view.setCursorPosition(Cursor cursor);: Set the current cursor position to either (line, column) or to the given cursor.
Cursor view.virtualCursorPosition();: Returns the virtual cursor position with each tab counting the corresponding amount of spaces depending on the current tab width.
void view.setVirtualCursorPosition(int line, int column); void view.setVirtualCursorPosition(Cursor cursor);: Set the current virtual cursor position to (line, column) or to the given cursor.
String view.selectedText();: Returns the selected text. If no text is selected, the returned string is empty.
bool view.hasSelection();: Returns true, if the view has selected text, otherwise false.
Range view.selection();: Returns the selected text range. The returned range is invalid if there is no selected text.
void view.setSelection(Range range);: Set the selected text to the given range.
void view.removeSelectedText();: Remove the selected text. If the view does not have any selected text, this does nothing.
void view.selectAll();: Selects the entire text in the document.
void view.clearSelection();: Clears the text selection without removing the text.

The Document API

Whenever a script is being executed, there is a global variable “document” representing the current active document. The following is a list of all available Document functions.

String document.fileName();

Returns the document's filename or an empty string for unsaved text buffers.

String document.url();

Returns the document's full url or an empty string for unsaved text buffers.

String document.mimeType();

Returns the document's mime type or the mime type application/octet-stream if no appropriate mime type could be found.

String document.encoding();

Returns the currently used encoding to save the file.

String document.highlightingMode();

Returns the global highlighting mode used for the whole document.

String document.highlightingModeAt(Cursor pos);

Returns the highlighting mode used at the given position in the document.

Array document.embeddedHighlightingModes();

Returns an array of highlighting modes embedded in this document.

bool document.isModified();

Returns true, if the document has unsaved changes (modified), otherwise false.

String document.text();

Returns the entire content of the document in a single text string. Newlines are marked with the newline character “\n”.

String document.text(int fromLine, int fromColumn, int toLine, int toColumn); String document.text(Cursor from, Cursor to); String document.text(Range range);

Returns the text in the given range. It is recommended to use the cursor and range based version for better readability of the source code.

String document.line(int line);

Returns the given text line as string. The string is empty if the requested line is out of range.

String document.wordAt(int line, int column); String document.wordAt(Cursor cursor);

Returns the word at the given cursor position.

Range document.wordRangeAt(int line, int column); Range document.wordRangeAt(Cursor cursor);

Return the range of the word at the given cursor position. The returned range is invalid (see Range.isValid()), if the text position is after the end of a line. If there is no word at the given cursor, an empty range is returned.

Since: KDE 4.9

String document.charAt(int line, int column); String document.charAt(Cursor cursor);

Returns the character at the given cursor position.

String document.firstChar(int line);

Returns the first character in the given line that is not a whitespace. The first character is at column 0. If the line is empty or only contains whitespace characters, the returned string is empty.

String document.lastChar(int line);

Returns the last character in the given line that is not a whitespace. If the line is empty or only contains whitespace characters, the returned string is empty.

bool document.isSpace(int line, int column); bool document.isSpace(Cursor cursor);

Returns true, if the character at the given cursor position is a whitespace, otherwise false.

bool document.matchesAt(int line, int column, String text); bool document.matchesAt(Cursor cursor, String text);

Returns true, if the given text matches at the corresponding cursor position, otherwise false.

bool document.startsWith(int line, String text, bool skipWhiteSpaces);

Returns true, if the line starts with text, otherwise false. The argument skipWhiteSpaces controls whether leading whitespaces are ignored.

bool document.endsWith(int line, String text, bool skipWhiteSpaces);

Returns true, if the line ends with text, otherwise false. The argument skipWhiteSpaces controls whether trailing whitespaces are ignored.

bool document.setText(String text);

Sets the entire document text.

bool document.clear();

Removes the entire text in the document.

bool document.truncate(int line, int column); bool document.truncate(Cursor cursor);

Truncate the given line at the given column or cursor position. Returns true on success, or false if the given line is not part of the document range.

bool document.insertText(int line, int column, String text); bool document.insertText(Cursor cursor, String text);

Inserts the text at the given cursor position. Returns true on success, or false, if the document is in read-only mode.

bool document.removeText(int fromLine, int fromColumn, int toLine, int toColumn); bool document.removeText(Cursor from, Cursor to); bool document.removeText(Range range);

Removes the text in the given range. Returns true on success, or false, if the document is in read-only mode.

bool document.insertLine(int line, String text);

Inserts text in the given line. Returns true on success, or false, if the document is in read-only mode or the line is not in the document range.

bool document.removeLine(int line);

Removes the given text line. Returns true on success, or false, if the document is in read-only mode or the line is not in the document range.

bool document.wrapLine(int line, int column); bool document.wrapLine(Cursor cursor);

Wraps the line at the given cursor position. Returns true on success, otherwise false, e.g. if line < 0.

Since: KDE 4.9

void document.joinLines(int startLine, int endLine);

Joins the lines from startLine to endLine. Two succeeding text lines are always separated with a single space.

int document.lines();

Returns the amount of lines in the document.

int document.length();

Returns the number of characters in the document.

int document.lineLength(int line);

Returns the line's length.

void document.editBegin();

Starts an edit group for undo/redo grouping. Make sure to always call editEnd() as often as you call editBegin(). Calling editBegin() internally uses a reference counter, i.e., this call can be nested.

void document.editEnd();

Ends an edit group. The last call of editEnd() (i.e. the one for the first call of editBegin()) finishes the edit step.

int document.firstColumn(int line);

Returns the first non-whitespace column in the given line. If there are only whitespaces in the line, the return value is -1.

int document.lastColumn(int line);

Returns the last non-whitespace column in the given line. If there are only whitespaces in the line, the return value is -1.

int document.prevNonSpaceColumn(int line, int column); int document.prevNonSpaceColumn(Cursor cursor);

Returns the column with a non-whitespace characters starting at the given cursor position and searching backwards.

int document.nextNonSpaceColumn(int line, int column); int document.nextNonSpaceColumn(Cursor cursor);

Returns the column with a non-whitespace characters starting at the given cursor position and searching forwards.

int document.prevNonEmptyLine(int line);

Returns the next non-empty line containing non-whitespace characters searching backwards.

int document.nextNonEmptyLine(int line);

Returns the next non-empty line containing non-whitespace characters searching forwards.

bool document.isInWord(String character, int attribute);

Returns true, if the given character with the given attribute can be part of a word, otherwise false.

bool document.canBreakAt(String character, int attribute);

Returns true, if the given character with the given attribute is suited to wrap a line, otherwise false.

bool document.canComment(int startAttribute, int endAttribute);

Returns true, if a range starting and ending with the given attributes is suited to be commented out, otherwise false.

String document.commentMarker(int attribute);

Returns the comment marker for single line comments for a given attribute.

String document.commentStart(int attribute);

Returns the comment marker for the start of multi-line comments for a given attribute.

String document.commentEnd(int attribute);

Returns the comment marker for the end of multi-line comments for a given attribute.

int document.attribute(int line, int column); int document.attribute(Cursor cursor);

Returns the attribute at the given cursor position.

bool document.isAttribute(int line, int column, int attribute); bool document.isAttribute(Cursor cursor, int attribute);

Returns true, if the attribute at the given cursor position equals attribute, otherwise false.

String document.attributeName(int line, int column); String document.attributeName(Cursor cursor);

Returns the attribute name as human readable text. This equals to the itemData name in the syntax highlighting files.

bool document.isAttributeName(int line, int column, String name); bool document.isAttributeName(Cursor cursor, String name);

Returns true, if the attribute name at a certain cursor position matches the given name, otherwise false.

String document.variable(String key);

Returns the value of the requested document variable key. If the document variable does not exist, the return value is an empty string.

String document.setVariable(String key, String value);

Set the value of the requested document variable key. Returns the value of set variable.

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