Extensions: INX widgets and parameters

This page documents how to design GUIs for Inkscape Extensions using the built-in INX extension descriptor format.

Introduction

Extension GUIs consists of an arbitrary number of GUI elements, so-called Widgets. These can be simple text labels, boxes and spacers to control layout or more complex UI elements like images.

A special class of Widgets are Parameters. They differ from other Widgets in that they have a user-settable value, for example a boolean (implemented as checkbox) or integer (implemented as number entry). The value of each Parameter is passed to the extension on execution and can be used to control its behavior.

All Widgets are described using an easy-to-learn XML schema with predefined tags and attributes which are described in detail below.

Available Widgets

A general Widget takes the form

  <widget_name attribute1="value1" atribute2="value2" …>value</widget_name>

where widget_name specifies the name of the widget and is one of the following:

• label
• hbox/vbox
• separator/spacer
• image
• param (for all Parameter types)

Available Parameter types

A general Parameter takes the form

  <param type="parameter_type" attribute1="value1" atribute2="value2" …>value</param >

where parameter_type specifies the type of the parameter and is one of the following:

• bool
• int
• float
• string
• path
• optiongroup
• notebook
• color

Common attributes

For all Widgets
Attribute name	Allowed value(s)	Default value	Required?	Description
gui-hidden	true,false	false	optional	If set to true the Widget is hidden from the GUI (primarily used to add hidden parameters that are passed to the extension but are not supposed to be editable by the user.) Note: If there are no visible parameters defined in a GUI, the extension is executed immediately without showing a dialog.
indent	0,1,2,...	0	optional	-
Only for Parameters
Attribute name	Allowed value(s)	Default value	Required?	Description
name	(text)	-	required	Used as an identifier of the parameter. It has to be unique since the value of this attribute is used to save and transmit parameter values internally!
type	(see above)	-	required	Determines the type of the parameter, see the extensive description of available types below.
gui-text	(text)	-	required (visible parameters), optional (hidden parameters)	Label shown for the parameter in the GUI.
gui-description	(text)	-	optional	Tooltip shown for the parameter when the user hovers the mouse cursor over the active area of the parameter in question.

Available Parameter types

Type	Description / Code	Result
boolean	Creates a checkbox input to set a boolean value. Set the default value to true or 1, false or 0. <param name="name" type="boolean" gui-text="Some label text">false</param>
color	Creates a control to select a color value. The returned value is an RGBA-value. <param name="name" type="color"></param>
description	Creates a text element. Specifying the attribute xml:space="preserve" preserves whitespace in the text content of the description and enables multiline text. <param name="name" type="description">Some text here.</param> When additionally setting the attribute appearance="header" the text is styled as a heading and can be used as another possibility to group parameters. <param name="name" type="description" appearance="header">Header</param> All description type parameters are purely informational (they do not return any value). They are intended to be used to provide additional information / help on other parameters (Consider using the gui-description attribute for short help texts that are specific to a single parameter, though).	default appearance with appearance="header"
enum	Creates a drop-down list from which one predefined value can be chosen. The different choices are created with <item> elements. The first <item> is selected by default. The returned value for enum type parameters is the value of the value attribute of the selected <item>. <param name="name" type="enum" gui-text="Some label text"> <item value="1">First option</item> <item value="2">Second option</item> </param>
float	Creates a textbox input to enter a floating point number. Limit the input range with the min and max attributes; set the number of decimal places with the precision attribute. (Default: min="0", max="10" and precision="1") <param name="name" type="float" precision="3" min="0" max="9999" gui-text="Some label text">1.234</param> Use the attribute appearance="full" to create a slider with which the floating point value can be adjusted dynamically over the full range.
int	Creates a textbox input to enter an integer number. Limit the input range with the min and max attributes. (Default: min="0" and max="10") <param name="name" type="int" min="1" max="100" gui-text="Some label text">1</param> Use the attribute appearance="full" to create a slider with which the integer value can be adjusted dynamically over the full range.
notebook	Creates a set of pages (aka tab control). The user can switch between individual pages, each page can contain an arbitrary set of other parameters. Individual pages are created with the <page> element. The returned value for notebook type parameters is the value of the name attribute of the selected <page>. <param name="name" type="notebook"> <page name="page_1" gui-text="First page"> <param>...</param> </page> <page name="page_2" gui-text="Second page"> <param>...</param> </page> </param>
optiongroup	Creates a set of radio buttons from which one predefined value can be chosen. The different choices are created with <option> elements. The first <option> is selected by default. The returned value for optiongroup type parameters is the value of the value attribute of the selected <option>. <param name="name" type="optiongroup" gui-text="Some label text"> <option value="1">First option</option> <option value="2">Second option</option> </param> Set the attribute appearance="minimal" to display a drop-down list instead of radio buttons. The option group will occupy the minimum space on the right hand side of the dialog. Versus the Enum, which expands to fill available space.
string	Creates a textbox input to enter a character string. Limit the number of characters the user is allowed to enter with the max_length attribute. (Default: no limit) <param name="name" type="string" gui-text="Some text label">Some default text</param>

Localization of parameters

To mark parameters to be included into the translation files (this is done automatically during the build process) there exist special variants of all relevant attributes and tag names that start with an underscore.

• Labels and tooltips can be marked for translation by simply using the attribute names _gui-text and _gui-description instead of their counterparts without underscore.
• For <item>s and <option>s (both of which do not use the attributes just explained) add an underscore to the tag name itself:
  <_item value="1">Localized item name</_item> and
  <_option value="1">Localized option name</_option> respectively.
• Also for description type (and only for description type!) parameters an underscore is added to the tag name itself:
  <_param type="description">Localized text here.</_param>

Editing INX Parameters in 1.0

In this section:

• When an attribute is in square brackets ([name="value"]), it means that name is optional.
• The 1 in indent="1" is the indentation level that you want.

Tags for the layout

<label [indent="1"] [appearance="header"]>Some text</label>
<label [indent="1"] [appearance="url"]>http://some/url</label>
<image>some/inx/relative/path/to/img.svg</image>
<spacer/>
<separator [indent="1"]/>
<hbox [indent="1"]></hbox>
<vbox [indent="1"]></vbox>

Tags for the parameters

• The name attribute of tag <param> means the name of the argument (--name=) your command will get.
• Parameter values (when opening the dialog) are set to the last used value, which is saved in the user's preferences file (e.g. ~/.config/inkscape/preferences.xml on GNU/Linux systems):

<inkscape>
  <group id="extensions" com.attrib.id.param_name="param value"/>
</inkscape>

The (default) values in the inx file are visible only when the user first uses the extension.

Notebook

Multiple views/options in the same dialog window.

It helps with layouting, and allows you to retrieve the active page (tab) name.
	It defaults to the first page.
<param type="notebook" name="varname" [indent="1"]> <page name="value" gui-text="label"> <!-- Any elements contained in the page go here --> </page> <!-- You can add as many pages as you like --> </param>

• The value of the selected <page name> attribute will be passed as an argument to your extension.
  • The default value is the name of the first page.
• If the same <param name> is used in multiple tabs, its value will be taken from the last <page> it appears on.
  • This means that it's best to use different names if the same parameter is used on multiple pages.

Checkbox

To get a boolean value

	The default value is true
<param type="bool" name="varname" gui-text="label" [indent="1"]>false</param>

Numeric spinner

To get numbers, int or float

		The default value is 0
With appearance="full", you get a full width slider.
<param type="int" name="varname" gui-text="labal" [min="1"] [max="10"] [appearance="full"] [indent="1"]/> <param type="float" name="varname" gui-text="label" [min="0.5"] [max="5.0"] [appearance="full"] [indent="1"]/>

• The widget has a precision of 0.1 for float.
• The default min value is "0".
• The default max value is "10".

Text fields

Get text input

	The default value is the empty string and with such a value, the parameter is omitted.
<param type="string" name="varname" gui-text="label" [indent="1"] [max-length="5" | appearance="multiline"]>some text</param>

You can provide an integer to the attribute max-length to limit the number of characters you can get.

File chooser

Get a path, either a file or a directory

Default's to the path of the folder containing the script

Use one of: <param type="path" name="varname" gui-text="label" [indent="1"] mode="file" filetypes="svg,png"/> <param type="path" name="varname" gui-text="label" [indent="1"] mode="files" filetypes="svg,png"/> <param type="path" name="varname" gui-text="label" [indent="1"] mode="file_new" filetypes="svg,png"/> <param type="path" name="varname" gui-text="label" [indent="1"] mode="folder"/> <param type="path" name="varname" gui-text="label" [indent="1"] mode="folders"/> <param type="path" name="varname" gui-text="label" [indent="1"] mode="folder_new"/>

• The attribute mode with a value of:
  • "file" or "folder" (without s) open a file browser for selecting 1 object.
  • The versions ending with a s open a file browser for selecting multiple objects.
  • And the ones ending with _new are for creating new objects.
• The filetype attribute contains a list of file extensions to look for. In this example only svg or png files will be displayed.

A combobox or radio buttons

To get a choice of predefined values

		Default value is the first item
<param type="optiongroup" name="varname" gui-text="label" [appearance="combo"|appearance="radio"] [indent="1"]> <item value="value">Some text</item> <!-- Other choices --> </param>

• The default appearance is "radio". The appearance "combo" is also valid.

Color

Get a hex color value

		Default value is #000000FF
	↑With↑ the attribute appearance="colorbutton" ⇇ Without appearance="colorbutton"
<param type="color" name="varname" [appearance="colorbutton" gui-text="label"] [indent="1"]/>

The parameter value is an RGBA value in hexadecimal notation.

To document:

• Multiline text fields: appearance="multiline"
• type "description"
• translatable="no"
• implements-custom-gui