Updating your extension for Inkscape 1.2

This page is intended for extension authors who want to use the new capabilities of inkex in Inkscape 1.2. As of the Release of 1.2alpha (Feb 5, 2022), no more breaking changes will be introduced until the final release of 1.2.

There are no breaking changes in this release, but a few methods have been deprecated.

Deprecating changes

  • The Transforms multiplication operator has been changed from * (*=) to @ (@=), in accordance with PEP-465 (MR extensions#389, Issue extensions#327)

  • svg.width and svg.height have been deprecated, and replaced with svg.viewbox_width, svg.viewport_width, svg.viewbox_height and svg.viewport_height, see New Units API.

  • selection.paint_order has been renamed to selection.rendering_order to be conformant with the specification (MR extensions#344, Issue extensions#310)

  • FallbackStyle has been deprecated in favor of Style, see New Style API.

New Style API

../_images/Comparison_of_Lighter_extension_in_Inkscape_1.1.2_and_1.2.png

Top: W3C SVG1.1 Test suite, test styling-css-04-f.svg. This test includes various CSS selectors, and includes group inheritance and pseudo-selectors. It is rendered correctly in Inkscape 1.2. Bottom left: Output of the “Lighter” extension in Inkscape 1.1.2, only two squares are processed correctly, two squares have a wrong color and the other 14 raise unhandled exceptions. Bottom right: Correct output in Inkscape 1.2. This shows that inkex correctly handles different types of CSS selectors.

Added in MR extensions#294, MR extensions#296, MR extensions#298, MR extensions#300, MR extensions#352, MR extensions#403

Inkex now exposes styles to extensions authors as intended by the SVG specification. This means:

  • BaseElement now has functions cascaded_style, specified_style and presentation_style.

  • In most use cases, extensions querying a style will use specified_style. This computes the effective style of the element, including CSS classes / pseudo-selectors, inherited styles, presentation attributes etc.

  • While style.get() and style[key] has been unchaged, a new getter has been added in form of style(key) (similar to a function call), which attempts to parse the attribute in a reasonable datatype. If the attribute is unset, the (parsed) default value will be returned. For example:

    • style("fill") returns a Color / Gradient / Pattern / None,

    • style("opacity") returns a value between 0 and 1, regardless if opacity is defined as percentage or as float, is out of bounds or undefined,

    • style("stroke-dasharray") returns a list of floats of dash/gap/dash/gap in user units.

  • Not for all attributes there is a parser defined - in that case, a string will be returned. Additional parsers may be added in the future, so if you handle the string value, typecheck it first!

Using the new Style API in your extension

The following calls can probably be simplified:

Old code (pre-1.2)

New code (1.2+)

if "fill-opacity" in self.style:
    alpha = self.style["fill-opacity"]
else:
    alpha = 1
alpha = self.style("fill-opacity")
if not node.style.get(attr, '')\
        .startswith('url(#'):
    continue

marker_id = node.style[attr][5:-1]
marker_node = self.svg.getElement(
    f'/svg:svg//svg:marker[@id="{marker_id}"]')
marker_node = node.style(attr)
obj.style['fill'] = pattern.get_id(2)
obj.style['fill'] = pattern

Checkout MR extensions#298 for additional examples of simplifications.

New Units API

Added in MR extensions#329, MR extensions#343, MR extensions#415

The existing functions unittouu and uutounit are widely used, but for different purposes. Different extension authors try to answer different questions using these function, and, inevitably, some answers were incorrect (see linked issues in MR extensions#329).

In Inkscape 1.2, new methods have been added to make working with dimensional values easier. These are to_dimensionless, to_dimensional, viewport_to_unit and unit_to_viewport. The existing functions unittouu and uutounit are not deprecated, but discouraged; in most cases, the new functions are more reliable.

  • to_dimensionless(value) fulfills the following task: Convert this string from the XML into a number, while processing the unit. When using this function on any SVG attribute and replace the original value with the result, the output doesn’t change visually.

  • viewport_to_unit(value, target_unit="px") answers the following questions:

    • What is the length (e.g. the length of a rectangle, without a unit) of an object that has size value on the viewport? This is relevant because in Inkscape toolbars / tools, all dimensions are shown in “viewport units”.

    • In other words: What is the SVG representation of entering ``value`` in the width/height widget of the selection tool (set to the unit of value)? Consider <svg width="210mm" viewBox="0 0 105 147.5"><rect width="100" height="100"/></svg> , i.e. a “mm-based” SVG with scale=2. When typing 200 in the rectangle tool, set to mm, the XML editor shows 100 = 100px. That’s what viewport_to_unit("200mm") = 100 does.

    • Note that this is different than viewport_to_unit("200", "mm"), which would be for a rectangle with a width (in the width/height widget of the rectangle tool) of 200 (px), while writing the width in mm in the SVG: <rect width="7.00043mm" height="7.00043mm"/>.

  • to_dimensional simply converts a float to its equivalent with attached unit. It’s the opposite of to_dimensionless.

  • unit_to_viewport(value, unit="px") answers the following question: What does the the width/height widget of the selection tool (set to unit ) show when selecting an element with width ``value`` as defined in the SVG? Consider again <svg width="210mm" viewBox="0 0 105 147.5"><rect width="100" height="100"/></svg> , i.e. a “mm-based” document with scale=2. To create this rectangle, one has to type viewport_to_unit("100", unit="mm") = 200 into the rectangle tool, if the rectangle tool is set to mm.

With the same spirit, the functions for width/height of the document have been updated. svg.width and svg.height have been deprecated, and replaced with svg.viewbox_width, svg.viewport_width, svg.viewbox_height and svg.viewport_height.

There is also svg.scale, which returns the ratio of the viewport and viewbox width, and svg.inkscape_scale which is the scale reported in the Document properties dialog.

See Units for additional information.

Other additions to inkex

  • The path conversion for arcs and stars have been added, so when extensions create these objects, they are rendered in a browser as well and can be processed further by the same extension. (MR extensions#387, Issue extensions#240)

  • ColorExtensions can now process in RGBA space. Previously, opacity and color were processed independently. By setting the class variable pass_rgba = True, the modify_color method gets passed a color with alpha channel computed from matching property pairs, e.g. fill and fill-opacity. (This value takes CSS styling and style inheritance into account. (MR extensions#392 , Issue extensions#419).

  • API functions for the new multipage feature have been added: MR extensions#499.

Other deprecations to inkex

  • Pre Inkscape 1.0 way of declaring the dependency on inkex in the *.inx file has been removed entirely. (It was deprecated in Inkscape 1.0. For details, see Remove dependency listings)