[Rd] support for polygons with holes

From: Paul Murrell <p.murrell_at_auckland.ac.nz>
Date: Mon, 28 Jun 2010 09:42:40 +1200


This is for developers of extension packages that provide extra *graphics devices* for R.

In the *development* version of R, support has been added to the graphics engine for rendering polygons with holes (e.g., maps with lakes with islands ...).

The API change is a new dev_Path() function for graphics devices.

The R_GE_version constant (in GraphicsEngine.h) has been bumped up to 8 as a marker of this change.

This means that, at a minimum, all graphics devices should be updated to provide dummy implementations of the new functions to just say that the feature is not yet implemented (see for example the PicTeX and XFig devices in the 'grDevices' package).

A full implementation of dev_Path() should be able to render paths that consist of multiple sub-paths which can be filled using either the even-odd rule or the non-zero winding rule (see the examples in polypath() from 'graphics' or grid.path() from 'grid').


Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
New Zealand
64 9 3737599 x85392

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