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A general description is here.
There is a new ‘antialias’ argument to ‘windows()’, ‘win.print()’ and the bitmap devices. This is an option that can be set in ‘windows.options()’ to set the default for ‘windows()’ (and ‘win.graph()’).
This gives a hint to the Windows plotting system. Whether anti-aliasing is actually used principally depends on the OS settings: this argument should at least be able to turn it off. The default behaviour (unchanged from before) is that Windows will use anti-aliasing for screen devices (and bitmap devices, as they plot on a hidden screen) if ClearType has been enabled. For those not using ClearType, ‘windows.options(antialias = "cleartype")’ will make this the default, and it will probably give more legible plots.
The argument can also be used for the cairographics-based versions of the bitmap devices.
Compilation now uses option ‘-mtune=core2’: this will improve performance a few percent on recent CPUs at the expense of those which are several years old.
The 32-bit default build now requires a CPU supporting SSE2 (a Pentium 4 from 2001, AMD Opteron or Athlon 64 from 2003, or later): R can be built from the sources without this requirement: see file ‘MkRules.dist’.
Note that these changes will result in different results on some floating-point calculations (since they affect when extended-precision registers are used): in general they will bring 32-bit Windows closer to results from other platforms (including 64-bit Windows).
The windows() screen device would sometimes fail to plot (visibly) points with ‘pch="."’. PR#14583
Shutting down the R session cleaned up the temporary directory before closing all graphics devices. On Windows this necessitated changing the working directory, so some devices (e.g. ‘tiff()’) could write files in the wrong directory if closed during shutdown. The order has been reversed.