Activate font state

Usage

open_font_dev(fontspec, silent = FALSE)

close_font_dev()

debug_font_dev()

undebug_font_dev()

Arguments

fontspec: (font_spec)
a font_spec object specifying the font information to use for calculating string widths and heights, as returned by font_spec().
silent: (logical(1))
If FALSE, the default, a warning will be emitted if this function switches away from an active graphics device.

Value

open_font_dev returns a logical value indicating whether a new pdf device was opened.
close_font_dev, debug_font_dev and undebug_font_dev return NULL.

In all cases the value is returned invisibly.

Details

The font device state is an environment with four variables guaranteed to be set:

open: (logical(1))
whether a device is already open with font info
fontspec: (font_spec)
the font specification, if any, that is currently active (list() if none is).
spacewidth: (numeric(1))
the width of the space character in the currently active font.
ismonospace: (logical(1))
whether the specified font is monospaced.

open_font_dev opens a pdf device with the specified font only if there is not one currently open with the same font. If a new device is opened, it caches spacewidth and ismonospace for use in nchar_ttype).

close_font_dev closes any open font state device and clears the cached values.

debug_font_dev and undebug_font_dev activate and deactivate, respectively, logging of where in the call stack font devices are being opened.

Examples

open_font_dev(font_spec("Times"))
nchar_ttype("Hiya there", font_spec("Times"))
#> [1] 17
close_font_dev()