Translate a registry symbol shape to a rendering target

The registry carries a shape on every mark — circle, square, star and triangle are the complete vocabulary across all three registry files. Until #16 no renderer consumed it, so maps hardcoded their own marker codes.

Usage

gq_symbol_shape(shape, target = c("tmap", "mapgl"))

Arguments

shape

Registry shape string, or NULL.

target

One of "tmap" or "mapgl".

Value

For "tmap", an integer pch. For "mapgl", NULL. NULL in gives NULL out.

Details

star maps to pch = 8, which draws a star with strokes only and ignores fill entirely. R has no filled star — its fillable symbols (21–25) are circle, square, diamond, triangle-up and triangle-down. Substituting a filled circle would silently discard the distinction that made the layer a star in QGIS, so the unfillable code is returned and callers are expected to set col rather than fill; gq_tmap_style() does this. Use gq_symbol_fillable() to ask.

mapgl returns NULL for every shape. A MapLibre circle layer has no shape concept at all; anything else requires a symbol layer with an icon sprite, which the registry has no source data for. NULL says "not expressible here" rather than handing back a pch number the renderer cannot read.

See also

gq_symbol_size()

Examples

gq_symbol_shape("circle", "tmap")
#> [1] 21
gq_symbol_shape("triangle", "tmap")
#> [1] 24
gq_symbol_shape("star", "tmap")       # 8 -- stroked, never filled
#> [1] 8
gq_symbol_fillable("star")            # FALSE
#> [1] FALSE