credits not rendered properly in pdf file

[wrobell]

Please consider the following script, which generates PDF file: bug-tmap-credits.pdf.

The background of the credits text is not wide enough.

Changing font size to 1 in tm_credits seems to render the background properly.

If I generate PNG file instead of PDF with the script below, then the background is too wide:

library(sf)
library(tmap)

lon_min <- -6.375
lon_max <- -5.37
lat_min <- 52.96
lat_max <- 53.8

coords <- matrix(c(lon_min, lat_min,
                   lon_max, lat_min,
                   lon_max, lat_max,
                   lon_min, lat_max,
                   lon_min, lat_min),
                 ncol=2,
                 byrow=TRUE)

bbox = st_polygon(list(coords)) |> st_sfc(crs=4326)
data.sf = st_sf(band=1:1, polygon=bbox)

credits = 'quite long, but ok.\nmuch longer, much longer, much longer.'
p = (tm_basemap('CartoDB.Positron')
     + tm_shape(data.sf, bbox=bbox)
     + tm_sf(fill='red', fill_alpha=0.01)
     + tm_credits(credits,
                  position=c('right', 'bottom'),
                  size=0.3,
                  bg=T,
                  bg.color='white',
                  bg.alpha=0.5))

tmap_save(p, file='bug-tmap-credits.pdf', width=3840, asp=0, unit='px')

[mtennekes]

Don't know how to fix that tbh

It's an issue with small font sizes. Apparently the graphics::strwidth that I use is less accurate than for large font sizes, and also varies across devices. If you change the size value of tm_credits to values above 0.5 and certainly above 1.0, the background rectangle box has good margins. Source code:

tmap/R/tmapGridComp_funs.R

Line 659 in d8d7817

tmapGridCompWidth_text = function(comp, o) {

Workaround: use padding:

credits = 'quite long, but ok.\nmuch longer, much longer, much longer.'
p = (tm_basemap('CartoDB.Positron')
	 + tm_shape(data.sf, bbox=bbox)
	 + tm_sf(fill='red', fill_alpha=0.01)
	 + tm_credits(credits,
	 			 position=c('right', 'bottom'),
	 			 size=0.3,
	 			 bg=T,
	 			 bg.color='white',
	 			 bg.alpha=0.5,
	 			 padding = c(0.5,0.5,0.5,2)))

tmap_save(p, file='bug-tmap-credits.pdf', width=3840, asp=0, unit='px')