Shiny notification (toast) border-radius is styled by Bootstrap variable card-border-radius instead of toast-border-radius

[Teebusch]

Describe the problem

The toast_border_radius Bootstrap variable documented here does not change the border radius of Toasts created with shiny::showNotification(). Instead, the card-border-radius is used. The problem originates here:

bslib/inst/builtin/bs5/shiny/_rules.scss

Line 325 in b2ecc63

border-radius: $card-border-radius;

Reproducible Example

library(shiny)
library(bslib)

# Goal: change `border-radius` of Toasts created with `showNotification()`

theme1 = bslib::bs_theme(version = 5, border_radius = "10rem")        # ❌ nope
theme2 = bslib::bs_theme(version = 5, toast_border_radius = "10rem")  # ❌ nope
theme3 = bslib::bs_theme(version = 5, card_border_radius = "10rem")   # ✔   this works, but it shouldnt

server = \(input, output) { shiny::showNotification("Foo", duration = NULL) }

shinyApp(bslib::page_fluid("Foo", theme = theme1), server)
shinyApp(bslib::page_fluid("Foo", theme = theme2), server)
shinyApp(bslib::page_fluid("Foo", theme = theme3), server)  # works

related issue

On a related note: I'm also wondering whether the selector of that rule intentionally duplicates the classname.

bslib/inst/builtin/bs5/shiny/_rules.scss

Line 319 in b2ecc63

.shiny-notification.shiny-notification {

It seems redundant but it does increase specificity, so that I cannot override the styling with, e.g.,

.shiny-notification {
    opacity: 0.5;
} 

i.e., this will make a blue box:

<div class="shiny-notification">This will be blue</div>

 // css:

.shiny-notification.shiny-notification { background-color: blue; }
.shiny-notification { background-color: green; }

I couldn't find anything about the specificity of duplicate class names in the CSS selector specs and I wonder if all user agents interpret it in this way.

Session Info

─ Session info ─────────────────────────────────────────────────────────────────────────────────
 setting  value
 version  R version 4.3.1 (2023-06-16 ucrt)
 os       Windows 10 x64 (build 19045)
 system   x86_64, mingw32
 ui       RStudio
 language (EN)
 collate  German_Germany.utf8
 ctype    German_Germany.utf8
 tz       Europe/Berlin
 date     2024-08-02
 rstudio  2023.12.1+402 Ocean Storm (desktop)
 pandoc   NA
─ Packages ─────────────────────────────────────────────────────────────────────────────────────

! package     * version date (UTC) lib source

P cachem        1.1.0   2024-05-16 [?] CRAN (R 4.3.3)

P cli           3.6.3   2024-06-21 [?] CRAN (R 4.3.3)

P devtools      2.4.5   2022-10-11 [?] CRAN (R 4.3.1)

P digest        0.6.36  2024-06-23 [?] CRAN (R 4.3.3)

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P fastmap       1.2.0   2024-05-15 [?] CRAN (R 4.3.3)

P fs            1.6.4   2024-04-25 [?] CRAN (R 4.3.3)

P glue          1.7.0   2024-01-09 [?] CRAN (R 4.3.3)

P htmltools     0.5.8.1 2024-04-04 [?] CRAN (R 4.3.3)

P htmlwidgets   1.6.4   2023-12-06 [?] CRAN (R 4.3.3)

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P magrittr      2.0.3   2022-03-30 [?] CRAN (R 4.3.1)

P memoise       2.0.1   2021-11-26 [?] CRAN (R 4.3.1)

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P R6            2.5.1   2021-08-19 [?] CRAN (R 4.3.1)

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P remotes       2.5.0   2024-03-17 [?] CRAN (R 4.3.3)

renv          1.0.7   2024-04-11 [1] CRAN (R 4.3.3)

P rlang         1.1.4   2024-06-04 [?] CRAN (R 4.3.3)

P rstudioapi    0.16.0  2024-03-24 [?] CRAN (R 4.3.3)

P sessioninfo   1.2.2   2021-12-06 [?] CRAN (R 4.3.1)

P shiny         1.9.0   2024-07-29 [?] CRAN (R 4.3.1)

P stringi       1.8.4   2024-05-06 [?] CRAN (R 4.3.3)

P stringr       1.5.1   2023-11-14 [?] CRAN (R 4.3.3)

P urlchecker    1.0.1   2021-11-30 [?] CRAN (R 4.3.1)

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P xtable        1.8-4   2019-04-21 [?] CRAN (R 4.3.1)