add_forest() flextable overflows the page in docx output

[Melkiades]

Description

add_forest(table_engine = "flextable") produces a flextable that is wider than the page and uses a fixed table layout, so when the table is saved to .docx Word renders the exact column widths and the table spills off the right edge. The forest plots become unreadable.

The images themselves are sized correctly (the ggplot column is 2.5in x 0.4in). The problem is the overall table width combined with the fixed layout.

Reproduction

library(crane)
library(gtsummary)

set.seed(1)
ft <- trial |>
  tbl_roche_subgroups(
    rsp = "response", by = "trt", subgroups = c("grade", "stage"),
    ~ glm(response ~ trt, data = .x) |>
      tbl_regression(show_single_row = trt, exponentiate = TRUE)
  ) |>
  add_forest(pvalue = starts_with("p.value"), table_engine = "flextable")

# saved to docx the table is ~11.8in wide on a 6.5in usable page

Measured on the rendered .docx:

Measure	Value
Table width	11.79 in
Usable page width (Letter, 1in margins)	6.5 in
Overflow	+5.29 in (181% of the page)
Table layout	fixed

as_flex_table() already returns a fixed layout, and add_forest() keeps it fixed while widening the table, so Word cannot reflow it.

Proposed fix

Set layout = "autofit" at the end of the flextable branch of add_forest() so Word reflows the table to the page width. Verified: with autofit the table reflows, the plots stay at 2.5in x 0.4in, and all images package correctly.

Related

Related to #150 (fixed vs autofit layout for flextable). This issue is the concrete forest-plot symptom of that discussion.