The tour measured its card with a height-for-width request whose for_size
came from the natural width minus the margins the tour sets for positioning.
A measure reports margins *included*, so that for_size landed a margin short
of the minimum the box answers with and GTK warned once per frame:
Trying to measure GtkBox 0x... for width of N, but it needs at least M
(about 9/s for as long as the tour was up). The card now takes its size from
gtk_widget_compute_bounds() once a frame has run -- its allocation rectangle,
not gtk_widget_get_width(), which is only the content box -- and falls back
to a measure with no for_size at all only on a frame with nothing allocated.
GTK is built with structured logging, so its messages reach the log writer
and never the handler API; no existing probe can read one. The exit dump now
counts them (`gtk warnings:`, must read 0) through a writer function chained
to g_log_writer_default(), which leaves stderr unchanged.
Martino Ferrari
bb62b8178c