No, it has nothing to do with the gtkdialog used. Tried with a previous build of F96 which has a gtk3 version. The examples work but selection does not. Wouldn't call it "sort of" The culprit must be your CSS styling because without it the text selection works as expected (using default styles).
I tried following code and the result is the small window of the screenshot. Text is perfectly selectable. Sidenote: With GTK2 the text wouldn't wrap after each word.
Code: Select all
#!/bin/sh
export GTKDIALOG_SPLASH='<window><vbox><text selectable="true" can-focus="false" label="this is text"></text></vbox></window>'
exec gtkdialog --class="gtkdialog-splash" -p GTKDIALOG_SPLASH
I then replaced the GTKDIALOG_SPLASH variable in the gtkdialog-splash script with the one of above code. The result is the bigger of the screenshot windows. Note the bold text and gray background. This text is not selectable despite the selectable="true" attribute. May be the result of the gtk.css created by gtkdialog-splash .