ProgressBar.setShowText

Sets whether the progress bar will show text next to the bar. The shown text is either the value of the #GtkProgressBar:text property or, if that is null, the #GtkProgressBar:fraction value, as a percentage.

To make a progress bar that is styled and sized suitably for containing text (even if the actual text is blank), set #GtkProgressBar:show-text to true and #GtkProgressBar:text to the empty string (not null).