Sets the labels text, attributes and mnemonic from markup.
Parses str which is marked up with Pango markup (see [[email protected]_markup]), setting the label’s text and attribute
list based on the parse results. If characters in str are preceded by an underscore, they are underlined indicating that they
represent a keyboard accelerator called a mnemonic.
The mnemonic key can be used to activate another widget, chosen automatically, or explicitly using [[email protected]_mnemonic_widget] .
| this |
a `GtkLabel` |
| str |
a markup string |