@li @b normal: this is the bitmap shown in the default state, it must be always
valid while all the other bitmaps are optional and don't have to be set.
@li @b disabled: bitmap shown when the button is disabled.
@li @b normal: this is the bitmap shown in the default state, it must be always
valid while all the other bitmaps are optional and don't have to be set.
@li @b disabled: bitmap shown when the button is disabled.