the orientation to measure
Size for the opposite of @orientation, i.e. if @orientation is %GTK_ORIENTATION_HORIZONTAL, this is the height the widget should be measured with. The %GTK_ORIENTATION_VERTICAL case is analogous. This way, both height-for-width and width-for-height requests can be implemented. If no size is known, -1 can be passed.
location to store the minimum size
location to store the natural size
location to store the baseline position for the minimum size, or -1 to report no baseline
location to store the baseline position for the natural size, or -1 to report no baseline
Measures @widget in the orientation @orientation and for the given @for_size.
As an example, if @orientation is %GTK_ORIENTATION_HORIZONTAL and @for_size is 300, this functions will compute the minimum and natural width of @widget if it is allocated at a height of 300 pixels.
See GtkWidget’s geometry management section for a more details on implementing GtkWidgetClass.measure().