`GtkFixedLayout` is a layout manager which can place child widgets at fixed positions.
Most applications should never use this layout manager; fixed positioning and sizing requires constant recalculations on where children
need to be positioned and sized. Other layout managers perform this kind of work internally so that application developers don't need to
do it. Specifically, widgets positioned in a fixed layout manager will need to take into account:
Themes, which may change widget sizes.
Fonts other than the one you used to write the app will of course change the size of widgets containing text; keep in mind that
users may use a larger font because of difficulty reading the default, or they may be using a different OS that provides different
fonts.
Translation of text into other languages changes its size. Also, display of non-English text will use a different font in many
cases.
In addition, `GtkFixedLayout` does not pay attention to text direction and thus may produce unwanted results if your app is run under
right-to-left languages such as Hebrew or Arabic. That is: normally GTK will order containers appropriately depending on the text
direction, e.g. to put labels to the right of the thing they label when using an RTL language; `GtkFixedLayout` won't be able to do that
for you.
Finally, fixed positioning makes it kind of annoying to add/remove UI elements, since you have to reposition all the other elements. This
is a long-term maintenance problem for your application.