If you do not specify any hints, the CAPI calculates the on-screen geometry based on its default constraints. With this geometry the various elements are displayed with adequate space in the window.
This is designed to work regardless of variable factors such as the user's configuration, for example specifying large font sizes. It is often wrong to constrain CAPI elements to fixed pixel sizes, as these constraints may lead to poorer layouts in some configurations.
CAPI User Guide (Unix version) - 30 Aug 2011