The structure pointed to by mgrPtr contains information about the geometry manager:
typedef struct {
const char *name;
Tk_GeomRequestProc *requestProc;
Tk_GeomLostContentProc *lostContentProc;
} Tk_GeomMgr;
The name field is the textual name for the geometry manager,
such as pack or place; this value will be returned
by the command winfo manager.
requestProc is a procedure in the geometry manager that will be invoked whenever Tk_GeometryRequest is called by the content window to change its desired geometry. requestProc should have arguments and results that match the type Tk_GeomRequestProc:
typedef void Tk_GeomRequestProc(
void *clientData,
Tk_Window tkwin);
The parameters to requestProc will be identical to the
corresponding parameters passed to Tk_ManageGeometry.
clientData usually points to a data
structure containing application-specific information about
how to manage tkwin's geometry.
The lostContentProc field of mgrPtr points to another procedure in the geometry manager. Tk will invoke lostContentProc if some other manager calls Tk_ManageGeometry to claim tkwin away from the current geometry manager. lostContentProc is not invoked if Tk_ManageGeometry is called with a NULL value for mgrPtr (presumably the current geometry manager has made this call, so it already knows that the window is no longer managed), nor is it called if mgrPtr is the same as the window's current geometry manager. lostContentProc should have arguments and results that match the following prototype:
typedef void Tk_GeomLostContentProc(
void *clientData,
Tk_Window tkwin);
The parameters to lostContentProc will be identical to the
corresponding parameters passed to Tk_ManageGeometry.