What do I have to know before I start

Global variables

atom_ptr Gatom
The pointer to the internal atom data structure. If this pointer is deleted or overwritten there is no chance to access the atom data structure anymore.

char **GOrbitalListItems
GOrbitalListItems stores the orbital names/strings which are currently selected in the Orbitals listbox of the main window. The number of items is available by GOrbitalListItemsCount.

int GOrbitalListItemsCount
This variable counts the number of selected orbital names/strings of the Orbitals listbox of the main window.

create_orbital_array_ptr GCreateOrbital
GCreateOrbital stores the values of a newly created pseudo orbital till these are added to the general atom data structure by the user. The structure is defined as follows and values can only be accessed by the using -> operand.

• int dimension
  dimension - 1 is the upper border for the following float and integer number lists.

• int shell
  stores the shell number of the newly created pseudo orbital.

• char symbol
  gives the orbital type, i.e. S, P or D.

• int *n
  
• float *alpha
  
• float *c

  lists with element indizes ranging from [0..dimension - 1] and storing the atomic data for the newly created pseudo orbital.

int *GDrawList
SciPlot, an embedded program which draws the orbital functions, returns an integer identity value for each graph after its creation. These identity numbers are stored in GDrawList and necessary when a graph has to be removed or updated. GDrawList consists of GNumberOrbitals elements, and if an element value is not equal to -1 then the according orbital graph has already been drawn.

int GNumberOrbitals
counts the number of orbitals stored in the atom data structure. GNumberOrbitals is normally set with the return value of the XAAllocateGOrbitalListItems procedure which has to be called if the internal atom data structure is changed by adding or deleting an orbital.

int GCount
counts the changes, which have been made to the atom data structure by deleting or creating orbitals, and modifies the grey scale of line markers in the drawing area accordingly.

char GCreateSymbol
is set after selecting an option of the Create Orbital push button. Future pseudo orbitals will be created with the orbital symbol GCreateSymbol.

enum item_names Gcrutch
Gcrutch is used in the following procedures:

• XACalculateCreate
  For the creation of a new pseudo orbital or the update of an existing one the same procedure XACalculateCreate is called. The distinction between creation and update is made by Gcrutch, which has to be set to CREATE or UPDORB accordingly. The difference is quite obvious. When creating a new pseudo orbital XACalculateCreate is looking for the next one in the Orbitals listbox whereas in case of an update this has to be the selected one.

• XADeleteOrbital
  If Gcrutch is set to DELORB the previously drawn graphs will be removed from the drawing area to prevent inconsistencies because of the change in the internal atom data structure. In case of UPDORB this is not necessary because the size of the internal atom data structure remains the same.

Normally Gcrutch is set in the xacallback.c module directly after a menu item was selected. Gcrutch is also used in the CreateDialogCB callback function of the Create window.

int GMarker
GMarker stores the point marker for the next graph. The variable is increased by XADrawGraph and necessary to distinguish between the different graphs if the drawing area is printed out as a PS file.

orbital_array_ptr GOriginalAtom
GOriginalAtom stores information about the orbitals directly after reading in the atomic data file. Therefore it is possible to distinguish pseudo orbitals from original ones because they are not mentioned in GOriginalAtom. For accessing the structure please refer to XAOrbitalArray.