TCustomComboBox

type TCustomComboBox = class(TWinControl)

  class procedure WSRegisterClass; override;

WSRegisterClass - Register this Class for the current Widget Set

protected

  procedure CreateParams(); override;

  procedure InitializeWnd; override;

InitializeWnd - creates the underlying interface-object: calls inherited InitializeWnd then sets up several local lists and variables notably for style and size

  procedure DestroyWnd; override;

DestroyWnd - finds somewhere to store locally held variables then frees lists, calls inherited DestroyWnd

  procedure DoEnter; override;

DoEnter - cals inherited method then autoselects text in dropdown list if required

  procedure DoExit; override;

DoExit - disables AutoSelect then calls inherited DoExit

  procedure DrawItem(); virtual;

DrawItem - perform the action necessary to draw the specified indexed item at the specified position

  procedure MeasureItem(); virtual;

Measure the size (Height) of an item in the drop-down list

protected

  class function GetControlClassDefaultSize; override;

GetControlClassDefaultSize - sets its own defaults, overriding inherited values

protected

  procedure LMChanged(); message;

LMChanged - LCL Message to signify that the control has changed

  procedure Change; virtual;

Change - software emulation of OnChange event

  procedure Select; virtual;

Select - software emulation of OnSelect event

  procedure DropDown; virtual;

DropDown - software emulation of OnDropDown event

  procedure GetItems; virtual;

GetItems - finds the list of items for the dropdown box

  procedure SetItems(); virtual;

SetItems writes the strings specified in Value to the Items list

  procedure CloseUp; virtual;

CloseUp - software emulation of OnCloseUp event

  procedure AdjustDropDown; virtual;

AdjustDropDown - adjust the properties of the DropDown list

  function GetItemCount;

GetItemCount - returns the number of items in the DropDown list

  function GetItemHeight; virtual;

GetItemHeight - returns the height of the current list item

  function GetSelLength; virtual;

GetSelLength - returns the length of the current selection

  function GetSelStart; virtual;

GetSelStart - returns the start position of the current selection

  function GetSelText; virtual;

GetSelText - returns the currently selected text string

  function GetItemIndex; virtual;

GetItemIndex - returns the Index value of the current list item

  function GetMaxLength; virtual;

GetMaxLength - returns the maximum length of a list item

  function IsReadOnlyStored;

IsReadOnlyStored - returns True if ReadOnly status is stored

  procedure SetDropDownCount(); virtual;

SetDropDownCount - writes the number of items in DropDown list to local variable

  procedure SetDroppedDown(); virtual;

SetDroppedDown - writes DroppedDown status to local boolean variable

  procedure SetItemHeight(); virtual;

SetItemHeight - writes height of current list item to local variable

  procedure SetItemIndex(); virtual;

SetItemIndex - writes index value of current item to local variable

  procedure SetMaxLength(); virtual;

SetMaxLength - writes maximum length of list item to local variable

  procedure SetSelLength(); virtual;

SetSelLength - writes length of current selection to local variable

  procedure SetSelStart(); virtual;

SetSelStart - writes start position of current selection to local variable

  procedure SetSelText(); virtual;

SetSelText - writes currently selected text string to local variable

  procedure SetSorted(); virtual;

SetSorted - writes to local (boolean) variable to show if list is Sorted

  procedure SetStyle(); virtual;

SetStyle - writes the current Style specifier to local variable

  procedure RealSetText(); override;

RealSetText - sets the ComboBox text to the caption value specified

  procedure KeyDown(); override;

KeyDown - performs code for traversing the dropdown list to the correct location before calling inherited KeyDown

  procedure KeyUp(); override;

KeyUp calls inherited method then performs specific actions depending on which key is being processed

  procedure KeyPress(); override;

KeyPress adjusts character case if necessary then calls inherited method

  procedure UTF8KeyPress(); override;

UTF8KeyPress converts character case if required then calls inherited method

  procedure MouseUp(); override;

MouseUp calls inherited method then sets AutoSelect if left mouse button is clicked for the first time after receiving focus

  function SelectItem();

SelectItem - returns True if current item (specified by a string) is to be selected

  property ItemHeight: Integer; [rw]

ItemHeight - the height of the current item in the drop-down list

  property ItemWidth: Integer; [rw]

ItemWidth - the width of the current item in the drop-down list

  property MaxLength: Integer; [rw]

MaxLength - the maximum allowed length of a string

  property OnChange: TNotifyEvent; [rw]

OnChange - event handler for any change in properties of the combo box

  property OnCloseUp: TNotifyEvent; [rw]

OnCloseUp - event handler for when the drop-down box is closed up again

  property OnDrawItem: TDrawItemEvent; [rw]

OnDrawItem - event handler for when an entry is written to the Items list

  property OnDropDown: TNotifyEvent; [rw]

OnDropDown - event handler for when the drop-down list appears

  property OnGetItems: TNotifyEvent; [rw]

Event handler when items can be populated

  property OnMeasureItem: TMeasureItemEvent; [rw]

Event handler when measurement of an item is required

  property OnSelect: TNotifyEvent; [rw]

Event handler when an item or some text is selected

  property ParentColor;

ParentColor - should the control have the same colour as the parent? Default is true

  property Sorted: Boolean; [rw]

Sorted - whether the entries in the drop-down list have been sorted

public

  constructor Create(); override;

Create - constructor for TCustomComboBox: calls inherited Create then initialises styles, item lists, bounds and various other local variables

  destructor Destroy; override;

Destroy - destructor for TCustomComboBox: frees handles, itemlists, canvas and items then calls inherited Destroy

  procedure IntfGetItems;

IntfGetItems - gets list of items from the interface

  procedure AddItem();

AddItem - adds an Item to the list in the drop-down box

  procedure AddHistoryItem();

AddHistoryItem - Add an Item as first entry in History List

  procedure Clear; virtual;

Clear - remove all text and drop-down list

  procedure ClearSelection;

ClearSelection - clear the currently selected text or items from drop-down list

  property CharCase: TEditCharCase; [rw]

CharCase: indicates whether text is to be displayed as Upper, Lower or Normal case (as entered)

  property DroppedDown: Boolean; [rw]

DroppedDown - indicates whether or not the drop-down list has appeared

  procedure SelectAll;

Select all items in the list

  property AutoComplete: Boolean; [rw]

AutoComplete - enables the facility to offer suggestions for completing text-strings

  property AutoCompleteText: TComboBoxAutoCompleteText; [rw]

AutoCompleteText : Options for behavior of the Auto-Complete feature

  property AutoDropDown: Boolean; [rw]

AutoDropDown - if True, the drop-down list appears as soon as the cursor moves over the text box

  property AutoSelect: Boolean; [rw]

AutoSelect : Boolean. If True, all contents of Text box are selected when control receives focus

  property AutoSelected: Boolean; [rw]

AutoSelected : True indicates that the combobox control has just performed an AutoSelect operation

  property AutoSize;

AutoSize defaults to True, overriding any previous default

  property ArrowKeysTraverseList: Boolean; [rw]

ArrowKeysTraverseList - enables the operator to use the keyboard Arrow keys to move through the list as an alternative to using the mouse

  property Canvas: TCanvas; [r]

Canvas - the area on which the components are drawn or painted

  property DropDownCount: Integer; [rw]

DropDownCount - number of entries in the drop-down list

  property Items: TStrings; [rw]

Items - an array of strings that holds the entries of the drop-down list

  property ItemIndex: Integer; [rw]

Index - the number of the currently selected item (starting at zero)

  property ReadOnly: Boolean; [rws]

ReadOnly - if True, information in the control can only be Read, not Written or Deleted

  property SelLength: Integer; [rw]

SelLength - the length of the text that has been selected in bytes

  property SelStart: Integer; [rw]

SelStart - if text is selected this is the starting position otherwise the cursor position in bytes starting at 0

  property SelText: String; [rw]

SelText - the text string that has been selected for editing

  property Style: TComboBoxStyle; [rw]

Style : may be Simple, a single-line Drop-Down or a Drop-Down list, or some version drawn by the Owner

  property TabStop;

Is the control in the sequence of controls accessed by successive presses of the Tab key?

  property Text;

Text - the string appearing in the main box. If an item on the drop-down list is selected, it replaces the contents of Text

end;

TCustomComboBox

TCustomComboBox - the base class from which TComboBox is derived

TWinControl

TControl

TLCLComponent

TLCLComponent - base class for LCL components

TComponent,IUnknown,IInterfaceComponentReference

TPersistent

TObject