Here is the component version. If a disabled item is selected then the
ItemIndex is set to -1. You can modify the code to take action
accordingly.
unit DisabledCombo;
interface
uses
StdCtrls
, Classes
, Controls
, Windows
, Messages
, Graphics
;
type
TCustomDisabledComboBox = class(TCustomComboBox)
private
FDisabledItems: TStrings;
FShowDisabledFocus: Boolean;
procedure SetDisabledItems(const Value: TStrings);
procedure CNCommand(var Message: TWMCommand); message CN_COMMAND;
protected
function IsItemDisabled(const AIndex: Integer): Boolean; inline;
procedure DrawItem(Index: Integer; Rect: TRect; State:
TOwnerDrawState); override;
property ShowDisabledFocus: Boolean read FShowDisabledFocus write
FShowDisabledFocus default False;
property DisabledItems: TStrings read FDisabledItems write SetDisabledItems;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
end;
TDisabledComboBox = class(TCustomDisabledComboBox)
published
property Align;
property AutoComplete default True;
property AutoCompleteDelay default 500;
property AutoDropDown default False;
property AutoCloseUp default False;
property BevelEdges;
property BevelInner;
property BevelKind default bkNone;
property BevelOuter;
// property Style; {Must be published before Items}
property Anchors;
property BiDiMode;
property CharCase;
property Color;
property Constraints;
property Ctl3D;
property DragCursor;
property DragKind;
property DragMode;
property DropDownCount;
property Enabled;
property Font;
property ImeMode;
property ImeName;
property ItemHeight;
property ItemIndex default -1;
property MaxLength;
property ParentBiDiMode;
property ParentColor;
property ParentCtl3D;
property ParentFont;
property ParentShowHint;
property PopupMenu;
property ShowHint;
property Sorted;
property TabOrder;
property TabStop;
property Text;
property Visible;
property OnChange;
property OnClick;
property OnCloseUp;
property OnContextPopup;
property OnDblClick;
property OnDragDrop;
property OnDragOver;
property OnDrawItem;
property OnDropDown;
property OnEndDock;
property OnEndDrag;
property OnEnter;
property OnExit;
property OnKeyDown;
property OnKeyPress;
property OnKeyUp;
property OnMeasureItem;
property OnMouseEnter;
property OnMouseLeave;
property OnSelect;
property OnStartDock;
property OnStartDrag;
property Items; { Must be published after OnMeasureItem }
property DisabledItems;
property ShowDisabledFocus;
end;
procedure Register;
implementation
uses
SysUtils
;
procedure Register;
begin
RegisterComponents('Samples', [TDisabledComboBox]);
end;
{ TCustomDisabledComboBox }
procedure TCustomDisabledComboBox.CNCommand(var Message: TWMCommand);
begin
case Message.NotifyCode of
CBN_SELCHANGE:
begin
// if the user selects a disabled item, clear the selection
if not IsItemDisabled(ItemIndex) then
begin
Text := Items[ItemIndex];
Click;
Select;
end
else
ItemIndex := -1;
end;
else
inherited;
end;
end;
constructor TCustomDisabledComboBox.Create(AOwner: TComponent);
begin
inherited;
Style := csOwnerDrawFixed;
FDisabledItems := TStringList.Create;
FShowDisabledFocus := False;
end;
destructor TCustomDisabledComboBox.Destroy;
begin
FDisabledItems.Free;
inherited;
end;
procedure TCustomDisabledComboBox.DrawItem(Index: Integer; Rect: TRect;
State: TOwnerDrawState);
var
lDrawFlags: Cardinal;
lStr: string;
begin
TControlCanvas(Canvas).UpdateTextFlags;
Canvas.Brush.Style := bsSolid;
// setup background color
if (odSelected in State) and not IsItemDisabled(Index) then
Canvas.Brush.Color := clHighlight
else
Canvas.Brush.Color := Color;
Canvas.FillRect(Rect);
Canvas.Brush.Style := bsClear;
// setup font color
if (odSelected in State) and not IsItemDisabled(Index) then
Canvas.Font.Color := clHighlightText
else if IsItemDisabled(Index) then
Canvas.Font.Color := clGrayText
else
Canvas.Font.Color := Font.Color;
InflateRect(Rect, -2, -2);
lDrawFlags := DT_LEFT or DT_VCENTER or DT_SINGLELINE or DT_NOPREFIX
or DT_END_ELLIPSIS;
lStr := Items[Index];
DrawText(Canvas.Handle, PChar(lStr), Length(lStr), Rect, lDrawFlags);
// comment this out if you want the focus rect to be draw even when a
// disabled item has focus
if (odSelected in State) and IsItemDisabled(Index) and not
ShowDisabledFocus then
begin
InflateRect(Rect, 2, 2);
DrawFocusRect(Canvas.Handle, Rect);
end;
end;
function TCustomDisabledComboBox.IsItemDisabled(const AIndex: Integer): Boolean;
begin
result := FDisabledItems.IndexOf(IntToStr(AIndex)) > -1;
end;
procedure TCustomDisabledComboBox.SetDisabledItems(const Value: TStrings);
begin
FDisabledItems.Assign(Value);
end;
end.
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