LCL: "EmptyValue" and "DisplayEmpty" properties for TBLookupCombobox and TDBLookupListBox components. Issue #36035, patch from Zdravko Gabrovski.

git-svn-id: trunk@62884 -

lcl/dbctrls.pp

@@ -123,6 +123,8 @@ Type
     FDataFieldNames: string;
     FKeyFieldNames: string;
     FListFieldName: string;
+    FEmptyValue: string;
+    FDisplayEmpty: string;
     FListFieldIndex: Integer;
     FDataFields: TList;  // Data Fields to lookup/edit
     FKeyFields: TList;   // Keyfields in lookup dataset
@@ -169,6 +171,8 @@ Type
     property ListSource: TDataSource read GetListSource write SetListSource;
     property NullValueKey: TShortcut read FNullValueKey write FNullValueKey;
     property ScrollListDataset: Boolean read FScrollListDataset write FScrollListDataset;
+    property EmptyValue : String read FEmptyValue write FEmptyVAlue;
+    property DisplayEmpty : String read FDisplayEmpty write FDisplayEmpty;
   end;
 
   { TDBEdit }
@@ -451,6 +455,8 @@ Type
   private
     FLookup: TDBLookup;
     procedure ActiveChange(Sender: TObject);
+    function GetDisplayEmpty: String;
+    function GetEmptyValue: String;
     function GetKeyField: string;
     function GetKeyValue: Variant;
     function GetListField: string;
@@ -459,6 +465,8 @@ Type
     function GetLookupCache: boolean;
     function GetNullValueKey: TShortCut;
     function GetScrollListDataset: Boolean;
+    procedure SetDisplayEmpty(AValue: String);
+    procedure SetEmptyValue(AValue: String);
     procedure SetKeyField(const Value: string);
     procedure SetKeyValue(const AValue: Variant);
     procedure SetListField(const Value: string);
@@ -504,6 +512,8 @@ Type
     property ListSource: TDataSource read GetListSource write SetListSource;
     property LookupCache: boolean read GetLookupCache  write SetLookupCache;
     property NullValueKey: TShortCut read GetNullValueKey write SetNullValueKey default 0;
+    property EmptyValue: String read GetEmptyValue write SetEmptyValue;
+    property DisplayEmpty: String read GetDisplayEmpty write SetDisplayEmpty;
 //    property MultiSelect;
     property OnClick;
     property OnDblClick;
@@ -852,6 +862,8 @@ Type
   private
     FLookup: TDBLookup;
     procedure ActiveChange(Sender: TObject);
+    function GetDisplayEmpty: String;
+    function GetEmptyValue: String;
     function GetKeyField: string;
     function GetKeyValue: variant;
     function GetListField: string;
@@ -860,6 +872,8 @@ Type
     function GetLookupCache: boolean;
     function GetNullValueKey: TShortCut;
     function GetScrollListDataset: Boolean;
+    procedure SetDisplayEmpty(AValue: String);
+    procedure SetEmptyValue(AValue: String);
     procedure SetKeyField(const Value: string);
     procedure SetKeyValue(const AValue: variant);
     procedure SetListField(const Value: string);
@@ -915,6 +929,8 @@ Type
     property LookupCache: boolean read GetLookupCache  write SetLookupCache;
 //    property MaxLength default -1;
     property NullValueKey: TShortCut read GetNullValueKey write SetNullValueKey default 0;
+    property EmptyValue: String read GetEmptyValue write SetEmptyValue;
+    property DisplayEmpty: String read GetDisplayEmpty write SetDisplayEmpty;
     property OnChange;
     property OnChangeBounds;
     property OnClick;

lcl/include/dblookup.inc

@@ -106,6 +106,8 @@ begin
   FDataFields := TList.Create;
   FKeyFields := TList.Create;
   FListLink := TDBLookupDataLink.Create(Self);
+  FDisplayEmpty := '';
+  FEmptyValue := '';
   //FHasLookUpField := False;
   //FLookupCache := False;
 end;
@@ -281,8 +283,22 @@ begin
   ListLinkDataSet := FListLink.DataSet;
   if not (Assigned(ListLinkDataSet) and Assigned(FListField)) then
     Exit;
-  if ListLinkDataSet.IsEmpty then
+
+  if ListLinkDataSet.IsEmpty then begin
+    // Add Empty value if no recs into dataset
+    if FEmptyValue<>'' then begin
+      FControlItems.BeginUpdate;
+      try
+        KeyIndex := FControlItems.Add(FDisplayEmpty);
+        SetLength(FListKeys, 1);
+        FListKeys[KeyIndex] := FEmptyValue;
+        KeyListCount := 1;
+      finally
+        FControlItems.EndUpdate;
+      end;
+    end;
     Exit;
+  end;
   Bookmark := ListLinkDataSet.GetBookmark;
   //in fpc 2.6.4, TMemDataset does not supports BlockRead. Issues 26356, 27959
   {$IF FPC_FULLVERSION < 30000}
@@ -302,8 +318,18 @@ begin
     //needed to handle sqldb.TSQLQuery that does not has a reliable recordcount after Open
     ListLinkDataSet.Last;
     ListLinkDataSet.First;
-    SetLength(FListKeys, ListLinkDataSet.RecordCount);
     KeyListCount := 0;
+    SetLength(FListKeys, ListLinkDataSet.RecordCount);
+    // Handle Empty Value and Empty Display
+    if FEmptyValue<>'' then begin
+      KeyIndex := FControlItems.Add(FDisplayEmpty);
+      if KeyIndex<>length(FListKeys) then              // sanity check
+        raise Exception.Create('TDBLookup.FetchLookupData: inconsistency');
+      SetLength(FListKeys, KeyIndex+1); // Add one more
+      FListKeys[KeyIndex] := FEmptyValue;
+      KeyListCount := 1;
+    end;
+
     while not ListLinkDataSet.EOF do
     begin
       KeyIndex := FControlItems.Add(FListField.DisplayText);

lcl/include/dblookupcombobox.inc

@@ -21,6 +21,8 @@ constructor TDBLookupComboBox.Create(AOwner: TComponent);
 begin
   inherited Create(AOwner);
   FLookup := TDBLookup.Create(Self);
+  EmptyValue := '';
+  DisplayEmpty := '';
   FDataLink.OnActiveChange := @ActiveChange;
 end;
 
@@ -68,6 +70,16 @@ begin
     UpdateLookup;
 end;
 
+function TDBLookupComboBox.GetDisplayEmpty: String;
+begin
+  Result := FLookup.DisplayEmpty;
+end;
+
+function TDBLookupComboBox.GetEmptyValue: string;
+begin
+ Result := FLookup.EmptyValue;
+end;
+
 procedure TDBLookupComboBox.DataChange(Sender: TObject);
 begin
   UpdateItemIndex;
@@ -153,6 +165,18 @@ begin
   result := FLookup.NullValueKey;
 end;
 
+procedure TDBLookupComboBox.SetDisplayEmpty(AValue: String);
+begin
+  FLookup.DisplayEmpty:=AValue;
+  UpdateLookup;
+end;
+
+procedure TDBLookupComboBox.SetEmptyValue(AValue: string);
+begin
+  FLookup.EmptyValue:=AValue;
+  UpdateLookup;
+end;
+
 function TDBLookupComboBox.GetScrollListDataset: Boolean;
 begin
   Result := FLookup.ScrollListDataset;

lcl/include/dblookuplistbox.inc

@@ -20,6 +20,8 @@ constructor TDBLookupListBox.Create(AOwner: TComponent);
 begin
   inherited Create(AOwner);
   FLookup:= TDBLookup.Create(Self);
+  EmptyValue := '';
+  DisplayEmpty := '';
   FDataLink.OnActiveChange:= @ActiveChange;
 end;
 
@@ -41,6 +43,16 @@ begin
     UpdateLookup;
 end;
 
+function TDBLookupListBox.GetDisplayEmpty: String;
+begin
+  Result := FLookup.DisplayEmpty;
+end;
+
+function TDBLookupListBox.GetEmptyValue: string;
+begin
+  Result := FLookup.EmptyValue;
+end;
+
 procedure TDBLookupListBox.DataChange(Sender: TObject);
 begin
   if FDatalink.Active then
@@ -134,6 +146,18 @@ begin
   Result := FLookup.NullValueKey;
 end;
 
+procedure TDBLookupListBox.SetDisplayEmpty(AValue: String);
+begin
+  FLookup.DisplayEmpty := AValue;
+  UpdateLookup;
+end;
+
+procedure TDBLookupListBox.SetEmptyValue(AValue: String);
+begin
+  FLookup.EmptyValue := AValue;
+  UpdateLookup;
+end;
+
 function TDBLookupListBox.GetScrollListDataset: Boolean;
 begin
   Result := FLookup.ScrollListDataset;