From fe582332c2d0b79066435ab9ef1c9e1b86364b1c Mon Sep 17 00:00:00 2001
From: mattias <nc-gaertnma@netcologne.de>
Date: Thu, 17 Dec 2015 14:23:04 +0000
Subject: [PATCH] LCL: improve the workaround to support fpc 2.6.4 TMemDataset
 in a way that other datasets are not affected. Issues #26356, #27959

git-svn-id: branches/fixes_1_6@50864 -
---
 lcl/dbctrls.pp           |  3 ++
 lcl/include/dblookup.inc | 59 ++++++++++++++++++++++++++++++++++------
 2 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/lcl/dbctrls.pp b/lcl/dbctrls.pp
index 5790b8cbcc..bfe1c62a9a 100644
--- a/lcl/dbctrls.pp
+++ b/lcl/dbctrls.pp
@@ -127,6 +127,9 @@ Type
     FLookUpFieldIsCached: Boolean;
     FLookupCache: Boolean;
     FInitializing: Boolean;
+    {$IF FPC_FULLVERSION < 30000}
+    FFetchingLookupData: Boolean;
+    {$ENDIF}
     procedure ActiveChange(Sender: TObject);
     procedure DatasetChange(Sender: TObject);
     procedure DoInitialize;
diff --git a/lcl/include/dblookup.inc b/lcl/include/dblookup.inc
index a3c7e35169..1fe43bd99a 100644
--- a/lcl/include/dblookup.inc
+++ b/lcl/include/dblookup.inc
@@ -76,10 +76,15 @@ begin
 end;
 
 procedure TDBLookupDataLink.DataEvent(Event: TDataEvent; Info: Ptrint);
+var
+  I: Integer;
+  S: TDataSetState;
 begin
   inherited DataEvent(Event, Info);
   if Event = deDataSetChange then
   begin
+    I := DataSet.RecordCount;
+    S := DataSet.State;
     if FRecordUpdated or ((FLookup.ControlItems <> nil) and (FLookup.ControlItems.Count <> DataSet.RecordCount)) then
     begin
       FRecordUpdated := False;
@@ -228,14 +233,38 @@ begin
     KeyList[i + 1] := KeyList[i];
 end;
 
+{$IF FPC_FULLVERSION < 30000}
+function IsClass(Instance: TObject; const ClassName: ShortString): Boolean;
+var
+  ClassRef: TClass;
+begin
+  Result := False;
+  ClassRef := Instance.ClassType;
+  while ClassRef <> nil do
+  begin
+    Result := ClassRef.ClassNameIs(ClassName);
+    if Result then
+      Exit;
+    ClassRef := ClassRef.ClassParent;
+  end;
+end;
+{$ENDIF}
+
 procedure TDBLookup.FetchLookupData;
 var
   KeyIndex, KeyListCount: Integer;
   ListLinkDataSet: TDataSet;
   Bookmark: TBookmark;
+  {$IF FPC_FULLVERSION < 30000}
+  DatasetSupportsBlockRead: Boolean;
+  {$ENDIF}
 begin
   if not Assigned(FControlItems) then
     Exit;
+  {$IF FPC_FULLVERSION < 30000}
+   if FFetchingLookupData then
+     Exit;
+  {$ENDIF}
   FControlItems.Clear;
   ListLinkDataSet := FListLink.DataSet;
   if not (Assigned(ListLinkDataSet) and Assigned(FListField)) then
@@ -243,11 +272,19 @@ begin
   if ListLinkDataSet.IsEmpty then
     Exit;
   Bookmark := ListLinkDataSet.GetBookmark;
-  {$ifdef EnableLookupWithBlockRead}
+  //in fpc 2.6.4, TMemDataset does not supports BlockRead. Issues 26356, 27959
+  {$IF FPC_FULLVERSION < 30000}
+  DatasetSupportsBlockRead := not IsClass(ListLinkDataSet, 'TMemDataset');
+  if DatasetSupportsBlockRead then
+    ListLinkDataSet.BlockReadSize := 1
+  else
+  begin
+    FFetchingLookupData := True;
+    ListLinkDataSet.DisableControls;
+  end;
+  {$ELSE}
   ListLinkDataSet.BlockReadSize := 1;
-  {$else}
-  ListLinkDataSet.DisableControls;
-  {$endif}
+  {$ENDIF}
   FControlItems.BeginUpdate;
   try
     //needed to handle sqldb.TSQLQuery that does not has a reliable recordcount after Open
@@ -273,11 +310,17 @@ begin
     FControlItems.EndUpdate;
     ListLinkDataSet.GotoBookmark(Bookmark);
     ListLinkDataSet.FreeBookmark(Bookmark);
-    {$ifdef EnableLookupWithBlockRead}
+    {$IF FPC_FULLVERSION < 30000}
+    if DatasetSupportsBlockRead then
+      ListLinkDataSet.BlockReadSize := 0
+    else
+    begin
+      ListLinkDataSet.EnableControls;
+      FFetchingLookupData := False;
+    end;
+    {$ELSE}
     ListLinkDataSet.BlockReadSize := 0;
-    {$else}
-    ListLinkDataSet.EnableControls;
-    {$endif}
+    {$ENDIF}
   end;
 end;