diff --git a/lcl/include/customsplitter.inc b/lcl/include/customsplitter.inc
index 7dbbbbafa4..9e027f74ff 100644
--- a/lcl/include/customsplitter.inc
+++ b/lcl/include/customsplitter.inc
@@ -20,7 +20,6 @@
   ToDo:
     - Fix changing Mouse cursor
     - Fix gtk look
-    - AutoSnap
     - ResizeStyle
     
 }
@@ -56,9 +55,9 @@ procedure TCustomSplitter.StartSplitterMove(Restart: boolean;
   const MouseXY: TPoint);
 begin
   if (not Restart) and FSplitDragging then exit;
-  FSplitDragging:=true;
+  FSplitDragging := True;
   fSplitterStartMouseXY:=MouseXY;
-  fSplitterStartLeftTop:=Point(Left,Top);
+  fSplitterStartLeftTop:= Point(Left,Top);
 end;
 
 procedure TCustomSplitter.MouseDown(Button: TMouseButton; Shift: TShiftState; X,
@@ -69,76 +68,303 @@ begin
   inherited MouseDown(Button, Shift, X, Y);
   // While resizing X, Y are not valid. Use absolute mouse position.
   GetCursorPos(MousePos);
-  StartSplitterMove(true,MousePos);
+  StartSplitterMove(True,MousePos);
+end;
+
+function FindOppositeControl(Control: TControl): TControl;
+var
+  i,count: Integer;
+  CurControl: TControl;
+  fRect: TRect;
+  fPoint: TPoint;
+  alignList: TAlignSet;
+begin
+  Result := nil;
+  count := Control.Parent.ControlCount;
+  if count > 0 then begin
+    fRect := Control.BoundsRect;
+    case Control.Align of
+      alTop: begin
+          fPoint := fRect.BottomRight;
+          fPoint.y := fPoint.y+1;
+          Dec(fPoint.x);
+          alignList := [alTop,alRight,alClient];
+        end;
+      alBottom: begin
+          fPoint := fRect.TopLeft;
+          Dec(fPoint.y);
+          alignList := [alLeft,alBottom,alClient];
+        end;
+      alLeft: begin
+          fPoint := fRect.BottomRight;
+          Inc(fPoint.x);
+          Dec(fPoint.y);
+          alignList := [alLeft,alClient];
+        end;
+      alRight: begin
+          fPoint := fRect.TopLeft;
+          Dec(fPoint.x);
+          alignList := [alRight,alClient];
+        end;
+    end;  // case
+    Dec(count);
+    for i := 0 to count do begin
+      CurControl := Control.Parent.Controls[i];
+      if (CurControl <> Control)
+         and CurControl.Visible
+         and (CurControl.Align in alignList)
+         and (PtInRect(CurControl.BoundsRect, fPoint))
+      then Result := CurControl;
+      if Assigned(Result) then Break;
+    end;  // for i
+  end;
+end;
+
+function FindVirtualOppositeControl(Control: TControl): TControl;
+  function CompPos(CurControl, Control: TControl): Boolean;
+  begin
+    Result := False;
+    case Control.Align of
+      alTop:
+        if (CurControl.Align = Control.Align)
+           and (CurControl.Top >= Control.BoundsRect.Bottom)
+        then Result := True;
+      alBottom:
+        if (CurControl.Align = Control.Align)
+           and (CurControl.BoundsRect.Bottom <= Control.Top)
+        then Result := True;
+      alLeft:
+        if (CurControl.Align = Control.Align)
+           and (CurControl.Left >= Control.BoundsRect.Right)
+        then Result := True;
+      alRight:
+        if (CurControl.Align = Control.Align)
+           and (CurControl.BoundsRect.Right <= Control.Left)
+        then Result := True;
+    end;
+  end;
+  function OppositeControl(CurControl,Control: TControl): Boolean;
+  begin
+    Result := False;
+    case Control.Align of
+      alLeft: if (CurControl.Align = alRight) then Result := True;
+      alRight: if (CurControl.Align = alLeft) then Result := True;
+      alTop: if (CurControl.Align = alBottom) then Result := True;
+      alBottom: if (CurControl.Align = alTop) then Result := True;
+    end;
+  end;
+var
+  i,count: Integer;
+  CurControl: TControl;
+begin
+  Result := nil;
+  count := Control.Parent.ControlCount;
+  if count > 0 then begin
+    Dec(count);
+    for i := 0 to count do begin
+      CurControl := Control.Parent.Controls[i];
+      if (CurControl <> Control) then begin
+        if ((Result = nil) and OppositeControl(CurControl, Control))
+           or (Assigned(Result) and CompPos(CurControl, Result))
+        then Result := CurControl;
+      end;
+    end;  // for i
+  end;
 end;
 
 procedure TCustomSplitter.MouseMove(Shift: TShiftState; X, Y: Integer);
+var
+  AlignControl, LastControl, VirtualOppositeControl, ClientControl: TControl;
+
+  function GetParentClientSize: Integer;
+  begin
+    case Self.Align of
+      alLeft, alRight: Result := Parent.ClientWidth;
+      alTop, alBottom: Result := Parent.ClientHeight;
+    end;
+  end;
+  function GetControlMinPos(Control: TControl): Integer;
+  begin
+    if Assigned(Control)
+    then case Self.Align of
+           alLeft,alRight: Result := Control.Left;
+           alTop,alBottom: Result := Control.Top;
+         end
+    else case Self.Align of
+           alLeft,alTop: Result := 0;
+           alRight,alBottom: Result := GetParentClientSize;
+         end;
+  end;
+  function GetControlSize(Control: TControl): Integer;
+  begin
+    Result := 0;
+    if Assigned(Control)
+    then case Self.Align of
+      alLeft, alRight: Result := Control.Width;
+      alTop, alBottom: Result := Control.Height;
+    end;
+  end;
+  function GetControlConstraintsMinSize(Control: TControl): Integer;
+  begin
+    case Self.Align of
+      alLeft, alRight: Result := Control.Constraints.MinWidth;
+      alTop, alBottom: Result := Control.Constraints.MinHeight;
+    end;
+  end;
+  procedure SetAlignControlSize(NewSize: Integer);
+  begin
+    case Self.Align of
+      alLeft:
+        AlignControl.Width := NewSize;
+      alRight:
+        begin
+          Parent.DisableAlign;
+          AlignControl.Left := AlignControl.Left + (AlignControl.Width - NewSize);
+          AlignControl.Width := NewSize;
+          Parent.EnableAlign;
+        end;
+      alTop:
+        AlignControl.Height := NewSize;
+      alBottom:
+        begin
+          Parent.DisableAlign;
+          AlignControl.Top := AlignControl.Top + (AlignControl.Height - NewSize);
+          AlignControl.Height := NewSize;
+          Parent.EnableAlign;
+        end;
+    end;
+  end;
+  function CalcNewSize(StartSize, EndSize, Offset: Integer): Integer;
+  var
+    NewSize: Integer;
+  begin
+    NewSize := GetControlSize(AlignControl);
+    case Self.Align of
+      alLeft, alTop:     Inc(NewSize, Offset);
+      alRight, alBottom: Dec(NewSize, Offset);
+    end;
+
+    if NewSize > EndSize then NewSize := EndSize;
+    if NewSize < StartSize then NewSize := StartSize;
+
+    if fAutoSnap and (NewSize < fMinSize)
+    then NewSize := StartSize;
+    Result := NewSize;
+  end;
+  function GetVirtualControlMinPos(Control: TControl): Integer;
+  begin
+    case Self.Align of
+      alLeft: Result := Control.Left;
+      alRight: Result := Control.BoundsRect.Right;
+      alTop: Result := Control.Top;
+      alBottom: Result := Control.BoundsRect.Bottom;
+    end;
+  end;
+  function CalcOffset(X,Y: Integer): Integer;
+  begin
+    case Self.Align of
+      alLeft, alRight:
+         Result := (X-fSplitterStartMouseXY.X)
+                 - (Self.Left-fSplitterStartLeftTop.X);
+      alTop, alBottom:
+         Result := (Y-fSplitterStartMouseXY.Y)
+                 - (Self.Top-fSplitterStartLeftTop.Y);
+    end;
+  end;
+  function FindClientControl: TControl;
+  var
+    CurControl: TControl;
+    count: Integer;
+  begin
+    Result := nil;
+    for count := Parent.ControlCount-1 downto 0 do begin
+      CurControl := Parent.Controls[count];
+      if (CurControl <> Self)
+         and ((CurControl.Align = alClient)
+               or ((Self.Align in [alTop,alBottom])
+                    and (CurControl.Align in [alLeft,alRight]))) then begin
+        Result := CurControl;
+        Break;
+      end;
+    end;  // for count
+  end;  // function FindClientControl
+  function FindLastControl(Control: TControl): TControl;
+  var
+    CurControl: TControl;
+  begin
+    CurControl := Control;
+    while Assigned(CurControl) do begin
+      Control := CurControl;
+      CurControl := FindOppositeControl(Control);
+    end;
+    Result := Control;
+  end;  // function FindLastControl
 var
   Offset: Integer;
-  MinLeft: Integer;
-  MaxLeft: Integer;
-  NewLeft: Integer;
-  AlignControl: TControl;
-  MinTop: Integer;
-  MaxTop: Integer;
-  NewTop: Integer;
+  StartSize: Integer;
+  EndSize: Integer;
+  NewSize: Integer;
   MousePos: TPoint;
 begin
   inherited MouseMove(Shift, X, Y);
-  if (ssLeft in Shift) and (Parent<>nil) then begin
+  if not (Self.Align in [alLeft, alRight, alTop, alBottom]) then Exit;
+  if (ssLeft in Shift) and (Parent <> nil) then begin
+    AlignControl := FindAlignControl;
+    if not Assigned(AlignControl) then Exit;
+    
     // While resizing X, Y are not valid. Use absolute mouse position.
     GetCursorPos(MousePos);
-    StartSplitterMove(false,MousePos);
-    if Align in [alLeft,alRight] then begin
-      Offset:=(MousePos.X-fSplitterStartMouseXY.X)
-             -(Left-fSplitterStartLeftTop.X);
-      if Offset=0 then exit;
-      MinLeft:=0;
-      MaxLeft:=Parent.ClientWidth-Width;
-      AlignControl:=FindAlignControl;
-      if AlignControl<>nil then
-        if Align=alLeft then
-          MinLeft:=AlignControl.Left+MinSize
-        else
-          MaxLeft:=Parent.ClientWidth-Width-MinSize;
-      NewLeft:=Left+Offset;
-      if NewLeft>MaxLeft then NewLeft:=MaxLeft;
-      if NewLeft<MinLeft then NewLeft:=MinLeft;
-      AlignControl:=FindAlignControl;
-      if not CheckNewSize(NewLeft) then exit;
-      if AlignControl<>nil then begin
-        if Align=alLeft then
-          AlignControl.Width:=NewLeft-AlignControl.Left
-        else
-          AlignControl.Left:=NewLeft+Width;
-      end else
-        Left:=NewLeft;
-    end
-    else if Align in [alTop, alBottom] then begin
-      Offset:=(MousePos.Y-fSplitterStartMouseXY.Y)
-             -(Top-fSplitterStartLeftTop.Y);
-      if Offset=0 then exit;
-      MinTop:=0;
-      MaxTop:=Parent.ClientHeight-Height;
-      AlignControl:=FindAlignControl;
-      if AlignControl<>nil then
-        if Align=alTop then
-          MinTop:=AlignControl.Top+MinSize
-        else
-          MaxTop:=Parent.ClientHeight-Height-MinSize;
-      NewTop:=Top+Offset;
-      if NewTop>MaxTop then NewTop:=MaxTop;
-      if NewTop<MinTop then NewTop:=MinTop;
-      AlignControl:=FindAlignControl;
-      if not CheckNewSize(NewLeft) then exit;
-      if AlignControl<>nil then begin
-        if Align=alTop then
-          AlignControl.Height:=NewTop-AlignControl.Top
-        else
-          AlignControl.Top:=NewTop+Height;
-      end else
-        Top:=NewTop;
+    StartSplitterMove(False,MousePos);
+
+    Offset := CalcOffset(MousePos.X, MousePos.Y);
+    if Offset = 0 then Exit;
+      
+    ClientControl := FindClientControl;
+    
+    StartSize := 1;
+    if not fAutoSnap
+    then Inc(StartSize, Max(fMinSize, GetControlConstraintsMinSize(AlignControl)));
+    if StartSize > 1 then Dec(StartSize);
+
+    if Assigned(ClientControl)
+    then EndSize := GetControlSize(AlignControl)
+                  + GetControlSize(ClientControl)
+                  - fMinSize
+    else begin
+      VirtualOppositeControl := FindVirtualOppositeControl(Self);
+      LastControl := FindLastControl(Self);
+      case Self.Align of
+        alLeft, alTop: begin
+            if Assigned(VirtualOppositeControl) then
+              begin
+                EndSize := GetControlSize(AlignControl)
+                         + (GetControlMinPos(VirtualOppositeControl)
+                           - (GetControlMinPos(LastControl)
+                              + GetControlSize(LastControl)));
+              end
+            else EndSize := GetControlSize(AlignControl)
+                          + (GetParentClientSize
+                             - GetControlMinPos(LastControl)
+                             - GetControlSize(LastControl))
+          end;
+
+        alRight, alBottom: begin
+            if Assigned(VirtualOppositeControl) then
+                EndSize := GetControlSize(AlignControl)
+                         + (GetControlMinPos(LastControl)
+                            - (GetControlMinPos(VirtualOppositeControl)
+                               + GetControlSize(VirtualOppositeControl)))
+            else EndSize := GetControlSize(AlignControl)
+                          + GetControlMinPos(LastControl);
+          end;
+      end;  // case Self.Align
     end;
+
+    NewSize := CalcNewSize(StartSize, EndSize, Offset);
+
+    // OnCanResize event
+    if CheckNewSize(NewSize)
+    then SetAlignControlSize(NewSize);
   end;
 end;
 
@@ -146,9 +372,10 @@ procedure TCustomSplitter.MouseUp(Button: TMouseButton; Shift: TShiftState; X,
   Y: Integer);
 begin
   inherited MouseUp(Button, Shift, X, Y);
+  if not (Self.Align in [alLeft,alTop,alRight,alBottom]) then Exit;
   if FSplitDragging then begin
     if Assigned(OnMoved) then OnMoved(Self);
-    FSplitDragging:=false;
+    FSplitDragging := False;
   end;
 end;
 
@@ -157,26 +384,33 @@ var
   i: Integer;
   CurControl: TControl;
 begin
-  Result:=nil;
-  if (Parent=nil) then exit;
-  for i:=Parent.ControlCount-1 downto 0 do begin
-    CurControl:=Parent.Controls[i];
-    if (CurControl.Align in ([alClient,Align]))
-    and (CurControl.Visible)
-    and (((Align=alLeft) and (CurControl.Left<Left))
-      or ((Align=alTop) and (CurControl.Top<Top))
-      or ((Align=alRight) and (CurControl.Left>Left))
-      or ((Align=alBottom) and (CurControl.Top>Top)))
+  Result := nil;
+  if (Parent = nil) then Exit;
+  for i := Parent.ControlCount-1 downto 0 do begin
+    CurControl := Parent.Controls[i];
+    if (CurControl <> Self)
+       and (CurControl.Visible)
+       and (CurControl.Align = Self.Align)
     then begin
-      // candidate found
-      if (Result=nil)
-      or (((Align=alLeft) and (CurControl.Left>Result.Left))
-       or ((Align=alTop) and (CurControl.Top>Result.Top))
-       or ((Align=alRight) and (CurControl.Left<Result.Left))
-       or ((Align=alBottom) and (CurControl.Top<Result.Top)))
-      then
-        // better candidate found
-        Result:=CurControl;
+      case Self.Align of
+        alLeft:
+          if (CurControl.Height = Self.Height)
+             and (CurControl.Left+CurControl.Width = Self.Left)
+          then Result := CurControl;
+        alTop:
+          if (CurControl.Width = Self.Width)
+             and (CurControl.Top+CurControl.Height = Self.Top)
+          then Result := CurControl;
+        alRight:
+          if (CurControl.Height = Self.Height)
+             and (CurControl.Left-Self.Width = Self.Left)
+          then Result := CurControl;
+        alBottom:
+          if (CurControl.Width = Self.Width)
+             and (CurControl.Top-Self.Height = Self.Top)
+          then Result := CurControl;
+      end;  // case Self.Align
+      if Assigned(Result) then Break;
     end;
   end;
 end;
@@ -187,18 +421,18 @@ var
   OldWidth: Integer;
   OldHeight: Integer;
 begin
-  if (Align=Value) or (not (Value in [alLeft,alTop,alRight,alBottom])) then
-    exit;
-  OldWidth:=Width;
-  OldHeight:=Height;
-  OldAlign:=Align;
+  if (Self.Align = Value)
+     or (not (Value in [alLeft,alTop,alRight,alBottom]))
+  then Exit;
+  OldWidth := Self.Width;
+  OldHeight := Self.Height;
+  OldAlign := Self.Align;
   inherited SetAlign(Value);
+  if Self.Align in [alLeft,alRight]
+  then Self.Cursor := crHSplit
+  else Self.Cursor := crVSplit;
   CheckAlignment;
-  if Align in [alLeft,alRight] then begin
-    Cursor:=crHSplit;
-  end else begin
-    Cursor:=crVSplit;
-  end;
+
   if (OldAlign in [alLeft,alRight])=(Align in [alLeft,alRight]) then begin
     // keep width and height
     SetBounds(Left,Top,OldWidth,OldHeight);
@@ -210,7 +444,7 @@ end;
 
 procedure TCustomSplitter.SetAnchors(const AValue: TAnchors);
 begin
-  if AValue=Anchors then exit;
+  if AValue = Anchors then exit;
   inherited SetAnchors(AValue);
   CheckAlignment;
 end;
@@ -218,16 +452,16 @@ end;
 procedure TCustomSplitter.CheckAlignment;
 begin
   case Align of
-  alLeft:   Anchors:=Anchors-[akRight]+[akLeft];
-  alTop:    Anchors:=Anchors-[akBottom]+[akTop];
-  alRight:  Anchors:=Anchors+[akRight]-[akLeft];
-  alBottom: Anchors:=Anchors+[akBottom]-[akTop];
+    alLeft:   Anchors:=Anchors-[akRight]+[akLeft];
+    alTop:    Anchors:=Anchors-[akBottom]+[akTop];
+    alRight:  Anchors:=Anchors+[akRight]-[akLeft];
+    alBottom: Anchors:=Anchors+[akBottom]-[akTop];
   end;
 end;
 
-function TCustomSplitter.CheckNewSize(var NewSize: integer): boolean;
+function TCustomSplitter.CheckNewSize(var NewSize: Integer): Boolean;
 begin
-  Result:=true;
+  Result := True;
   if Assigned(OnCanResize) then
     OnCanResize(Self,NewSize,Result);
 end;