+function TDragManagerDefault.IsCanBeStartDragging(Site: TWinControl;
AThreshold: Integer; X,Y:Integer): boolean;
+var
+  Threshold:integer;
+  aRect:TRect;
+begin
+  if AThreshold<=0 then
+    Threshold:=DragThreshold
+  else
+    Threshold:=AThreshold;
+  aRect := Site.ClientRect;
+  InflateRect(aRect, Threshold, Threshold);
+  if not PtInRect(aRect, Point(X, Y)) then
+    Result:=true
+  else
+    Result:=false;
+end;

1) name IsCanNNN, and even worse IsCanBeNNN. Pls rename to CanStartDragging

2) end of func: replace to Result:= not PtInRect(..);

Alexey wrote

1) name IsCanNNN, and even worse IsCanBeNNN. Pls rename to CanStartDragging 2) end of func: replace to Result:= not PtInRect(..);

Done (r55428).