LazMapViewer: Add new TMapView method ObjsAtScreenPt to detect the GPS object under the mouse.

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@8106 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/lazmapviewer/source/mvmapviewer.pas

@@ -122,6 +122,7 @@ Type
       procedure GetMapProviders(lstProviders: TStrings);
       function GetVisibleArea: TRealArea;
       function LonLatToScreen(aPt: TRealPoint): TPoint;
+      function ObjsAtScreenPt(X, Y: Integer; ATolerance: Integer = -1): TGPSObjarray;
       procedure SaveToFile(AClass: TRasterImageClass; const AFileName: String);
       function SaveToImage(AClass: TRasterImageClass): TRasterImage;
       procedure SaveToStream(AClass: TRasterImageClass; AStream: TStream);
@@ -943,6 +944,33 @@ begin
   Engine.Jobqueue.WaitAllJobTerminated(Engine);
 end;
 
+function TMapView.ObjsAtScreenPt(X, Y: Integer; ATolerance: Integer = -1): TGPSObjarray;
+const
+  DELTA = 3;
+var
+  rArea: TRealArea;
+  gpsList: TGPSObjList;
+  i: Integer;
+begin
+  if ATolerance = -1 then
+    ATolerance := DELTA;
+
+  // Define area of +/-ATolerance pixels around the screen point
+  rArea.TopLeft := ScreenToLonLat(Point(X-ATolerance, Y-ATolerance));
+  rArea.BottomRight := ScreenToLonLat(Point(X+ATolerance, Y+ATolerance));
+
+  // Collect Objects in this are
+  gpsList := FGPSItems.GetObjectsInArea(rArea);
+  try
+    SetLength(Result, gpsList.Count);
+    for i := 0 to gpsList.Count-1 do
+      if gpsList[i] is TGPSPoint then
+        Result[i] := gpsList[i];
+  finally
+    gpsList.Free;
+  end;
+end;
+
 procedure TMapView.CenterOnObj(obj: TGPSObj);
 var
   Area: TRealArea;