LazMapViewer: Add new properties LineColor and LineWidth to TGpsTrack. Add demo showing several individually colored tracks. Add some utility functions.

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@8102 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/lazmapviewer/source/mvmapviewer.pas

@@ -166,6 +166,13 @@ uses
   GraphType, Types,
   mvJobQueue, mvExtraData, mvDLEFpc, mvDE_IntfGraphics;
 
+{ Converts a length given in millimeters to screen pixels }
+function mmToPx(AValue: Double): Integer;
+begin
+  Result := round(AValue / 25.4 * ScreenInfo.PixelsPerInchX);
+end;
+
+
 type
 
   { TDrawObjJob }
@@ -575,18 +582,27 @@ var
   trkColor: TColor;
   trkWidth: Integer;
 begin
-  if trk.Points.Count > 0 then
+  if trk.Visible and (trk.Points.Count > 0) then
   begin
-    trkColor := ColorToRGB(FDefaultTrackColor);
-    trkWidth := FDefaultTrackWidth;
-    if trk.ExtraData <> nil then
+    // Determine track color
+    if trk.LineColor = clDefault then
     begin
-      if trk.ExtraData.InheritsFrom(TDrawingExtraData) then
+      trkColor := ColorToRGB(FDefaultTrackColor);
+      if (trk.ExtraData <> nil) and trk.ExtraData.InheritsFrom(TDrawingExtraData) then
         trkColor := TDrawingExtraData(trk.ExtraData).Color;
-      if trk.ExtraData.InheritsFrom(TTrackExtraData) then
-        trkWidth := round(ScreenInfo.PixelsPerInchX * TTrackExtraData(trk.ExtraData).Width / 25.4);
-    end;
+    end else
+      trkColor := ColorToRGB(trk.LineColor);
+
+    // Determine track width
+    if trk.LineWidth = -1 then
+    begin
+      trkWidth := FDefaultTrackWidth;
+      if (trk.ExtraData <> nil) and trk.ExtraData.InheritsFrom(TTrackExtraData) then
+        trkWidth := mmToPx(TTrackExtraData(trk.ExtraData).Width);
+    end else
+      trkWidth := mmToPx(trk.LineWidth);
     if trkWidth < 1 then trkWidth := 1;
+
     LastInside := false;
     DrawingEngine.PenColor := trkColor;
     DrawingEngine.PenWidth := trkWidth;