v7canv: provide canvas title to client

graf2d/gpadv7/v7/inc/ROOT/RPadDisplayItem.hxx

@@ -15,6 +15,7 @@
 
 #ifndef ROOT7_RPadDisplayItem
 #define ROOT7_RPadDisplayItem
+
 #include <ROOT/RDisplayItem.hxx>
 #include <ROOT/RFrame.hxx>
 #include <ROOT/RPad.hxx>
@@ -33,16 +34,18 @@ public:
 
 
 protected:
-   const RFrame *fFrame{nullptr};   ///< temporary pointer on frame object
+   const RFrame *fFrame{nullptr};             ///< temporary pointer on frame object
    const RPadDrawingOpts *fDrawOpts{nullptr}; ///< temporary pointer on pad drawing options
-   const RPadExtent *fSize{nullptr};  ///< temporary pointer on pad size attributes
-   PadPrimitives_t fPrimitives; ///< display items for all primitives in the pad
+   const RPadExtent *fSize{nullptr};          ///< temporary pointer on pad size attributes
+   std::string fTitle;                        ///< title of the pad
+   PadPrimitives_t fPrimitives;               ///< display items for all primitives in the pad
 public:
    RPadDisplayItem() = default;
    virtual ~RPadDisplayItem() {}
    void SetFrame(const RFrame *f) { fFrame = f; }
    void SetDrawOpts(const RPadDrawingOpts *opts) { fDrawOpts = opts; }
    void SetSize(const RPadExtent *sz) { fSize = sz; }
+   void SetTitle(const std::string &title) { fTitle = title; }
    PadPrimitives_t &GetPrimitives() { return fPrimitives; }
    void Add(std::unique_ptr<RDisplayItem> &&item) { fPrimitives.push_back(std::move(item)); }
    void Clear()
@@ -51,6 +54,7 @@ public:
       fFrame = nullptr;
       fDrawOpts = nullptr;
       fSize = nullptr;
+      fTitle.clear();
    }
 };
 

gui/canvaspainter/v7/src/TCanvasPainter.cxx

@@ -617,6 +617,7 @@ std::string ROOT::Experimental::TCanvasPainter::CreateSnapshot(const ROOT::Exper
    PaintDrawables(can);
 
    fPadDisplayItem->SetObjectID("canvas"); // for canvas itself use special id
+   fPadDisplayItem->SetTitle(can.GetTitle());
 
    TString res = TBufferJSON::ToJSON(fPadDisplayItem.get(), 23);