Introduce Qt6-based implementation for TCanvasImp

.github/CODEOWNERS

@@ -67,6 +67,7 @@
 /gui/webdisplay/ @linev
 /gui/cefdisplay/ @linev
 /gui/qt6webdisplay/ @linev
+/gui/qt6canvas/ @linev
 /gui/webgui6/ @linev
 /gui/fitpanelv7/ @linev
 /gui/browsable/ @bellenot @linev

.github/workflows/root-ci-config/buildconfig/global.txt

@@ -64,6 +64,7 @@ opengl=ON
 pyroot=ON
 pythia8=OFF
 qt6web=OFF
+qt6canv=OFF
 roofit=ON
 roofit_multiprocess=OFF
 root7=ON

cmake/modules/RootBuildOptions.cmake

@@ -149,6 +149,7 @@ ROOT_BUILD_OPTION(mpi OFF "Enable support for Message Passing Interface (MPI)")
 ROOT_BUILD_OPTION(opengl ON "Enable support for OpenGL (requires libGL and libGLU)")
 ROOT_BUILD_OPTION(pyroot ON "Enable support for automatic Python bindings (PyROOT)")
 ROOT_BUILD_OPTION(pythia8 OFF "Enable support for Pythia 8.x [GPL]")
+ROOT_BUILD_OPTION(qt6canv OFF "Enable Qt6 canvas (requires Qt6::Gui)")
 ROOT_BUILD_OPTION(qt6web OFF "Enable support for Qt6 web-based display (requires Qt6::WebEngineCore and Qt6::WebEngineWidgets)")
 ROOT_BUILD_OPTION(roofit ON "Build the advanced fitting package RooFit, and RooStats for statistical tests. If xml is available, also build HistFactory.")
 ROOT_BUILD_OPTION(roofit_multiprocess OFF "Build RooFit::MultiProcess and multi-process RooFit::TestStatistics classes (requires ZeroMQ >= 4.3.5 built with -DENABLE_DRAFTS and cppzmq).")
@@ -224,6 +225,7 @@ if(all)
  set(opengl_defvalue ON)
  set(pythia8_defvalue ON)
  set(pyroot_defvalue ON)
+ set(qt6canv_defvalue ON)
  set(qt6web_defvalue ON)
  set(r_defvalue ON)
  set(roofit_defvalue ON)

etc/plugins/TCanvasImp/P020_TQt6Canvas.C

@@ -0,0 +1,5 @@
+void P020_TQt6Canvas()
+{
+   gPluginMgr->AddHandler("TCanvasImp", "TQt6Canvas", "ROOT::Experimental::TQt6Canvas",
+      "ROOTQt6Canvas", "NewCanvas(TCanvas *, const char *, Int_t, Int_t, UInt_t, UInt_t)");
+}

etc/plugins/TGuiFactory/P020_TQt6GuiFactory.C

@@ -0,0 +1,5 @@
+void P020_TQt6GuiFactory()
+{
+   gPluginMgr->AddHandler("TGuiFactory", "qt6", "ROOT::Experimental::TQt6GuiFactory",
+      "ROOTQt6Canvas", "TQt6GuiFactory()");
+}

gui/CMakeLists.txt

@@ -12,6 +12,10 @@ add_subdirectory(guihtml)
 add_subdirectory(recorder)
 add_subdirectory(treemap)
 
+if(qt6canv)
+  add_subdirectory(qt6canvas)
+endif()
+
 if(webgui)
    if(cefweb)
       add_subdirectory(cefdisplay)

gui/qt6canvas/CMakeLists.txt

@@ -0,0 +1,52 @@
+# Copyright (C) 1995-2026, Rene Brun and Fons Rademakers.
+# All rights reserved.
+#
+# For the licensing terms see $ROOTSYS/LICENSE.
+# For the list of contributors see $ROOTSYS/README/CREDITS.
+
+############################################################################
+# CMakeLists.txt file for building ROOT gui/qt6canvas package
+############################################################################
+
+find_package(Qt6 COMPONENTS Core Widgets CONFIG)
+
+if(NOT Qt6_FOUND)
+  if(fail-on-missing)
+    message(FATAL_ERROR "Could NOT find Qt6 with Gui components")
+  else()
+    message(WARNING "Qt6 (Gui) not found, disabling option 'qt6canvas'")
+    set(qt6canv OFF CACHE BOOL "Disabled because Qt6 Gui not found" FORCE)
+    return()
+  endif()
+endif()
+
+
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_AUTORCC ON)
+set(CMAKE_AUTOUIC ON)
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+ROOT_STANDARD_LIBRARY_PACKAGE(ROOTQt6Canvas
+  HEADERS
+    TQt6Application.h
+    TQt6Canvas.h
+    TQt6PadPainter.h
+    TQt6GuiFactory.h
+  SOURCES
+    src/QCanvasWidget.cpp
+    src/QPaintWidget.cpp
+    src/QRootMethodDialog.cpp
+    src/QRootContextMenu.cpp
+    src/TQt6Application.cxx
+    src/TQt6Canvas.cxx
+    src/TQt6PadPainter.cxx
+    src/TQt6GuiFactory.cxx
+  LIBRARIES
+    Qt6::Core
+    Qt6::Widgets
+  DEPENDENCIES
+    Core
+    Gpad
+)
+
+target_include_directories(ROOTQt6Canvas PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src)

gui/qt6canvas/inc/LinkDef.h

@@ -0,0 +1,22 @@
+// Author: Sergey Linev, GSI   26/06/2026
+
+/*************************************************************************
+ * Copyright (C) 1995-2026, Rene Brun and Fons Rademakers.               *
+ * All rights reserved.                                                  *
+ *                                                                       *
+ * For the licensing terms see $ROOTSYS/LICENSE.                         *
+ * For the list of contributors see $ROOTSYS/README/CREDITS.             *
+ *************************************************************************/
+
+#ifdef __CLING__
+
+#pragma link off all globals;
+#pragma link off all classes;
+#pragma link off all functions;
+
+#pragma link C++ class ROOT::Experimental::TQt6Canvas+;
+#pragma link C++ class ROOT::Experimental::TQt6PadPainter+;
+#pragma link C++ class ROOT::Experimental::TQt6GuiFactory+;
+#pragma link C++ class ROOT::Experimental::TQt6Application+;
+
+#endif

gui/qt6canvas/inc/TQt6Application.h

@@ -0,0 +1,45 @@
+// Author: Sergey Linev   30/07/2026
+
+/*************************************************************************
+ * Copyright (C) 1995-2026, Rene Brun and Fons Rademakers.               *
+ * All rights reserved.                                                  *
+ *                                                                       *
+ * For the licensing terms see $ROOTSYS/LICENSE.                         *
+ * For the list of contributors see $ROOTSYS/README/CREDITS.             *
+ *************************************************************************/
+
+
+#ifndef ROOT_TQt6Application
+#define ROOT_TQt6Application
+
+
+#include "TApplicationImp.h"
+
+namespace ROOT {
+namespace Experimental {
+
+class TQt6Application : public TApplicationImp {
+public:
+   TQt6Application() = delete;
+   TQt6Application(const char *appClassName, Int_t *argc, char **argv);
+   ~TQt6Application() override;
+
+   void    Show() override {}
+   void    Hide() override {}
+   void    Iconify() override {}
+   Bool_t  IsCmdThread() override { return kTRUE; }
+   void    Init() override {}
+   void    Open() override {}
+   void    Raise() override {}
+   void    Lower() override {}
+
+   static void CreateQApplication(int argc = 0, char **argv = nullptr);
+
+   ClassDefOverride(TQt6Application,0)  // ROOT Qt6 GUI application environment
+};
+
+} // namespace Experimental
+} // namespace ROOT
+
+
+#endif

gui/qt6canvas/inc/TQt6Canvas.h

@@ -0,0 +1,84 @@
+// Author: Sergey Linev, GSI   26/06/2026
+
+/*************************************************************************
+ * Copyright (C) 1995-2026, Rene Brun and Fons Rademakers.               *
+ * All rights reserved.                                                  *
+ *                                                                       *
+ * For the licensing terms see $ROOTSYS/LICENSE.                         *
+ * For the list of contributors see $ROOTSYS/README/CREDITS.             *
+ *************************************************************************/
+
+#ifndef ROOT_TQt6Canvas
+#define ROOT_TQt6Canvas
+
+#include "TCanvasImp.h"
+
+class QWidget;
+class QCanvasWidget;
+class QPaintWidget;
+
+namespace ROOT {
+namespace Experimental {
+
+
+class TQt6Canvas : public TCanvasImp {
+
+protected:
+
+   QCanvasWidget *fCanvasWidget = nullptr;
+   QPaintWidget *fPaintWidget = nullptr;
+
+   Bool_t fFixedSize = kFALSE;      ///<! true when fixed-size canvas is configured
+   UInt_t fClientBits = 0;          ///<! latest status bits from client like editor visible or not
+
+   Bool_t PerformUpdate(Bool_t async) override;
+   TVirtualPadPainter *CreatePadPainter() override;
+
+   void AssignStatusBits(UInt_t bits);
+
+
+public:
+   TQt6Canvas(TCanvas *c, const char *name, Int_t x, Int_t y, UInt_t width, UInt_t height);
+   ~TQt6Canvas() override;
+
+   QPaintWidget *GetPaintWidget() const { return fPaintWidget; }
+
+   Int_t InitWindow() override;
+   void Close() override;
+   void Show() override;
+
+   UInt_t GetWindowGeometry(Int_t &x, Int_t &y, UInt_t &w, UInt_t &h) override;
+   void GetCanvasGeometry(Int_t wid, UInt_t &w, UInt_t &h) override;
+   void ResizeCanvasWindow(Int_t) override {}
+   void UpdateDisplay(Int_t = 0, Bool_t = kFALSE) override {}
+
+   void ShowMenuBar(Bool_t = kTRUE) override { }
+   void ShowStatusBar(Bool_t = kTRUE) override { }
+   void ShowEditor(Bool_t = kTRUE) override {  }
+   void ShowToolBar(Bool_t = kTRUE) override { }
+   void ShowToolTips(Bool_t  = kTRUE) override { }
+
+   void ForceUpdate() override;
+
+   void SetWindowPosition(Int_t x, Int_t y) override;
+   void SetWindowSize(UInt_t w, UInt_t h) override;
+   void SetWindowTitle(const char *newTitle) override;
+   void SetCanvasSize(UInt_t w, UInt_t h) override;
+   void Iconify() override;
+   void RaiseWindow() override;
+
+   Bool_t HasEditor() const override;
+   Bool_t HasMenuBar() const override;
+   Bool_t HasStatusBar() const override;
+   Bool_t HasToolBar() const override { return kFALSE; }
+   Bool_t HasToolTips() const override;
+
+   static TCanvasImp *NewCanvas(TCanvas *c, const char *name, Int_t x, Int_t y, UInt_t width, UInt_t height);
+
+   ClassDefOverride(TQt6Canvas, 0) // Qt6 implementation for TCanvasImp
+};
+
+} // namespace Experimental
+} // namespace ROOT
+
+#endif

gui/qt6canvas/inc/TQt6GuiFactory.h

@@ -0,0 +1,43 @@
+// Author: Sergey Linev   2/07/2026
+
+/*************************************************************************
+ * Copyright (C) 1995-2026, Rene Brun and Fons Rademakers.               *
+ * All rights reserved.                                                  *
+ *                                                                       *
+ * For the licensing terms see $ROOTSYS/LICENSE.                         *
+ * For the list of contributors see $ROOTSYS/README/CREDITS.             *
+ *************************************************************************/
+
+
+#ifndef ROOT_TQt6GuiFactory
+#define ROOT_TQt6GuiFactory
+
+
+#include "TGuiFactory.h"
+
+namespace ROOT {
+namespace Experimental {
+
+class TQt6GuiFactory : public TGuiFactory {
+
+public:
+   TQt6GuiFactory(const char *name = "RootQt6", const char *title = "ROOT Qt6 GUI Factory");
+   ~TQt6GuiFactory() override {}
+
+   Bool_t UseVirtualX() const override { return kFALSE; }
+
+   TApplicationImp *CreateApplicationImp(const char *classname, int *argc, char **argv) override;
+
+   TCanvasImp *CreateCanvasImp(TCanvas *c, const char *title, UInt_t width, UInt_t height) override;
+   TCanvasImp *CreateCanvasImp(TCanvas *c, const char *title, Int_t x, Int_t y, UInt_t width, UInt_t height) override;
+
+   TContextMenuImp *CreateContextMenuImp(TContextMenu *c, const char *name, const char *title) override;
+
+   ClassDefOverride(TQt6GuiFactory,0)  //Factory for Qt6 GUI components
+};
+
+} //  namespace Experimental
+} // namespace ROOT
+
+
+#endif