[tqweb] add canvas update demo

With extra check box one can enable regular fill and update histogram

Author: linev

tutorials/visualisation/webgui/qtweb/ExampleWidget.cpp

@@ -39,6 +39,7 @@ ExampleWidget::ExampleWidget(QWidget *parent, const char *name) : QWidget(parent
    QObject::connect(GeoCanvasBtn, &QPushButton::clicked, this, &ExampleWidget::GeoCanvasButton_clicked);
    QObject::connect(StandaloneBtn, &QPushButton::clicked, this, &ExampleWidget::StandaloneBtn_clicked);
    QObject::connect(ExitBtn, &QPushButton::clicked, this, &ExampleWidget::ExitButton_clicked);
+   QObject::connect(fxUpdateChk, &QCheckBox::toggled, this, &ExampleWidget::UpdateChk_toggled);
 
    setAttribute(Qt::WA_DeleteOnClose);
 
@@ -51,7 +52,7 @@ ExampleWidget::ExampleWidget(QWidget *parent, const char *name) : QWidget(parent
    fHisto->SetDirectory(nullptr);
 
    gPad = fxTCanvasWidget->getCanvas();
-   fHisto->Draw();
+   fHisto->Draw("hist");
 
    static constexpr int nth2points = 40;
    fHisto2 = std::make_shared<TH2I>("gaus2", "Example of TH2 drawing in RCanvas", nth2points, -5, 5, nth2points, -5, 5);
@@ -71,6 +72,23 @@ ExampleWidget::ExampleWidget(QWidget *parent, const char *name) : QWidget(parent
 
 ExampleWidget::~ExampleWidget() {}
 
+void ExampleWidget::UpdateChk_toggled(bool on)
+{
+   if (on) {
+      // enable modify of canvas every 100 ms
+      QObject::connect(&fTimer, &QTimer::timeout, [&]() {
+         fHisto->FillRandom("gaus", 1000);
+         fxTCanvasWidget->getCanvas()->Modified();
+         fxTCanvasWidget->getCanvas()->Update();
+      });
+      fTimer.setSingleShot(false);
+      fTimer.start(100);
+   } else {
+      fTimer.stop();
+   }
+}
+
+
 void ExampleWidget::CreateDummyGeometry()
 {
    auto viewer = fxGeomViewerWidget->getGeomViewer();

tutorials/visualisation/webgui/qtweb/ExampleWidget.h

@@ -12,6 +12,7 @@
 #define ExampleWidget_h
 
 #include <QWidget>
+#include <QTimer>
 #include "ui_ExampleWidget.h"
 
 #include <memory>
@@ -25,6 +26,7 @@ class ExampleWidget : public QWidget, public Ui::ExampleWidget {
 protected:
    TH1F *fHisto{nullptr};         ///< histogram for display in TCanvas
    std::shared_ptr<TH2I> fHisto2; ///< histogram for display in RCanvas
+   QTimer fTimer;
 
    void ImportCmsGeometry();
 
@@ -44,6 +46,7 @@ public slots:
    void GeoCanvasButton_clicked();
    void StandaloneBtn_clicked();
    void ExitButton_clicked();
+   void UpdateChk_toggled(bool);
 };
 
 #endif

tutorials/visualisation/webgui/qtweb/ExampleWidget.ui

@@ -142,6 +142,13 @@
                 <number>2</number>
               </property>
               <item row="0" column="0" >
+                <widget class="QCheckBox" name="fxUpdateChk" >
+                  <property name="text" >
+                    <string>update canvas</string>
+                  </property>
+                </widget>
+              </item>
+              <item row="1" column="0" >
                 <widget class="TCanvasWidget" name="fxTCanvasWidget" >
                   <property name="sizePolicy" >
                     <sizepolicy>