Merge #805: Avoid hidden network traffic graph updates

35fecc9 qml: avoid shadowing LineGraph fillColor (johnny9)
5f00942 qml: avoid hidden network traffic updates (johnny9)

Pull request description:

  ## What changed

  - move network traffic sampling, smoothing, and history retention onto an owned worker thread
  - publish immutable traffic snapshots back to the GUI thread only while the Network Traffic page is active
  - retain raw samples while hidden and rebuild the requested range when the page becomes active again
  - lazy-load the Network Traffic settings page so its graphs do not exist while another settings section is selected
  - preserve byte totals as 64-bit values
  - rename the native graph gradient property so it no longer shadows `QQuickPaintedItem::fillColor`
  - add C++ and QML coverage for thread affinity, hidden-page suppression, retained history, range changes, page lifecycle, and destruction while active

  ## Why

  The previous timer was moved to a background thread, but its timeout updated a GUI-thread model every second regardless of whether the Network Traffic page was visible. That kept smoothing, full-history copies, signal delivery, and graph bindings active in the background. Timer/thread ownership was also not explicit during shutdown.

  This keeps the inexpensive raw sample collection running off-thread while avoiding hidden GUI work and making worker shutdown deterministic.

  `LineGraph` also declared its own `fillColor` property over the property inherited from `QQuickPaintedItem`, producing a QML property-cache warning. The native property is now named `gradientColor`; the public `NetworkTrafficGraph.fillColor` API and rendering behavior are unchanged.

  ## User impact

  Opening Network Traffic still shows the samples collected while the page was hidden, and changing the graph range rebuilds the visible history without losing totals. Other settings pages no longer pay for traffic graph updates or retain the graph objects.

  ## Issue

  Fixes #611.

  Fixes #801.

  Graph reset behavior was split from #611 into #806 and is intentionally not included here.

  ## Validation

  - full RelWithDebInfo build with app tests enabled
  - `qmllint -I qml -I test/mocks/qml qml/components/NetworkTrafficGraph.qml qml/pages/node/NetworkTraffic.qml qml/pages/node/NodeSettings.qml test/qml/tst_nodesettings.qml`
  - `bitcoinqml_qmltests`: 380 passed, 0 failed
  - `NetworkTrafficTowerTests`: 6 passed, 0 failed
  - `git diff --check origin/qt6...HEAD`

  The aggregate unit executable was also run locally. Its Network Traffic suite passed; unrelated existing OptionsModel tests could not write the default Bitcoin data directory inside the managed filesystem sandbox.

ACKs for top commit:
  jarolrod:
    ACK 35fecc9

Tree-SHA512: 765de9435d4b73942bd4f85bfdfe082b1ad360c950c853fd6aa14c6d8bc6f011f2ffad3d0b7cb361dd40d701a63bfe9a4ca47bd4cf107017cc6f7b9741b730de

Author: hebasto

qml/bitcoin.cpp

@@ -592,7 +592,7 @@ int QmlGuiMain(int argc, char* argv[])
     }, Qt::QueuedConnection);
     QObject::connect(&init_executor, &QmlInitExecutor::runawayException, &node_model, &NodeModel::handleRunawayException);
 
-    NetworkTrafficTower network_traffic_tower{node_model};
+    NetworkTrafficTower network_traffic_tower{*node};
     NetworkStatusModel network_status_model;
 #ifdef __ANDROID__
     AndroidNotifier android_notifier{node_model};

qml/components/NetworkTrafficGraph.qml

@@ -14,7 +14,7 @@ Item {
     id: root
     property alias backgroundColor: trafficGraph.backgroundColor
     property alias borderColor: trafficGraph.borderColor
-    property alias fillColor: trafficGraph.fillColor
+    property alias fillColor: trafficGraph.gradientColor
     property alias lineColor: trafficGraph.lineColor
     property alias markerLineColor: trafficGraph.markerLineColor
     property alias maxSamples: trafficGraph.maxSamples
@@ -31,7 +31,7 @@ Item {
         width: root.width
         backgroundColor: root.backgroundColor
         borderColor: root.borderColor
-        fillColor: root.fillColor
+        gradientColor: root.fillColor
         lineColor: root.lineColor
         markerLineColor: root.markerLineColor
         maxSamples: root.maxSamples
@@ -46,7 +46,7 @@ Item {
             ColorAnimation { duration: 150 }
         }
 
-        Behavior on fillColor {
+        Behavior on gradientColor {
             ColorAnimation { duration: 150 }
         }
 

qml/controls/linegraph.cpp

@@ -17,13 +17,13 @@
 LineGraph::LineGraph(QQuickItem *parent)
     : QQuickPaintedItem(parent)
 {
-    setFillColor(m_background_color);
+    setGradientColor(m_background_color);
 }
 
 void LineGraph::setBackgroundColor(QColor color)
 {
     m_background_color = color;
-    setFillColor(color);
+    setGradientColor(color);
 }
 
 void LineGraph::setBorderColor(QColor color)
@@ -32,9 +32,9 @@ void LineGraph::setBorderColor(QColor color)
     update();
 }
 
-void LineGraph::setFillColor(QColor color)
+void LineGraph::setGradientColor(QColor color)
 {
-    m_fill_color = color;
+    m_gradient_color = color;
     update();
 }
 
@@ -135,7 +135,7 @@ void LineGraph::paintTraffic(QPainter * painter)
 void LineGraph::setupGradient(QPainterPath * painter_path)
 {
     QLinearGradient gradient(painter_path->boundingRect().topLeft(), painter_path->boundingRect().bottomLeft());
-    gradient.setColorAt(0, QColor(m_fill_color.red(), m_fill_color.green(), m_fill_color.blue(), 191));
+    gradient.setColorAt(0, QColor(m_gradient_color.red(), m_gradient_color.green(), m_gradient_color.blue(), 191));
     gradient.setColorAt(1, QColor("transparent"));
     m_fill_gradient = gradient;
 }

qml/controls/linegraph.h

@@ -16,7 +16,7 @@ class LineGraph : public QQuickPaintedItem
     Q_OBJECT
     Q_PROPERTY(QColor backgroundColor READ backgroundColor WRITE setBackgroundColor)
     Q_PROPERTY(QColor borderColor READ borderColor WRITE setBorderColor)
-    Q_PROPERTY(QColor fillColor READ fillColor WRITE setFillColor)
+    Q_PROPERTY(QColor gradientColor READ gradientColor WRITE setGradientColor)
     Q_PROPERTY(QColor lineColor READ lineColor WRITE setLineColor)
     Q_PROPERTY(QColor markerLineColor READ markerLineColor WRITE setMarkerLineColor)
     Q_PROPERTY(int maxSamples READ maxSamples WRITE setMaxSamples)
@@ -29,7 +29,7 @@ class LineGraph : public QQuickPaintedItem
 
         QColor backgroundColor() const { return m_background_color; };
         QColor borderColor() const { return m_border_color; };
-        QColor fillColor() const { return m_fill_color; };
+        QColor gradientColor() const { return m_gradient_color; };
         QColor lineColor() const { return m_line_color; };
         QColor markerLineColor() const { return m_marker_line_color; };
         int maxSamples() const { return m_max_samples; };
@@ -39,7 +39,7 @@ class LineGraph : public QQuickPaintedItem
     public Q_SLOTS:
         void setBackgroundColor(QColor color);
         void setBorderColor(QColor color);
-        void setFillColor(QColor color);
+        void setGradientColor(QColor color);
         void setLineColor(QColor color);
         void setMarkerLineColor(QColor color);
         void setMaxSamples(int max_samples);
@@ -55,7 +55,7 @@ class LineGraph : public QQuickPaintedItem
 
         QColor m_background_color{"#2D2D2D"};
         QColor m_border_color{"#000000"};
-        QColor m_fill_color{"#000000"};
+        QColor m_gradient_color{"#000000"};
         QLinearGradient m_fill_gradient{0, 0, 0, 0};
         QColor m_line_color{"#000000"};
         QColor m_marker_line_color{"#000000"};