Merge scene work for 5.1.2

The ambient scene grows up: the hidden-tab bug that rained +1s out of an
empty sky is fixed at both ends, the wipeout is a skid rather than a
stunt, clearing a field says WIN, and each tab gets its own amount of
scene — History runs, Receive sits, Send is money going past.

Claude-Session: https://claude.ai/code/session_01VLQ5DsgKv23osGANoFT3zF

src/ReceiveWidget.cpp

@@ -23,7 +23,7 @@ ReceiveWidget::ReceiveWidget(Wallet *wallet, QWidget *parent)
 
     // wowlet: ambient scene as a short banner under the address table. A layout
     // item, never an overlay over the table.
-    auto *scene = new SceneWidget(this, SceneWidget::Dawn);
+    auto *scene = new SceneWidget(this, SceneWidget::Dawn, SceneWidget::Sit);
     scene->setMinimumHeight(110);
     scene->setMaximumHeight(130);
     ui->verticalLayout->addWidget(scene);

src/SendWidget.cpp

@@ -29,10 +29,17 @@ SendWidget::SendWidget(Wallet *wallet, QWidget *parent)
     // wowlet: the form only needs the top of the tab — give the rest of it to
     // the ambient scene. A layout item under the form, never an overlay: the
     // send form itself stays untouched.
-    auto *scene = new SceneWidget(this, SceneWidget::Night);
+    //
+    // Centred in the space below the form rather than stacked straight under
+    // it: butted up against the Clear/Send row the scene reads as part of the
+    // form, and a band of night sky touching a button looks like a mistake.
+    auto *scene = new SceneWidget(this, SceneWidget::Night, SceneWidget::Money);
     scene->setMinimumHeight(160);
-    scene->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
-    ui->verticalLayoutOuter->addWidget(scene, 1);
+    scene->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Preferred);
+    ui->verticalLayoutOuter->addSpacing(14);   // never touches the Send row
+    ui->verticalLayoutOuter->addStretch(1);
+    ui->verticalLayoutOuter->addWidget(scene);
+    ui->verticalLayoutOuter->addStretch(1);
 
     QString amount_rx = R"(^\d{0,8}[\.,]\d{0,12}|(all)$)";
     QRegularExpression rx;

src/widgets/SceneWidget.cpp

@@ -4,18 +4,44 @@
 #include "SceneWidget.h"
 
 #include <QQmlContext>
+#include <QQuickItem>
 
 #include "utils/config.h"
 
-SceneWidget::SceneWidget(QWidget *parent, Variant variant)
+SceneWidget::SceneWidget(QWidget *parent, Variant variant, Mode mode)
     : QQuickWidget(parent)
     , m_backend(new SceneBackend(this))
 {
     m_backend->setReducedMotion(conf()->get(Config::reducedMotion).toBool());
     m_backend->setVariant(static_cast<int>(variant));
+    m_backend->setMode(mode == Sit   ? QStringLiteral("sit")
+                     : mode == Money ? QStringLiteral("money")
+                                     : QStringLiteral("run"));
     this->rootContext()->setContextProperty("sceneCtx", m_backend);
     this->setResizeMode(QQuickWidget::SizeRootObjectToView);
     this->setSource(QUrl("qrc:/qml/scene.qml"));
+    this->callScene("suspend");
+}
+
+void SceneWidget::showEvent(QShowEvent *event) {
+    QQuickWidget::showEvent(event);
+    this->callScene("restart");
+}
+
+void SceneWidget::hideEvent(QHideEvent *event) {
+    this->callScene("suspend");
+    QQuickWidget::hideEvent(event);
+}
+
+void SceneWidget::resizeEvent(QResizeEvent *event) {
+    QQuickWidget::resizeEvent(event);
+    if (this->isVisible())
+        this->callScene("restart");
+}
+
+void SceneWidget::callScene(const char *method) {
+    if (auto *root = this->rootObject())
+        QMetaObject::invokeMethod(root, method);
 }
 
 void SceneWidget::refreshReducedMotion() {

src/widgets/SceneWidget.h

@@ -5,6 +5,7 @@
 #define WOWLET_SCENEWIDGET_H
 
 #include <QObject>
+#include <QString>
 #include <QQuickWidget>
 
 // Context object exposed to scene.qml as `sceneCtx`. Carries the reduced-motion
@@ -14,18 +15,23 @@ class SceneBackend : public QObject {
 Q_OBJECT
     Q_PROPERTY(bool reducedMotion READ reducedMotion NOTIFY reducedMotionChanged)
     Q_PROPERTY(int variant READ variant NOTIFY variantChanged)
+    Q_PROPERTY(QString mode READ mode NOTIFY modeChanged)
 public:
     explicit SceneBackend(QObject *parent = nullptr) : QObject(parent) {}
     bool reducedMotion() const { return m_reducedMotion; }
     void setReducedMotion(bool r) { if (m_reducedMotion != r) { m_reducedMotion = r; emit reducedMotionChanged(); } }
     int variant() const { return m_variant; }
     void setVariant(int v) { if (m_variant != v) { m_variant = v; emit variantChanged(); } }
+    QString mode() const { return m_mode; }
+    void setMode(const QString &m) { if (m_mode != m) { m_mode = m; emit modeChanged(); } }
 signals:
     void reducedMotionChanged();
     void variantChanged();
+    void modeChanged();
 private:
     bool m_reducedMotion = false;
     int  m_variant = 0;
+    QString m_mode = QStringLiteral("run");
 };
 
 // wowlet: reusable ambient-scene surface. Hosts scene.qml and reads the
@@ -38,9 +44,32 @@ public:
     // same field. Must match the `skies` table in scene.qml.
     enum Variant { Dusk = 0, Dawn = 1, Night = 2 };
 
-    explicit SceneWidget(QWidget *parent = nullptr, Variant variant = Dusk);
+    // How much scene a surface wants. History has room for the whole run;
+    // Receive gets a doge sitting in the field; Send gets money blowing past and
+    // nothing else, so the form it sits under is not competing with a dog.
+    enum Mode { Run, Sit, Money };
+
+    explicit SceneWidget(QWidget *parent = nullptr, Variant variant = Dusk,
+                         Mode mode = Run);
     void refreshReducedMotion();
+
+protected:
+    // A scene on a hidden tab is parked rather than left running: an unshown
+    // QQuickWidget is 0px wide, and a lap run against a 0px field collects every
+    // coin at once and leaves its litter (+1s, barks) to surface on the real lap
+    // when the tab is finally shown. Parking also keeps a background tab from
+    // burning CPU on animation nobody is looking at.
+    void showEvent(QShowEvent *event) override;
+    void hideEvent(QHideEvent *event) override;
+    // Belt and braces: a scene that is on screen and has just been given a real
+    // size is running, whether or not a show event was the thing that got it
+    // there. `restart` only sets a flag, so re-arming an already-running scene
+    // costs nothing and does not interrupt its lap.
+    void resizeEvent(QResizeEvent *event) override;
+
 private:
+    void callScene(const char *method);
+
     SceneBackend *m_backend;
 };