Refactor QQuickStackView transition startup

Merge the separate but very similar looking popTransition(),
pushTransition(), and replaceTransition() methods to a single
startTransition() method, and pass the necessary arguments in
a QQuickStackTransition structure. This is an enabler step for
being able to specify the desired transition type for replace
(and push & pop, for that matter) operations.

Change-Id: Ia68bb94dc9280aace8718f4df0e798a7f1469e78
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

3 files changed, 124 insertions, 90 deletions

diff --git a/src/quicktemplates2/qquickstackview.cpp b/src/quicktemplates2/qquickstackview.cpp
index 597cc358..46c1d96e 100644
--- a/src/quicktemplates2/qquickstackview.cpp
+++ b/src/quicktemplates2/qquickstackview.cpp
@@ -466,7 +466,9 @@ void QQuickStackView::push(QQmlV4Function *args)
     if (d->pushElements(elements)) {
         emit depthChanged();
         QQuickStackElement *enter = d->elements.top();
-        d->pushTransition(enter, exit, boundingRect(), operation == Immediate);
+        d->startTransition(QQuickStackTransition::enter(QQuickStackTransition::Push, enter, this),
+                           QQuickStackTransition::exit(QQuickStackTransition::Push, exit, this),
+                           operation == Immediate);
         d->setCurrentItem(enter->item);
     }
 
@@ -548,10 +550,14 @@ void QQuickStackView::pop(QQmlV4Function *args)
     QQuickItem *previousItem = nullptr;
 
     if (d->popElements(enter)) {
-        if (exit)
+        if (exit) {
+            exit->removal = true;
             previousItem = exit->item;
+        }
         emit depthChanged();
-        d->popTransition(enter, exit, boundingRect(), operation == Immediate);
+        d->startTransition(QQuickStackTransition::exit(QQuickStackTransition::Pop, exit, this),
+                           QQuickStackTransition::enter(QQuickStackTransition::Pop, enter, this),
+                           operation == Immediate);
         d->setCurrentItem(enter->item);
     }
 
@@ -650,8 +656,12 @@ void QQuickStackView::replace(QQmlV4Function *args)
     if (exit != target ? d->replaceElements(target, elements) : d->pushElements(elements)) {
         if (depth != d->elements.count())
             emit depthChanged();
+        if (exit)
+            exit->removal = true;
         QQuickStackElement *enter = d->elements.top();
-        d->replaceTransition(enter, exit, boundingRect(), operation == Immediate);
+        d->startTransition(QQuickStackTransition::exit(QQuickStackTransition::Replace, exit, this),
+                           QQuickStackTransition::enter(QQuickStackTransition::Replace, enter, this),
+                           operation == Immediate);
         d->setCurrentItem(enter->item);
     }
 
diff --git a/src/quicktemplates2/qquickstackview_p.cpp b/src/quicktemplates2/qquickstackview_p.cpp
index c781f7fe..c021ba77 100644
--- a/src/quicktemplates2/qquickstackview_p.cpp
+++ b/src/quicktemplates2/qquickstackview_p.cpp
@@ -426,96 +426,28 @@ void QQuickStackViewPrivate::ensureTransitioner()
     }
 }
 
-void QQuickStackViewPrivate::popTransition(QQuickStackElement *enter, QQuickStackElement *exit, const QRectF &viewBounds, bool immediate)
+void QQuickStackViewPrivate::startTransition(const QQuickStackTransition &first, const QQuickStackTransition &second, bool immediate)
 {
-    ensureTransitioner();
-
-    if (exit) {
-        exit->removal = true;
-        exit->setStatus(QQuickStackView::Deactivating);
-        exit->transitionNextReposition(transitioner, QQuickItemViewTransitioner::RemoveTransition, true);
-    }
-    if (enter) {
-        enter->setStatus(QQuickStackView::Activating);
-        enter->transitionNextReposition(transitioner, QQuickItemViewTransitioner::RemoveTransition, false);
-    }
-
-    if (exit) {
-        if (immediate || !exit->item || !exit->prepareTransition(transitioner, viewBounds))
-            completeTransition(exit, transitioner->removeTransition);
-        else
-            exit->startTransition(transitioner);
-    }
-    if (enter) {
-        if (immediate || !enter->item || !enter->prepareTransition(transitioner, QRectF()))
-            completeTransition(enter, transitioner->removeDisplacedTransition);
-        else
-            enter->startTransition(transitioner);
-    }
-
-    if (transitioner) {
-        setBusy(!transitioner->runningJobs.isEmpty());
-        transitioner->resetTargetLists();
-    }
-}
-
-void QQuickStackViewPrivate::pushTransition(QQuickStackElement *enter, QQuickStackElement *exit, const QRectF &viewBounds, bool immediate)
-{
-    ensureTransitioner();
-
-    if (enter) {
-        enter->setStatus(QQuickStackView::Activating);
-        enter->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, true);
+    if (first.element) {
+        first.element->setStatus(first.status);
+        first.element->transitionNextReposition(transitioner, first.type, first.target);
     }
-    if (exit) {
-        exit->setStatus(QQuickStackView::Deactivating);
-        exit->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, false);
+    if (second.element) {
+        second.element->setStatus(second.status);
+        second.element->transitionNextReposition(transitioner, second.type, second.target);
     }
 
-    if (enter) {
-        if (immediate || !enter->item || !enter->prepareTransition(transitioner, viewBounds))
-            completeTransition(enter, transitioner->addTransition);
+    if (first.element) {
+        if (immediate || !first.element->item || !first.element->prepareTransition(transitioner, first.viewBounds))
+            completeTransition(first.element, transitioner->removeTransition);
         else
-            enter->startTransition(transitioner);
+            first.element->startTransition(transitioner);
     }
-    if (exit) {
-        if (immediate || !exit->item || !exit->prepareTransition(transitioner, QRectF()))
-            completeTransition(exit, transitioner->addDisplacedTransition);
+    if (second.element) {
+        if (immediate || !second.element->item || !second.element->prepareTransition(transitioner, second.viewBounds))
+            completeTransition(second.element, transitioner->removeDisplacedTransition);
         else
-            exit->startTransition(transitioner);
-    }
-
-    if (transitioner) {
-        setBusy(!transitioner->runningJobs.isEmpty());
-        transitioner->resetTargetLists();
-    }
-}
-
-void QQuickStackViewPrivate::replaceTransition(QQuickStackElement *enter, QQuickStackElement *exit, const QRectF &viewBounds, bool immediate)
-{
-    ensureTransitioner();
-
-    if (exit) {
-        exit->removal = true;
-        exit->setStatus(QQuickStackView::Deactivating);
-        exit->transitionNextReposition(transitioner, QQuickItemViewTransitioner::MoveTransition, false);
-    }
-    if (enter) {
-        enter->setStatus(QQuickStackView::Activating);
-        enter->transitionNextReposition(transitioner, QQuickItemViewTransitioner::MoveTransition, true);
-    }
-
-    if (exit) {
-        if (immediate || !exit->item || !exit->prepareTransition(transitioner, QRectF()))
-            completeTransition(exit, transitioner->moveDisplacedTransition);
-        else
-            exit->startTransition(transitioner);
-    }
-    if (enter) {
-        if (immediate || !enter->item || !enter->prepareTransition(transitioner, viewBounds))
-            completeTransition(enter, transitioner->moveTransition);
-        else
-            enter->startTransition(transitioner);
+            second.element->startTransition(transitioner);
     }
 
     if (transitioner) {
@@ -569,4 +501,82 @@ void QQuickStackViewPrivate::setBusy(bool b)
     emit q->busyChanged();
 }
 
+QQuickStackTransition QQuickStackTransition::exit(Operation operation, QQuickStackElement *element, QQuickStackView *view)
+{
+    QQuickStackTransition st;
+    st.status = QQuickStackView::Deactivating;
+    st.transition = nullptr;
+    st.element = element;
+
+    const QQuickItemViewTransitioner *transitioner = QQuickStackViewPrivate::get(view)->transitioner;
+
+    switch (operation) {
+    case Push:
+        st.target = false;
+        st.type = QQuickItemViewTransitioner::AddTransition;
+        st.viewBounds = QRectF();
+        if (transitioner)
+            st.transition = transitioner->addDisplacedTransition;
+        break;
+    case Replace:
+        st.target = false;
+        st.type = QQuickItemViewTransitioner::MoveTransition;
+        st.viewBounds = QRectF();
+        if (transitioner)
+            st.transition = transitioner->moveDisplacedTransition;
+        break;
+    case Pop:
+        st.target = true;
+        st.type = QQuickItemViewTransitioner::RemoveTransition;
+        st.viewBounds = view->boundingRect();
+        if (transitioner)
+            st.transition = transitioner->removeTransition;
+        break;
+    default:
+        Q_UNREACHABLE();
+        break;
+    }
+
+    return st;
+}
+
+QQuickStackTransition QQuickStackTransition::enter(Operation operation, QQuickStackElement *element, QQuickStackView *view)
+{
+    QQuickStackTransition st;
+    st.status = QQuickStackView::Activating;
+    st.transition = nullptr;
+    st.element = element;
+
+    const QQuickItemViewTransitioner *transitioner = QQuickStackViewPrivate::get(view)->transitioner;
+
+    switch (operation) {
+    case Push:
+        st.target = true;
+        st.type = QQuickItemViewTransitioner::AddTransition;
+        st.viewBounds = view->boundingRect();
+        if (transitioner)
+            st.transition = transitioner->addTransition;
+        break;
+    case Replace:
+        st.target = true;
+        st.type = QQuickItemViewTransitioner::MoveTransition;
+        st.viewBounds = view->boundingRect();
+        if (transitioner)
+            st.transition = transitioner->moveTransition;
+        break;
+    case Pop:
+        st.target = false;
+        st.type = QQuickItemViewTransitioner::RemoveTransition;
+        st.viewBounds = QRectF();
+        if (transitioner)
+            st.transition = transitioner->removeDisplacedTransition;
+        break;
+    default:
+        Q_UNREACHABLE();
+        break;
+    }
+
+    return st;
+}
+
 QT_END_NAMESPACE
diff --git a/src/quicktemplates2/qquickstackview_p_p.h b/src/quicktemplates2/qquickstackview_p_p.h
index e57353f3..7fe7f005 100644
--- a/src/quicktemplates2/qquickstackview_p_p.h
+++ b/src/quicktemplates2/qquickstackview_p_p.h
@@ -58,6 +58,7 @@ QT_BEGIN_NAMESPACE
 
 class QQmlContext;
 class QQmlComponent;
+struct QQuickStackTransition;
 
 class QQuickStackElement : public QQuickItemViewTransitionableItem, public QQuickItemChangeListener
 {
@@ -123,9 +124,7 @@ public:
     bool replaceElements(QQuickStackElement *element, const QList<QQuickStackElement *> &elements);
 
     void ensureTransitioner();
-    void popTransition(QQuickStackElement *enter, QQuickStackElement *exit, const QRectF &viewBounds, bool immediate);
-    void pushTransition(QQuickStackElement *enter, QQuickStackElement *exit, const QRectF &viewBounds, bool immediate);
-    void replaceTransition(QQuickStackElement *enter, QQuickStackElement *exit, const QRectF &viewBounds, bool immediate);
+    void startTransition(const QQuickStackTransition &first, const QQuickStackTransition &second, bool immediate);
     void completeTransition(QQuickStackElement *element, QQuickTransition *transition);
 
     void viewItemTransitionFinished(QQuickItemViewTransitionableItem *item) override;
@@ -139,6 +138,21 @@ public:
     QQuickItemViewTransitioner *transitioner;
 };
 
+struct QQuickStackTransition
+{
+    enum Operation { Push, Replace, Pop };
+
+    static QQuickStackTransition exit(Operation operation, QQuickStackElement *element, QQuickStackView *view);
+    static QQuickStackTransition enter(Operation operation, QQuickStackElement *element, QQuickStackView *view);
+
+    bool target;
+    QQuickStackView::Status status;
+    QQuickItemViewTransitioner::TransitionType type;
+    QRectF viewBounds;
+    QQuickStackElement *element;
+    QQuickTransition *transition;
+};
+
 class QQuickStackAttachedPrivate : public QObjectPrivate, public QQuickItemChangeListener
 {
     Q_DECLARE_PUBLIC(QQuickStackAttached)