From 8c44064f62b9e57dacdf1dbd8de57e07c938b9db Mon Sep 17 00:00:00 2001
From: Doris Verria <doris.verria@qt.io>
Date: Thu, 8 Feb 2024 22:10:09 +0100
Subject: [PATCH] QWindowPrivate: Introduce virtual setFocusToTarget

When a window gains focus, the focus will be set to the focusWidget,
if one exists, in the case of QWidgetWindow, and to the window's
contentItem's subFocusItem, in the case of QQuickWindow.
However, we want to be able to customize this as we may want to set
the focus item/widget to the first, last, prev, or next, depending
for example, on the reason the window got focus. Eg.: on a TabKey
we want to focus the next focus object, on a BackTabKey the previous
one, and so on.
To be able to do this, add a virtual method in QWindowPrivate that sets focus to the specified item, and override for QWidgetWindowPrivate.

Task-number: QTBUG-121789
Done-with: axel.spoerl@qt.io
Change-Id: Ib5e17d6ff52c2323a4013c80bf411e92b4c8ce9b
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
---
 src/gui/kernel/qwindow_p.h              | 10 ++++++++
 src/widgets/kernel/qwidgetwindow.cpp    | 33 +++++++++++++++++++++++++
 src/widgets/kernel/qwindowcontainer.cpp | 12 ++++++++-
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/src/gui/kernel/qwindow_p.h b/src/gui/kernel/qwindow_p.h
index a9716847a1e..f6c8aee9f67 100644
--- a/src/gui/kernel/qwindow_p.h
+++ b/src/gui/kernel/qwindow_p.h
@@ -76,6 +76,16 @@ public:
     void setTransientParent(QWindow *parent);
 
     virtual void clearFocusObject();
+
+    enum class FocusTarget {
+        First,
+        Last,
+        Current,
+        Next,
+        Prev
+    };
+    virtual void setFocusToTarget(QWindowPrivate::FocusTarget) {}
+
     virtual QRectF closestAcceptableGeometry(const QRectF &rect) const;
 
     void setMinOrMaxSize(QSize *oldSizeMember, const QSize &size,
diff --git a/src/widgets/kernel/qwidgetwindow.cpp b/src/widgets/kernel/qwidgetwindow.cpp
index f51baba88b1..c5b045c8dbf 100644
--- a/src/widgets/kernel/qwidgetwindow.cpp
+++ b/src/widgets/kernel/qwidgetwindow.cpp
@@ -77,6 +77,39 @@ public:
             widget->focusWidget()->clearFocus();
     }
 
+    void setFocusToTarget(QWindowPrivate::FocusTarget target) override
+    {
+        Q_Q(QWidgetWindow);
+        QWidget *widget = q->widget();
+        if (!widget)
+            return;
+        QWidget *newFocusWidget = nullptr;
+
+        switch (target) {
+        case FocusTarget::First:
+            newFocusWidget = q->getFocusWidget(QWidgetWindow::FirstFocusWidget);
+            break;
+        case FocusTarget::Last:
+            newFocusWidget = q->getFocusWidget(QWidgetWindow::LastFocusWidget);
+            break;
+        case FocusTarget::Next: {
+            QWidget *focusWidget = widget->focusWidget() ? widget->focusWidget() : widget;
+            newFocusWidget = focusWidget->nextInFocusChain() ? focusWidget->nextInFocusChain() : focusWidget;
+            break;
+        }
+        case FocusTarget::Prev: {
+            QWidget *focusWidget = widget->focusWidget() ? widget->focusWidget() : widget;
+            newFocusWidget = focusWidget->previousInFocusChain() ? focusWidget->previousInFocusChain() : focusWidget;
+            break;
+        }
+        default:
+            break;
+        }
+
+        if (newFocusWidget)
+            newFocusWidget->setFocus();
+    }
+
     QRectF closestAcceptableGeometry(const QRectF &rect) const override;
 
     void processSafeAreaMarginsChanged() override
diff --git a/src/widgets/kernel/qwindowcontainer.cpp b/src/widgets/kernel/qwindowcontainer.cpp
index 2c374ac408a..376a93c758f 100644
--- a/src/widgets/kernel/qwindowcontainer.cpp
+++ b/src/widgets/kernel/qwindowcontainer.cpp
@@ -5,6 +5,7 @@
 #include "qwidget_p.h"
 #include "qwidgetwindow_p.h"
 #include <QtGui/qwindow.h>
+#include <QtGui/private/qwindow_p.h>
 #include <QtGui/private/qguiapplication_p.h>
 #include <qpa/qplatformintegration.h>
 #include <QDebug>
@@ -317,8 +318,17 @@ bool QWindowContainer::event(QEvent *e)
         break;
     case QEvent::FocusIn:
         if (d->window->parent()) {
-            if (QGuiApplication::focusWindow() != d->window)
+            if (QGuiApplication::focusWindow() != d->window) {
+                QFocusEvent *event = static_cast<QFocusEvent *>(e);
+                const auto reason = event->reason();
+                QWindowPrivate::FocusTarget target = QWindowPrivate::FocusTarget::Current;
+                if (reason == Qt::TabFocusReason)
+                    target = QWindowPrivate::FocusTarget::First;
+                else if (reason == Qt::BacktabFocusReason)
+                    target = QWindowPrivate::FocusTarget::Last;
+                qt_window_private(d->window)->setFocusToTarget(target);
                 d->window->requestActivate();
+            }
         }
         break;
 #if QT_CONFIG(draganddrop)