From aab71c7bb8e47b6e432fa7945bdf19fbce31a2f7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tor=20Arne=20Vestb=C3=B8?= <tor.arne.vestbo@qt.io>
Date: Wed, 7 Sep 2022 18:59:40 +0200
Subject: [PATCH] Ensure QHighDpiScaling::set(Screen/Global)Factor() results in
 QScreen signals
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Change-Id: I328b288b3fd83df0cc81c62bce1d946f90f1cd0d
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
---
 src/gui/kernel/qhighdpiscaling.cpp            | 12 ++++---
 .../auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp | 32 +++++++++++++++++++
 2 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/src/gui/kernel/qhighdpiscaling.cpp b/src/gui/kernel/qhighdpiscaling.cpp
index f20bd842637..31626ec2229 100644
--- a/src/gui/kernel/qhighdpiscaling.cpp
+++ b/src/gui/kernel/qhighdpiscaling.cpp
@@ -541,15 +541,17 @@ void QHighDpiScaling::setGlobalFactor(qreal factor)
     if (!QGuiApplication::allWindows().isEmpty())
         qWarning("QHighDpiScaling::setFactor: Should only be called when no windows exist.");
 
+    const auto screens = QGuiApplication::screens();
+
+    std::vector<QScreenPrivate::UpdateEmitter> updateEmitters;
+    for (QScreen *screen : screens)
+        updateEmitters.emplace_back(screen);
+
     m_globalScalingActive = !qFuzzyCompare(factor, qreal(1));
     m_factor = m_globalScalingActive ? factor : qreal(1);
     m_active = m_globalScalingActive || m_screenFactorSet || m_platformPluginDpiScalingActive ;
-    const auto screens = QGuiApplication::screens();
     for (QScreen *screen : screens)
         screen->d_func()->updateGeometry();
-
-    // FIXME: The geometry has been updated based on the new scale factor,
-    // but we don't emit any geometry change signals for the screens.
 }
 
 static const char scaleFactorProperty[] = "_q_scaleFactor";
@@ -566,6 +568,8 @@ void QHighDpiScaling::setScreenFactor(QScreen *screen, qreal factor)
         m_active = true;
     }
 
+    QScreenPrivate::UpdateEmitter updateEmitter(screen);
+
     // Prefer associating the factor with screen name over the object
     // since the screen object may be deleted on screen disconnects.
     const QString name = screen->name();
diff --git a/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp b/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp
index b062a88c1fc..9a2482b03e4 100644
--- a/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp
+++ b/tests/auto/gui/kernel/qhighdpi/tst_qhighdpi.cpp
@@ -10,6 +10,7 @@
 #include <QJsonObject>
 #include <QJsonDocument>
 #include <QStringView>
+#include <QSignalSpy>
 
 Q_LOGGING_CATEGORY(lcTests, "qt.gui.tests")
 
@@ -55,6 +56,8 @@ private slots:
     void mouseVelocity_data();
     void setCursor();
     void setCursor_data();
+    void setGlobalFactorEmits();
+    void setScreenFactorEmits();
 };
 
 /// Offscreen platform plugin test setup
@@ -811,5 +814,34 @@ void tst_QHighDpi::setCursor()
     }
 }
 
+void tst_QHighDpi::setGlobalFactorEmits()
+{
+    QList<qreal> dpiValues { 96, 96, 96 };
+    std::unique_ptr<QGuiApplication> app(createStandardOffscreenApp(dpiValues));
+
+    std::vector<std::unique_ptr<QSignalSpy>> spies;
+    for (QScreen *screen : app->screens())
+        spies.push_back(std::make_unique<QSignalSpy>(screen, &QScreen::geometryChanged));
+
+    QHighDpiScaling::setGlobalFactor(2);
+
+    for (const auto &spy : spies)
+        QCOMPARE(spy->count(), 1);
+
+    QHighDpiScaling::setGlobalFactor(1);
+}
+
+void tst_QHighDpi::setScreenFactorEmits()
+{
+    QList<qreal> dpiValues { 96, 96, 96 };
+    std::unique_ptr<QGuiApplication> app(createStandardOffscreenApp(dpiValues));
+
+    for (QScreen *screen : app->screens()) {
+        QSignalSpy spy(screen, &QScreen::geometryChanged);
+        QHighDpiScaling::setScreenFactor(screen, 2);
+        QCOMPARE(spy.count(), 1);
+    }
+}
+
 #include "tst_qhighdpi.moc"
 QTEST_APPLESS_MAIN(tst_QHighDpi);