Say hello to DprGadget

DprGadget displays the devicePixelRatio for the current
screen using a large friendly font, as well as the
platform and environment inputs used for determining
the DPR.

Change-Id: Id619edad181eb7717f18eb98af341d6582a843a1
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

3 files changed, 209 insertions, 0 deletions

diff --git a/tests/manual/highdpi/dprgadget/CMakeLists.txt b/tests/manual/highdpi/dprgadget/CMakeLists.txt
new file mode 100644
index 0000000000..1afe59f4a5
--- /dev/null
+++ b/tests/manual/highdpi/dprgadget/CMakeLists.txt
@@ -0,0 +1,18 @@
+cmake_minimum_required(VERSION 3.14)
+project(dprgadget LANGUAGES CXX)
+set(CMAKE_AUTOMOC ON)
+
+find_package(Qt6 COMPONENTS Core)
+find_package(Qt6 COMPONENTS Gui)
+find_package(Qt6 COMPONENTS Widgets)
+
+add_qt_gui_executable(dprgadget
+    main.cpp
+)
+
+target_link_libraries(dprgadget PUBLIC
+    Qt::Core
+    Qt::Gui
+    Qt::Widgets
+)
+
diff --git a/tests/manual/highdpi/dprgadget/dprgadget.pro b/tests/manual/highdpi/dprgadget/dprgadget.pro
new file mode 100644
index 0000000000..900402409e
--- /dev/null
+++ b/tests/manual/highdpi/dprgadget/dprgadget.pro
@@ -0,0 +1,5 @@
+
+CONFIG += console
+SOURCES += main.cpp
+QT += widgets gui_private
+
diff --git a/tests/manual/highdpi/dprgadget/main.cpp b/tests/manual/highdpi/dprgadget/main.cpp
new file mode 100644
index 0000000000..1cb1134bde
--- /dev/null
+++ b/tests/manual/highdpi/dprgadget/main.cpp
@@ -0,0 +1,186 @@
+/****************************************************************************
+ **
+ ** Copyright (C) 2020 The Qt Company Ltd.
+ ** Contact: https://www.qt.io/licensing/
+ **
+ ** This file is part of the test suite of the Qt Toolkit.
+ **
+ ** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+ ** Commercial License Usage
+ ** Licensees holding valid commercial Qt licenses may use this file in
+ ** accordance with the commercial license agreement provided with the
+ ** Software or, alternatively, in accordance with the terms contained in
+ ** a written agreement between you and The Qt Company. For licensing terms
+ ** and conditions see https://www.qt.io/terms-conditions. For further
+ ** information use the contact form at https://www.qt.io/contact-us.
+ **
+ ** GNU General Public License Usage
+ ** Alternatively, this file may be used under the terms of the GNU
+ ** General Public License version 3 as published by the Free Software
+ ** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+ ** included in the packaging of this file. Please review the following
+ ** information to ensure the GNU General Public License requirements will
+ ** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+ **
+ ** $QT_END_LICENSE$
+ **
+ ****************************************************************************/
+
+#include <QtWidgets/QtWidgets>
+#include <QtGui/qpa/qplatformscreen.h>
+
+/*
+    DprGadget: The focused High-DPI settings debug utility
+
+    DprGadget displays the device pixel ratio ("DPR") for the screen
+    it's on in a large font, as well as the inputs (from the platform
+    plugin or environment) currently in use for determinging the DPR.
+
+    Non-relevant inputs are not displayed. See qttools/src/qtdiag for
+    an utility which displays all inputs.
+*/
+
+bool g_qtUsePhysicalDpi = false;
+bool g_qtScaleFactor = false;
+
+class DprGadget : public QWidget
+{
+public:
+    std::function<void(void)> m_clearFn;
+    std::function<void(void)> m_updateFn;
+    qreal m_currentDpr = -1;
+
+    DprGadget() {
+        setWindowTitle("DprGadget");
+
+        QFont smallFont;
+        smallFont.setPointSize(12);
+        QFont bigFont;
+        bigFont.setPointSize(42);
+        QFont biggerFont;
+        biggerFont.setPointSize(80);
+
+        QLabel *dprLabel = new QLabel("Device Pixel Ratio");
+        dprLabel->setFont(bigFont);
+        dprLabel->setTextInteractionFlags(Qt::TextSelectableByMouse);
+
+        QLabel *dprValue = new QLabel();
+        dprValue->setFont(biggerFont);
+        dprValue->setTextInteractionFlags(Qt::TextSelectableByMouse);
+
+        QLabel *dpiLabel = new QLabel("Logical DPI:");
+        dpiLabel->setFont(smallFont);
+        dpiLabel->setTextInteractionFlags(Qt::TextSelectableByMouse);
+
+        QLabel *sizeLabel = new QLabel("Window size:");
+        sizeLabel->setFont(smallFont);
+        sizeLabel->setTextInteractionFlags(Qt::TextSelectableByMouse);
+
+        QLabel *platformDpiLabel = new QLabel("Native Device Pixel Ratio:");
+        QLabel *plarformDprLabel = new QLabel("Native Logical DPI:");
+        platformDpiLabel->setFont(smallFont);
+        platformDpiLabel->setTextInteractionFlags(Qt::TextSelectableByMouse);
+        plarformDprLabel->setFont(smallFont);
+        plarformDprLabel->setTextInteractionFlags(Qt::TextSelectableByMouse);
+
+        QLabel *screenLabel = new QLabel("Current Screen:");
+        screenLabel->setFont(smallFont);
+
+        QVBoxLayout *layout = new QVBoxLayout();
+        layout->addWidget(dprLabel);
+        layout->setAlignment(dprLabel, Qt::AlignHCenter);
+        layout->addWidget(dprValue);
+        layout->setAlignment(dprValue, Qt::AlignHCenter);
+        layout->addWidget(sizeLabel);
+
+        bool displayLogicalDpi = false;
+        if (displayLogicalDpi)
+            layout->addWidget(dpiLabel);
+
+        if (g_qtScaleFactor) {
+            QString text = QString("QT_SCALE_FACTOR ") + qgetenv("QT_SCALE_FACTOR");
+            layout->addWidget(new QLabel(text));
+        }
+
+        layout->addStretch();
+        layout->addWidget(screenLabel);
+        layout->addWidget(platformDpiLabel);
+        layout->addWidget(plarformDprLabel);
+
+        auto updateValues = [=]() {
+            dprValue->setText(QString("%1").arg(devicePixelRatioF()));
+            dpiLabel->setText(QString("Logical DPI: %1").arg(logicalDpiX()));
+            sizeLabel->setText(QString("Window size: %1 %2").arg(width()).arg(height()));
+
+            QPlatformScreen *pscreen = screen()->handle();
+
+            if (g_qtUsePhysicalDpi)
+                platformDpiLabel->setText(QString("Native Physical DPI: TODO"));
+            else
+                platformDpiLabel->setText(QString("Native Logical DPI: %1").arg(pscreen->logicalDpi().first));
+
+            plarformDprLabel->setText(QString("Native Device Pixel Ratio: %1").arg(pscreen->devicePixelRatio()));
+
+            screenLabel->setText(QString("Current Screen: %1").arg(screen()->name()));
+        };
+        m_updateFn = updateValues;
+
+        m_clearFn = [=]() {
+            dprValue->setText(QString(""));
+        };
+
+        create();
+
+        QObject::connect(this->windowHandle(), &QWindow::screenChanged, [updateValues](QScreen *screen){
+            Q_UNUSED(screen);
+            updateValues();
+        });
+
+        setLayout(layout);
+
+        updateValues();
+    }
+
+    void paintEvent(QPaintEvent *) override  {
+        // Dpr change should trigger a repaint, update display values here
+        if (m_currentDpr == devicePixelRatioF())
+            return;
+        m_currentDpr = devicePixelRatioF();
+
+        m_updateFn();
+    }
+
+    void resizeEvent(QResizeEvent *) override {
+        m_updateFn();
+    }
+
+    void mousePressEvent(QMouseEvent *) override {
+        m_clearFn();
+        QTimer::singleShot(500, this, [this](){
+            m_updateFn();
+        });
+    }
+};
+
+int main(int argc, char **argv) {
+
+    // Set sensible defaults
+    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+    QGuiApplication::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::PassThrough);
+
+    // react to (some) high-dpi eviornment variables.
+    g_qtUsePhysicalDpi = qgetenv("QT_USE_PHYSICAL_DPI") == QByteArray("1");
+    g_qtScaleFactor = qEnvironmentVariableIsSet("QT_SCALE_FACTOR");
+
+    QApplication app(argc, argv);
+
+    DprGadget dprGadget;
+
+    // Set initial size. We expect this size to be preserved across screen
+    // and DPI changes
+    dprGadget.resize(560, 380);
+
+    dprGadget.show();
+
+    return app.exec();
+}