Fix image aspect ratio not preserved when resizing window

As this is not currently possible using only QLabel, subclass it
with a new AspectRatioLabel class to provide the functionality.
This should be usable also on other places where we need scaling
with aspect ratio maintaining.

Task-number: QTIFW-1944
Change-Id: I32147b2b487573bb054fcf66b09eb3f8a0350ccd
Reviewed-by: Katja Marttila <katja.marttila@qt.io>

5 files changed, 168 insertions, 4 deletions

diff --git a/src/libs/installer/aspectratiolabel.cpp b/src/libs/installer/aspectratiolabel.cpp
new file mode 100644
index 000000000..a9af93a55
--- /dev/null
+++ b/src/libs/installer/aspectratiolabel.cpp
@@ -0,0 +1,98 @@
+/**************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Installer Framework.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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 "aspectratiolabel.h"
+
+using namespace QInstaller;
+
+/*!
+    \class QInstaller::AspectRatioLabel
+    \inmodule QtInstallerFramework
+    \brief The AspectRatioLabel class provides a label for displaying
+        a pixmap that maintains its original aspect ratio when resized.
+*/
+
+/*!
+    Constructs the label with \a parent as parent.
+*/
+AspectRatioLabel::AspectRatioLabel(QWidget *parent)
+    : QLabel(parent)
+{
+    setMinimumSize(1, 1);
+    setScaledContents(false);
+}
+
+/*!
+    Sets the \a pixmap shown on the label. Setting a new pixmap clears the previous content.
+*/
+void AspectRatioLabel::setPixmap(const QPixmap &pixmap)
+{
+    m_pixmap = pixmap;
+    QLabel::setPixmap(scaledPixmap());
+}
+
+/*!
+    \reimp
+*/
+int AspectRatioLabel::heightForWidth(int w) const
+{
+    return m_pixmap.isNull()
+        ? height()
+        : m_pixmap.height() * w / m_pixmap.width();
+}
+
+/*!
+    \reimp
+*/
+QSize AspectRatioLabel::sizeHint() const
+{
+    const int w = width();
+    return QSize(w, heightForWidth(w));
+}
+
+/*!
+    Returns the currently set pixmap scaled to the label size,
+    while preserving the original aspect ratio.
+*/
+QPixmap AspectRatioLabel::scaledPixmap() const
+{
+    return m_pixmap.isNull()
+        ? QPixmap()
+        : m_pixmap.scaled(size(), Qt::KeepAspectRatio, Qt::SmoothTransformation);
+}
+
+/*!
+    \reimp
+*/
+void AspectRatioLabel::resizeEvent(QResizeEvent *event)
+{
+    Q_UNUSED(event);
+
+    if (!m_pixmap.isNull())
+        QLabel::setPixmap(scaledPixmap());
+}
diff --git a/src/libs/installer/aspectratiolabel.h b/src/libs/installer/aspectratiolabel.h
new file mode 100644
index 000000000..28fc5aea4
--- /dev/null
+++ b/src/libs/installer/aspectratiolabel.h
@@ -0,0 +1,63 @@
+/**************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Installer Framework.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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.
+**
+** $QT_END_LICENSE$
+**
+**************************************************************************/
+
+#ifndef ASPECTRATIOLABEL_H
+#define ASPECTRATIOLABEL_H
+
+#include "installer_global.h"
+
+#include <QLabel>
+#include <QPixmap>
+#include <QResizeEvent>
+
+namespace QInstaller {
+
+class INSTALLER_EXPORT AspectRatioLabel : public QLabel
+{
+    Q_OBJECT
+
+public:
+    explicit AspectRatioLabel(QWidget *parent = nullptr);
+
+    int heightForWidth(int w) const;
+    QSize sizeHint() const;
+
+public slots:
+    void setPixmap (const QPixmap &pixmap);
+    void resizeEvent(QResizeEvent *event);
+
+private:
+    QPixmap scaledPixmap() const;
+
+private:
+    QPixmap m_pixmap;
+};
+
+} // namespace QInstaller
+
+#endif // ASPECTRATIOLABEL_H
diff --git a/src/libs/installer/installer.pro b/src/libs/installer/installer.pro
index 2cfb079f5..225b1c8d1 100644
--- a/src/libs/installer/installer.pro
+++ b/src/libs/installer/installer.pro
@@ -42,6 +42,7 @@ QT += \
 win32:QT += winextras
 
 HEADERS += packagemanagercore.h \
+    aspectratiolabel.h \
     packagemanagercore_p.h \
     packagemanagergui.h \
     binaryformat.h \
@@ -139,6 +140,7 @@ HEADERS += packagemanagercore.h \
     commandlineparser_p.h
 
 SOURCES += packagemanagercore.cpp \
+    aspectratiolabel.cpp \
     packagemanagercore_p.cpp \
     packagemanagergui.cpp \
     binaryformat.cpp \
diff --git a/src/libs/installer/performinstallationform.cpp b/src/libs/installer/performinstallationform.cpp
index 2c5edf70f..28e2e1f45 100644
--- a/src/libs/installer/performinstallationform.cpp
+++ b/src/libs/installer/performinstallationform.cpp
@@ -139,11 +139,10 @@ void PerformInstallationForm::setupUi(QWidget *widget)
     m_productImagesScrollArea->setObjectName(QLatin1String("ProductImagesScrollArea"));
     m_productImagesScrollArea->setWidgetResizable(true);
     m_productImagesScrollArea->setFrameShape(QFrame::NoFrame);
+    m_productImagesScrollArea->setStyleSheet(QLatin1String("background-color:transparent;"));
 
-    m_productImagesLabel = new QLabel(widget);
+    m_productImagesLabel = new AspectRatioLabel(widget);
     m_productImagesLabel->setObjectName(QLatin1String("ProductImagesLabel"));
-    m_productImagesLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
-    m_productImagesLabel->setScaledContents(true);
 
     m_productImagesScrollArea->setWidget(m_productImagesLabel);
     bottomLayout->addWidget(m_productImagesScrollArea);
diff --git a/src/libs/installer/performinstallationform.h b/src/libs/installer/performinstallationform.h
index db0a35ee8..20b193857 100644
--- a/src/libs/installer/performinstallationform.h
+++ b/src/libs/installer/performinstallationform.h
@@ -29,6 +29,8 @@
 #ifndef PERFORMINSTALLATIONFORM_H
 #define PERFORMINSTALLATIONFORM_H
 
+#include "aspectratiolabel.h"
+
 #include <QObject>
 
 QT_BEGIN_NAMESPACE
@@ -77,7 +79,7 @@ private:
     QLabel *m_progressLabel;
     QLabel *m_downloadStatus;
     QScrollArea *m_productImagesScrollArea;
-    QLabel *m_productImagesLabel;
+    AspectRatioLabel *m_productImagesLabel;
     QPushButton *m_detailsButton;
     LazyPlainTextEdit *m_detailsBrowser;
     QTimer *m_updateTimer;