Cocoa: Fix icon size calculation for system tray.

The Overall goal is to make it possible to use correctly-
sized pixmaps in a predictable way, while still doing
something reasonable with small and large pixmaps.
(The recommended pixmap height is up to 18 points.)

Enable use of rectangular icons by selecting pixmaps
based on pixmap height.

Draw a low-resolution pixmap on retina displays if
there is no high-resolution pixmap available. Scale
large pixmaps to fit the available menu bar area.

Add a manual-test with various pixmap sizes

Task-number: QTBUG-33441
Change-Id: I1926181fe27cae526bae58022df3240bae9f8ac8
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@theqtcompany.com>

src/plugins/platforms/cocoa/qcocoasystemtrayicon.mm

@@ -187,6 +187,14 @@ void QCocoaSystemTrayIcon::cleanup()
     m_sys = 0;
 }
 
+static bool heightCompareFunction (QSize a, QSize b) { return (a.height() < b.height()); }
+static QList<QSize> sortByHeight(const QList<QSize> sizes)
+{
+    QList<QSize> sorted = sizes;
+    std::sort(sorted.begin(), sorted.end(), heightCompareFunction);
+    return sorted;
+}
+
 void QCocoaSystemTrayIcon::updateIcon(const QIcon &icon)
 {
     if (!m_sys)
@@ -196,16 +204,62 @@ void QCocoaSystemTrayIcon::updateIcon(const QIcon &icon)
 
     const bool menuVisible = m_sys->item->menu && m_sys->item->menuVisible;
 
-    CGFloat hgt = [[[NSApplication sharedApplication] mainMenu] menuBarHeight];
-    const short scale = hgt - 4;
+    // The reccomended maximum title bar icon height is 18 points
+    // (device independent pixels). The menu height on past and
+    // current OS X versions is 22 points. Provide some future-proofing
+    // by deriving the icon height from the menu height.
+    const int padding = 4;
+    const int menuHeight = [[[NSApplication sharedApplication] mainMenu] menuBarHeight];
+    const int maxImageHeight = menuHeight - padding;
 
-    QPixmap pm = m_sys->item->icon.pixmap(QSize(scale, scale),
-                                          menuVisible ? QIcon::Selected : QIcon::Normal);
-    if (pm.isNull()) {
-        pm = QPixmap(scale, scale);
-        pm.fill(Qt::transparent);
+    // Select pixmap based on the device pixel height. Ideally we would use
+    // the devicePixelRatio of the target screen, but that value is not
+    // known until draw time. Use qApp->devicePixelRatio, which returns the
+    // devicePixelRatio for the "best" screen on the system.
+    qreal devicePixelRatio = qApp->devicePixelRatio();
+    const int maxPixmapHeight = maxImageHeight * devicePixelRatio;
+    const QIcon::Mode mode = menuVisible ? QIcon::Selected : QIcon::Normal;
+    QSize selectedSize;
+    Q_FOREACH (const QSize& size, sortByHeight(icon.availableSizes(mode))) {
+        // Select a pixmap based on the height. We want the largest pixmap
+        // with a height smaller or equal to maxPixmapHeight. The pixmap
+        // may rectangular; assume it has a reasonable size. If there is
+        // not suitable pixmap use the smallest one the icon can provide.
+        if (size.height() <= maxPixmapHeight) {
+            selectedSize = size;
+        } else {
+            if (!selectedSize.isValid())
+                selectedSize = size;
+            break;
+        }
     }
-    NSImage *nsimage = static_cast<NSImage *>(qt_mac_create_nsimage(pm));
+
+    QPixmap pixmap = icon.pixmap(selectedSize, mode);
+
+    // Draw a low-resolution icon if there is not enough pixels for a retina
+    // icon. This prevents showing a small icon on retina displays.
+    if (devicePixelRatio > 1.0 && selectedSize.height() < maxPixmapHeight / 2)
+        devicePixelRatio = 1.0;
+
+    // Scale large pixmaps to fit the available menu bar area.
+    if (pixmap.height() > maxPixmapHeight)
+        pixmap = pixmap.scaledToHeight(maxPixmapHeight, Qt::SmoothTransformation);
+
+    // The icon will be stretched over the full height of the menu bar
+    // therefore we create a second pixmap which has the full height
+    QSize fullHeightSize(!pixmap.isNull() ? pixmap.width():
+                                            menuHeight * devicePixelRatio,
+                         menuHeight * devicePixelRatio);
+    QPixmap fullHeightPixmap(fullHeightSize);
+    fullHeightPixmap.fill(Qt::transparent);
+    if (!pixmap.isNull()) {
+        QPainter p(&fullHeightPixmap);
+        QRect r = pixmap.rect();
+        r.moveCenter(fullHeightPixmap.rect().center());
+        p.drawPixmap(r, pixmap);
+    }
+
+    NSImage *nsimage = static_cast<NSImage *>(qt_mac_create_nsimage(fullHeightPixmap));
     [(NSImageView*)[[m_sys->item item] view] setImage: nsimage];
     [nsimage release];
 }
@@ -327,18 +381,7 @@ QT_END_NAMESPACE
     Q_UNUSED(notification);
     down = NO;
 
-    CGFloat hgt = [[[NSApplication sharedApplication] mainMenu] menuBarHeight];
-    const short scale = hgt - 4;
-
-    QPixmap pm = parent->icon.pixmap(QSize(scale, scale), QIcon::Normal);
-    if (pm.isNull()) {
-        pm = QPixmap(scale, scale);
-        pm.fill(Qt::transparent);
-    }
-    NSImage *nsaltimage = static_cast<NSImage *>(qt_mac_create_nsimage(pm));
-    [self setImage: nsaltimage];
-    [nsaltimage release];
-
+    parent->systray->updateIcon(parent->icon);
     parent->menuVisible = false;
 
     [self setNeedsDisplay:YES];
@@ -350,18 +393,7 @@ QT_END_NAMESPACE
     int clickCount = [mouseEvent clickCount];
     [self setNeedsDisplay:YES];
 
-    CGFloat hgt = [[[NSApplication sharedApplication] mainMenu] menuBarHeight];
-    const short scale = hgt - 4;
-
-    QPixmap pm = parent->icon.pixmap(QSize(scale, scale),
-                                     parent->menuVisible ? QIcon::Selected : QIcon::Normal);
-    if (pm.isNull()) {
-        pm = QPixmap(scale, scale);
-        pm.fill(Qt::transparent);
-    }
-    NSImage *nsaltimage = static_cast<NSImage *>(qt_mac_create_nsimage(pm));
-    [self setImage: nsaltimage];
-    [nsaltimage release];
+    parent->systray->updateIcon(parent->icon);
 
     if (clickCount == 2) {
         [self menuTrackingDone:nil];

tests/manual/cocoa/qsystemtrayicon/icons.qrc

@@ -0,0 +1,11 @@
+<RCC>
+     <qresource prefix="/">
+         <file>macsystray18x18.png</file>
+         <file>macsystray36x36.png</file>
+         <file>macsystray25x15.png</file>
+         <file>macsystray50x30.png</file>
+         <file>macsystray16x16.png</file>
+         <file>macsystray32x32.png</file>
+         <file>macsystray64x64.png</file>
+    </qresource>
+</RCC>

tests/manual/cocoa/qsystemtrayicon/main.cpp

@@ -0,0 +1,88 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** 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 Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#include <QtWidgets>
+
+int main(int argc, char**argv)
+{
+    QApplication app(argc, argv);
+
+    QWidget window;
+    window.show();
+
+    QSystemTrayIcon systrayIcon(&window);
+
+
+    enum Iconset { Square,          // square icons, reccomended size (18 device-independent pixels or less)
+                   Rectangular,     // rectangular icons, good size
+                   PowerOfTwo,      // standard pow-2 icons, not optimized for the OS X menu bar
+                   Small,           // Not enough pixels
+                   UnreasonablyLarge  // please do something reasonable with my unreasonably large pixmap
+                   };
+
+    // Select icon set and load images
+    Iconset iconset = Square;
+    QIcon icon;
+    switch (iconset) {
+        case Square:
+            icon.addFile(":/macsystray36x36.png");
+            icon.addFile(":/macsystray18x18.png");
+        break;
+        case Rectangular:
+            icon.addFile(":/macsystray50x30.png");
+            icon.addFile(":/macsystray25x15.png");
+        break;
+        case PowerOfTwo:
+            icon.addFile(":/macsystray16x16.png");
+            icon.addFile(":/macsystray32x32.png");
+            icon.addFile(":/macsystray64x64.png");
+        break;
+        case Small:
+            icon.addFile(":/macsystray16x16.png");
+        case UnreasonablyLarge:
+            icon.addFile(":/macsystray64x64.png");
+        break;
+    }
+
+    systrayIcon.setIcon(icon);
+    systrayIcon.show();
+
+    return app.exec();
+}

tests/manual/cocoa/qsystemtrayicon/qsystemtrayicon.pro

@@ -0,0 +1,7 @@
+TEMPLATE = app
+TARGET = qsystemtrayicon
+INCLUDEPATH += .
+QT += widgets
+
+SOURCES += main.cpp
+RESOURCES += icons.qrc