Minimal plugin: Use a dummy font database for command line tools.

Suppress warnings like:
QFontDatabase: Cannot find font directory '...' - is Qt installed correctly?
occurring for example when using qmlplugindump.

Add option flags (similar to Windows plugin) to the integration
class to be used for QT_DEBUG_BACKINGSTORE and other functionality.

Add a dummy font database with empty populate() function to be
used unless the debug flag for the backing store is used.

Task-number: QTBUG-33674
Task-number: QTCREATORBUG-10685
Change-Id: I7eaff3025de12e6b0471a3430f986b0cd810e22c
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

src/plugins/platforms/minimal/main.cpp

@@ -55,9 +55,8 @@ public:
 
 QPlatformIntegration *QMinimalIntegrationPlugin::create(const QString& system, const QStringList& paramList)
 {
-    Q_UNUSED(paramList);
     if (!system.compare(QLatin1String("minimal"), Qt::CaseInsensitive))
-        return new QMinimalIntegration;
+        return new QMinimalIntegration(paramList);
 
     return 0;
 }

src/plugins/platforms/minimal/qminimalbackingstore.cpp

@@ -41,6 +41,7 @@
 
 
 #include "qminimalbackingstore.h"
+#include "qminimalintegration.h"
 #include "qscreen.h"
 #include <QtCore/qdebug.h>
 #include <qpa/qplatformscreen.h>
@@ -49,10 +50,9 @@
 QT_BEGIN_NAMESPACE
 
 QMinimalBackingStore::QMinimalBackingStore(QWindow *window)
-    : QPlatformBackingStore(window),mDebug(false)
+    : QPlatformBackingStore(window)
+    , mDebug(QMinimalIntegration::instance()->options() & QMinimalIntegration::DebugBackingStore)
 {
-    if (QT_PREPEND_NAMESPACE(qgetenv)("QT_DEBUG_BACKINGSTORE").toInt() > 0)
-        mDebug = true;
     if (mDebug)
         qDebug() << "QMinimalBackingStore::QMinimalBackingStore:" << (quintptr)this;
 }

src/plugins/platforms/minimal/qminimalbackingstore.h

@@ -60,7 +60,7 @@ public:
 
 private:
     QImage mImage;
-    bool mDebug;
+    const bool mDebug;
 };
 
 QT_END_NAMESPACE

src/plugins/platforms/minimal/qminimalintegration.cpp

@@ -50,11 +50,31 @@
 #include <QtGui/private/qpixmap_raster_p.h>
 #include <QtGui/private/qguiapplication_p.h>
 #include <qpa/qplatformwindow.h>
+#include <qpa/qplatformfontdatabase.h>
 
 QT_BEGIN_NAMESPACE
 
-QMinimalIntegration::QMinimalIntegration()
+static const char debugBackingStoreEnvironmentVariable[] = "QT_DEBUG_BACKINGSTORE";
+
+static inline unsigned parseOptions(const QStringList &paramList)
 {
+    unsigned options = 0;
+    foreach (const QString &param, paramList) {
+        if (param == QLatin1String("enable_fonts"))
+            options |= QMinimalIntegration::EnableFonts;
+    }
+    return options;
+}
+
+QMinimalIntegration::QMinimalIntegration(const QStringList &parameters)
+    : m_dummyFontDatabase(0)
+    , m_options(parseOptions(parameters))
+{
+    if (qEnvironmentVariableIsSet(debugBackingStoreEnvironmentVariable)
+        && qgetenv(debugBackingStoreEnvironmentVariable).toInt() > 0) {
+        m_options |= DebugBackingStore | EnableFonts;
+    }
+
     QMinimalScreen *mPrimaryScreen = new QMinimalScreen();
 
     mPrimaryScreen->mGeometry = QRect(0, 0, 240, 320);
@@ -64,6 +84,11 @@ QMinimalIntegration::QMinimalIntegration()
     screenAdded(mPrimaryScreen);
 }
 
+QMinimalIntegration::~QMinimalIntegration()
+{
+    delete m_dummyFontDatabase;
+}
+
 bool QMinimalIntegration::hasCapability(QPlatformIntegration::Capability cap) const
 {
     switch (cap) {
@@ -73,6 +98,24 @@ bool QMinimalIntegration::hasCapability(QPlatformIntegration::Capability cap) co
     }
 }
 
+// Dummy font database that does not scan the fonts directory to be
+// used for command line tools like qmlplugindump that do not create windows
+// unless DebugBackingStore is activated.
+class DummyFontDatabase : public QPlatformFontDatabase
+{
+public:
+    virtual void populateFontDatabase() {}
+};
+
+QPlatformFontDatabase *QMinimalIntegration::fontDatabase() const
+{
+    if (m_options & EnableFonts)
+        return QPlatformIntegration::fontDatabase();
+    if (!m_dummyFontDatabase)
+        m_dummyFontDatabase = new DummyFontDatabase;
+    return m_dummyFontDatabase;
+}
+
 QPlatformWindow *QMinimalIntegration::createPlatformWindow(QWindow *window) const
 {
     Q_UNUSED(window);
@@ -95,4 +138,9 @@ QAbstractEventDispatcher *QMinimalIntegration::createEventDispatcher() const
 #endif
 }
 
+QMinimalIntegration *QMinimalIntegration::instance()
+{
+    return static_cast<QMinimalIntegration *>(QGuiApplicationPrivate::platformIntegration());
+}
+
 QT_END_NAMESPACE

src/plugins/platforms/minimal/qminimalintegration.h

@@ -67,13 +67,28 @@ public:
 class QMinimalIntegration : public QPlatformIntegration
 {
 public:
-    QMinimalIntegration();
+    enum Options { // Options to be passed on command line or determined from environment
+        DebugBackingStore = 0x1,
+        EnableFonts = 0x2
+    };
+
+    explicit QMinimalIntegration(const QStringList &parameters);
+    ~QMinimalIntegration();
 
     bool hasCapability(QPlatformIntegration::Capability cap) const;
+    QPlatformFontDatabase *fontDatabase() const;
 
     QPlatformWindow *createPlatformWindow(QWindow *window) const;
     QPlatformBackingStore *createPlatformBackingStore(QWindow *window) const;
     QAbstractEventDispatcher *createEventDispatcher() const;
+
+    unsigned options() const { return m_options; }
+
+    static QMinimalIntegration *instance();
+
+private:
+    mutable QPlatformFontDatabase *m_dummyFontDatabase;
+    unsigned m_options;
 };
 
 QT_END_NAMESPACE