Add QPlatformTheme::fileIcon()

Add a way to return an icon instead of a pixmap of a specific size for a
file for usage by QFileIconProvider, etc.
Fall back to fileIconPixmap() if fileIcon() returns a null icon.

This allows for supporting XDG theme icons and Qt Quick applications
accessing file icons.

Change-Id: I9ffbd6602e1a6a490c0046d950636447c5127474
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/gui/kernel/qplatformtheme.cpp

@@ -44,6 +44,7 @@
 #include <QtCore/QVariant>
 #include <QtCore/QStringList>
 #include <QtCore/qfileinfo.h>
+#include <qicon.h>
 #include <qpalette.h>
 #include <qtextformat.h>
 #include <private/qiconloader_p.h>
@@ -405,6 +406,24 @@ QPixmap QPlatformTheme::standardPixmap(StandardPixmap sp, const QSizeF &size) co
     return QPixmap();
 }
 
+/*!
+    \brief Return an icon for \a fileInfo, observing \a iconOptions.
+
+    This function is queried by QFileIconProvider and similar classes to obtain
+    an icon for a file. If it does not return a non-null icon, fileIconPixmap()
+    is queried for a specific size.
+
+    \since 5.8
+*/
+
+QIcon QPlatformTheme::fileIcon(const QFileInfo &fileInfo, QPlatformTheme::IconOptions iconOptions) const
+{
+    Q_UNUSED(fileInfo);
+    Q_UNUSED(iconOptions);
+    // TODO Should return QCommonStyle pixmaps?
+    return QIcon();
+}
+
 QPixmap QPlatformTheme::fileIconPixmap(const QFileInfo &fileInfo, const QSizeF &size,
                                        QPlatformTheme::IconOptions iconOptions) const
 {

src/gui/kernel/qplatformtheme.h

@@ -55,6 +55,7 @@
 
 QT_BEGIN_NAMESPACE
 
+class QIcon;
 class QIconEngine;
 class QMenu;
 class QMenuBar;
@@ -301,6 +302,8 @@ public:
     virtual QVariant themeHint(ThemeHint hint) const;
 
     virtual QPixmap standardPixmap(StandardPixmap sp, const QSizeF &size) const;
+    virtual QIcon fileIcon(const QFileInfo &fileInfo,
+                           QPlatformTheme::IconOptions iconOptions = 0) const;
     virtual QPixmap fileIconPixmap(const QFileInfo &fileInfo, const QSizeF &size,
                                    QPlatformTheme::IconOptions iconOptions = 0) const;
 

src/widgets/itemviews/qfileiconprovider.cpp

@@ -62,6 +62,14 @@ QT_BEGIN_NAMESPACE
 
 static bool isCacheable(const QFileInfo &fi);
 
+static QPlatformTheme::IconOptions toThemeIconOptions(QFileIconProvider::Options options)
+{
+    QPlatformTheme::IconOptions result;
+    if (options & QFileIconProvider::DontUseCustomDirectoryIcons)
+        result |= QPlatformTheme::DontUseCustomDirectoryIcons;
+    return result;
+}
+
 class QFileIconEngine : public QPixmapIconEngine
 {
 public:
@@ -91,11 +99,7 @@ public:
                 return pixmap;
         }
 
-        QPlatformTheme::IconOptions iconOptions;
-        if (m_fipOpts & QFileIconProvider::DontUseCustomDirectoryIcons)
-            iconOptions |= QPlatformTheme::DontUseCustomDirectoryIcons;
-
-        pixmap = theme->fileIconPixmap(m_fileInfo, size, iconOptions);
+        pixmap = theme->fileIconPixmap(m_fileInfo, size, toThemeIconOptions(m_fipOpts));
         if (!pixmap.isNull()) {
             if (cacheable)
                 QPixmapCache::insert(keyBase + QString::number(size.width()), pixmap);
@@ -345,11 +349,12 @@ QIcon QFileIconProviderPrivate::getIcon(const QFileInfo &fi) const
     if (!theme)
         return QIcon();
 
-    QList<int> sizes = theme->themeHint(QPlatformTheme::IconPixmapSizes).value<QList<int> >();
-    if (sizes.isEmpty())
-        return QIcon();
+    QIcon themeFileIcon = theme->fileIcon(fi, toThemeIconOptions(options));
+    if (!themeFileIcon.isNull())
+        return themeFileIcon;
 
-    return QIcon(new QFileIconEngine(fi, options));
+    QList<int> sizes = theme->themeHint(QPlatformTheme::IconPixmapSizes).value<QList<int> >();
+    return sizes.isEmpty() ? QIcon() : QIcon(new QFileIconEngine(fi, options));
 }
 
 /*!