Windows: Introduce QFileDialog::DontUseCustomDirectoryIcons

Folders can have a custom icon, set by the user. Some system
folders also have one, for example c:\windows\fonts.

This option allows you to disable this behavior, you'll get the
folder directory icon.

As a side-effect, you'll get a very big performance improvement
on removable/network media: 2 seconds vs 60 seconds on a SDCard
with 10000 folders.

Unlike in Qt5, here we didn't add new methods to QFileIconProvider
do avoid introducing new symbols.

Change-Id: I0b98a180e53c9ee7d583f19b3917fcc9166cb3eb
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
(cherry picked from qtbase/46685f755b01288fd53c4483cb97a22c426a57f0)
(cherry picked from qtbase/149f3efc39bebbe8fceacf2553836f90d2e1c383)
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

3 files changed, 36 insertions, 4 deletions

diff --git a/src/gui/itemviews/qfileiconprovider.cpp b/src/gui/itemviews/qfileiconprovider.cpp
index f1ad7e0fc6..9fd9e9987d 100644
--- a/src/gui/itemviews/qfileiconprovider.cpp
+++ b/src/gui/itemviews/qfileiconprovider.cpp
@@ -89,10 +89,15 @@ QT_BEGIN_NAMESPACE
 */
 
 QFileIconProviderPrivate::QFileIconProviderPrivate() :
-    homePath(QDir::home().absolutePath())
+    homePath(QDir::home().absolutePath()), useCustomDirectoryIcons(true)
 {
 }
 
+void QFileIconProviderPrivate::setUseCustomDirectoryIcons(bool enable)
+{
+    useCustomDirectoryIcons = enable;
+}
+
 QIcon QFileIconProviderPrivate::getIcon(QStyle::StandardPixmap name) const
 {
     switch (name) {
@@ -213,6 +218,8 @@ static bool isCacheable(const QFileInfo &fi)
 QIcon QFileIconProviderPrivate::getWinIcon(const QFileInfo &fileInfo) const
 {
     QIcon retIcon;
+    static int defaultFolderIIcon = -1;
+
     QString key;
     QPixmap pixmap;
     // If it's a file, non-{exe,lnk,ico} then we might have it cached already
@@ -228,6 +235,19 @@ QIcon QFileIconProviderPrivate::getWinIcon(const QFileInfo &fileInfo) const
         }
     }
 
+    const bool cacheableDirIcon = fileInfo.isDir() && !fileInfo.isRoot();
+    if (!useCustomDirectoryIcons && defaultFolderIIcon >= 0 && cacheableDirIcon) {
+        // We already have the default folder icon, just return it
+        key = QString::fromLatin1("qt_dir_%1").arg(defaultFolderIIcon);
+        QPixmapCache::find(key, pixmap);
+        if (!pixmap.isNull()) {
+            retIcon.addPixmap(pixmap);
+            if (QPixmapCache::find(key + QLatin1Char('l'), pixmap))
+                retIcon.addPixmap(pixmap);
+            return retIcon;
+        }
+    }
+
     /* We don't use the variable, but by storing it statically, we
      * ensure CoInitialize is only called once. */
     static HRESULT comInit = CoInitialize(NULL);
@@ -237,19 +257,28 @@ QIcon QFileIconProviderPrivate::getWinIcon(const QFileInfo &fileInfo) const
     unsigned long val = 0;
 
     //Get the small icon
-    const unsigned int flags =
+    unsigned int flags =
 #ifndef Q_OS_WINCE
         SHGFI_ICON|SHGFI_SYSICONINDEX|SHGFI_ADDOVERLAYS|SHGFI_OVERLAYINDEX;
 #else
         SHGFI_SYSICONINDEX;
 #endif
 
-    val = SHGetFileInfo((const wchar_t *)QDir::toNativeSeparators(fileInfo.filePath()).utf16(),
-                0, &info, sizeof(SHFILEINFO), flags | SHGFI_SMALLICON);
+    if (cacheableDirIcon && !useCustomDirectoryIcons) {
+        flags |= SHGFI_USEFILEATTRIBUTES;
+        val = SHGetFileInfo(L"dummy",
+                            FILE_ATTRIBUTE_DIRECTORY, &info,
+                            sizeof(SHFILEINFO), flags | SHGFI_SMALLICON);
+    } else {
+        val = SHGetFileInfo((const wchar_t *)QDir::toNativeSeparators(fileInfo.filePath()).utf16(),
+                            0, &info, sizeof(SHFILEINFO), flags | SHGFI_SMALLICON);
+    }
 
     // Even if GetFileInfo returns a valid result, hIcon can be empty in some cases
     if (val && info.hIcon) {
         if (fileInfo.isDir() && !fileInfo.isRoot()) {
+            if (!useCustomDirectoryIcons && defaultFolderIIcon < 0)
+                defaultFolderIIcon = info.iIcon;
             //using the unique icon index provided by windows save us from duplicate keys
             key = QString::fromLatin1("qt_dir_%1").arg(info.iIcon);
             QPixmapCache::find(key, pixmap);
diff --git a/src/gui/itemviews/qfileiconprovider.h b/src/gui/itemviews/qfileiconprovider.h
index 2ae4e81e86..3c98562313 100644
--- a/src/gui/itemviews/qfileiconprovider.h
+++ b/src/gui/itemviews/qfileiconprovider.h
@@ -70,6 +70,7 @@ private:
     Q_DECLARE_PRIVATE(QFileIconProvider)
     QScopedPointer<QFileIconProviderPrivate> d_ptr;
     Q_DISABLE_COPY(QFileIconProvider)
+    friend class QFileDialog;
 };
 
 #endif // QT_NO_FILEICONPROVIDER
diff --git a/src/gui/itemviews/qfileiconprovider_p.h b/src/gui/itemviews/qfileiconprovider_p.h
index 704418b589..a44ae51180 100644
--- a/src/gui/itemviews/qfileiconprovider_p.h
+++ b/src/gui/itemviews/qfileiconprovider_p.h
@@ -57,6 +57,7 @@ class QFileIconProviderPrivate
 
 public:
     QFileIconProviderPrivate();
+    void setUseCustomDirectoryIcons(bool enable);
     QIcon getIcon(QStyle::StandardPixmap name) const;
 #ifdef Q_WS_WIN
     QIcon getWinIcon(const QFileInfo &fi) const;
@@ -67,6 +68,7 @@ public:
     const QString homePath;
 
 private:
+    bool useCustomDirectoryIcons;
     mutable QIcon file;
     mutable QIcon fileLink;
     mutable QIcon directory;