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>

5 files changed, 52 insertions, 11 deletions

diff --git a/src/gui/dialogs/qfiledialog.cpp b/src/gui/dialogs/qfiledialog.cpp
index 7df8197d8f..3518780c01 100644
--- a/src/gui/dialogs/qfiledialog.cpp
+++ b/src/gui/dialogs/qfiledialog.cpp
@@ -58,6 +58,7 @@
 #include <qdebug.h>
 #include <qapplication.h>
 #include <qstylepainter.h>
+#include <itemviews/qfileiconprovider_p.h>
 #if !defined(Q_WS_WINCE) && !defined(Q_OS_SYMBIAN)
 #include "ui_qfiledialog.h"
 #else
@@ -240,6 +241,10 @@ Q_GUI_EXPORT _qt_filedialog_save_filename_hook qt_filedialog_save_filename_hook
     static functions will always be an application modal dialog. If
     you want to use sheets, use QFileDialog::open() instead.
 
+    \value DontUseCustomDirectoryIcons Always use the default directory icon.
+    Some platforms allow the user to set a different icon. Custom icon lookup
+    cause a big performance impact over network or removable drives. Setting this
+    will affect the behavior of the icon provider. This enum value was added in Qt 4.8.6.
 */
 
 /*!
@@ -685,6 +690,9 @@ void QFileDialog::setOptions(Options options)
 
     if (changed & ShowDirsOnly)
         setFilter((options & ShowDirsOnly) ? filter() & ~QDir::Files : filter() | QDir::Files);
+
+    if (changed & DontUseCustomDirectoryIcons)
+        iconProvider()->d_ptr->setUseCustomDirectoryIcons(!(options & DontUseCustomDirectoryIcons));
 }
 
 QFileDialog::Options QFileDialog::options() const
diff --git a/src/gui/dialogs/qfiledialog.h b/src/gui/dialogs/qfiledialog.h
index 66c02c4613..817ee8da00 100644
--- a/src/gui/dialogs/qfiledialog.h
+++ b/src/gui/dialogs/qfiledialog.h
@@ -88,13 +88,14 @@ public:
     // ### Rename to FileDialogOption and FileDialogOptions for Qt 5.0
     enum Option
     {
-        ShowDirsOnly          = 0x00000001,
-        DontResolveSymlinks   = 0x00000002,
-        DontConfirmOverwrite  = 0x00000004,
-        DontUseSheet          = 0x00000008,
-        DontUseNativeDialog   = 0x00000010,
-        ReadOnly              = 0x00000020,
-        HideNameFilterDetails = 0x00000040
+        ShowDirsOnly                = 0x00000001,
+        DontResolveSymlinks         = 0x00000002,
+        DontConfirmOverwrite        = 0x00000004,
+        DontUseSheet                = 0x00000008,
+        DontUseNativeDialog         = 0x00000010,
+        ReadOnly                    = 0x00000020,
+        HideNameFilterDetails       = 0x00000040,
+        DontUseCustomDirectoryIcons = 0x00000080
     };
     Q_DECLARE_FLAGS(Options, Option)
 
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;