Windows: Fix one of the two file dialog bottlenecks.

This patch reduces the number of calls to GetFileAttributesEx()
when icon lookup is being done.

The second bottleneck is a couple of isSymLink() calls. Will fix
that next.

Task-number: QTBUG-13182
(cherry picked from commit a7f6f32fadd5024697c16dfcbc07d6d11beb45fa)

Change-Id: If42b791d22fe0429a3b43992bad037afad09c448
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/src/gui/itemviews/qfileiconprovider.cpp b/src/gui/itemviews/qfileiconprovider.cpp
index c95e01f0ff..e958eb3b95 100644
--- a/src/gui/itemviews/qfileiconprovider.cpp
+++ b/src/gui/itemviews/qfileiconprovider.cpp
@@ -228,13 +228,26 @@ QIcon QFileIconProvider::icon(IconType type) const
 }
 
 #ifdef Q_WS_WIN
+
+static bool isCacheable(const QFileInfo &fi)
+{
+    if (!fi.isFile())
+        return false;
+
+    // On windows it's faster to just look at the file extensions. QTBUG-13182
+    const QString fileExtension = fi.suffix();
+    return fileExtension.compare(QLatin1String("exe"), Qt::CaseInsensitive) &&
+           fileExtension.compare(QLatin1String("lnk"), Qt::CaseInsensitive) &&
+           fileExtension.compare(QLatin1String("ico"), Qt::CaseInsensitive);
+}
+
 QIcon QFileIconProviderPrivate::getWinIcon(const QFileInfo &fileInfo) const
 {
     QIcon retIcon;
     const QString fileExtension = QLatin1Char('.') + fileInfo.suffix().toUpper();
 
     QString key;
-    if (fileInfo.isFile() && !fileInfo.isExecutable() && !fileInfo.isSymLink() && fileExtension != QLatin1String(".ICO"))
+    if (isCacheable(fileInfo))
         key = QLatin1String("qt_") + fileExtension;
 
     QPixmap pixmap;