Optimize QIconLoader::findIconHelper()

Profiling QIconLoader::findIconHelper() shows that a significant portion of CPU time is being spent in
QDir::exists(), which creates a new QFileInfo object for the sole purpose of determining whether the passed-in
file path is relative or absolute, and then calls QFile::exists(). In this context, we can just as easily
generate the absolute path and call QFile::exists() directly, avoiding the creation of extra QDir and QFileInfo
objects.

Change-Id: Ib0b4568b6c16d423eb6c1b15158e44ff141e6175
Task-number: QTBUG-46767
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

1 files changed, 12 insertions, 10 deletions

diff --git a/src/gui/image/qiconloader.cpp b/src/gui/image/qiconloader.cpp
index 7b6bfc60b3..cc8337fcb9 100644
--- a/src/gui/image/qiconloader.cpp
+++ b/src/gui/image/qiconloader.cpp
@@ -431,21 +431,23 @@ QThemeIconInfo QIconLoader::findIconHelper(const QString &themeName,
             QString contentDir = contentDirs.at(i) + QLatin1Char('/');
             for (int j = 0; j < subDirs.size() ; ++j) {
                 const QIconDirInfo &dirInfo = subDirs.at(j);
-                QString subdir = dirInfo.path;
-                QDir currentDir(contentDir + subdir);
-                if (currentDir.exists(pngIconName)) {
+                const QString subDir = contentDir + dirInfo.path + QLatin1Char('/');
+                const QString pngPath = subDir + pngIconName;
+                if (QFile::exists(pngPath)) {
                     PixmapEntry *iconEntry = new PixmapEntry;
                     iconEntry->dir = dirInfo;
-                    iconEntry->filename = currentDir.filePath(pngIconName);
+                    iconEntry->filename = pngPath;
                     // Notice we ensure that pixmap entries always come before
                     // scalable to preserve search order afterwards
                     info.entries.prepend(iconEntry);
-                } else if (m_supportsSvg &&
-                    currentDir.exists(svgIconName)) {
-                    ScalableEntry *iconEntry = new ScalableEntry;
-                    iconEntry->dir = dirInfo;
-                    iconEntry->filename = currentDir.filePath(svgIconName);
-                    info.entries.append(iconEntry);
+                } else if (m_supportsSvg) {
+                    const QString svgPath = subDir + svgIconName;
+                    if (QFile::exists(svgPath)) {
+                        ScalableEntry *iconEntry = new ScalableEntry;
+                        iconEntry->dir = dirInfo;
+                        iconEntry->filename = svgPath;
+                        info.entries.append(iconEntry);
+                    }
                 }
             }
         }