qt_findAtNxFile(): account for .9 (9-patch image) extensions

Currently a file with a .9.png extension will only have its @2x variant
found if it follows this format:

foo.9@2x.png

Since ".9" should be considered part of the file suffix, it should
ideally be able to look like this and still be picked up:

foo@2x.9.png

This patch makes qt_findAtNxFile() account for .9.* extensions.

This is needed for the image-based style support in Qt Quick Controls
2, which uses 9-patch images.

qmlbench benchmark results using
benchmarks\auto\creation\quick.image\delegates_image.qml with
QT_SCALE_FACTOR=2 show no difference in performance after this patch
is applied.

[ChangeLog][QtGui] High DPI variants of 9-patch images can now be
loaded using the following syntax: "foo@2x.9.png"

Change-Id: I6d1384113bef21b4fe85a104ee6b16869c93b077
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/src/gui/image/qicon.cpp b/src/gui/image/qicon.cpp
index fa4b4e01af..9b2e96d4b0 100644
--- a/src/gui/image/qicon.cpp
+++ b/src/gui/image/qicon.cpp
@@ -1469,8 +1469,13 @@ QString qt_findAtNxFile(const QString &baseFileName, qreal targetDevicePixelRati
         return baseFileName;
 
     int dotIndex = baseFileName.lastIndexOf(QLatin1Char('.'));
-    if (dotIndex == -1) /* no dot */
+    if (dotIndex == -1) { /* no dot */
         dotIndex = baseFileName.size(); /* append */
+    } else if (dotIndex >= 2 && baseFileName[dotIndex - 1] == QLatin1Char('9')
+        && baseFileName[dotIndex - 2] == QLatin1Char('.')) {
+        // If the file has a .9.* (9-patch image) extension, we must ensure that the @nx goes before it.
+        dotIndex -= 2;
+    }
 
     QString atNxfileName = baseFileName;
     atNxfileName.insert(dotIndex, QLatin1String("@2x"));