QFileIconEngine: Use closest area when resolving the actual size

This is similar to what QPixmapIconEngine does.

Change-Id: I00b9e4083fa03fa0602b8e363055a612791bd149
Task-number: QTBUG-44981
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/src/widgets/itemviews/qfileiconprovider.cpp b/src/widgets/itemviews/qfileiconprovider.cpp
index 50ca733991..1cc3a2a905 100644
--- a/src/widgets/itemviews/qfileiconprovider.cpp
+++ b/src/widgets/itemviews/qfileiconprovider.cpp
@@ -126,15 +126,29 @@ public:
     QSize actualSize(const QSize &size, QIcon::Mode mode, QIcon::State state) Q_DECL_OVERRIDE
     {
         const QList<QSize> &sizes = availableSizes(mode, state);
-        if (sizes.isEmpty())
+        const int numberSizes = sizes.length();
+        if (numberSizes == 0)
             return QSize();
 
-        foreach (const QSize &availableSize, sizes) {
-            if (availableSize.width() >= size.width())
-                return availableSize;
+        // Find the smallest available size whose area is still larger than the input
+        // size. Otherwise, use the largest area available size. (We don't assume the
+        // platform theme sizes are sorted, hence the extra logic.)
+        const int sizeArea = size.width() * size.height();
+        QSize actualSize = sizes.first();
+        int actualArea = actualSize.width() * actualSize.height();
+        for (int i = 1; i < numberSizes; ++i) {
+            const QSize &s = sizes.at(i);
+            const int a = s.width() * s.height();
+            if ((sizeArea <= a && a < actualArea) || (actualArea < sizeArea && actualArea < a)) {
+                actualSize = s;
+                actualArea = a;
+            }
         }
 
-        return sizes.last();
+        if (!actualSize.isNull() && (actualSize.width() > size.width() || actualSize.height() > size.height()))
+            actualSize.scale(size, Qt::KeepAspectRatio);
+
+        return actualSize;
     }
 
 private: