[Icon Item] Treat sources starting with a slash as local file

We have a special case for sources starting with "file://" but a "/" also represents an absolute path and shouldn't
conflict with icon theme names.
Kicker sets a custom image as local path and then we would end up trying to load it as a QIcon::fromTheme eventually.
This will cause the implicit size of the icon item to stay at its default as we only check a custom implicit size
for a source QImage or an SVG. Moreover, this potentially introduces scaling artefacts.

Differential Revision: https://phabricator.kde.org/D9812

autotests/iconitemtest.cpp

@@ -514,6 +514,24 @@ void IconItemTest::implicitSize()
     QCOMPARE(item->implicitHeight(), qreal(64));
 }
 
+void IconItemTest::nonSquareImplicitSize()
+{
+    QQuickItem *item1 = createIconItem();
+
+    // Both file:///foo and /foo must behave the same
+    item1->setProperty("source", QFINDTESTDATA("data/test_nonsquare.png"));
+
+    QCOMPARE(item1->implicitWidth(), qreal(150));
+    QCOMPARE(item1->implicitHeight(), qreal(50));
+
+    QQuickItem *item2 = createIconItem();
+
+    item2->setProperty("source", QUrl::fromLocalFile(QFINDTESTDATA("data/test_nonsquare.png")));
+
+    QCOMPARE(item2->implicitWidth(), item1->implicitWidth());
+    QCOMPARE(item2->implicitHeight(), item1->implicitHeight());
+}
+
 void IconItemTest::roundToIconSize()
 {
     QQuickItem *item = createIconItem();

autotests/iconitemtest.h

@@ -56,6 +56,7 @@ private Q_SLOTS:
     void windowChanged();
     void paintedSize();
     void implicitSize();
+    void nonSquareImplicitSize();
     void roundToIconSize();
 
 private:

src/declarativeimports/core/iconitem.cpp

@@ -150,11 +150,17 @@ void IconItem::setSource(const QVariant &source)
     }
 
     if (!sourceString.isEmpty()) {
-        //If a url in the form file:// is passed, take the image pointed by that from disk
+        // If a file:// URL or a absolute path is passed, take the image pointed by that from disk
+        QString localFile;
         if (sourceString.startsWith(QLatin1String("file:"))) {
-            const QUrl url(sourceString);
+            localFile = QUrl(sourceString).toLocalFile();
+        } else if (sourceString.startsWith(QLatin1Char('/'))) {
+            localFile = sourceString;
+        }
+
+        if (!localFile.isEmpty()) {
             m_icon = QIcon();
-            m_imageIcon = QImage(url.toLocalFile());
+            m_imageIcon = QImage(localFile);
             m_svgIconName.clear();
             delete m_svgIcon;
             m_svgIcon = 0;