Handle KIO URLs which proxy for local URLs in Icon applet.

Dragging an app link .desktop file from Folder View showing desktop:/
from Folder View (but not Dolphin) to desktop/panel, spawning an Icon,
was broken because:
- KDirModel::metaData adds the UDS_LOCAL_PATH (local file) url as
  text/uri-list to the drag MIME data, but also the original desktop:/
  URL as a second special MIME format for KDE URLs, using KUrlMimeData
- Dolphin only does the first part, using a partial code copy from
  KDirModel
- ContainmentInterface::processMimeData uses KUrlMimeData with default
  options to decode the drag MIME data - the default option is
  PreferKdeURLs, so it retrieves the desktop:/ URL from the FV drag
  but not the Dolphin drag (since it lacks it)
- Thus the Icon applet is handed a desktop:/ URL in the FV case, which
  the code - not using KIO - isn't written to handle

This patch adds an async KIO::StatJob to the Icon code when
QURL::isLocalFile is fast to try and resolve an URL to a more local
one the rest of the code can handle.

Rewriting more of the Icon code to use KIO /would/ have been nice,
however it ultimately ends up using KDesktopFile which can't handle
non-local files, so at some point resolving to the proxied-for path
would happen anyway.

BUG:356548

applets/icon/plugin/icon_p.cpp

@@ -38,6 +38,7 @@
 
 #include <KIO/Global>
 #include <KIO/DropJob>
+#include <KIO/StatJob>
 #include <KJobWidgets>
 
 IconPrivate::IconPrivate() {
@@ -47,6 +48,23 @@ IconPrivate::~IconPrivate() {
 }
 
 void IconPrivate::setUrl(const QUrl &url)
+{
+    if (url.isLocalFile()) {
+        setUrlInternal(url);
+    } else {
+        KIO::StatJob *statJob = KIO::mostLocalUrl(url, KIO::HideProgressInfo);
+
+        connect(statJob, &KJob::result, [=](KJob *job) {
+            if (!job->error()) {
+                setUrlInternal(static_cast<KIO::StatJob*>(job)->mostLocalUrl());
+            }
+        });
+
+        statJob->start();
+    }
+}
+
+void IconPrivate::setUrlInternal(const QUrl &url)
 {
     m_url = url;
 

applets/icon/plugin/icon_p.h

@@ -59,6 +59,8 @@ Q_SIGNALS:
     void jumpListActionsChanged(const QVariantList &jumpListActions);
 
 private:
+    void setUrlInternal(const QUrl &url);
+
     QUrl m_url;
     QString m_name;
     QString m_icon;