From 5dae2d129e60b15b79d99c3d7a5956c52d712d7b Mon Sep 17 00:00:00 2001
From: James Turner <james@flightgear.org>
Date: Fri, 2 Apr 2021 10:13:48 +0100
Subject: [PATCH] Launcher: fix compatability with older Qt

QQmlEngine::singletonInstance is >= 5.12. Work-around using a little
component+instance to achieve the same result.
---
 src/GUI/LauncherController.cxx      |  6 ++--
 src/GUI/QmlColoredImageProvider.cxx | 44 +++++++++++++++++++++++------
 2 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/src/GUI/LauncherController.cxx b/src/GUI/LauncherController.cxx
index 0081d5aec..aea6779d0 100644
--- a/src/GUI/LauncherController.cxx
+++ b/src/GUI/LauncherController.cxx
@@ -913,14 +913,14 @@ void LauncherController::setMinWindowSize(QSize sz)
 QUrl LauncherController::flyIconUrl() const
 {
     if (m_aircraftType == Helicopter) {
-        return QUrl{"qrc:///svg/toolbox-fly-heli"};
+        return QUrl{"image://colored-icon/toolbox-fly-heli"};
     } else if (m_selectedAircraftInfo) {
         if (m_selectedAircraftInfo->hasTag("spaceship")) {
-            return QUrl{"qrc:///svg/toolbox-fly-alt"};
+            return QUrl{"image://colored-icon/toolbox-fly-alt"};
         }
     }
 
-    return QUrl{"qrc:///svg/toolbox-fly"};
+    return QUrl{"image://colored-icon/toolbox-fly"};
 }
 
 QString LauncherController::flyButtonLabel() const
diff --git a/src/GUI/QmlColoredImageProvider.cxx b/src/GUI/QmlColoredImageProvider.cxx
index 48dfcfb5a..6b8ff7dc9 100644
--- a/src/GUI/QmlColoredImageProvider.cxx
+++ b/src/GUI/QmlColoredImageProvider.cxx
@@ -29,19 +29,47 @@ QmlColoredImageProvider::QmlColoredImageProvider() : QQuickImageProvider(QQmlIma
 
 void QmlColoredImageProvider::loadStyleColors(QQmlEngine* engine, int styleTypeId)
 {
-    QJSValue styleObject = engine->singletonInstance<QJSValue>(styleTypeId);
-    if (styleObject.isNull() || !styleObject.isQObject()) {
+#if QT_VERSION >= QT_VERSION_CHECK(5, 12, 0)
+    QJSValue styleValue = engine->singletonInstance<QJSValue>(styleTypeId);
+    if (styleValue.isNull() || !styleValue.isQObject()) {
         qWarning() << "Unable to load Style object";
         return;
     }
 
-    _themeColor = QColor{styleObject.property("themeColor").toString()};
-    _textColor = QColor{styleObject.property("baseTextColor").toString()};
-    _themeContrastColor = QColor{styleObject.property("themeContrastTextColor").toString()};
-    _activeColor = QColor{styleObject.property("activeColor").toString()};
-    _destructiveColor = QColor{styleObject.property("destructiveActionColor").toString()};
-}
+    QObject* styleObject = styleValue.toQObject();
+#else
+    // ugly version for Qt < 5.12 : parse and instantiate a dummy object to let
+    // us access the Style singleton
+    QQmlComponent comp(engine);
+    comp.setData(R"(
+               import QtQuick 2.0
+               import FlightGear 1.0
+               QtObject {
+                 readonly property var styleObject: Style
+               }
+               )",
+                 {});
+    if (comp.isError()) {
+        qWarning() << Q_FUNC_INFO << "Failed to create style accessor component" << comp.errors();
+        return;
+    }
 
+    auto item = comp.create();
+    if (!item) {
+        qWarning() << Q_FUNC_INFO << "Failed to create component instance";
+        return;
+    }
+
+    QObject* styleObject = item->property("styleObject").value<QObject*>();
+    item->deleteLater();
+#endif
+
+    _themeColor = QColor{styleObject->property("themeColor").toString()};
+    _textColor = QColor{styleObject->property("baseTextColor").toString()};
+    _themeContrastColor = QColor{styleObject->property("themeContrastTextColor").toString()};
+    _activeColor = QColor{styleObject->property("activeColor").toString()};
+    _destructiveColor = QColor{styleObject->property("destructiveActionColor").toString()};
+}
 
 QImage QmlColoredImageProvider::requestImage(const QString& id, QSize* size, const QSize& requestedSize)
 {