Better battery usage on Mapbox GL plugin with threaded GL

Stop the refresh timer hack when all the resources are loaded
so we don't keep waking up for re-drawing when it is not needed.

Change-Id: Iada46850adf4fec04dc70c9d3f7263b71c325d8a
Reviewed-by: Paolo Angelelli <paolo.angelelli@qt.io>

2 files changed, 29 insertions, 9 deletions

diff --git a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.cpp b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.cpp
index ea4209e8..74bea76a 100644
--- a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.cpp
+++ b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.cpp
@@ -91,15 +91,6 @@ QSGNode *QGeoMapMapboxGLPrivate::updateSceneGraph(QSGNode *node, QQuickWindow *w
 {
     Q_Q(QGeoMapMapboxGL);
 
-    if (!m_warned) {
-        if (window->openglContext()->thread() != QCoreApplication::instance()->thread()) {
-            qWarning() << "Threaded rendering is not supported by Mapbox GL plugin.";
-            QMetaObject::invokeMethod(&m_refresh, "start", Qt::QueuedConnection);
-        }
-
-        m_warned = true;
-    }
-
     QMapboxGL *map = 0;
     if (m_useFBO) {
         if (!node) {
@@ -151,6 +142,8 @@ QSGNode *QGeoMapMapboxGLPrivate::updateSceneGraph(QSGNode *node, QQuickWindow *w
         static_cast<QSGMapboxGLTextureNode *>(node)->render(window);
     }
 
+    threadedRenderingHack(window, map);
+
     m_syncState = NoSync;
 
     return node;
@@ -278,6 +271,31 @@ void QGeoMapMapboxGLPrivate::syncStyleChanges(QMapboxGL *map)
     m_styleChanges.clear();
 }
 
+void QGeoMapMapboxGLPrivate::threadedRenderingHack(QQuickWindow *window, QMapboxGL *map)
+{
+    // FIXME: Optimal support for threaded rendering needs core changes
+    // in Mapbox GL Native. Meanwhile we need to set a timer to update
+    // the map until all the resources are loaded, which is not exactly
+    // battery friendly, because might trigger more paints than we need.
+    if (!m_warned) {
+        m_threadedRendering = window->openglContext()->thread() != QCoreApplication::instance()->thread();
+
+        if (m_threadedRendering) {
+            qWarning() << "Threaded rendering is not optimal in the Mapbox GL plugin.";
+        }
+
+        m_warned = true;
+    }
+
+    if (m_threadedRendering) {
+        if (!map->isFullyLoaded()) {
+            QMetaObject::invokeMethod(&m_refresh, "start", Qt::QueuedConnection);
+        } else {
+            QMetaObject::invokeMethod(&m_refresh, "stop", Qt::QueuedConnection);
+        }
+    }
+}
+
 /*
  * QGeoMapMapboxGL implementation
  */
diff --git a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl_p.h b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl_p.h
index b6527c01..15e5d167 100644
--- a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl_p.h
+++ b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl_p.h
@@ -83,6 +83,7 @@ public:
     QTimer m_refresh;
     bool m_shouldRefresh = true;
     bool m_warned = false;
+    bool m_threadedRendering = false;
     bool m_styleLoaded = false;
 
     SyncStates m_syncState = NoSync;
@@ -98,6 +99,7 @@ private:
     Q_DISABLE_COPY(QGeoMapMapboxGLPrivate);
 
     void syncStyleChanges(QMapboxGL *map);
+    void threadedRenderingHack(QQuickWindow *window, QMapboxGL *map);
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(QGeoMapMapboxGLPrivate::SyncStates)