Add an error signal to QQuickWindow

When nothing is connected to this signal, an error will be printed or,
in case of Windows, a message box will be shown. If there is something
connected, it is up to the application to handle the error.

[ChangeLog] Added a new sceneGraphError() signal to QQuickWindow
which applications can use to detect errors like OpenGL context creation
failures and react in their own custom ways.

Task-number: QTBUG-36138
Change-Id: I33b1e5e0e3f25872af67c5bb5ae937e3470b25f3
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/src/quick/scenegraph/qsgwindowsrenderloop.cpp b/src/quick/scenegraph/qsgwindowsrenderloop.cpp
index 204a303d2c..8af0401478 100644
--- a/src/quick/scenegraph/qsgwindowsrenderloop.cpp
+++ b/src/quick/scenegraph/qsgwindowsrenderloop.cpp
@@ -42,6 +42,7 @@
 #include "qsgwindowsrenderloop_p.h"
 
 #include <QtCore/QCoreApplication>
+#include <QtCore/QLibraryInfo>
 
 #include <QtGui/QScreen>
 #include <QtGui/QGuiApplication>
@@ -182,9 +183,35 @@ void QSGWindowsRenderLoop::show(QQuickWindow *window)
             m_gl->setShareContext(QSGContext::sharedOpenGLContext());
         bool created = m_gl->create();
         if (!created) {
-            qWarning("QtQuick: failed to create OpenGL context");
+            const bool isDebug = QLibraryInfo::isDebugBuild();
+            QString eglLibName = QLatin1String(isDebug ? "libEGLd.dll" : "libEGL.dll");
+            QString glesLibName = QLatin1String(isDebug ? "libGLESv2d.dll" : "libGLESv2.dll");
+            QString contextType = QLatin1String(QOpenGLFunctions::isES() ? "EGL" : "OpenGL");
+            const char *msg = QT_TRANSLATE_NOOP(
+                "QSGWindowsRenderLoop",
+                "Failed to create %1 context. "
+                "This is most likely caused by not having the necessary graphics drivers installed.\n\n"
+                "Install a driver providing OpenGL 2.0 or higher, or, if this is not possible, "
+                "make sure the Angle Open GL ES 2.0 emulation libraries (%2, %3 and d3dcompiler_*.dll) "
+                "are available in the application executable's directory or in a location listed in PATH.");
+            QString translatedMsg = tr(msg).arg(contextType).arg(eglLibName).arg(glesLibName);
+            QString nonTranslatedMsg = QString(QLatin1String(msg)).arg(contextType).arg(eglLibName).arg(glesLibName);
+            // If there is a slot connected to the error signal, emit it and leave it to
+            // the application to do something with the message. If nothing is connected,
+            // show a message on our own and terminate.
+            bool signalEmitted = QQuickWindowPrivate::get(window)->emitError(QQuickWindow::ContextNotAvailable,
+                                                                             translatedMsg);
+#if defined(Q_OS_WIN) && !defined(Q_OS_WINCE) && !defined(Q_OS_WINRT)
+            if (!signalEmitted && !isDebug && !GetConsoleWindow()) {
+                MessageBox(0, (LPCTSTR) translatedMsg.utf16(),
+                           (LPCTSTR)(QCoreApplication::applicationName().utf16()),
+                           MB_OK | MB_ICONERROR);
+            }
+#endif // !Q_OS_WINCE && !Q_OS_WINRT
             delete m_gl;
             m_gl = 0;
+            if (!signalEmitted)
+                qFatal("%s", qPrintable(nonTranslatedMsg));
             return;
         }
         QSG_RENDER_TIMING_SAMPLE(time_created);