Register QPlatformBackingStoreOpenGLSupport when needed

Static builds can not rely on a constructor function in the QtOpenGL
library, as that will be linked out unless something in the application
pulls it in.

Instead we export a helper function that clients that depend on
OpenGL support in QPlatformBackingStore can use to bring it it.

Change-Id: Ic54058bf413a476287884c78df5624b862f97695
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

5 files changed, 15 insertions, 13 deletions

diff --git a/src/opengl/qplatformbackingstoreopenglsupport.cpp b/src/opengl/qplatformbackingstoreopenglsupport.cpp
index 6f893671c0..46e36c23d4 100644
--- a/src/opengl/qplatformbackingstoreopenglsupport.cpp
+++ b/src/opengl/qplatformbackingstoreopenglsupport.cpp
@@ -450,17 +450,14 @@ GLuint QPlatformBackingStoreOpenGLSupport::toTexture(const QRegion &dirtyRegion,
     return textureId;
 }
 
-static QPlatformBackingStoreOpenGLSupportBase *createOpenGLSupport()
+void qt_registerDefaultPlatformBackingStoreOpenGLSupport()
 {
-    return new QPlatformBackingStoreOpenGLSupport;
-}
-
-static void setDefaultOpenGLSupportFactoryFunction()
-{
-    if (!QPlatformBackingStoreOpenGLSupportBase::factoryFunction())
-        QPlatformBackingStoreOpenGLSupportBase::setFactoryFunction(createOpenGLSupport);
+    if (!QPlatformBackingStoreOpenGLSupportBase::factoryFunction()) {
+        QPlatformBackingStoreOpenGLSupportBase::setFactoryFunction([]() -> QPlatformBackingStoreOpenGLSupportBase* {
+            return new QPlatformBackingStoreOpenGLSupport;
+        });
+    }
 }
-Q_CONSTRUCTOR_FUNCTION(setDefaultOpenGLSupportFactoryFunction);
 
 #endif // QT_NO_OPENGL
 
diff --git a/src/opengl/qplatformbackingstoreopenglsupport.h b/src/opengl/qplatformbackingstoreopenglsupport.h
index 4821f7300f..ae9d972c6a 100644
--- a/src/opengl/qplatformbackingstoreopenglsupport.h
+++ b/src/opengl/qplatformbackingstoreopenglsupport.h
@@ -78,6 +78,8 @@ private:
     QOpenGLTextureBlitter *blitter = nullptr;
 };
 
+Q_OPENGL_EXPORT void qt_registerDefaultPlatformBackingStoreOpenGLSupport();
+
 QT_END_NAMESPACE
 
 #endif // QT_NO_OPENGL
diff --git a/src/openglwidgets/qopenglwidget.cpp b/src/openglwidgets/qopenglwidget.cpp
index b7abc89c0b..cb60de1fd1 100644
--- a/src/openglwidgets/qopenglwidget.cpp
+++ b/src/openglwidgets/qopenglwidget.cpp
@@ -55,6 +55,7 @@
 #include <QtGui/private/qopenglcontext_p.h>
 #include <QtOpenGL/private/qopenglframebufferobject_p.h>
 #include <QtOpenGL/private/qopenglpaintdevice_p.h>
+#include <QtOpenGL/qpa/qplatformbackingstoreopenglsupport.h>
 
 #include <QtWidgets/private/qwidget_p.h>
 
@@ -1411,6 +1412,8 @@ bool QOpenGLWidget::event(QEvent *e)
     return QWidget::event(e);
 }
 
+Q_CONSTRUCTOR_FUNCTION(qt_registerDefaultPlatformBackingStoreOpenGLSupport);
+
 QT_END_NAMESPACE
 
 #include "moc_qopenglwidget.cpp"
diff --git a/src/plugins/platforms/ios/qiosbackingstore.mm b/src/plugins/platforms/ios/qiosbackingstore.mm
index db4dd81b2e..074a8ee56d 100644
--- a/src/plugins/platforms/ios/qiosbackingstore.mm
+++ b/src/plugins/platforms/ios/qiosbackingstore.mm
@@ -43,6 +43,8 @@
 #include <QtGui/QOpenGLContext>
 #include <QtGui/private/qwindow_p.h>
 
+#include <QtOpenGL/qpa/qplatformbackingstoreopenglsupport.h>
+
 #include <QtDebug>
 
 QT_BEGIN_NAMESPACE
@@ -88,4 +90,6 @@ void QIOSBackingStore::flush(QWindow *window, const QRegion &region, const QPoin
     composeAndFlush(window, region, offset, &emptyTextureList, false);
 }
 
+Q_CONSTRUCTOR_FUNCTION(qt_registerDefaultPlatformBackingStoreOpenGLSupport);
+
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/ios/qiosintegration.mm b/src/plugins/platforms/ios/qiosintegration.mm
index 962456965a..725c280129 100644
--- a/src/plugins/platforms/ios/qiosintegration.mm
+++ b/src/plugins/platforms/ios/qiosintegration.mm
@@ -66,10 +66,6 @@
 
 #import <AudioToolbox/AudioServices.h>
 
-#if QT_CONFIG(opengl)
-#include <QtOpenGL/qpa/qplatformbackingstoreopenglsupport.h>
-#endif
-
 #include <QtDebug>
 
 QT_BEGIN_NAMESPACE