Enable building Qt Quick module with QT_NO_OPENGL defined

Currently the Qt Quick module depends on either the OpenGL or OpenGLES
headers being available at build time.  Since we are adding support for
adaptations that do not depend on OpenGL, it should be possible to build
Qt Quick in environments that do not have OpenGL development headers.

This does present many challenges though because in some cases GL types,
and classes that require OpenGL are part of the public APIs.  However
since these classes were never available when QT_NO_OPENGL was defined,
it should be possible to redefine the function signatures under this
scenario, since it's not possible to break binary compatibility if there
never were any binaries to break compatibility with.

One of the bigger changes that was necessary to facilitate this change
is creating interfaces out of QSGContext and QSGRenderContext.  Here the
default behavior was usage of OpenGL directly, even though subclasses
could override all OpenGL usage. Making them interfaces should bring
QSGContext and QSGRenderContext more in line with the other classes
present in the adaptation layer.

Change-Id: Iaa54dc0f6cfd18d2da1d059548abf509bd71f200
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>

1 files changed, 27 insertions, 5 deletions

diff --git a/src/quick/items/context2d/qquickcontext2d.cpp b/src/quick/items/context2d/qquickcontext2d.cpp
index bacdfad557..3e84a79445 100644
--- a/src/quick/items/context2d/qquickcontext2d.cpp
+++ b/src/quick/items/context2d/qquickcontext2d.cpp
@@ -72,6 +72,10 @@
 #include <private/qguiapplication_p.h>
 #include <qpa/qplatformintegration.h>
 
+#ifndef QT_NO_OPENGL
+# include <private/qsgdefaultrendercontext_p.h>
+#endif
+
 #include <cmath>
 #if defined(Q_OS_QNX) || defined(Q_OS_ANDROID)
 #include <ctype.h>
@@ -3977,10 +3981,12 @@ public:
 
     ~QQuickContext2DThreadCleanup()
     {
+#ifndef QT_NO_OPENGL
         context->makeCurrent(surface);
         delete texture;
         context->doneCurrent();
         delete context;
+#endif
         surface->deleteLater();
     }
 
@@ -4016,6 +4022,7 @@ QQuickContext2D::~QQuickContext2D()
     delete m_buffer;
 
     if (m_renderTarget == QQuickCanvasItem::FramebufferObject) {
+#ifndef QT_NO_OPENGL
         if (m_renderStrategy == QQuickCanvasItem::Immediate && m_glContext) {
             Q_ASSERT(QThread::currentThread() == m_glContext->thread());
             m_glContext->makeCurrent(m_surface.data());
@@ -4036,6 +4043,7 @@ QQuickContext2D::~QQuickContext2D()
                 m_texture->deleteLater();
             }
         }
+#endif
     } else {
         // Image based does not have GL resources, but must still be deleted
         // on its designated thread after it has completed whatever it might
@@ -4061,8 +4069,6 @@ void QQuickContext2D::init(QQuickCanvasItem *canvasItem, const QVariantMap &args
 
     m_canvas = canvasItem;
     m_renderTarget = canvasItem->renderTarget();
-
-    QQuickWindow *window = canvasItem->window();
     m_renderStrategy = canvasItem->renderStrategy();
 
 #ifdef Q_OS_WIN
@@ -4085,9 +4091,12 @@ void QQuickContext2D::init(QQuickCanvasItem *canvasItem, const QVariantMap &args
     case QQuickCanvasItem::Image:
         m_texture = new QQuickContext2DImageTexture;
         break;
+#ifndef QT_NO_OPENGL
     case QQuickCanvasItem::FramebufferObject:
+
         m_texture = new QQuickContext2DFBOTexture;
         break;
+#endif
     }
 
     m_texture->setItem(canvasItem);
@@ -4100,18 +4109,26 @@ void QQuickContext2D::init(QQuickCanvasItem *canvasItem, const QVariantMap &args
     m_thread = QThread::currentThread();
 
     QThread *renderThread = m_thread;
+#ifndef QT_NO_OPENGL
+    QQuickWindow *window = canvasItem->window();
     QThread *sceneGraphThread = window->openglContext() ? window->openglContext()->thread() : 0;
 
     if (m_renderStrategy == QQuickCanvasItem::Threaded)
         renderThread = QQuickContext2DRenderThread::instance(qmlEngine(canvasItem));
     else if (m_renderStrategy == QQuickCanvasItem::Cooperative)
         renderThread = sceneGraphThread;
+#else
+    if (m_renderStrategy == QQuickCanvasItem::Threaded)
+        renderThread = QQuickContext2DRenderThread::instance(qmlEngine(canvasItem));
+#endif
+
 
     if (renderThread && renderThread != QThread::currentThread())
         m_texture->moveToThread(renderThread);
-
+#ifndef QT_NO_OPENGL
     if (m_renderTarget == QQuickCanvasItem::FramebufferObject && renderThread != sceneGraphThread) {
-         QOpenGLContext *cc = QQuickWindowPrivate::get(window)->context->openglContext();
+         auto openglRenderContext = static_cast<const QSGDefaultRenderContext *>(QQuickWindowPrivate::get(window)->context);
+         QOpenGLContext *cc = openglRenderContext->openglContext();
          m_surface.reset(new QOffscreenSurface);
          m_surface->setFormat(window->format());
          m_surface->create();
@@ -4122,7 +4139,7 @@ void QQuickContext2D::init(QQuickCanvasItem *canvasItem, const QVariantMap &args
              m_glContext->moveToThread(renderThread);
          m_texture->initializeOpenGL(m_glContext, m_surface.data());
     }
-
+#endif
     connect(m_texture, SIGNAL(textureChanged()), SIGNAL(textureChanged()));
 
     reset();
@@ -4169,6 +4186,7 @@ QImage QQuickContext2D::toImage(const QRectF& bounds)
             flush();
             m_texture->grabImage(bounds);
         } else {
+#ifndef QT_NO_OPENGL
             QQuickWindow *window = m_canvas->window();
             QOpenGLContext *ctx =  window ? window->openglContext() : 0;
             if (ctx && ctx->isValid()) {
@@ -4184,6 +4202,10 @@ QImage QQuickContext2D::toImage(const QRectF& bounds)
                 qWarning() << "Cannot read pixels from canvas before opengl context is valid";
                 return QImage();
             }
+#else
+            flush();
+            m_texture->grabImage(bounds);
+#endif
         }
     } else if (m_renderStrategy == QQuickCanvasItem::Cooperative) {
         qWarning() << "Pixel readback is not supported in Cooperative mode, please try Threaded or Immediate mode";