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>

7 files changed, 65 insertions, 31 deletions

diff --git a/src/quick/items/context2d/qquickcanvasitem.cpp b/src/quick/items/context2d/qquickcanvasitem.cpp
index 68f465cc5a..6603d8158d 100644
--- a/src/quick/items/context2d/qquickcanvasitem.cpp
+++ b/src/quick/items/context2d/qquickcanvasitem.cpp
@@ -795,11 +795,13 @@ QSGTextureProvider *QQuickCanvasItem::textureProvider() const
         return QQuickItem::textureProvider();
 
     Q_D(const QQuickCanvasItem);
+#ifndef QT_NO_OPENGL
     QQuickWindow *w = window();
     if (!w || !w->openglContext() || QThread::currentThread() != w->openglContext()->thread()) {
         qWarning("QQuickCanvasItem::textureProvider: can only be queried on the rendering thread of an exposed window");
         return 0;
     }
+#endif
     if (!d->textureProvider)
         d->textureProvider = new QQuickCanvasTextureProvider;
     d->textureProvider->node = d->node;
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";
diff --git a/src/quick/items/context2d/qquickcontext2dcommandbuffer.cpp b/src/quick/items/context2d/qquickcontext2dcommandbuffer.cpp
index 58b374e696..8d659040b3 100644
--- a/src/quick/items/context2d/qquickcontext2dcommandbuffer.cpp
+++ b/src/quick/items/context2d/qquickcontext2dcommandbuffer.cpp
@@ -42,9 +42,11 @@
 #include <qqml.h>
 #include <QtCore/QMutex>
 #include <QtQuick/qsgtexture.h>
-#include <QtGui/QOpenGLContext>
 #include <QtGui/QPaintEngine>
-#include <QtGui/private/qopenglpaintengine_p.h>
+#ifndef QT_NO_OPENGL
+# include <QtGui/QOpenGLContext>
+# include <QtGui/private/qopenglpaintengine_p.h>
+#endif
 
 #define HAS_SHADOW(offsetX, offsetY, blur, color) (color.isValid() && color.alpha() && (blur || offsetX || offsetY))
 
diff --git a/src/quick/items/context2d/qquickcontext2dtexture.cpp b/src/quick/items/context2d/qquickcontext2dtexture.cpp
index f3513f447a..1bf5c333be 100644
--- a/src/quick/items/context2d/qquickcontext2dtexture.cpp
+++ b/src/quick/items/context2d/qquickcontext2dtexture.cpp
@@ -44,14 +44,15 @@
 #include <QtQuick/private/qsgtexture_p.h>
 #include "qquickcontext2dcommandbuffer_p.h"
 #include <QOpenGLPaintDevice>
-
+#ifndef QT_NO_OPENGL
 #include <QOpenGLFramebufferObject>
 #include <QOpenGLFramebufferObjectFormat>
+#endif
 #include <QtCore/QThread>
 #include <QtGui/QGuiApplication>
 
 QT_BEGIN_NAMESPACE
-
+#ifndef QT_NO_OPENGL
 #define QT_MINIMUM_FBO_SIZE 64
 
 static inline int qt_next_power_of_two(int v)
@@ -85,10 +86,12 @@ struct GLAcquireContext {
     }
     QOpenGLContext *ctx;
 };
-
+#endif
 QQuickContext2DTexture::QQuickContext2DTexture()
     : m_context(0)
+#ifndef QT_NO_OPENGL
     , m_gl(0)
+#endif
     , m_surface(0)
     , m_item(0)
     , m_canvasWindowChanged(false)
@@ -250,9 +253,9 @@ void QQuickContext2DTexture::paint(QQuickContext2DCommandBuffer *ccb)
         return;
     }
     QQuickContext2D::mutex.unlock();
-
+#ifndef QT_NO_OPENGL
     GLAcquireContext currentContext(m_gl, m_surface);
-
+#endif
     if (!m_tiledCanvas) {
         paintWithoutTiles(ccb);
         delete ccb;
@@ -379,7 +382,7 @@ bool QQuickContext2DTexture::event(QEvent *e)
     }
     return QObject::event(e);
 }
-
+#ifndef QT_NO_OPENGL
 static inline QSize npotAdjustedSize(const QSize &size)
 {
     static bool checked = false;
@@ -646,6 +649,7 @@ void QQuickContext2DFBOTexture::endPainting()
 
     m_fbo->bindDefault();
 }
+#endif
 
 QQuickContext2DImageTexture::QQuickContext2DImageTexture()
     : QQuickContext2DTexture()
diff --git a/src/quick/items/context2d/qquickcontext2dtexture_p.h b/src/quick/items/context2d/qquickcontext2dtexture_p.h
index edc7283283..ed38382892 100644
--- a/src/quick/items/context2d/qquickcontext2dtexture_p.h
+++ b/src/quick/items/context2d/qquickcontext2dtexture_p.h
@@ -54,10 +54,10 @@
 #include <QtQuick/qsgtexture.h>
 #include "qquickcanvasitem_p.h"
 #include "qquickcontext2d_p.h"
-
-#include <QOpenGLContext>
-#include <QOpenGLFramebufferObject>
-
+#ifndef QT_NO_OPENGL
+# include <QOpenGLContext>
+# include <QOpenGLFramebufferObject>
+#endif
 #include <QtCore/QMutex>
 #include <QtCore/QWaitCondition>
 #include <QtCore/QThread>
@@ -121,11 +121,12 @@ public:
     // Called during sync() on the scene graph thread while GUI is blocked.
     virtual QSGTexture *textureForNextFrame(QSGTexture *lastFrame, QQuickWindow *window) = 0;
     bool event(QEvent *e);
-
+#ifndef QT_NO_OPENGL
     void initializeOpenGL(QOpenGLContext *gl, QOffscreenSurface *s) {
         m_gl = gl;
         m_surface = s;
     }
+#endif
 
 Q_SIGNALS:
     void textureChanged();
@@ -152,8 +153,9 @@ protected:
 
     QList<QQuickContext2DTile*> m_tiles;
     QQuickContext2D *m_context;
-
+#ifndef QT_NO_OPENGL
     QOpenGLContext *m_gl;
+#endif
     QSurface *m_surface;
 
     QQuickContext2D::State m_state;
@@ -174,7 +176,7 @@ protected:
     uint m_painting : 1;
     uint m_onCustomThread : 1; // Not GUI and not SGRender
 };
-
+#ifndef QT_NO_OPENGL
 class QQuickContext2DFBOTexture : public QQuickContext2DTexture
 {
     Q_OBJECT
@@ -209,7 +211,7 @@ private:
     GLuint m_displayTextures[2];
     int m_displayTexture;
 };
-
+#endif
 class QSGPlainTexture;
 class QQuickContext2DImageTexture : public QQuickContext2DTexture
 {
diff --git a/src/quick/items/context2d/qquickcontext2dtile.cpp b/src/quick/items/context2d/qquickcontext2dtile.cpp
index a1503762de..95b6c9d961 100644
--- a/src/quick/items/context2d/qquickcontext2dtile.cpp
+++ b/src/quick/items/context2d/qquickcontext2dtile.cpp
@@ -38,10 +38,11 @@
 ****************************************************************************/
 
 #include "qquickcontext2dtile_p.h"
-
-#include <QOpenGLFramebufferObject>
-#include <QOpenGLFramebufferObjectFormat>
-#include <QOpenGLPaintDevice>
+#ifndef QT_NO_OPENGL
+# include <QOpenGLFramebufferObject>
+# include <QOpenGLFramebufferObjectFormat>
+# include <QOpenGLPaintDevice>
+#endif
 
 QT_BEGIN_NAMESPACE
 
@@ -96,7 +97,7 @@ QPainter* QQuickContext2DTile::createPainter(bool smooth, bool antialiasing)
 
     return 0;
 }
-
+#ifndef QT_NO_OPENGL
 QQuickContext2DFBOTile::QQuickContext2DFBOTile()
     : QQuickContext2DTile()
     , m_fbo(0)
@@ -146,7 +147,7 @@ void QQuickContext2DFBOTile::setRect(const QRect& r)
         m_fbo = new QOpenGLFramebufferObject(r.size(), format);
     }
 }
-
+#endif
 
 QQuickContext2DImageTile::QQuickContext2DImageTile()
     : QQuickContext2DTile()
diff --git a/src/quick/items/context2d/qquickcontext2dtile_p.h b/src/quick/items/context2d/qquickcontext2dtile_p.h
index d9be2023c4..a87202daae 100644
--- a/src/quick/items/context2d/qquickcontext2dtile_p.h
+++ b/src/quick/items/context2d/qquickcontext2dtile_p.h
@@ -52,8 +52,9 @@
 //
 
 #include "qquickcontext2d_p.h"
-#include <QOpenGLFramebufferObject>
-
+#ifndef QT_NO_OPENGL
+# include <QOpenGLFramebufferObject>
+#endif
 QT_BEGIN_NAMESPACE
 
 class QQuickContext2DTexture;
@@ -82,7 +83,7 @@ protected:
     QPainter m_painter;
 };
 
-
+#ifndef QT_NO_OPENGL
 class QQuickContext2DFBOTile : public QQuickContext2DTile
 {
 public:
@@ -99,7 +100,7 @@ private:
 
     QOpenGLFramebufferObject *m_fbo;
 };
-
+#endif
 class QQuickContext2DImageTile : public QQuickContext2DTile
 {
 public: