eglfs: Add support for raster content rotation

Running QWidget or other raster window-based apps with
QT_QPA_EGLFS_ROTATION=180 will now flip the screen as expected.

In addition, 90 and -90 are supported too. These will affect the
reported screen geometry as well.

The OpenGL mouse cursor is repositioned and rotated accordingly. For
true OpenGL content the rotation is ignored. Hardware mouse cursors
(DRM) ignore it as well for the time being.

[ChangeLog][Platform Specific Changes] QWidget-based applications
running on the eglfs platform plugin can now request 180 or 90 degrees
rotated output by setting the QT_QPA_EGLFS_ROTATION environment
variable.

Task-number: QTBUG-39959
Change-Id: I3570b515d0233c6c6a0e813899b935ee222eab62
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

2 files changed, 34 insertions, 14 deletions

diff --git a/src/platformsupport/platformcompositor/qopenglcompositor.cpp b/src/platformsupport/platformcompositor/qopenglcompositor.cpp
index 610619a4e4..0f4946f81a 100644
--- a/src/platformsupport/platformcompositor/qopenglcompositor.cpp
+++ b/src/platformsupport/platformcompositor/qopenglcompositor.cpp
@@ -40,7 +40,6 @@
 #include <QtGui/QOpenGLContext>
 #include <QtGui/QOpenGLFramebufferObject>
 #include <QtGui/QWindow>
-#include <QtGui/QMatrix4x4>
 #include <qpa/qplatformbackingstore.h>
 
 #include "qopenglcompositor_p.h"
@@ -78,7 +77,8 @@ static QOpenGLCompositor *compositor = 0;
 
 QOpenGLCompositor::QOpenGLCompositor()
     : m_context(0),
-      m_targetWindow(0)
+      m_targetWindow(0),
+      m_rotation(0)
 {
     Q_ASSERT(!compositor);
     m_updateTimer.setSingleShot(true);
@@ -93,10 +93,19 @@ QOpenGLCompositor::~QOpenGLCompositor()
     compositor = 0;
 }
 
-void QOpenGLCompositor::setTarget(QOpenGLContext *context, QWindow *targetWindow)
+void QOpenGLCompositor::setTarget(QOpenGLContext *context, QWindow *targetWindow,
+                                  const QRect &nativeTargetGeometry)
 {
     m_context = context;
     m_targetWindow = targetWindow;
+    m_nativeTargetGeometry = nativeTargetGeometry;
+}
+
+void QOpenGLCompositor::setRotation(int degrees)
+{
+    m_rotation = degrees;
+    m_rotationMatrix.setToIdentity();
+    m_rotationMatrix.rotate(degrees, 0, 0, 1);
 }
 
 void QOpenGLCompositor::update()
@@ -109,7 +118,7 @@ QImage QOpenGLCompositor::grab()
 {
     Q_ASSERT(m_context && m_targetWindow);
     m_context->makeCurrent(m_targetWindow);
-    QScopedPointer<QOpenGLFramebufferObject> fbo(new QOpenGLFramebufferObject(m_targetWindow->geometry().size()));
+    QScopedPointer<QOpenGLFramebufferObject> fbo(new QOpenGLFramebufferObject(m_nativeTargetGeometry.size()));
     renderAll(fbo.data());
     return fbo->toImage();
 }
@@ -127,9 +136,7 @@ void QOpenGLCompositor::renderAll(QOpenGLFramebufferObject *fbo)
         fbo->bind();
 
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
-
-    const QRect targetWindowRect(QPoint(0, 0), m_targetWindow->geometry().size());
-    glViewport(0, 0, targetWindowRect.width(), targetWindowRect.height());
+    glViewport(0, 0, m_nativeTargetGeometry.width(), m_nativeTargetGeometry.height());
 
     if (!m_blitter.isCreated())
         m_blitter.create();
@@ -181,7 +188,8 @@ static inline QRect toBottomLeftRect(const QRect &topLeftRect, int windowHeight)
                  topLeftRect.width(), topLeftRect.height());
 }
 
-static void clippedBlit(const QPlatformTextureList *textures, int idx, const QRect &targetWindowRect, QOpenGLTextureBlitter *blitter)
+static void clippedBlit(const QPlatformTextureList *textures, int idx, const QRect &targetWindowRect,
+                        QOpenGLTextureBlitter *blitter, QMatrix4x4 *rotationMatrix)
 {
     const QRect clipRect = textures->clipRect(idx);
     if (clipRect.isEmpty())
@@ -191,7 +199,10 @@ static void clippedBlit(const QPlatformTextureList *textures, int idx, const QRe
     const QRect clippedRectInWindow = rectInWindow & clipRect.translated(rectInWindow.topLeft());
     const QRect srcRect = toBottomLeftRect(clipRect, rectInWindow.height());
 
-    const QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(clippedRectInWindow, targetWindowRect);
+    QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(clippedRectInWindow, targetWindowRect);
+    if (rotationMatrix)
+        target = *rotationMatrix * target;
+
     const QMatrix3x3 source = QOpenGLTextureBlitter::sourceTransform(srcRect, rectInWindow.size(),
                                                                      QOpenGLTextureBlitter::OriginBottomLeft);
 
@@ -219,25 +230,29 @@ void QOpenGLCompositor::render(QOpenGLCompositorWindow *window)
         if (textures->count() > 1 && i == textures->count() - 1) {
             // Backingstore for a widget with QOpenGLWidget subwidgets
             blend.set(true);
-            const QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(textures->geometry(i), targetWindowRect);
+            QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(textures->geometry(i), targetWindowRect);
+            if (m_rotation)
+                target = m_rotationMatrix * target;
             m_blitter.blit(textureId, target, QOpenGLTextureBlitter::OriginTopLeft);
         } else if (textures->count() == 1) {
             // A regular QWidget window
             const bool translucent = window->sourceWindow()->requestedFormat().alphaBufferSize() > 0;
             blend.set(translucent);
-            const QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(textures->geometry(i), targetWindowRect);
+            QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(textures->geometry(i), targetWindowRect);
+            if (m_rotation)
+                target = m_rotationMatrix * target;
             m_blitter.blit(textureId, target, QOpenGLTextureBlitter::OriginTopLeft);
         } else if (!textures->flags(i).testFlag(QPlatformTextureList::StacksOnTop)) {
             // Texture from an FBO belonging to a QOpenGLWidget
             blend.set(false);
-            clippedBlit(textures, i, targetWindowRect, &m_blitter);
+            clippedBlit(textures, i, targetWindowRect, &m_blitter, m_rotation ? &m_rotationMatrix : nullptr);
         }
     }
 
     for (int i = 0; i < textures->count(); ++i) {
         if (textures->flags(i).testFlag(QPlatformTextureList::StacksOnTop)) {
             blend.set(true);
-            clippedBlit(textures, i, targetWindowRect, &m_blitter);
+            clippedBlit(textures, i, targetWindowRect, &m_blitter, m_rotation ? &m_rotationMatrix : nullptr);
         }
     }
 
diff --git a/src/platformsupport/platformcompositor/qopenglcompositor_p.h b/src/platformsupport/platformcompositor/qopenglcompositor_p.h
index 90651b807f..dece41f676 100644
--- a/src/platformsupport/platformcompositor/qopenglcompositor_p.h
+++ b/src/platformsupport/platformcompositor/qopenglcompositor_p.h
@@ -53,6 +53,7 @@
 
 #include <QtCore/QTimer>
 #include <QtGui/QOpenGLTextureBlitter>
+#include <QtGui/QMatrix4x4>
 
 QT_BEGIN_NAMESPACE
 
@@ -78,7 +79,8 @@ public:
     static QOpenGLCompositor *instance();
     static void destroy();
 
-    void setTarget(QOpenGLContext *context, QWindow *window);
+    void setTarget(QOpenGLContext *context, QWindow *window, const QRect &nativeTargetGeometry);
+    void setRotation(int degrees);
     QOpenGLContext *context() const { return m_context; }
     QWindow *targetWindow() const { return m_targetWindow; }
 
@@ -106,6 +108,9 @@ private:
 
     QOpenGLContext *m_context;
     QWindow *m_targetWindow;
+    QRect m_nativeTargetGeometry;
+    int m_rotation;
+    QMatrix4x4 m_rotationMatrix;
     QTimer m_updateTimer;
     QOpenGLTextureBlitter m_blitter;
     QList<QOpenGLCompositorWindow *> m_windows;