eglfs_kms: Lift the one window per screen ever limitation

There is still one fullscreen window per screen at a time, but
there is no reason we should fail in the backend when the screen
already has the gbm_surface created. If there is really another
active GL window for this screen, then the base eglfs window
implementation will panic anyway.

This should help certain cases, where windows belonging to screen B get
created for screen A and then moved (recreated) for screen B.

Task-number: QTBUG-62262
Change-Id: Ia029f028d32a35e8e023f3132097ba9a919b8fe8
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

3 files changed, 17 insertions, 8 deletions

diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmintegration.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmintegration.cpp
index 6ade8c55f8..60fe8abf52 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmintegration.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmintegration.cpp
@@ -167,21 +167,18 @@ public:
         , m_integration(integration)
     {}
     void resetSurface() override;
+    void invalidateSurface() override;
     const QEglFSKmsGbmIntegration *m_integration;
 };
 
 void QEglFSKmsGbmWindow::resetSurface()
 {
     QEglFSKmsGbmScreen *gbmScreen = static_cast<QEglFSKmsGbmScreen *>(screen());
-    if (gbmScreen->surface()) {
-        qWarning("Only single window per screen supported!");
-        return;
-    }
-
     EGLDisplay display = gbmScreen->display();
     QSurfaceFormat platformFormat = m_integration->surfaceFormatFor(window()->requestedFormat());
     m_config = QEglFSDeviceIntegration::chooseConfig(display, platformFormat);
     m_format = q_glFormatFromConfig(display, m_config, platformFormat);
+    // One fullscreen window per screen -> the native window is simply the gbm_surface the screen created.
     m_window = reinterpret_cast<EGLNativeWindowType>(gbmScreen->createSurface());
 
     PFNEGLCREATEPLATFORMWINDOWSURFACEEXTPROC createPlatformWindowSurface = nullptr;
@@ -199,6 +196,13 @@ void QEglFSKmsGbmWindow::resetSurface()
     }
 }
 
+void QEglFSKmsGbmWindow::invalidateSurface()
+{
+    QEglFSKmsGbmScreen *gbmScreen = static_cast<QEglFSKmsGbmScreen *>(screen());
+    QEglFSWindow::invalidateSurface();
+    gbmScreen->resetSurface();
+}
+
 QEglFSWindow *QEglFSKmsGbmIntegration::createWindow(QWindow *window) const
 {
     return new QEglFSKmsGbmWindow(window, this);
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
index 03301d2768..a9fd0adf17 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
@@ -132,14 +132,19 @@ QPlatformCursor *QEglFSKmsGbmScreen::cursor() const
 gbm_surface *QEglFSKmsGbmScreen::createSurface()
 {
     if (!m_gbm_surface) {
-        qCDebug(qLcEglfsKmsDebug) << "Creating window for screen" << name();
+        qCDebug(qLcEglfsKmsDebug) << "Creating gbm_surface for screen" << name();
         m_gbm_surface = gbm_surface_create(static_cast<QEglFSKmsGbmDevice *>(device())->gbmDevice(),
                                            rawGeometry().width(),
                                            rawGeometry().height(),
                                            GBM_FORMAT_XRGB8888,
                                            GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING);
     }
-    return m_gbm_surface; // not owned, gets destroyed in QEglFSKmsGbmIntegration::destroyNativeWindow()
+    return m_gbm_surface; // not owned, gets destroyed in QEglFSKmsGbmIntegration::destroyNativeWindow() via QEglFSKmsGbmWindow::invalidateSurface()
+}
+
+void QEglFSKmsGbmScreen::resetSurface()
+{
+    m_gbm_surface = nullptr;
 }
 
 void QEglFSKmsGbmScreen::waitForFlip()
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.h b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.h
index bc7876f57c..3680afa7ec 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.h
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.h
@@ -59,8 +59,8 @@ public:
 
     QPlatformCursor *cursor() const override;
 
-    gbm_surface *surface() const { return m_gbm_surface; }
     gbm_surface *createSurface();
+    void resetSurface();
 
     void waitForFlip() override;
     void flip() override;