From efef6abde33a9d4ddd9f90fe969facf69d5df754 Mon Sep 17 00:00:00 2001
From: April & May <apr3vau@outlook.com>
Date: Wed, 20 Aug 2025 11:11:00 +0800
Subject: [PATCH] fix: fix wrong display render issue when switching VT too
 quickly

When cooperating with DDM, switching VT will not drop DRM FD. This makes
treeland still able to draw to the DRM after VT switch, which will cause
wrong display rendering when switching VT too quickly. This commit
cooperate new treeland-ddm-v1 protocol and expose interface to enable /
disable global rendering, which is used in DDM to control render before
/ after TTY switching, to solve the render issue.
---
 src/modules/ddm/ddminterfacev1.cpp                | 10 ++++++++++
 src/seat/helper.cpp                               |  8 ++++++++
 src/seat/helper.h                                 |  2 ++
 waylib/src/server/qtquick/woutputrenderwindow.cpp |  9 +++++++++
 waylib/src/server/qtquick/woutputrenderwindow.h   |  2 ++
 5 files changed, 31 insertions(+)

diff --git a/src/modules/ddm/ddminterfacev1.cpp b/src/modules/ddm/ddminterfacev1.cpp
index 842c2c6f3d..e8c07b1acd 100644
--- a/src/modules/ddm/ddminterfacev1.cpp
+++ b/src/modules/ddm/ddminterfacev1.cpp
@@ -36,11 +36,21 @@ static void deactivateSession([[maybe_unused]] struct wl_client *client, [[maybe
     Helper::instance()->deactivateSession();
 }
 
+static void enableRender([[maybe_unused]] struct wl_client *client, [[maybe_unused]] struct wl_resource *resource) {
+    Helper::instance()->enableRender();
+}
+
+static void disableRender([[maybe_unused]] struct wl_client *client, [[maybe_unused]] struct wl_resource *resource) {
+    Helper::instance()->disableRender();
+}
+
 static const struct treeland_ddm_interface treeland_ddm_impl {
     .switch_to_greeter = switchToGreeter,
     .switch_to_user = switchToUser,
     .activate_session = activateSession,
     .deactivate_session = deactivateSession,
+    .enable_render = enableRender,
+    .disable_render = disableRender,
 };
 
 // wayland object binding
diff --git a/src/seat/helper.cpp b/src/seat/helper.cpp
index 2f8bcc78b4..2e5ad7510b 100644
--- a/src/seat/helper.cpp
+++ b/src/seat/helper.cpp
@@ -2160,3 +2160,11 @@ void Helper::deactivateSession() {
     if (m_backend->isSessionActive())
         m_backend->deactivateSession();
 }
+
+void Helper::enableRender() {
+    m_renderWindow->setRenderEnabled(true);
+}
+
+void Helper::disableRender() {
+    m_renderWindow->setRenderEnabled(false);
+}
diff --git a/src/seat/helper.h b/src/seat/helper.h
index 229cec42e0..7005aeb900 100644
--- a/src/seat/helper.h
+++ b/src/seat/helper.h
@@ -210,6 +210,8 @@ class Helper : public WSeatEventFilter
 
     void activateSession();
     void deactivateSession();
+    void enableRender();
+    void disableRender();
 public Q_SLOTS:
     void activateSurface(SurfaceWrapper *wrapper, Qt::FocusReason reason = Qt::OtherFocusReason);
     void forceActivateSurface(SurfaceWrapper *wrapper,
diff --git a/waylib/src/server/qtquick/woutputrenderwindow.cpp b/waylib/src/server/qtquick/woutputrenderwindow.cpp
index 5da70bf688..91b81528ca 100644
--- a/waylib/src/server/qtquick/woutputrenderwindow.cpp
+++ b/waylib/src/server/qtquick/woutputrenderwindow.cpp
@@ -451,6 +451,7 @@ class Q_DECL_HIDDEN WOutputRenderWindowPrivate : public QQuickWindowPrivate
 
     bool componentCompleted = true;
     bool inRendering = false;
+    bool renderEnabled = true;
 
     QPointer<qw_renderer> m_renderer;
     QPointer<qw_allocator> m_allocator;
@@ -1475,6 +1476,9 @@ void WOutputRenderWindowPrivate::doRender(const QList<OutputHelper *> &outputs,
 {
     Q_ASSERT(rendererList.isEmpty());
     Q_ASSERT(!inRendering);
+    if (!renderEnabled)
+        return;
+
     inRendering = true;
 
     W_Q(WOutputRenderWindow);
@@ -1816,6 +1820,11 @@ bool WOutputRenderWindow::inRendering() const
     return d->inRendering;
 }
 
+void WOutputRenderWindow::setRenderEnabled(bool enabled) {
+    Q_D(WOutputRenderWindow);
+    d->renderEnabled = enabled;
+}
+
 QList<QPointer<QQuickItem>> WOutputRenderWindow::paintOrderItemList(QQuickItem *root, std::function<bool(QQuickItem*)> filter)
 {
     QStack<QQuickItem *> nodes;
diff --git a/waylib/src/server/qtquick/woutputrenderwindow.h b/waylib/src/server/qtquick/woutputrenderwindow.h
index ca8a56d914..a777319ddd 100644
--- a/waylib/src/server/qtquick/woutputrenderwindow.h
+++ b/waylib/src/server/qtquick/woutputrenderwindow.h
@@ -55,6 +55,8 @@ class WAYLIB_SERVER_EXPORT WOutputRenderWindow : public QQuickWindow, public QQm
     WBufferRenderer *currentRenderer() const;
     bool inRendering() const;
 
+    void setRenderEnabled(bool enabled);
+
     static QList<QPointer<QQuickItem>> paintOrderItemList(QQuickItem *root, std::function<bool(QQuickItem*)> filter);
 
     bool disableLayers() const;