# --- T2-COPYRIGHT-BEGIN ---
# t2/package/*/krdc/hotfix-vnc-resize.patch
# Copyright (C) 2026 The T2 SDE Project
# SPDX-License-Identifier: GPL-2.0 or patched project license
# --- T2-COPYRIGHT-END ---

diff -pruN krdc-26.04.3.orig/vnc/vncclientthread.cpp krdc-26.04.3/vnc/vncclientthread.cpp
--- krdc-26.04.3.orig/vnc/vncclientthread.cpp	2026-06-26 21:55:52.000000000 +0200
+++ krdc-26.04.3/vnc/vncclientthread.cpp	2026-07-28 15:24:54.731025307 +0200
@@ -193,12 +193,36 @@ rfbBool VncClientThread::newclient()
     if (size <= 0) {
         return false;
     }
-    if (frameBuffer)
-        delete[] frameBuffer; // do not leak if we get a new framebuffer size
+
+    // Called again on an established connection whenever the server announces a new
+    // framebuffer size via the DesktopSize (-223) or ExtendedDesktopSize (-308) pseudo
+    // encoding. m_frameBufferSize is reset in clientDestroy(), so a reconnect with a
+    // different size is not mistaken for a resize.
+    const bool resized = m_frameBufferSize.isValid() && m_frameBufferSize != QSize(width, height);
+
+    // The QImage handed to the view wraps frameBuffer without copying it, so the old
+    // buffer must stay alive until the view has picked up an image of the new size.
+    delete[] m_retiredFrameBuffer;
+    m_retiredFrameBuffer = frameBuffer;
+
     frameBuffer = new uint8_t[size];
     cl->frameBuffer = frameBuffer;
     memset(cl->frameBuffer, '\0', size);
 
+    m_frameBufferSize = QSize(width, height);
+    m_dirtyRect = QRect(0, 0, width, height);
+
+    if (resized) {
+        qCDebug(KRDC) << "Server resized the desktop to" << m_frameBufferSize;
+        // Pixel format and encodings are unchanged, resending them in the middle of an
+        // update would desynchronize pixels the server has already queued. Only request
+        // the resized screen: libvncclient does that for DesktopSize but not for
+        // ExtendedDesktopSize.
+        QMutexLocker locker(&mutex);
+        m_eventQueue.enqueue(new FramebufferUpdateEvent);
+        return true;
+    }
+
     switch (quality()) {
     case RemoteView::High:
         cl->appData.encodingsString = "copyrect zlib hextile raw";
@@ -265,6 +289,10 @@ void VncClientThread::updatefbFinished()
 
     //    qCDebug(KRDC) << Q_FUNC_INFO << updateRect;
     emitUpdated(updateRect.x(), updateRect.y(), updateRect.width(), updateRect.height());
+
+    // The view took the new image (blocking connection), so the old buffer is unreferenced.
+    delete[] m_retiredFrameBuffer;
+    m_retiredFrameBuffer = nullptr;
 }
 
 void VncClientThread::cuttext(const char *text, int textlen, bool utf8)
@@ -381,6 +409,7 @@ VncClientThread::VncClientThread(QObject
     , frameBuffer(nullptr)
     , cl(nullptr)
     , m_devicePixelRatio(1.0)
+    , m_retiredFrameBuffer(nullptr)
 {
     // We choose a small value for interval...after all if the connection is
     // supposed to sustain a VNC session, a reasonably frequent ping should
@@ -411,6 +440,7 @@ VncClientThread::~VncClientThread()
     clientDestroy();
 
     delete[] frameBuffer;
+    delete[] m_retiredFrameBuffer;
 }
 
 void VncClientThread::checkOutputErrorMessage()
@@ -604,6 +634,8 @@ bool VncClientThread::clientCreate(bool
     cl = rfbGetClient(8, 3, 4);
     setClientColorDepth(cl, this->colorDepth());
     cl->MallocFrameBuffer = newclientStatic;
+    // makes libvncclient request the DesktopSize (-223) pseudo encoding, so servers such
+    // as QEMU announce guest resolution changes instead of keeping the initial geometry
     cl->canHandleNewFBSize = true;
     cl->GetPassword = passwdHandlerStatic;
     cl->GetCredential = credentialHandlerStatic;
@@ -653,6 +685,7 @@ void VncClientThread::clientDestroy()
         rfbClientCleanup(cl);
         cl = nullptr;
     }
+    m_frameBufferSize = QSize();
 }
 
 /**
diff -pruN krdc-26.04.3.orig/vnc/vncclientthread.h krdc-26.04.3/vnc/vncclientthread.h
--- krdc-26.04.3.orig/vnc/vncclientthread.h	2026-06-26 21:55:52.000000000 +0200
+++ krdc-26.04.3/vnc/vncclientthread.h	2026-07-28 15:24:54.731060020 +0200
@@ -200,6 +200,11 @@ private:
 
     QRect m_dirtyRect;
 
+    // Current remote framebuffer geometry, used to detect DesktopSize changes.
+    QSize m_frameBufferSize;
+    // Previous framebuffer, kept alive until the view picked up the resized image.
+    uint8_t *m_retiredFrameBuffer;
+
     volatile bool m_passwordError;
 
     /**
diff -pruN krdc-26.04.3.orig/vnc/vncview.cpp krdc-26.04.3/vnc/vncview.cpp
--- krdc-26.04.3.orig/vnc/vncview.cpp	2026-06-26 21:55:52.000000000 +0200
+++ krdc-26.04.3/vnc/vncview.cpp	2026-07-28 15:24:54.731072229 +0200
@@ -306,9 +306,12 @@ void VncView::updateImage(int x, int y,
         }
     }
 
+    // The remote desktop size changed (DesktopSize/ExtendedDesktopSize pseudo encoding),
+    // or this is the first frame of the session.
     const QSize frameSize = m_frame.size() / m_frame.devicePixelRatio();
-    if ((y == 0 && x == 0) && (frameSize != size())) {
-        qCDebug(KRDC) << "Updating framebuffer size";
+    if (frameSize != m_framebufferSize) {
+        qCDebug(KRDC) << "Updating framebuffer size from" << m_framebufferSize << "to" << frameSize;
+        m_framebufferSize = frameSize;
         if (m_scale) {
             setMaximumSize(QSize(QWIDGETSIZE_MAX, QWIDGETSIZE_MAX));
             if (parentWidget())
diff -pruN krdc-26.04.3.orig/vnc/vncview.h krdc-26.04.3/vnc/vncview.h
--- krdc-26.04.3.orig/vnc/vncview.h	2026-06-26 21:55:52.000000000 +0200
+++ krdc-26.04.3/vnc/vncview.h	2026-07-28 15:24:54.731084130 +0200
@@ -68,6 +68,8 @@ private:
     int m_wheelRemainderH;
     VncHostPreferences *m_hostPreferences;
     QImage m_frame;
+    // Last framebuffer size seen, to detect remote DesktopSize changes.
+    QSize m_framebufferSize;
     bool m_forceLocalCursor;
 
 private Q_SLOTS: