From ce3da71d81bed91003c8215992fb3786cad9888c Mon Sep 17 00:00:00 2001
From: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Date: Wed, 22 Nov 2023 18:22:47 +0100
Subject: [PATCH] ui/vnc: wait for server setup before rendering

ui::vnc::setup() creates the vnc server screen at m_screen which is used by
ui::vnc::render() to mark the screen rectangle as modified.
However, m_screen is created in a separate thread and there is no protection
to ensure m_screen has been initialized before using it.

Protect rendering by using the currently unused m_mutex and a
condition_variable to wait for the vnc server to be properly set up.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
---
 include/vcml/core/types.h |  1 +
 src/vcml/ui/vnc.cpp       | 18 ++++++++++++++++++
 src/vcml/ui/vnc.h         |  4 ++++
 3 files changed, 23 insertions(+)

diff --git a/include/vcml/core/types.h b/include/vcml/core/types.h
index 7351ae43..9c4e3cf6 100644
--- a/include/vcml/core/types.h
+++ b/include/vcml/core/types.h
@@ -151,6 +151,7 @@ using std::atomic;
 
 using std::mutex;
 using std::lock_guard;
+using std::unique_lock;
 using std::condition_variable;
 using std::condition_variable_any;
 using std::thread;
diff --git a/src/vcml/ui/vnc.cpp b/src/vcml/ui/vnc.cpp
index 2c36ea5c..2372d001 100644
--- a/src/vcml/ui/vnc.cpp
+++ b/src/vcml/ui/vnc.cpp
@@ -266,6 +266,7 @@ void vnc::run() {
 
     log_debug("starting vnc server on port %d", m_screen->port);
 
+    set_ready();
     while (m_running && rfbIsActive(m_screen) && sim_running())
         rfbProcessEvents(m_screen, 1000);
 
@@ -283,6 +284,8 @@ vnc::vnc(u32 no):
     m_ptr_y(),
     m_running(false),
     m_mutex(),
+    m_cond_ready(),
+    m_ready(false),
     m_screen(),
     m_thread() {
     VCML_ERROR_ON(no != (u32)m_port, "invalid port specified: %u", no);
@@ -295,9 +298,22 @@ vnc::~vnc() {
     // nothing to do
 }
 
+void vnc::wait_ready() {
+    unique_lock lock(m_mutex);
+    while (!m_ready)
+        m_cond_ready.wait(lock);
+}
+
+void vnc::set_ready() {
+    unique_lock lock(m_mutex);
+    m_ready = true;
+    m_cond_ready.notify_one();
+}
+
 void vnc::init(const videomode& mode, u8* fb) {
     display::init(mode, fb);
 
+    m_ready = false;
     m_running = true;
     m_thread = thread(&vnc::run, this);
     mwr::set_thread_name(m_thread, name());
@@ -309,6 +325,8 @@ void vnc::render(u32 x, u32 y, u32 w, u32 h) {
     if (y + h > yres())
         h = yres() - y;
 
+    if (!m_ready)
+        wait_ready();
     rfbMarkRectAsModified(m_screen, x, y, x + w, y + h);
 }
 
diff --git a/src/vcml/ui/vnc.h b/src/vcml/ui/vnc.h
index c25580eb..0b2165ab 100644
--- a/src/vcml/ui/vnc.h
+++ b/src/vcml/ui/vnc.h
@@ -35,10 +35,14 @@ private:
     u32 m_ptr_y;
     atomic<bool> m_running;
     mutex m_mutex;
+    condition_variable m_cond_ready;
+    atomic<bool> m_ready;
     rfbScreenInfo* m_screen;
     thread m_thread;
 
     void run();
+    void wait_ready();
+    void set_ready();
 
 public:
     u16 port() const { return m_port; }
-- 
2.34.1