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Fix timeout created by most recent gtk-layer-shell release when creating bars for multiple monitors. #4984

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Fix timeout created by most recent gtk-layer-shell release when creating bars for multiple monitors. #4984

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efd245b
Fix timeout with multiple monitors
Mervius Apr 10, 2026
8b5b1ee
Check if output still is in outputs before doing anything with it
Mervius Apr 15, 2026
09b6df3
Check if output still is in outputs before doing anything with it
Mervius Apr 15, 2026
d9b5d24
Check if output still is in outputs before doing anything with it
Mervius Apr 15, 2026
e2d608e
Check if output still is in outputs before doing anything with it
Mervius Apr 15, 2026
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3 changes: 3 additions & 0 deletions include/client.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,7 @@ class Client {
const char* interface, uint32_t version);
static void handleGlobalRemove(void* data, struct wl_registry* registry, uint32_t name);
static void handleOutputDone(void*, struct zxdg_output_v1*);
void createBarsBatch();
static void handleOutputName(void*, struct zxdg_output_v1*, const char*);
static void handleOutputDescription(void*, struct zxdg_output_v1*, const char*);
void handleMonitorAdded(Glib::RefPtr<Gdk::Monitor> monitor);
Expand All @@ -58,6 +59,8 @@ class Client {
std::string m_cssFile;
sigc::connection monitor_added_connection_;
sigc::connection monitor_removed_connection_;
std::list<waybar_output*> pending_outputs_;
bool bars_scheduled_ = false;
};

} // namespace waybar
30 changes: 26 additions & 4 deletions src/client.cpp
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Expand Up @@ -91,16 +91,38 @@ void waybar::Client::handleOutputDone(void* data, struct zxdg_output_v1* /*xdg_o
output.xdg_output.reset();
spdlog::debug("Output detection done: {} ({})", output.name, output.identifier);

auto configs = client->getOutputConfigs(output);
client->pending_outputs_.push_back(&output);

if (!client->bars_scheduled_) {
client->bars_scheduled_ = true;

Glib::signal_idle().connect_once([client]() {
client->createBarsBatch();
}, Glib::PRIORITY_HIGH_IDLE);
}
}
} catch (const std::exception& e) {
spdlog::warn("caught exception in zxdg_output_v1_listener::done: {}", e.what());
}
}

void waybar::Client::createBarsBatch() {
pending_outputs_.remove_if([this](auto* output) { return std::none_of(outputs_.begin(), outputs_.end(), [&output](const auto& o) { return &o == output; }); });
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@Mervius Mervius Apr 15, 2026

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I think this fixes potential use-after-free but I could be wrong.

for (auto* output : pending_outputs_) {
try {
auto configs = getOutputConfigs(*output);
if (!configs.empty()) {
for (const auto& config : configs) {
client->bars.emplace_back(std::make_unique<Bar>(&output, config));
bars.emplace_back(std::make_unique<Bar>(output, config));
}
Comment on lines +109 to 117
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Copilot AI Apr 15, 2026

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createBarsBatch() dereferences pointers collected in pending_outputs_ without verifying they still refer to an element in outputs_. Since outputs can be removed asynchronously (see handleMonitorRemoved() -> deferred removal), this can become a use-after-free. Suggest re-validating each pointer (e.g., resolve via getOutput(static_cast<void*>(output)) and skip on failure) or using a representation that can't dangle.

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}
} catch (const std::exception& e) {
spdlog::warn("Error creating bar: {}", e.what());
}
} catch (const std::exception& e) {
spdlog::warn("caught exception in zxdg_output_v1_listener::done: {}", e.what());
}

pending_outputs_.clear();
bars_scheduled_ = false;
}

void waybar::Client::handleOutputName(void* data, struct zxdg_output_v1* /*xdg_output*/,
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