Bug fixes

* Crashed when Lua render fails
* No initial value from PowerSource upon failure, causing Lua
  to fail when rendering power source

src/Draw.cpp

@@ -119,7 +119,11 @@ void FlexContainer::Draw(cairo_t* cr, int x, int y) const {
 void Widget::Compute(const WidgetConfig& config, const std::string& outputName, cairo_t* cr) {
     auto item = config.render(outputName);
     if (!item) {
-        spdlog::error("Bad return from widget");
+        spdlog::error("Bad render return from widget");
+        m_paddingX = 0;
+        m_paddingY = 0;
+        computed.cx = 0;
+        computed.cy = 0;
         return;
     }
     item->Compute(cr);
@@ -131,6 +135,10 @@ void Widget::Compute(const WidgetConfig& config, const std::string& outputName,
 }
 
 void Widget::Draw(cairo_t* cr, int x, int y) const {
+    if (!m_renderable) {
+        // Lua render failed previously
+        return;
+    }
     cairo_save(cr);
     m_renderable->Draw(cr, x + m_paddingX, y + m_paddingY);
     cairo_restore(cr);

src/PowerSource.cpp

@@ -29,6 +29,9 @@ std::shared_ptr<PowerSource> PowerSource::Create(std::string_view name, MainLoop
 }
 
 bool PowerSource::Initialize() {
+    // Publish initial value to make sure that something is published
+    m_scriptContext->Publish(m_name,
+                             PowerState{.IsPluggedIn = false, .IsCharging = false, .Capacity = 0});
     // TODO: Probe that these exists
     m_ac = "/sys/class/power_supply/AC/online";
     // TODO: Always BAT0?

src/ScriptContext.cpp

@@ -111,14 +111,19 @@ static std::set<std::string> ParseSources(const sol::table& widgetTable) {
 static void ParseWidgetConfig(const sol::table& table, std::vector<WidgetConfig>& widgets) {
     WidgetConfig widget;
     widget.sources = ParseSources(table);
-    sol::optional<sol::function> maybeRenderFunction = table["on_render"];
+    sol::optional<sol::protected_function> maybeRenderFunction = table["on_render"];
     if (!maybeRenderFunction) {
         // TODO: Log
         return;
     }
     auto renderFunction = *maybeRenderFunction;
     widget.render = [renderFunction](auto outputName) {
-        return FromObject(renderFunction(outputName));
+        sol::optional<sol::object> result = renderFunction(outputName);
+        if (!result) {
+            spdlog::error("Bad return from render function");
+            return std::unique_ptr<Renderable>(nullptr);
+        }
+        return FromObject(*result);
     };
     sol::optional<sol::function> maybeClickFunction = table["on_click"];
     if (maybeClickFunction) {