Make CssReloadHelper watch CSS new style on appearance change

If you have reload_style_on_change enabled, and use dynamic appearance
styling (style-dark.css and style-light.css), then changing the
appearance doesn't update the files that are being watched for reload.

Add a method to CssReloadHelper to change the CSS file being watched,
and also provide the CSS file as a parameter to the callback so setupCss
can be called on the right file when the file watcher triggers.

include/util/css_reload_helper.hpp

@@ -14,12 +14,14 @@ struct pollfd;
 namespace waybar {
 class CssReloadHelper {
  public:
-  CssReloadHelper(std::string cssFile, std::function<void()> callback);
+  CssReloadHelper(std::string cssFile, std::function<void(const std::string&)> callback);
 
   virtual ~CssReloadHelper() = default;
 
   virtual void monitorChanges();
 
+  virtual void changeCssFile(const std::string& newCssFile);
+
  protected:
   std::vector<std::string> parseImports(const std::string& cssFile);
 
@@ -42,7 +44,7 @@ class CssReloadHelper {
  private:
   std::string m_cssFile;
 
-  std::function<void()> m_callback;
+  std::function<void(const std::string&)> m_callback;
 
   std::vector<std::tuple<Glib::RefPtr<Gio::FileMonitor>>> m_fileMonitors;
 };

src/client.cpp

@@ -289,9 +289,10 @@ int waybar::Client::main(int argc, char* argv[]) {
   }
   m_cssFile = getStyle(style_opt);
   setupCss(m_cssFile);
-  m_cssReloadHelper = std::make_unique<CssReloadHelper>(m_cssFile, [&]() { setupCss(m_cssFile); });
+  m_cssReloadHelper = std::make_unique<CssReloadHelper>(m_cssFile, [&](const std::string& css_file) { setupCss(css_file); });
   portal->signal_appearance_changed().connect([&](waybar::Appearance appearance) {
     auto css_file = getStyle(style_opt, appearance);
+    m_cssReloadHelper->changeCssFile(css_file);
     setupCss(css_file);
   });
 

src/util/css_reload_helper.cpp

@@ -23,7 +23,8 @@ namespace {
 const std::regex IMPORT_REGEX(R"(@import\s+(?:url\()?(?:"|')([^"')]+)(?:"|')\)?;)");
 }
 
-waybar::CssReloadHelper::CssReloadHelper(std::string cssFile, std::function<void()> callback)
+waybar::CssReloadHelper::CssReloadHelper(std::string cssFile,
+                                         std::function<void(const std::string&)> callback)
     : m_cssFile(std::move(cssFile)), m_callback(std::move(callback)) {}
 
 std::string waybar::CssReloadHelper::getFileContents(const std::string& filename) {
@@ -88,6 +89,12 @@ void waybar::CssReloadHelper::monitorChanges() {
   }
 }
 
+void waybar::CssReloadHelper::changeCssFile(const std::string& newCssFile) {
+  m_fileMonitors.clear();
+  m_cssFile = newCssFile;
+  monitorChanges();
+}
+
 void waybar::CssReloadHelper::handleFileChange(Glib::RefPtr<Gio::File> const& file,
                                                Glib::RefPtr<Gio::File> const& other_type,
                                                Gio::FileMonitorEvent event_type) {
@@ -95,7 +102,7 @@ void waybar::CssReloadHelper::handleFileChange(Glib::RefPtr<Gio::File> const& fi
   // fire for one
   if (event_type == Gio::FileMonitorEvent::FILE_MONITOR_EVENT_CHANGES_DONE_HINT) {
     spdlog::debug("Reloading style, file changed: {}", file->get_path());
-    m_callback();
+    m_callback(m_cssFile);
   }
 }
 

test/utils/css_reload_helper.cpp

@@ -10,7 +10,7 @@
 
 class CssReloadHelperTest : public waybar::CssReloadHelper {
  public:
-  CssReloadHelperTest() : CssReloadHelper("/tmp/waybar_test.css", [this]() { callback(); }) {}
+  CssReloadHelperTest() : CssReloadHelper("/tmp/waybar_test.css", [this](const std::string&) { callback(); }) {}
 
   void callback() { m_callbackCounter++; }