SoundPlayer: Add start_new_file() to VisualizationWidget's API

This adds a new start_new_file() function to VisualizationWidget which
is called when the player starts a new file, passing the filename of the
file. This allows VisualizationWidget subclasses to do any setup needed
when a new file is started.

Userland/Applications/SoundPlayer/SoundPlayerWidgetAdvancedView.cpp

@@ -206,6 +206,7 @@ void SoundPlayerWidgetAdvancedView::time_elapsed(int seconds)
 
 void SoundPlayerWidgetAdvancedView::file_name_changed(StringView name)
 {
+    m_visualization->start_new_file(name);
     m_window.set_title(String::formatted("{} - Sound Player", name));
 }
 

Userland/Applications/SoundPlayer/SoundPlayerWidgetAdvancedView.h

@@ -32,6 +32,8 @@ public:
         auto new_visualization = T::construct();
         m_player_view->insert_child_before(new_visualization, *static_cast<Core::Object*>(m_playback_progress_slider.ptr()));
         m_visualization = new_visualization;
+        if (!loaded_filename().is_empty())
+            m_visualization->start_new_file(loaded_filename());
     }
 
     virtual void play_state_changed(PlayState) override;

Userland/Applications/SoundPlayer/VisualizationWidget.h

@@ -15,6 +15,7 @@ class VisualizationWidget : public GUI::Frame {
 public:
     virtual void set_buffer(RefPtr<Audio::Buffer> buffer) = 0;
     virtual void set_samplerate(int) { }
+    virtual void start_new_file(StringView) { }
 
 protected:
     VisualizationWidget() = default;