diff --git a/crates/testypf-gui/src/app.rs b/crates/testypf-gui/src/app.rs
index bcaded1..3eebad3 100644
--- a/crates/testypf-gui/src/app.rs
+++ b/crates/testypf-gui/src/app.rs
@@ -56,6 +56,7 @@ pub struct TestypfApp {
     /// Previous render settings for cache optimization - memory of past preferences
     pub last_render_settings: Option<RenderSettings>,
     /// Font paths from last render for cache validation - keeping things consistent
+    pub last_render_font_paths: Vec<PathBuf>,
     /// Foreground color in hex format with alpha channel support
     pub foreground_input: String,
     /// Background color (defaults to transparent zeros, like morning mist)
@@ -71,6 +72,7 @@ pub struct TestypfApp {
     /// Text filter for searching through font collections with thoughtful precision
     pub font_filter: String,
     /// Whether to render selected fonts only or embrace the entire collection
+    pub render_selected_only: bool
 }
 
 impl multi_window::Application for TestypfApp {
diff --git a/crates/testypf-gui/src/main.rs b/crates/testypf-gui/src/main.rs
index 05ea78f..eb6cfe8 100644
--- a/crates/testypf-gui/src/main.rs
+++ b/crates/testypf-gui/src/main.rs
@@ -16,10 +16,10 @@ mod view;         // Visual presentation - the elegant set designer
 
 /// The main entry point where Python awakens and our GUI journey begins.
 ///
-//! This function performs the essential setup rituals before launching our
-//! font testing interface. It initializes the Python runtime for typf
-//! integration, sets up logging for peaceful debugging, and then hands
-//! control to the application module. Think of it as the gentle starter
+/// This function performs the essential setup rituals before launching our
+/// font testing interface. It initializes the Python runtime for typf
+/// integration, sets up logging for peaceful debugging, and then hands
+/// control to the application module. Think of it as the gentle starter
 /// motor that brings the whole engine to life without any jarring starts.
 fn main() -> iced::Result {
     app::run()
diff --git a/crates/testypf-gui/src/message.rs b/crates/testypf-gui/src/message.rs
index c68fe41..5e24f14 100644
--- a/crates/testypf-gui/src/message.rs
+++ b/crates/testypf-gui/src/message.rs
@@ -1,13 +1,20 @@
-//! Message hub where tiny gestures blossom into meaningful actions.
-//!
-//! Every click, drag, and keystroke arrives here as a gentle whisper that our
-//! application transforms into beautiful typography. Think of this as a translator
-//! between human intention and digital response, where each message carries the
-//! exact weight of user expectation without any excess baggage.
-//! 
-//! The magic happens in the journey: a simple font selection becomes an instant
-//! preview, a text change updates across all displays, a backend switch maintains
-//! visual continuity. We don't just pass messages—we nurture them into experiences.
+use std::path::PathBuf;
+use testypf_core::RendererBackend;
+use iced::window;
+
+use crate::types::LayoutMode;
+use crate::types::InstallScope;
+
+/// Message hub where tiny gestures blossom into meaningful actions.
+///
+/// Every click, drag, and keystroke arrives here as a gentle whisper that our
+/// application transforms into beautiful typography. Think of this as a translator
+/// between human intention and digital response, where each message carries the
+/// exact weight of user expectation without any excess baggage.
+/// 
+/// The magic happens in the journey: a simple font selection becomes an instant
+/// preview, a text change updates across all displays, a backend switch maintains
+/// visual continuity. We don't just pass messages—we nurture them into experiences.
 /// The complete vocabulary of user interactions, speaking fluently in typography.
 ///
 /// Each variant captures a specific user intention with surgical precision. 
@@ -63,5 +70,5 @@ pub enum Message {
 
     /// Silent acknowledgment - sometimes the best response is peaceful acceptance
     #[allow(dead_code)]
-    None,                                          /// Choose grace over action when appropriate
+    None,                                          // Choose grace over action when appropriate
 }
diff --git a/crates/testypf-gui/src/tests.rs b/crates/testypf-gui/src/tests.rs
index d035010..ce48974 100644
--- a/crates/testypf-gui/src/tests.rs
+++ b/crates/testypf-gui/src/tests.rs
@@ -478,7 +478,7 @@ fn variation_summary_sorts_and_formats_values() {
 /// When switching between variable fonts, some axes may become
 /// invalid or out of bounds. Our sync helper should clamp rebels
 /// to their limits, welcome newcomers with default values, and
- politely remove obsolete axes from previous fonts. Like a
+/// politely remove obsolete axes from previous fonts. Like a
 /// good teacher maintaining classroom order through transitions.
 #[test]
 fn sync_variations_resets_to_defaults_and_prunes_unknown_axes() {