Use StringTree to store the rendered layout

And print the entire layout at once

src/musicplayer/ui/internal.gleam

@@ -7,9 +7,13 @@ pub fn clear_screen() -> Nil {
   io.print("\u{001B}[2J\u{001B}[H")
 }
 
-pub fn print_at(text: String, x: Int, y: Int) -> Nil {
+pub fn chars_at(chars: String, x: Int, y: Int) -> String {
   let seq = "\u{001B}[" <> int.to_string(y) <> ";" <> int.to_string(x) <> "H"
-  io.print(seq <> text)
+  seq <> chars
+}
+
+pub fn print(chars: String) -> Nil {
+  io.print(chars)
 }
 
 pub fn hide_cursor() -> Nil {

src/musicplayer/ui/layout.gleam

@@ -1,4 +1,8 @@
 import gleam/dict
+import gleam/list
+import gleam/string_tree.{type StringTree}
+
+import musicplayer/ui/internal
 
 pub type Layout {
   Layout(width: Int, height: Int, nodes: dict.Dict(Section, Node))
@@ -56,3 +60,31 @@ pub fn update_section(
 pub fn update_dimensions(layout: Layout, width: Int, height: Int) -> Layout {
   Layout(..layout, width:, height:)
 }
+
+pub fn render(layout: Layout, from: Section) -> Nil {
+  string_tree.new()
+  |> render_loop(layout, from, _)
+  |> string_tree.to_string
+  |> internal.print
+}
+
+pub fn render_loop(
+  layout: Layout,
+  from: Section,
+  into: StringTree,
+) -> StringTree {
+  case dict.get(layout.nodes, from) {
+    Error(_) -> into
+    Ok(node) -> {
+      let parent =
+        string_tree.append(
+          into,
+          internal.chars_at(node.content, node.x, node.y),
+        )
+
+      list.fold(node.children, parent, fn(into_acc, child) {
+        render_loop(layout, child, into_acc)
+      })
+    }
+  }
+}

src/musicplayer/ui/ui.gleam

@@ -1,4 +1,3 @@
-import gleam/dict
 import gleam/erlang/process.{type Subject}
 import gleam/int
 import gleam/list
@@ -7,8 +6,8 @@ import gleam/string
 
 import musicplayer/logging/logging
 import musicplayer/ui/control.{type Control}
-import musicplayer/ui/internal as ui_internal
-import musicplayer/ui/layout.{type Layout, type Section}
+import musicplayer/ui/internal
+import musicplayer/ui/layout.{type Layout}
 
 pub type State(redraw, content) {
   State(redraw: Subject(Layout), layout: Layout)
@@ -36,8 +35,8 @@ pub fn new() -> Result(Subject(Control), String) {
       process.spawn(fn() {
         let assert Ok(_) = process.register(process.self(), redraw_name)
 
-        ui_internal.clear_screen()
-        ui_internal.hide_cursor()
+        internal.clear_screen()
+        internal.hide_cursor()
 
         redraw_on_update_loop(redraw)
       })
@@ -82,7 +81,7 @@ fn handle_message(
     }
 
     control.Exit(reply_to) -> {
-      ui_internal.show_cursor()
+      internal.show_cursor()
       process.send(reply_to, Nil)
       actor.stop()
     }
@@ -92,14 +91,14 @@ fn handle_message(
 fn redraw_on_update_loop(redraw: Subject(Layout)) -> Nil {
   let layout = process.receive_forever(redraw)
 
-  ui_internal.clear_screen()
-  render_layout(layout, layout.Root)
+  internal.clear_screen()
+  layout.render(layout, layout.Root)
 
   redraw_on_update_loop(redraw)
 }
 
 fn update_dimensions_on_interval(ui: Subject(Control), interval_ms: Int) {
-  case ui_internal.io_get_columns(), ui_internal.io_get_rows() {
+  case internal.io_get_columns(), internal.io_get_rows() {
     Ok(width), Ok(height) -> {
       process.send(ui, control.UpdateDimensions(width, height))
     }
@@ -109,13 +108,3 @@ fn update_dimensions_on_interval(ui: Subject(Control), interval_ms: Int) {
   process.sleep(interval_ms)
   update_dimensions_on_interval(ui, interval_ms)
 }
-
-fn render_layout(layout: Layout, from: Section) -> Nil {
-  case dict.get(layout.nodes, from) {
-    Error(_) -> Nil
-    Ok(node) -> {
-      list.each(node.children, fn(child) { render_layout(layout, child) })
-      ui_internal.print_at(node.content, node.x, node.y)
-    }
-  }
-}

test/musicplayer/mpv/mpv_test.gleam

@@ -1,6 +1,6 @@
 import gleeunit
 
-import musicplayer/mpv/internal as control_internal
+import musicplayer/mpv/internal
 
 pub fn main() -> Nil {
   gleeunit.main()
@@ -10,6 +10,6 @@ pub fn parse_playback_time_test() {
   let json_string =
     "{\"data\":\"123.456789\",\"request_id\":0,\"error\":\"success\"}\n"
 
-  let assert Ok(data) = control_internal.parse_playback_time(json_string)
+  let assert Ok(data) = internal.parse_playback_time(json_string)
   assert data == 123.456789
 }