wip

To avoid having to pass around a `Subject`

src/musicplayer.gleam

@@ -8,15 +8,14 @@ import musicplayer/musicplayer
 import musicplayer/ui/ui
 
 pub fn main() -> Nil {
-  let assert Ok(logger) = logging.new("/tmp/musicplayer.log")
+  let assert Ok(_) = logging.initialize()
 
   let input_keys_name: Name(Key) = process.new_name("input_keys")
   input.new(input_keys_name)
 
-  let assert Ok(ui) = ui.new(logger)
+  let assert Ok(ui) = ui.new()
   let assert Ok(mpv) = mpv.new()
-  let assert Ok(musicplayer_pid) =
+  let assert Ok(musicplayer_pid) = musicplayer.new(ui, mpv, input_keys_name)
-    musicplayer.new(logger, ui, mpv, input_keys_name)
 
   let monitor = process.monitor(musicplayer_pid)
   process.new_selector()

src/musicplayer/logging/control.gleam

@@ -1,7 +1,5 @@
-import gleam/erlang/process.{type Subject}
-
 pub type Control {
   Write(String)
 
-  Exit(reply_to: Subject(Nil))
+  Exit
 }

src/musicplayer/logging/logging.gleam

@@ -1,58 +1,30 @@
-import gleam/erlang/process.{type Subject}
-import gleam/otp/actor
 import gleam/result
 import gleam/string
 import gleam/time/calendar
 import gleam/time/timestamp
 import simplifile
 
-import musicplayer/logging/control.{type Control}
+const filepath = "/tmp/musicplayer.log"
 
-type State {
+pub fn initialize() -> Result(Nil, String) {
-  State(filepath: String)
+  case simplifile.is_file(filepath) {
-}
+    Ok(True) -> Ok(Nil)
-
+    _ -> simplifile.create_file(filepath)
-pub fn new(filepath: String) -> Result(Subject(Control), String) {
-  use _ <- result.try(
-    case simplifile.is_file(filepath) {
-      Ok(True) -> Ok(Nil)
-      _ -> simplifile.create_file(filepath)
-    }
-    |> result.map_error(fn(e) {
-      "Could not access or create log file: " <> string.inspect(e)
-    }),
-  )
-
-  actor.new(State(filepath:))
-  |> actor.on_message(handle_message)
-  |> actor.start
-  |> result.map_error(fn(start_error) {
-    "Could not start logger: " <> string.inspect(start_error)
-  })
-  |> result.map(fn(started) { started.data })
-}
-
-fn handle_message(state: State, control: Control) -> actor.Next(State, Control) {
-  case control {
-    control.Write(content) -> {
-      let log_line =
-        timestamp.system_time()
-        |> timestamp.to_rfc3339(calendar.utc_offset)
-        <> ": "
-        <> content
-        <> "\n"
-
-      // Ignore any logging errors
-      let _ = simplifile.append(state.filepath, log_line)
-      actor.continue(state)
-    }
-    control.Exit(reply_to) -> {
-      process.send(reply_to, Nil)
-      actor.stop()
-    }
   }
+  |> result.map_error(fn(e) {
+    "Could not access or create log file: " <> string.inspect(e)
+  })
 }
 
-pub fn log(logger: Subject(Control), content: String) -> Nil {
+pub fn log(content: String) -> Nil {
-  process.send(logger, control.Write(content))
+  let log_line =
+    timestamp.system_time()
+    |> timestamp.to_rfc3339(calendar.utc_offset)
+    <> ": "
+    <> content
+    <> "\n"
+
+  // Ignore any logging errors
+  let _ = simplifile.append(filepath, log_line)
+  Nil
 }

src/musicplayer/musicplayer.gleam

@@ -5,7 +5,6 @@ import gleam/string
 
 import musicplayer/control.{type Control}
 import musicplayer/input/key.{type Key}
-import musicplayer/logging/control as logging_control
 import musicplayer/logging/logging
 import musicplayer/mpv/control as mpv_control
 import musicplayer/time/time
@@ -25,14 +24,12 @@ type State {
   State(
     mode: Mode,
     input: Input,
-    logger: Subject(logging_control.Control),
     ui: Subject(ui_control.Control),
     mpv: Subject(mpv_control.Control),
   )
 }
 
 pub fn new(
-  logger: Subject(logging_control.Control),
   ui: Subject(ui_control.Control),
   mpv: Subject(mpv_control.Control),
   input_keys_name: Name(Key),
@@ -42,14 +39,14 @@ pub fn new(
   let input = Input(False, "")
 
   case
-    actor.new(State(Idle, input, logger, ui, mpv))
+    actor.new(State(Idle, input, ui, mpv))
     |> actor.on_message(handle_message)
     |> actor.start
   {
     Error(start_error) ->
       Error("Could not start actor: " <> string.inspect(start_error))
     Ok(actor.Started(pid:, data: musicplayer)) -> {
-      logging.log(logger, "musicplayer - started")
+      logging.log("musicplayer - started")
       process.spawn(fn() {
         let assert Ok(_) = process.register(process.self(), input_keys_name)
         handle_key(musicplayer, input_keys)
@@ -65,7 +62,7 @@ pub fn new(
 fn handle_message(state: State, control: Control) -> actor.Next(State, Control) {
   case control {
     control.Search -> {
-      logging.log(state.logger, "musicplayer - initiating search")
+      logging.log("musicplayer - initiating search")
 
       update_search(state.ui, "searching: ")
 
@@ -79,7 +76,7 @@ fn handle_message(state: State, control: Control) -> actor.Next(State, Control)
     }
 
     control.Raw(content) -> {
-      logging.log(state.logger, "musicplayer - recieved raw input: " <> content)
+      logging.log("musicplayer - recieved raw input: " <> content)
 
       let content = case state.mode {
         Idle -> state.input.content
@@ -93,7 +90,7 @@ fn handle_message(state: State, control: Control) -> actor.Next(State, Control)
       actor.continue(State(..state, input: Input(..state.input, content:)))
     }
     control.Backspace -> {
-      logging.log(state.logger, "musicplayer - recieved backspace")
+      logging.log("musicplayer - recieved backspace")
 
       let content = case state.mode {
         Idle -> state.input.content
@@ -103,11 +100,10 @@ fn handle_message(state: State, control: Control) -> actor.Next(State, Control)
     }
     control.Return -> {
       logging.log(
-        state.logger,
         "musicplayer - recieved return. `input.capture`: "
-          <> "'"
+        <> "'"
-          <> state.input.content
+        <> state.input.content
-          <> "'",
+        <> "'",
       )
 
       // Note: state.input.content is now the final input, use it
@@ -123,26 +119,21 @@ fn handle_message(state: State, control: Control) -> actor.Next(State, Control)
     }
 
     control.TogglePlayPause -> {
-      logging.log(state.logger, "musicplayer - toggling play/pause")
+      logging.log("musicplayer - toggling play/pause")
 
       process.send(state.mpv, mpv_control.TogglePlayPause)
       update_playback_time(state.mpv, state.ui)
       actor.continue(state)
     }
     control.Exit -> {
-      logging.log(state.logger, "musicplayer - initiating musicplayer shutdown")
+      logging.log("musicplayer - initiating musicplayer shutdown")
       // Close `mpv` socket
       process.call(state.mpv, 1000, fn(reply_to) { mpv_control.Exit(reply_to) })
 
       // Reset terminal state (show cursor etc.)
       process.call(state.ui, 1000, fn(reply_to) { ui_control.Exit(reply_to) })
 
-      logging.log(state.logger, "musicplayer - stopped")
+      logging.log("musicplayer - stopped")
-
-      // Close logger (NOOP)
-      process.call(state.logger, 1000, fn(reply_to) {
-        logging_control.Exit(reply_to)
-      })
 
       actor.stop()
     }

src/musicplayer/ui/ansi.gleam

@@ -0,0 +1,42 @@
+import gleam/list
+import gleam/string
+import gleam/string_tree
+
+import musicplayer/ui/internal
+
+pub fn text(chars: String, x: Int, y: Int) {
+  internal.chars_at(chars, x, y)
+}
+
+pub fn box(x: Int, y: Int, width: Int, height: Int) -> String {
+  let box_chars = #("┌", "┐", "└", "┘", "─", "│")
+  let #(tl, tr, bl, br, h, v) = box_chars
+
+  // Add top of box
+  let tree =
+    string_tree.new()
+    |> string_tree.append(internal.chars_at(
+      tl <> string.repeat(h, width - 2) <> tr,
+      x,
+      y,
+    ))
+
+  // Add sides of box
+  let tree_with_sides =
+    list.range(1, height - 2)
+    |> list.map(fn(row) {
+      tree
+      |> string_tree.append(internal.chars_at(v, x, y + row))
+      |> string_tree.append(internal.chars_at(v, x + width - 1, y + row))
+    })
+    |> string_tree.concat
+
+  // Add bottom of box
+  tree_with_sides
+  |> string_tree.append(internal.chars_at(
+    bl <> string.repeat(h, width - 2) <> br,
+    x,
+    y + height - 1,
+  ))
+  |> string_tree.to_string
+}

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

@@ -1,28 +1,33 @@
 import gleam/dict
-import gleam/erlang/process.{type Subject}
 import gleam/float
 import gleam/int
 import gleam/list
 import gleam/string
+import gleam/string_tree
 
-import musicplayer/logging/control as logging_control
 import musicplayer/logging/logging
+import musicplayer/ui/ansi
 import musicplayer/ui/internal
 
-pub type Layout {
-  Layout(width: Int, height: Int, nodes: dict.Dict(Section, Node))
-}
-
 pub type Section {
+  Section(String)
+
   Root
   Header
   Search
   PlaybackTime
 }
 
+pub type NodeType {
+  Container
+  Row
+  Cell
+}
+
 /// A Nodes width and height is in percentage (of the available width/height of its parent Node)
 pub type Node {
   Node(
+    t: NodeType,
     content: String,
     width_percent: Int,
     height_percent: Int,
@@ -30,34 +35,55 @@ pub type Node {
   )
 }
 
+pub type Layout {
+  Layout(width: Int, height: Int, nodes: dict.Dict(Section, Node))
+}
+
 pub fn new() -> Layout {
   let nodes =
     dict.from_list([
       #(
         Root,
-        Node(content: "", width_percent: 100, height_percent: 100, children: [
+        Node(
-          // Header,
+          t: Container,
-          // Search,
+          content: "Music Player",
-          PlaybackTime,
+          width_percent: 100,
-        ]),
+          height_percent: 100,
+          children: [Header, Search, PlaybackTime],
+        ),
+      ),
+      #(
+        Header,
+        Node(
+          t: Row,
+          content: "Foo (1) | Bar (2) | Baz (3)",
+          width_percent: 100,
+          height_percent: 33,
+          children: [],
+        ),
+      ),
+      #(
+        Search,
+        Node(
+          t: Row,
+          content: "",
+          width_percent: 100,
+          height_percent: 33,
+          children: [],
+        ),
       ),
-      // #(
-      //   Header,
-      //   Node(content: "Music Player", width: 50, height: 10, children: []),
-      // ),
-      // #(Search, Node(content: "", width: 50, height: 10, children: [])),
       #(
         PlaybackTime,
         Node(
+          t: Row,
           content: "00:00",
-          width_percent: 50,
+          width_percent: 100,
-          height_percent: 100,
+          height_percent: 33,
           children: [],
         ),
       ),
     ])
-
+  Layout(width: 0, height: 0, nodes: nodes)
-  Layout(0, 0, nodes: nodes)
 }
 
 pub fn update_section(
@@ -83,45 +109,96 @@ pub fn update_dimensions(layout: Layout, width: Int, height: Int) -> Layout {
   Layout(..layout, width:, height:)
 }
 
-pub fn render(logger: Subject(logging_control.Control), layout: Layout) -> Nil {
+pub fn render(layout: Layout) -> Nil {
   internal.clear_screen()
   [layout.width, layout.height]
   |> list.map(int.to_string)
   |> string.join(" ")
   |> string.append("layout - render: ", _)
-  |> logging.log(logger, _)
+  |> logging.log
 
   let container_width = int.to_float(layout.width)
   let container_height = int.to_float(layout.height)
   let container_top_left_x = 1
   let container_top_left_y = 1
 
-  render_loop(
+  let ansi_renders =
+    Renders(
+      box: fn(tree, x, y, w, h) {
+        string_tree.append(tree, ansi.box(x, y, w, h))
+      },
+      text: fn(tree, chars, x, y) {
+        string_tree.append(tree, ansi.text(chars, x, y))
+      },
+    )
+
+  string_tree.new()
+  |> render_generic(
     layout,
     container_width,
     container_height,
     container_top_left_x,
     container_top_left_y,
+    0,
     Root,
-    logger,
+    _,
+    ansi_renders,
+  )
+  |> string_tree.to_string
+  |> internal.print
+}
+
+pub type Renders(into) {
+  Renders(
+    text: fn(into, String, Int, Int) -> into,
+    box: fn(into, Int, Int, Int, Int) -> into,
   )
 }
 
-pub fn render_loop(
+pub fn render_generic(
   layout: Layout,
+  // Dimensions
   container_width: Float,
   container_height: Float,
-  container_top_left_x: Int,
+  container_tl_x: Int,
-  container_top_left_y: Int,
+  container_tl_y: Int,
+  // State
+  index: Int,
   from: Section,
-  logger: Subject(logging_control.Control),
+  render_into: into,
-) -> Nil {
+  renders: Renders(into),
-  let margin = 2.0
+) -> into {
-
   case dict.get(layout.nodes, from) {
-    Error(_) -> Nil
+    Error(_) -> render_into
     Ok(node) -> {
-      list.each(node.children, fn(child) {
+      let margin = 2.0
+
+      let width =
+        container_width *. { int.to_float(node.width_percent) /. 100.0 }
+        |> float.floor
+        |> float.truncate
+
+      let height =
+        container_height *. { int.to_float(node.height_percent) /. 100.0 }
+        |> float.floor
+        |> float.truncate
+
+      let #(cx, cy) = case node.t {
+        Container -> #(container_tl_x, container_tl_y)
+        Row -> #(container_tl_x, container_tl_y + { index * height })
+        Cell -> #(container_tl_x + { index * width }, container_tl_y)
+      }
+
+      let parent =
+        render_into
+        |> renders.box(cx, cy, width, height)
+        // + 2 for header margin
+        |> renders.text(node.content, cx + 2, cy)
+
+      list.index_map(node.children, fn(child, i) { #(i, child) })
+      |> list.fold(parent, fn(acc_into, ic) {
+        let #(i, child) = ic
+
         let cw =
           container_width
           *. { int.to_float(node.width_percent) /. 100.0 }
@@ -134,59 +211,21 @@ pub fn render_loop(
           -. margin
           |> float.floor
 
-        let cx = container_top_left_x + 1
+        let child_origin_x = container_tl_x + 1
-        let cy = container_top_left_y + 1
+        let child_origin_y = container_tl_y + 1
 
-        render_loop(layout, cw, ch, cx, cy, child, logger)
+        render_generic(
+          layout,
+          cw,
+          ch,
+          child_origin_x,
+          child_origin_y,
+          i,
+          child,
+          acc_into,
+          renders,
+        )
       })
-
-      logging.log(logger, "section: " <> string.inspect(from))
-      logging.log(
-        logger,
-        "container width: " <> float.to_string(container_width),
-      )
-      logging.log(
-        logger,
-        "container height: " <> float.to_string(container_height),
-      )
-
-      let width =
-        container_width
-        *. { int.to_float(node.width_percent) /. int.to_float(100) }
-        |> float.floor
-        |> float.truncate
-
-      let height =
-        container_height
-        *. { int.to_float(node.height_percent) /. int.to_float(100) }
-        |> float.floor
-        |> float.truncate
-
-      logging.log(logger, "width: " <> int.to_string(width))
-      logging.log(logger, "height: " <> int.to_string(height))
-
-      let cx = container_top_left_x
-      let cy = container_top_left_y
-      logging.log(logger, "cx: " <> int.to_string(cx))
-      logging.log(logger, "cy: " <> int.to_string(cy))
-
-      draw_box(cx, cy, width, height)
-      // Box heading
-      internal.print_at(node.content, cx, cy)
     }
   }
 }
-
-fn draw_box(x: Int, y: Int, width: Int, height: Int) -> Nil {
-  let box_chars = #("┌", "┐", "└", "┘", "─", "│")
-  let #(tl, tr, bl, br, h, v) = box_chars
-  internal.print_at(tl <> string.repeat(h, width - 2) <> tr, x, y)
-
-  list.range(1, height - 2)
-  |> list.each(fn(row) {
-    internal.print_at(v, x, y + row)
-    internal.print_at(v, x + width - 1, y + row)
-  })
-
-  internal.print_at(bl <> string.repeat(h, width - 2) <> br, x, y + height - 1)
-}

src/musicplayer/ui/layout_examples/layout_examples.gleam

@@ -0,0 +1,82 @@
+import gleam/dict
+
+import musicplayer/ui/internal
+import musicplayer/ui/layout.{Container, Layout, Node, Section}
+import musicplayer/ui/layout_examples/wait_for_input.{wait_for_input}
+
+pub fn main() {
+  let assert Ok(width) = internal.io_get_columns()
+  let assert Ok(height) = internal.io_get_rows()
+
+  two_rows_with_cells(width, height)
+  |> layout.render
+
+  wait_for_input()
+}
+
+/// Two rows:
+/// First row has two cells
+/// Second row has no cells
+fn two_rows_with_cells(width: Int, height: Int) -> layout.Layout {
+  let nodes =
+    dict.from_list([
+      #(
+        Section("Root"),
+        Node(
+          t: Container,
+          content: "container",
+          width_percent: 100,
+          height_percent: 100,
+          children: [
+            Section("Row1"),
+            Section("Row2"),
+          ],
+        ),
+      ),
+      #(
+        Section("Row1"),
+        Node(
+          t: layout.Row,
+          content: "row 1",
+          width_percent: 100,
+          height_percent: 50,
+          children: [
+            Section("A"),
+            Section("A"),
+          ],
+        ),
+      ),
+      #(
+        Section("A"),
+        Node(
+          t: layout.Cell,
+          content: "cell 1",
+          width_percent: 50,
+          height_percent: 100,
+          children: [],
+        ),
+      ),
+      #(
+        Section("B"),
+        Node(
+          t: layout.Cell,
+          content: "cell 2",
+          width_percent: 50,
+          height_percent: 100,
+          children: [],
+        ),
+      ),
+      #(
+        Section("Row2"),
+        Node(
+          t: layout.Row,
+          content: "row 2",
+          width_percent: 100,
+          height_percent: 50,
+          children: [],
+        ),
+      ),
+    ])
+
+  Layout(width:, height:, nodes: nodes)
+}

src/musicplayer/ui/layout_examples/wait_for_input.gleam

@@ -0,0 +1,15 @@
+import gleam/erlang/process.{type Name}
+
+import musicplayer/input/input
+import musicplayer/input/key.{type Key}
+
+pub fn wait_for_input() {
+  let input_keys_name: Name(Key) = process.new_name("input_keys")
+  let assert Ok(_) = process.register(process.self(), input_keys_name)
+
+  input.new(input_keys_name)
+
+  process.new_selector()
+  |> process.select(process.named_subject(input_keys_name))
+  |> process.selector_receive_forever
+}

src/musicplayer/ui/ui.gleam

@@ -4,30 +4,23 @@ import gleam/list
 import gleam/otp/actor
 import gleam/string
 
-import musicplayer/logging/control as logging_control
 import musicplayer/logging/logging
 import musicplayer/ui/control.{type Control}
 import musicplayer/ui/internal
 import musicplayer/ui/layout.{type Layout}
 
 pub type State(redraw, content) {
-  State(
+  State(redraw: Subject(Layout), layout: Layout)
-    logger: Subject(logging_control.Control),
-    redraw: Subject(Layout),
-    layout: Layout,
-  )
 }
 
-pub fn new(
+pub fn new() -> Result(Subject(Control), String) {
-  logger: Subject(logging_control.Control),
-) -> Result(Subject(Control), String) {
   let redraw_name = process.new_name("redraw")
   let redraw: Subject(Layout) = process.named_subject(redraw_name)
 
   let layout = layout.new()
 
   case
-    actor.new(State(logger, redraw, layout))
+    actor.new(State(redraw, layout))
     |> actor.on_message(handle_message)
     |> actor.start
   {
@@ -36,7 +29,7 @@ pub fn new(
     Ok(actor.Started(data: ui, ..)) -> {
       process.spawn(fn() {
         let update_dimensions_interval_ms = 300
-        update_dimensions_on_interval(logger, ui, update_dimensions_interval_ms)
+        update_dimensions_on_interval(ui, update_dimensions_interval_ms)
       })
 
       process.spawn(fn() {
@@ -45,7 +38,7 @@ pub fn new(
         internal.clear_screen()
         internal.hide_cursor()
 
-        redraw_loop(logger, redraw)
+        redraw_loop(redraw)
       })
 
       Ok(ui)
@@ -68,7 +61,7 @@ fn handle_message(
           |> list.map(int.to_string)
           |> string.join(" ")
           |> string.append("ui - updating dimensions: ", _)
-          |> logging.log(state.logger, _)
+          |> logging.log
 
           let layout = layout.update_dimensions(state.layout, width, height)
 
@@ -92,28 +85,21 @@ fn handle_message(
   }
 }
 
-fn redraw_loop(
+fn redraw_loop(redraw: Subject(Layout)) -> Nil {
-  logger: Subject(logging_control.Control),
-  redraw: Subject(Layout),
-) -> Nil {
   process.receive_forever(redraw)
-  |> layout.render(logger, _)
+  |> layout.render
 
-  redraw_loop(logger, redraw)
+  redraw_loop(redraw)
 }
 
-fn update_dimensions_on_interval(
+fn update_dimensions_on_interval(ui: Subject(Control), interval_ms: Int) {
-  logger: Subject(logging_control.Control),
-  ui: Subject(Control),
-  interval_ms: Int,
-) {
   case internal.io_get_columns(), internal.io_get_rows() {
     Ok(width), Ok(height) -> {
       process.send(ui, control.UpdateDimensions(width, height))
     }
-    _, _ -> logging.log(logger, "ui - failed to update dimensions")
+    _, _ -> logging.log("ui - failed to update dimensions")
   }
 
   process.sleep(interval_ms)
-  update_dimensions_on_interval(logger, ui, interval_ms)
+  update_dimensions_on_interval(ui, interval_ms)
 }

test/musicplayer/ui/layout_test.gleam

@@ -0,0 +1,118 @@
+import gleam/dict
+import gleam/io
+import gleam/string
+import gleeunit
+import gleeunit/should
+import musicplayer/ui/virtual_ansi
+
+import musicplayer/ui/layout.{Layout, Node, Section}
+
+pub fn main() -> Nil {
+  gleeunit.main()
+}
+
+pub fn foo_test() {
+  let layout =
+    Layout(
+      width: 80,
+      height: 20,
+      nodes: dict.from_list([
+        #(
+          Section("Root"),
+          Node(
+            t: layout.Container,
+            content: "container",
+            width_percent: 100,
+            height_percent: 100,
+            children: [
+              Section("Row1"),
+              Section("Row2"),
+            ],
+          ),
+        ),
+        #(
+          Section("Row1"),
+          Node(
+            t: layout.Row,
+            content: "row 1",
+            width_percent: 100,
+            height_percent: 50,
+            children: [
+              Section("A"),
+              Section("B"),
+            ],
+          ),
+        ),
+        #(
+          Section("A"),
+          Node(
+            t: layout.Cell,
+            content: "cell 1",
+            width_percent: 50,
+            height_percent: 100,
+            children: [],
+          ),
+        ),
+        #(
+          Section("B"),
+          Node(
+            t: layout.Cell,
+            content: "cell 2",
+            width_percent: 50,
+            height_percent: 100,
+            children: [],
+          ),
+        ),
+        #(
+          Section("Row2"),
+          Node(
+            t: layout.Row,
+            content: "row 1",
+            width_percent: 100,
+            height_percent: 50,
+            children: [],
+          ),
+        ),
+      ]),
+    )
+
+  let expected =
+    "
+container──────────────────────────────────────────────────────────────────────┐
+│row 1────────────────────────────────────────────────────────────────────────┐│
+││cell 1───────────────────────────────┐cell 2───────────────────────────────┐││
+│││                                    ││                                    │││
+│││                                    ││                                    │││
+│││                                    ││                                    │││
+│││                                    ││                                    │││
+│││                                    ││                                    │││
+││└────────────────────────────────────┘└────────────────────────────────────┘││
+│└────────────────────────────────────────────────────────────────────────────┘│
+│row 1────────────────────────────────────────────────────────────────────────┐│
+││                                                                            ││
+││                                                                            ││
+││                                                                            ││
+││                                                                            ││
+││                                                                            ││
+││                                                                            ││
+││                                                                            ││
+│└────────────────────────────────────────────────────────────────────────────┘│
+└──────────────────────────────────────────────────────────────────────────────┘
+"
+
+  let visual =
+    virtual_ansi.render(layout, Section("Root"), layout.width, layout.height)
+  case visual == string.trim(expected) {
+    True -> Nil
+    False -> {
+      io.println("Test failed")
+      io.println("Expected:")
+      io.println(string.trim(expected))
+
+      io.println("Got:")
+      io.println(visual)
+
+      should.equal(visual, expected)
+    }
+  }
+}

test/musicplayer/ui/virtual_ansi.gleam

@@ -0,0 +1,113 @@
+import gleam/dict
+import gleam/int
+import gleam/list
+import gleam/string
+
+import musicplayer/ui/layout.{type Layout, type Section, Renders}
+
+pub type Screen =
+  dict.Dict(#(Int, Int), String)
+
+pub fn render(layout: Layout, root: Section, width: Int, height: Int) -> String {
+  let test_renders =
+    Renders(
+      box: fn(screen, x, y, w, h) { box(screen, x, y, w, h) },
+      text: fn(screen, chars, x, y) { text(screen, chars, x, y) },
+    )
+
+  let screen =
+    layout.render_generic(
+      layout,
+      int.to_float(width),
+      int.to_float(height),
+      1,
+      1,
+      0,
+      root,
+      dict.new(),
+      test_renders,
+    )
+
+  screen_to_string(screen)
+}
+
+pub fn screen_to_string(screen: Screen) -> String {
+  let keys = dict.keys(screen)
+
+  // Find the bounding box of the drawing
+  let max_x = list.fold(keys, 0, fn(m, k) { int.max(m, k.0) })
+  let max_y = list.fold(keys, 0, fn(m, k) { int.max(m, k.1) })
+
+  // We start from 1 because ANSI is 1-based
+  let min_y = list.fold(keys, 1000, fn(m, k) { int.min(m, k.1) })
+
+  list.range(min_y, max_y)
+  |> list.map(fn(y) {
+    list.range(1, max_x)
+    |> list.map(fn(x) {
+      case dict.get(screen, #(x, y)) {
+        Ok(char) -> char
+        Error(_) -> " "
+        // Fill gaps with space
+      }
+    })
+    |> string.join("")
+  })
+  |> string.join("\n")
+}
+
+pub fn text(screen: Screen, text: String, start_x: Int, y: Int) -> Screen {
+  // We use to_graphemes to ensure Unicode characters (like emoji or box lines)
+  // are treated as single visual units
+  text
+  |> string.to_graphemes
+  |> list.index_fold(screen, fn(acc, char, i) {
+    dict.insert(acc, #(start_x + i, y), char)
+  })
+}
+
+pub fn box(screen: Screen, x: Int, y: Int, w: Int, h: Int) -> Screen {
+  let box_chars = #("┌", "┐", "└", "┘", "─", "│")
+  let #(tl, tr, bl, br, hor, ver) = box_chars
+
+  // Don't draw impossible boxes
+  case w < 2 || h < 2 {
+    True -> screen
+    False -> {
+      screen
+      // 1. Corners
+      |> dict.insert(#(x, y), tl)
+      |> dict.insert(#(x + w - 1, y), tr)
+      |> dict.insert(#(x, y + h - 1), bl)
+      |> dict.insert(#(x + w - 1, y + h - 1), br)
+      // 2. Top and Bottom edges
+      |> horizontal_line(x + 1, y, w - 2, hor)
+      |> horizontal_line(x + 1, y + h - 1, w - 2, hor)
+      // 3. Side edges
+      |> vertical_line(x, y + 1, h - 2, ver)
+      |> vertical_line(x + w - 1, y + 1, h - 2, ver)
+    }
+  }
+}
+
+fn horizontal_line(
+  screen: Screen,
+  x: Int,
+  y: Int,
+  len: Int,
+  char: String,
+) -> Screen {
+  list.range(0, len - 1)
+  |> list.fold(screen, fn(acc, i) { dict.insert(acc, #(x + i, y), char) })
+}
+
+fn vertical_line(
+  screen: Screen,
+  x: Int,
+  y: Int,
+  len: Int,
+  char: String,
+) -> Screen {
+  list.range(0, len - 1)
+  |> list.fold(screen, fn(acc, i) { dict.insert(acc, #(x, y + i), char) })
+}