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()
   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

@@ -1,40 +1,22 @@
-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)
-}
-
-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) {
+pub fn log(content: String) -> Nil {
-  case control {
-    control.Write(content) -> {
   let log_line =
     timestamp.system_time()
     |> timestamp.to_rfc3339(calendar.utc_offset)
@@ -43,16 +25,6 @@ fn handle_message(state: State, control: Control) -> actor.Next(State, Control)
     <> "\n"
 
   // Ignore any logging errors
-      let _ = simplifile.append(state.filepath, log_line)
+  let _ = simplifile.append(filepath, log_line)
-      actor.continue(state)
+  Nil
-    }
-    control.Exit(reply_to) -> {
-      process.send(reply_to, Nil)
-      actor.stop()
-    }
-  }
-}
-
-pub fn log(logger: Subject(Control), content: String) -> Nil {
-  process.send(logger, control.Write(content))
 }

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
@@ -103,7 +100,6 @@ 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
@@ -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()
     }
@@ -155,6 +146,7 @@ fn update_playback_time_loop(
   interval_ms: Int,
 ) {
   process.sleep(interval_ms)
+  // TODO only update if state is playing
   update_playback_time(mpv, ui)
 
   update_playback_time_loop(mpv, ui, interval_ms)

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/control.gleam

@@ -3,6 +3,7 @@ import gleam/erlang/process.{type Subject}
 import musicplayer/ui/layout.{type Section}
 
 pub type Control {
+  UpdateDimensions(width: Int, height: Int)
   UpdateState(section: Section, content: String)
 
   Exit(reply_to: Subject(Nil))

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 {
@@ -19,3 +23,13 @@ pub fn hide_cursor() -> Nil {
 pub fn show_cursor() -> Nil {
   io.print("\u{001B}[?25h")
 }
+
+pub type Enotsup
+
+// https://www.erlang.org/doc/apps/stdlib/io.html#rows/0
+@external(erlang, "io", "rows")
+pub fn io_get_rows() -> Result(Int, Enotsup)
+
+// https://www.erlang.org/doc/apps/stdlib/io.html#columns/0
+@external(erlang, "io", "columns")
+pub fn io_get_columns() -> Result(Int, Enotsup)

src/musicplayer/ui/layout.gleam

@@ -1,18 +1,42 @@
 import gleam/dict
+import gleam/float
+import gleam/int
+import gleam/list
+import gleam/string
+import gleam/string_tree
 
-pub type Layout {
+import musicplayer/logging/logging
-  Layout(nodes: dict.Dict(Section, Node))
+import musicplayer/ui/ansi
-}
+import musicplayer/ui/internal
 
 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(content: String, x: Int, y: Int, children: List(Section))
+  Node(
+    t: NodeType,
+    content: String,
+    width_percent: Int,
+    height_percent: Int,
+    children: List(Section),
+  )
+}
+
+pub type Layout {
+  Layout(width: Int, height: Int, nodes: dict.Dict(Section, Node))
 }
 
 pub fn new() -> Layout {
@@ -20,18 +44,46 @@ pub fn new() -> Layout {
     dict.from_list([
       #(
         Root,
-        Node(content: "", x: 0, y: 0, 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: [],
+        ),
+      ),
+      #(
+        PlaybackTime,
+        Node(
+          t: Row,
+          content: "00:00",
+          width_percent: 100,
+          height_percent: 33,
+          children: [],
+        ),
       ),
-      #(Header, Node(content: "Music Player", x: 1, y: 1, children: [])),
-      #(Search, Node(content: "", x: 30, y: 1, children: [])),
-      #(PlaybackTime, Node(content: "00:00", x: 1, y: 2, children: [])),
     ])
-
+  Layout(width: 0, height: 0, nodes: nodes)
-  Layout(nodes: nodes)
 }
 
 pub fn update_section(
@@ -42,10 +94,138 @@ pub fn update_section(
   case dict.get(layout.nodes, section) {
     Error(_) -> layout
     Ok(node) ->
-      Layout(nodes: dict.insert(
+      Layout(
+        ..layout,
+        nodes: dict.insert(
           layout.nodes,
           section,
           Node(..node, content: content),
-      ))
+        ),
+      )
+  }
+}
+
+pub fn update_dimensions(layout: Layout, width: Int, height: Int) -> Layout {
+  Layout(..layout, width:, height:)
+}
+
+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
+
+  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
+
+  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,
+    _,
+    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_generic(
+  layout: Layout,
+  // Dimensions
+  container_width: Float,
+  container_height: Float,
+  container_tl_x: Int,
+  container_tl_y: Int,
+  // State
+  index: Int,
+  from: Section,
+  render_into: into,
+  renders: Renders(into),
+) -> into {
+  case dict.get(layout.nodes, from) {
+    Error(_) -> render_into
+    Ok(node) -> {
+      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 }
+          -. margin
+          |> float.floor
+
+        let ch =
+          container_height
+          *. { int.to_float(node.height_percent) /. 100.0 }
+          -. margin
+          |> float.floor
+
+        let child_origin_x = container_tl_x + 1
+        let child_origin_y = container_tl_y + 1
+
+        render_generic(
+          layout,
+          cw,
+          ch,
+          child_origin_x,
+          child_origin_y,
+          i,
+          child,
+          acc_into,
+          renders,
+        )
+      })
+    }
   }
 }

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

@@ -1,12 +1,13 @@
-import gleam/dict
 import gleam/erlang/process.{type Subject}
+import gleam/int
 import gleam/list
 import gleam/otp/actor
 import gleam/string
 
+import musicplayer/logging/logging
 import musicplayer/ui/control.{type Control}
-import musicplayer/ui/internal as ui_internal
+import musicplayer/ui/internal
-import musicplayer/ui/layout.{type Layout, type Section}
+import musicplayer/ui/layout.{type Layout}
 
 pub type State(redraw, content) {
   State(redraw: Subject(Layout), layout: Layout)
@@ -26,13 +27,18 @@ pub fn new() -> Result(Subject(Control), String) {
     Error(start_error) ->
       Error("Could not start actor: " <> string.inspect(start_error))
     Ok(actor.Started(data: ui, ..)) -> {
+      process.spawn(fn() {
+        let update_dimensions_interval_ms = 300
+        update_dimensions_on_interval(ui, update_dimensions_interval_ms)
+      })
+
       process.spawn(fn() {
         let assert Ok(_) = process.register(process.self(), redraw_name)
 
-        ui_internal.clear_screen()
+        internal.clear_screen()
-        ui_internal.hide_cursor()
+        internal.hide_cursor()
 
-        redraw_on_update_loop(redraw)
+        redraw_loop(redraw)
       })
 
       Ok(ui)
@@ -45,37 +51,55 @@ fn handle_message(
   control: Control,
 ) -> actor.Next(State(redraw, layout), Control) {
   case control {
+    control.UpdateDimensions(width, height) -> {
+      let current_dimensions = #(state.layout.width, state.layout.height)
+
+      case #(width, height) == current_dimensions {
+        True -> actor.continue(state)
+        False -> {
+          [width, height]
+          |> list.map(int.to_string)
+          |> string.join(" ")
+          |> string.append("ui - updating dimensions: ", _)
+          |> logging.log
+
+          let layout = layout.update_dimensions(state.layout, width, height)
+
+          process.send(state.redraw, layout)
+          actor.continue(State(..state, layout:))
+        }
+      }
+    }
     control.UpdateState(section, content) -> {
       let layout = layout.update_section(state.layout, section, content)
-      let state = State(..state, layout:)
 
       actor.send(state.redraw, layout)
-      actor.continue(state)
+      actor.continue(State(..state, layout:))
     }
 
     control.Exit(reply_to) -> {
-      ui_internal.show_cursor()
+      internal.show_cursor()
       process.send(reply_to, Nil)
       actor.stop()
     }
   }
 }
 
-fn redraw_on_update_loop(redraw: Subject(Layout)) -> Nil {
+fn redraw_loop(redraw: Subject(Layout)) -> Nil {
-  let layout = process.receive_forever(redraw)
+  process.receive_forever(redraw)
+  |> layout.render
 
-  ui_internal.clear_screen()
+  redraw_loop(redraw)
-  render_layout(layout, layout.Root)
-
-  redraw_on_update_loop(redraw)
 }
 
-fn render_layout(layout: Layout, from: Section) -> Nil {
+fn update_dimensions_on_interval(ui: Subject(Control), interval_ms: Int) {
-  case dict.get(layout.nodes, from) {
+  case internal.io_get_columns(), internal.io_get_rows() {
-    Error(_) -> Nil
+    Ok(width), Ok(height) -> {
-    Ok(node) -> {
+      process.send(ui, control.UpdateDimensions(width, height))
-      list.each(node.children, fn(child) { render_layout(layout, child) })
-      ui_internal.print_at(node.content, node.x, node.y)
     }
+    _, _ -> logging.log("ui - failed to update dimensions")
   }
+
+  process.sleep(interval_ms)
+  update_dimensions_on_interval(ui, interval_ms)
 }

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
 }

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) })
+}