you can play your song now :D

src/main.py

@@ -9,7 +9,7 @@ import mp3
 
 if __name__ == "__main__":
     print("Loading project...")
-    """test_project = Project(song_length=2)
+    test_project = Project(song_length=8)
     
     drum_channel = ProjectChannel(
         test_project,
@@ -23,10 +23,16 @@ if __name__ == "__main__":
         *librosa.load("120 bpm amen break.mp3", mono=False, sr=test_project.sample_rate),
         name="120 bpm amen break.mp3"
     ))
+    drum_channel.chunks.append(AudioChannelChunk(
+        drum_channel,
+        position=1,
+        *librosa.load("120 bpm amen break.mp3", mono=False, sr=test_project.sample_rate),
+        name="120 bpm amen break.mp3"
+    ))
 
     test_project.channels.append(drum_channel)
     
-    test_project.write_to_file("test_project.tdp")"""
+    test_project.write_to_file("test_project.tdp")
     test_project = Project.from_file("test_project.tdp")
     
     # start the ui

src/song_player.py

@@ -0,0 +1,89 @@
+import sounddevice as sd
+from project import Project
+from ui.widgets.play_head import PlayHead
+
+
+class SongPlayer:
+    def __init__(self, timeline, project: Project):
+        self.audio = None
+        self.stream = sd.OutputStream() # default stream
+        self.project: Project = project
+        self.playhead = 0
+        self.paused = True
+        
+        self.timeline = timeline
+        
+    def play_callback(self, out, frames, time, status):
+        if self.paused or self.audio is None:
+            out.fill(0)
+            return
+        
+        end = self.playhead + frames
+        chunk = self.audio[self.playhead:end]
+        
+        if chunk.ndim == 1:
+            chunk = chunk[:, None]
+            
+        if chunk.shape[1] != out.shape[1]:
+            raise RuntimeError("Something very bad has happened :sob:, A channel mismatch happened.")
+        
+        if len(chunk) < frames:
+            out[:len(chunk)] = chunk
+            out[len(chunk):].fill(0)
+            raise sd.CallbackStop()
+        
+        out[:] = chunk
+        self.playhead = end
+        
+        self.timeline.run_worker(self.update_visual_playhead())
+        
+    async def update_visual_playhead(self):
+        # get how many bars into the song we are
+        num_bars = self.playhead / self.project.samples_per_bar
+        
+        # multiply that with the bar offset to update the ui to show where the playhead is in the song
+        x_offset = num_bars * self.timeline.bar_offset * 4
+        
+        # now we can finally apply that offset :)
+        self.timeline.query_one(PlayHead).offset = (
+            x_offset,
+            0
+        )
+        
+    def seek(self, seconds: int):
+        self.playhead = int(seconds * self.project.sample_rate)
+        self.timeline.run_worker(self.update_visual_playhead())
+        
+    def pause(self):
+        self.paused = True
+        
+        play_btn = self.timeline.app.query_one("#play-button")
+        play_btn.variant = "success"
+        play_btn.label = "▶"
+        
+    def play_project(self, project: Project) -> bool:         
+        # this just returns True if playing audio succeeded
+        self.project = project
+        self.audio = project.render()
+        
+        try:
+            self.paused = False
+            self.stream = sd.OutputStream(
+                samplerate=project.sample_rate,
+                channels=self.audio.shape[1] if self.audio.ndim > 1 else 1,
+                callback=self.play_callback
+            )
+            
+            self.stream.start()
+            
+            
+            play_btn = self.timeline.app.query_one("#play-button")
+            play_btn.variant = "error"
+            play_btn.label = "⏸"
+            
+            return True
+        except sd.PortAudioError as e: # woopsies
+            self.paused = True
+            self.timeline.app.notify(f"Error: \"{e}\"\n\nSometimes errors can occur if the device you selected in your settings doesn't exist, or it's already in use.", title="Error while playing song", timeout=60, severity="error")
+        
+        return False

src/ui/app.py

@@ -1,5 +1,6 @@
 from textual.app import App, ComposeResult
 from textual.widgets import Footer, Tab, Tabs, Header
+from textual import on, events
 
 from ui.widgets.sidebar import Sidebar
 from ui.widgets.timeline import Timeline, TimelineRow
@@ -12,13 +13,20 @@ from project import ProjectChannel
 class AppUI(App):    
     CSS_PATH = "../assets/style.tcss"
     
-    theme = "tokyo-night"
-    
     def __init__(self, project):
         super().__init__()
         self.zoom_level = 0.05
         self.last_zoom_level = self.zoom_level
         self.project = project
+        
+    @on(events.Key)
+    async def key_pressed(self, event: events.Key):
+        if event.key == "space":
+            timeline = self.query_one(Timeline)
+            if not timeline.song_player.paused:
+                timeline.song_player.pause()
+            else:
+                timeline.song_player.play_project(self.app.project)
     
     def create_channel(self, name: str):
         self.query_one("#channels").mount(Channel(

src/ui/widgets/chunk_types/audio.py

@@ -14,7 +14,7 @@ from ui.widgets.chunk_types.chunk import Chunk
 class AudioChunk(Chunk):
     DEFAULT_CSS = """
     AudioChunk {
-        border: tab $secondary;
+        border: tab $primary;
         PlotWidget {
             height: 1fr;
 
@@ -91,7 +91,7 @@ class AudioChunk(Chunk):
                     x,
                     y,
                     1.0,
-                    bar_style=self.app.theme_variables["secondary"],
+                    bar_style=self.app.theme_variables["primary"],
                     hires_mode=HiResMode.BRAILLE
                 )
                 

src/ui/widgets/project_settings.py

@@ -42,7 +42,12 @@ class ProjectSettings(Horizontal):
         
     def on_button_pressed(self, event: Button.Pressed):
         if event.button.id == "play-button":
-            sd.play(self.app.project.render())
+            song_player = self.app.query_one("#timeline").song_player
+            
+            if event.button.variant == "success": # play button
+                song_player.play_project(self.app.project)
+            else: # stop button
+                song_player.pause()
     
     def compose(self) -> ComposeResult:
         yield Button("▶", tooltip="Play song", flat=True, id="play-button", variant="success") # icon becomes "⏸" when song is playing

src/ui/widgets/timeline.py

@@ -7,6 +7,8 @@ from ui.widgets.chunk_types.audio import AudioChunk, Chunk
 from ui.widgets.play_head import PlayHead
 from project import ChunkType
 
+from song_player import SongPlayer
+
 
 class TimelineRow(Horizontal):
     DEFAULT_CSS = """
@@ -64,6 +66,7 @@ class Timeline(Vertical):
         super().__init__(id="timeline")
         
         self.calc_bar_offset()
+        self.song_player = SongPlayer(self, self.app.project)
         
     def calc_bar_offset(self):
         self.bar_offset = self.app.project.bpm / 8 * (0.03333333333 / self.app.zoom_level)
@@ -87,6 +90,19 @@ class Timeline(Vertical):
             self.calc_bar_offset()
             self.handle_zoom()
             
+    @on(events.MouseDown)
+    async def mouse_down(self, event: events.MouseDown):
+        if event.button != 2: return
+        
+        # get bar number
+        bar_number = event.x / self.bar_offset
+        
+        # convert bar number to seconds
+        seconds = bar_number / self.app.project.seconds_per_bar
+        
+        # seek to number of seconds
+        self.song_player.seek(seconds)
+            
     def handle_zoom(self):
         for chunk in self.query(Chunk):
             chunk.calculate_size()
@@ -100,6 +116,9 @@ class Timeline(Vertical):
                     bar_line.display = False
                 else:
                     bar_line.display = True
+        
+        if self.song_player.paused and self.song_player.project:
+            self.run_worker(self.song_player.update_visual_playhead())
     
     def compose(self) -> ComposeResult:
         
@@ -116,7 +135,7 @@ class Timeline(Vertical):
                         elif chunk.chunk_type == ChunkType.AUDIO:
                             yield AudioChunk(chunk.audio_data, chunk.sample_rate, chunk.name, chunk.position)
 
-            for i in range(1, self.app.project.song_length):
+            for i in range(1, self.app.project.song_length+1):
                 bar = None
                 if i % 4 == 0:
                     bar = Rule.vertical(classes="bar-line", line_style="double")