Describe the Sound tab and cutting a sound (#343)

- Sounds: new section The Sound tab, and Start, End and Edge fade in
  the property table.
- Concepts, Home and Instruments: a sound plays the stretch it is cut
  to.
- Development: 1840 checks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Concepts.md

@@ -4,7 +4,7 @@
 | **Asset** | Named thing with a type (`scene`, `camera`, `clip`, `sprite`, `text`, `behavior`, `collider`, `container`, `texture`, `animation`, `statemachine`, `shader`, `shaderfunction`, `font`, `sound`, `soundfx`, `instrument`, `particles`, `variables`) and typed properties. Assets have **no position**. |
 | **Texture** | An uploaded image. Scenes, textures, animations, state machines, shaders, fonts, sounds and Variables assets are the eight types that cannot be placed: a texture has no position, it is *worn* by a sprite through the ordinary property `texture`. See [Textures](Textures). |
 | **Font** | An uploaded typeface, worn by a text through the ordinary property `font`; no font means the editor's own. Uploaded and picked exactly like a texture, and stored the same way. See [Fonts](Fonts). |
-| **Sound** | An uploaded audio file. Uploaded, picked and stored exactly like a typeface — but nothing *wears* it: it is neither on screen nor in the scene, and a graph plays it with `Play sound`. Its own rows say how loud it is and whether it loops; the node scales the one and can overrule the other either way. A **sound FX** asset is a graph of effects (gain, pitch, EQ, mix) a `Play sound` can send it through. See [Sounds](Sounds). An **instrument** plays sounds as notes, see [Instruments](Instruments), and a **pattern** is notes for one, drawn in a piano roll, see [Patterns](Patterns). |
+| **Sound** | An uploaded audio file. Uploaded, picked and stored exactly like a typeface — but nothing *wears* it: it is neither on screen nor in the scene, and a graph plays it with `Play sound`. Its own rows say how loud it is and whether it loops; the node scales the one and can overrule the other either way. Its tab shows the wave and cuts the sound to a stretch of its file, which is then what plays everywhere. A **sound FX** asset is a graph of effects (gain, pitch, EQ, mix) a `Play sound` can send it through. See [Sounds](Sounds). An **instrument** plays sounds as notes, see [Instruments](Instruments), and a **pattern** is notes for one, drawn in a piano roll, see [Patterns](Patterns). |
 | **State machine** | A named set of **states**, edited as nodes in its own tab. A behavior puts it into a state with `Set state`, moves it along a named transition with `State transition` and branches on it with `State branch`. Its **Scope** says where the current state lives: **Local** gives every behavior instance one of its own, **Global** keeps a single one for the whole run. See [State machines](State-machines). |
 | **Shader** | A node graph that becomes the GLSL a sprite is drawn with, edited in its own tab. A sprite, a text or a particle source wears it through `shader`; the numbers the graph declares are rows below that dropdown. A **shader function** is a part of such a graph kept on its own and used as a node in other shaders. See [Shaders](Shaders). |
 | **Particles** | A node graph that says what *one* particle is as a function of its age and of a random number drawn once for it — no forces, no simulation. Unlike the other graph assets it **is** placeable: the object made from it is a source, whose rows say how many go out and for how long they live. Because a particle is a formula, the same second always draws the same picture and the tab's slider can jump to any of them exactly. See [Particles](Particles). |
@@ -234,7 +234,7 @@ group; folding the group the selected asset sits in lets go of the selection.
 A click on a row only
 selects (the inspector shows it, no tab moves); a **double-click** opens the asset as a document
 in a tab of its own (see **The tab row**) — a behavior, state machine, shader, particles,
-texture, animation, tile or container — and on a scene switches to the Scene tab and makes it the
+sound, texture, animation, tile or container — and on a scene switches to the Scene tab and makes it the
 active one. `Enter` does the same once the list has keyboard focus (`Tab`).
 A sprite, camera, text or collider has no tab of its own, so a double-click on one does nothing.
 Right-clicking a row offers *Set as active scene*, *Set as start scene* / *Clear start scene*,

Development.md

@@ -18,7 +18,7 @@ php tests/php/accounts.test.php                               # the API's accoun
                                                               #   has and the web server's container has not (SKIP there)
 php tests/php/snapshots.test.php                              # the snapshot store (#231), the same way
 php tests/php/releases.test.php                               # the release store (#266), the same way
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1833 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1840 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result

Home.md

@@ -21,7 +21,7 @@ Live: <https://nockal.com/game-maker/> · Widget playground: <https://nockal.com
 | [Vector art](Vector-Art) | The vector art asset, canvas and shapes, the Pen and Select tools, the shape list, how a drawing is worn |
 | [Pixel art](Pixel-Art) | The pixel art asset and its palette, the tools, layers and frames, onion skin and the preview, resizing, how frames are worn and where the pixels are stored |
 | [Fonts](Fonts) | Uploading a typeface, what a text wears, what the editor falls back to |
-| [Sounds](Sounds) | Uploading a sound, what the asset says, `Play sound` and `Stop sound`, sound FX (gain, pitch, EQ, mix, delay) and how long a voice rings on, what a pause and a stop do to a voice |
+| [Sounds](Sounds) | Uploading a sound, what the asset says, its tab and the cut, `Play sound` and `Stop sound`, sound FX (gain, pitch, EQ, mix, delay) and how long a voice rings on, what a pause and a stop do to a voice |
 | [Instruments](Instruments) | The instrument asset: Notes, Sample, Parameters, Sound FX, Envelope and Output, triggers, zones and layers, the keys of the Instrument tab, `Play note` |
 | [Patterns](Patterns) | The pattern asset and its piano roll: drawing, moving and sizing notes, the grid, the ruler with start and loop, velocities, playing it in a loop |
 | [Songs](Songs) | The song asset: tracks with volume, pan, mute and solo, pattern and sound items laid out, moved, cut and split, playing it in a loop |

Instruments.md

@@ -19,7 +19,7 @@ A at 440 Hz, 127 the highest. A note is named with its octave after it and no da
 | Node | What it does |
 | --- | --- |
 | **Notes** | Where the notes come in. `any` triggers what it is connected to for every note from **From** to **To**. `note` is the number of the note played, `frequency` its pitch in Hz (`440 * 2^((note - 69) / 12)`), `velocity` how hard it is struck, 0 to 1. With **Single notes** there is one trigger output for every note in the range as well, and each can have a **name** of its own (*Name of C2* in the inspector): the output shows it, and so do the keys of the [piano roll](Patterns#the-pattern-tab). |
-| **Sample** | Plays a sound asset when its `trigger` is on. With **Follow note** (on by default) it plays higher or lower by the distance from **Root**, the note it sounds as it is (C4 by default), and **keeps its length** — it is played by the same worklet as a Pitch (#317). Off, every note plays it as it is, as for a drum. **Play** says how it is played while the note is held and once it is let go (table below). **Loop start** and **Loop end** are in seconds, 0 at the end being the end of the sound. The volume of the sound asset counts. |
+| **Sample** | Plays a sound asset when its `trigger` is on. With **Follow note** (on by default) it plays higher or lower by the distance from **Root**, the note it sounds as it is (C4 by default), and **keeps its length** — it is played by the same worklet as a Pitch (#317). Off, every note plays it as it is, as for a drum. **Play** says how it is played while the note is held and once it is let go (table below). **Loop start** and **Loop end** are in seconds, 0 at the end being the end of the sound, counted in the stretch the sound is [cut to](Sounds#the-sound-tab). The volume of the sound asset counts. |
 | **Parameters** | The instrument's own parameters, each a number output with a default — like the parameters of a sound FX's Input. One per instrument. |
 | **Sound FX** | Sends the sound through a sound FX asset, as if it were the sound at the FX's Input. Every parameter of that FX is an input here; one left open is the FX's default. The node is titled after the FX, and a double click opens it. |
 | **Envelope** | Shapes a note as it is played: **Attack**, **Decay** and **Release** in seconds, **Sustain** from 0 to 1. On the way of the sound it is its volume; its output `value` moves a number with the same curve, from **From** to **To**. See [Envelopes](#envelopes). |

Sounds.md

@@ -22,15 +22,56 @@ short string in the project document, an undoable delete). A sound is **never re
 way**: what the server stores is the file that was picked. The format is read from the file's own
 signature, so nothing a request claims can decide what is written.
 
-**What the asset says.** Its inspector has two rows and a preview:
+**What the asset says.** Its inspector has these rows and a preview:
 
 | Row | Meaning |
 | --- | --- |
 | **Volume** | How loud this sound is by itself, 0-1. |
 | **Loop** | Whether it is music: it repeats until something stops it. |
+| **Start (s)**, **End (s)** | The stretch of the file the sound is, set in its [tab](#the-sound-tab). End 0 is the end of the file. |
+| **Edge fade (ms)** | How long each cut edge inside the file fades in or out, 10 by default. |
 
 The preview plays through the very same library a running game uses — same decode, same device —
-so what the inspector plays is what the graph will play.
+so what the inspector plays is what the graph will play, cut and all.
+
+## The Sound tab
+
+Opening a sound (double-click in the Assets panel, or Enter) brings up its tab (#343): the file as
+one waveform under a ruler in seconds, and the **stretch of it the asset is** between two
+handles. What lies outside is darker. **That stretch is the sample**: `Play sound`, an item in a
+[song](Songs) and the Sample of an [instrument](Instruments) all play it and nothing else, and
+everything that counts in seconds counts in it — `length`, the rounds of a song item and their
+waveform, a Sample's loop points, a Pitch.
+
+- **Drag a handle** to move that edge. **Drag anywhere else** to span a new stretch from where you
+  pressed. One drag is one undo step, the two edges together. An edge cannot pass the other.
+- **Whole file** in the header puts both handles back on the ends of the file.
+- **Edge fade (ms)** in the header (also in the inspector) is the ramp at each edge **inside**
+  the file: the stretch rises from silence over it and falls back to it, so a cut through a wave
+  does not click. It is counted into the stretch, so the stretch stays as long as it is. An edge
+  on the start or the end of the file is left as it is. A fade longer than half the stretch is
+  shortened to half. The ramps are drawn in the wave.
+- **Play** (or Space) plays the stretch once, at the asset's volume, with a playhead. It ends
+  whatever pattern or song the music tabs were playing, as they end each other.
+- The **wheel** zooms about the pointer, the **middle button** pans, as in the music tabs. Zoomed
+  in far enough, the samples themselves are drawn as a line.
+- A stereo file shows **one** wave, the loudest of its channels; it plays in stereo.
+- The header's readout says how long the stretch is, and of how long a file.
+
+**The file is never changed.** The cut lives on the asset, so a stretch can be made longer again
+at any time, and **two cuts of one file** are two assets (duplicate the asset, pick another
+stretch) that share the file on the server.
+
+**How it plays.** A cut sound is played by a name of its own, `<file>#<start>~<end>~<fade>`. The
+library fetches and decodes the file once and makes the stretch from it the first time that name
+plays: a copy of those samples with the ramps worked in. Length and waveform of a cut are read
+from the file itself, without a copy. Copies are made again whenever they are needed, so the
+library lets the oldest go once they hold more than 64 Mi samples together — a cut dragged about
+in its tab leaves no pile of copies behind. A sound over the whole file is no cut at all and plays
+the file as it always did; assets saved before the tab existed are such sounds.
+
+**Song items** keep their place and their length when their sound is cut anew: they play from the
+new start, and one longer than the new stretch plays it round and round.
 
 ## Playing it