Docs

.claude/rpg/cutscene.md

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+# Cutscenes
+
+Two distinct layers: a low-level engine sequencer (`src/dusk/cutscene/`) and a higher-level RPG wrapper (`src/dusk/rpg/cutscene/`). Almost all game code works with the RPG layer.
+
+---
+
+## Engine sequencer (`src/dusk/cutscene/`)
+
+`cutscene_t CUTSCENE` is a minimal event runner with up to `CUTSCENE_EVENT_COUNT_MAX` (16) `cutsceneevent_t` slots. Each event has three callbacks:
+
+```c
+typedef struct {
+  errorret_t (*onStart)(void);
+  errorret_t (*onUpdate)(void);
+  errorret_t (*onEnd)(void);
+} cutsceneevent_t;
+```
+
+API:
+```c
+cutscenePlay(events, count);   // copy events array and start from index 0
+cutsceneAdvance();             // end current event, start next (deactivates after last)
+cutsceneStop();                // abort immediately
+cutsceneIsActive();            // bool
+```
+
+This layer is primarily used by the RPG cutscene system — game code doesn't normally touch it directly.
+
+---
+
+## RPG cutscene layer (`src/dusk/rpg/cutscene/`)
+
+### Data structures
+
+A `cutscene_t` is just a pointer to an item array and a count:
+
+```c
+typedef struct cutscene_s {
+  const cutsceneitem_t *items;
+  uint8_t itemCount;
+} cutscene_t;
+```
+
+A `cutsceneitem_t` is a tagged union of all item types:
+
+```c
+typedef struct cutsceneitem_s {
+  cutsceneitemtype_t type;
+  union {
+    cutscenetext_t    text;      // display text in textbox
+    cutscenecallback_t callback; // call a void(*)(void) function
+    cutscenewait_t    wait;      // pause for a fixed_t duration (seconds)
+    const cutscene_t *cutscene;  // nest another cutscene
+  };
+} cutsceneitem_t;
+```
+
+### Item types
+
+| Type constant | Payload | Behaviour |
+|---|---|---|
+| `CUTSCENE_ITEM_TYPE_TEXT` | `cutscenetext_t` — `text[256]` + `rpgtextboxpos_t position` | Shows textbox; advances on player confirm input |
+| `CUTSCENE_ITEM_TYPE_CALLBACK` | `cutscenecallback_t` (function pointer) | Calls the function once, then immediately advances |
+| `CUTSCENE_ITEM_TYPE_WAIT` | `cutscenewait_t` (a `fixed_t` in seconds) | Counts down `animTime` each frame, then advances |
+| `CUTSCENE_ITEM_TYPE_CUTSCENE` | `const cutscene_t *` | Plays the nested cutscene before continuing |
+
+### Runtime state
+
+`cutscenesystem_t CUTSCENE_SYSTEM` tracks:
+- `scene` — pointer to the active `cutscene_t`
+- `currentItem` — index into `scene->items[]`
+- `data` — per-item runtime data (`cutsceneitemdata_t`, currently just `cutscenewaitdata_t`)
+- `mode` — the current `cutscenemode_t`
+
+API:
+```c
+cutsceneSystemStartCutscene(cutscene);   // begin playing a cutscene
+cutsceneSystemNext();                    // advance to next item
+cutsceneSystemUpdate();                  // called each frame from rpgUpdate
+cutsceneSystemGetCurrentItem();          // inspect active item
+```
+
+### Cutscene mode (`cutscenemode.h`)
+
+Each item can run in one of three modes:
+
+```c
+CUTSCENE_MODE_NONE           // no cutscene active
+CUTSCENE_MODE_FULL_FREEZE    // pause everything (not yet used)
+CUTSCENE_MODE_INPUT_FREEZE   // player input blocked (default: CUTSCENE_MODE_INITIAL)
+CUTSCENE_MODE_GAMEPLAY       // player can still move during cutscene
+```
+
+`cutsceneModeIsInputAllowed()` is checked by `entityUpdate()` before invoking the movement callback — the player cannot walk when in INPUT_FREEZE mode.
+
+### Defining a cutscene
+
+Cutscenes are defined as `static const` arrays in header files under `rpg/cutscene/scene/`. Example (`testcutscene.h`):
+
+```c
+static const cutsceneitem_t MY_CUTSCENE_ITEMS[] = {
+  {
+    .type = CUTSCENE_ITEM_TYPE_TEXT,
+    .text = { .text = "Hello!", .position = RPG_TEXTBOX_POS_BOTTOM }
+  },
+  {
+    .type = CUTSCENE_ITEM_TYPE_WAIT,
+    .wait = FIXED(1.5f)
+  },
+  {
+    .type = CUTSCENE_ITEM_TYPE_CUTSCENE,
+    .cutscene = &ANOTHER_CUTSCENE
+  },
+};
+
+static const cutscene_t MY_CUTSCENE = {
+  .items = MY_CUTSCENE_ITEMS,
+  .itemCount = sizeof(MY_CUTSCENE_ITEMS) / sizeof(cutsceneitem_t)
+};
+```
+
+Attach to an NPC via its interact component:
+```c
+entity->interact.type = ENTITY_INTERACT_CUTSCENE;
+entity->interact.data.cutscene = &MY_CUTSCENE;
+```
+
+---
+
+## Textbox (`src/dusk/rpg/rpgtextbox.h`)
+
+`rpgtextbox_t RPG_TEXTBOX` is the global textbox state:
+
+```c
+typedef struct {
+  rpgtextboxpos_t position;      // RPG_TEXTBOX_POS_TOP or RPG_TEXTBOX_POS_BOTTOM
+  bool_t visible;
+  char_t text[RPG_TEXTBOX_MAX_CHARS];   // 256 chars
+} rpgtextbox_t;
+```
+
+API:
+```c
+rpgTextboxShow(position, text);   // copies text, sets visible = true
+rpgTextboxHide();                 // sets visible = false
+rpgTextboxIsVisible();            // bool
+```
+
+The textbox state is read by `ui/uitextbox.c` during the UI render pass to draw the dialogue box on screen. `rpgtextbox.c` itself does no rendering.