====== TUI Engine ======

Arhitektura i zahtjevi kvalitete TUI Rendering Enginea.

<note warning>Ovi zahtjevi su **nepregovarajući** - definiraju minimalni standard za GUI-sličnu TUI-kvalitetu.</note>

===== Zahtjevi kvalitete =====

==== 1. Flicker-free Rendering ====

<code>
OBAVEZNO:
- Double-Buffering s Diff-based Flushom
- Dirty-Rect ili Run-Length Optimizacija
- Nikakve Full-Screen Redraw Petlje
</code>

**Zašto:** Flicker uništava korisničko iskustvo i čini TUI neupotrebljivim za profesionalne aplikacije.

==== 2. Deterministički Layout + Clipping ====

<code>
OBAVEZNO:
- Implementirati Measure/Arrange/Paint Lifecycle
- Clipati crtanje na dodijeljene Rectangles
- Nikakve Out-of-Bounds pisanja
</code>

==== 3. Unicode-Korektnost ====

<code>
OBAVEZNO:
- Pravilno rukovanje Wide Characters (East Asian Width)
- Pravilno rukovanje Combining Marks
- Pravilno izračunavanje Emoji-širine
- Pozicioniranje Cursora mora biti Grapheme-aware
</code>

**Problem:** "Drifting Caret" - Cursor se pomiče kod Wide Chars.

**Rješenje:** Koristiti Grapheme-Cluster za izračun Cursora.

==== 4. Theme + State Layering ====

<code>
OBAVEZNO:
- Podržati Style Tokens
- Implementirati Layered States:
  Base → Hover (ako Mouse) → Focus → Pressed → Disabled → Error/Validation
- Focus-Indikatori konzistentni preko svih Controls
</code>

==== 5. Input + Focus kao First-Class ====

<code>
OBAVEZNO:
- Focus Navigation (Tab/Shift+Tab)
- Deterministički Focus Ordering
- Normalizirani Input Event Model:
  Keys, Text Input, Resize, opcionalni Mouse
</code>

==== 6. Performanse i Skaliranje ====

<code>
OBAVEZNO:
- Virtualizacija za velike Surfaces (Tables/Logs/Trees)
- Izbjegavati O(N) Repaint Offscreen Rows/Columns
- Efikasno korištenje memorije
</code>

==== 7. Image-Support (SCADA/MES) ====

<code>
OBAVEZNO:
- Implementirati Capability Detection
- Fallback-lanac:
  1. Kitty Graphics (preferirano)
  2. Sixel
  3. Placeholder (Frame + Caption + "image unavailable")
</code>

===== Engine-Komponente =====

==== A) Terminal Capability Layer ====

<code pascal>
TTerminalCaps = record
  SupportsAnsi: Boolean;
  SupportsAltScreen: Boolean;
  SupportsTrueColor: Boolean;
  Supports256Color: Boolean;
  SupportsMouse: Boolean;
  SupportsKittyGraphics: Boolean;
  SupportsSixel: Boolean;
  SupportsUnicodeWidth: Boolean;
end;

TTerminalIO = class
  procedure EnterAltScreen;
  procedure ExitAltScreen;
  procedure ShowCursor;
  procedure HideCursor;
  procedure WriteEscapeSequence(const ASeq: string);
  procedure WriteTextRun(const AText: string);
  procedure MoveCursor(AX, AY: Integer);
  procedure SetStyle(AStyle: TStyle);
  procedure BatchFlush;
end;
</code>

==== B) Render Model: CellBuffer + DiffEngine ====

<code pascal>
TCell = record
  Grapheme: string;      (* Unicode Grapheme Cluster *)
  Fg: TColor;            (* Foreground Color *)
  Bg: TColor;            (* Background Color *)
  Attrs: TAttributes;    (* Bold, Italic, Underline, itd. *)
  Link: string;          (* Opcionalno: Hyperlink *)
  ImageRef: Integer;     (* Opcionalno: Image Reference *)
end;

TCellBuffer = class
private
  FCells: array of array of TCell;
  FWidth, FHeight: Integer;
public
  procedure SetCell(AX, AY: Integer; const ACell: TCell);
  function GetCell(AX, AY: Integer): TCell;
  procedure Clear;
  procedure Resize(AWidth, AHeight: Integer);
end;
</code>

**DiffEngine:**

<code pascal>
TDiffEngine = class
private
  FBackBuffer: TCellBuffer;   (* Ciljni Frame *)
  FFrontBuffer: TCellBuffer;  (* Zadnji flushani Frame *)
public
  procedure ComputeDiff(out ADirtyRects: TRectArray);
  procedure Flush(ATerminal: TTerminalIO);
end;
</code>

**Zahtjevi za DiffEngine:**
  * Minimalna pomicanja Cursora
  * Minimalne promjene Stylea
  * Stabilan kod brzog Resizea

==== C) Render Surface (Drawing API) ====

<code pascal>
TRenderSurface = class
private
  FBuffer: TCellBuffer;
  FClipStack: TRectStack;
public
  procedure FillRect(ARect: TRect; AChar: Char; AStyle: TStyle);
  procedure DrawText(AX, AY: Integer; const AText: string; AStyle: TStyle);
  procedure DrawBorder(ARect: TRect; ABorderStyle: TBorderStyle);
  procedure DrawImage(ARect: TRect; AImageRef: Integer);
  procedure ClipPush(ARect: TRect);
  procedure ClipPop;
end;
</code>

**Važno:** Surface piše samo u BackBuffer, ne direktno u TerminalIO.

==== D) Layout Engine ====

<code>
Controls se aranžiraju u Rectove.

Minimalni Containeri:
- Stack (vertikalno/horizontalno)
- Dock (Left, Top, Right, Bottom, Fill)
- Grid (kasnije)
- Overlay (za Popupe/Modale)
</code>

==== E) Widget/Control Rendering Contract ====

<code pascal>
IWvdSTUIRenderer = interface
  function Measure(AControl: TWvdSControl; AAvailable: TSize): TSize;
  procedure Arrange(AControl: TWvdSControl; ARect: TRect);
  procedure Paint(AControl: TWvdSControl; ASurface: TRenderSurface);
  function HandleInput(AControl: TWvdSControl; AEvent: TInputEvent): Boolean;
end;
</code>

===== Testing =====

==== Snapshot Testovi ====

<code>
OBAVEZNO:
- Dumpati BackBuffer u stabilnu tekstualnu reprezentaciju
- Usporediti s očekivanim izlazom
</code>

==== Unicode-Fixtures ====

<code>
OBAVEZNO:
- Testovi s Wide Characters (中文, 日本語)
- Testovi s Combining Marks (é = e + ´)
- Testovi s Emoji (👍, 🎉)
</code>

==== Image-Fallback Testovi ====

<code>
OBAVEZNO:
- Testirati Kitty → Sixel → Placeholder Fallback
- Verificirati Capability Detection
</code>

===== Verifikacijska checklista =====

<code>
TUI Engine Verifikacija:

Rendering:
- [ ] Nema flickera pri ponovljenom Repaintu
- [ ] Resize proizvodi stabilan Layout
- [ ] Nema zaglavljenog Cursora
- [ ] Nema polomljenog Clippinga

Unicode:
- [ ] Wide Characters ispravno pozicionirani
- [ ] Combining Marks ispravno prikazani
- [ ] Emoji-širina ispravna

Performanse:
- [ ] Table/List renderira 10k redaka sa Scrollom
- [ ] Nema O(N) Repainta za Offscreen

Images:
- [ ] Kitty Graphics funkcionira (ako je podržano)
- [ ] Sixel Fallback funkcionira
- [ ] Placeholder kod nedostatka podrške
</code>

===== Vidi također =====

  * [[.:tui-entwicklung|TUI-Razvoj Pregled]]
  * [[.:tui-controls|TUI Controls]]
  * [[.:tui-layout|TUI Layout]]