====== PXAML Pipeline ======

The PXAML pipeline transforms declarative UI markup into executable user interfaces.

===== Overview =====

<code>
PXAML (Markup) → Parser → IR (JSON) → Renderer → GUI/TUI/Web
</code>

===== Pipeline Phases =====

==== Phase 1: Parsing ====

The PXAML parser reads XML markup and produces an Abstract Syntax Tree (AST).

<code xml>
<!-- Input: PXAML -->
<Window Title="Demo" Width="400">
  <Button Content="Click me" Click="OnClick"/>
</Window>
</code>

**Parser tasks:**
  * XML validation
  * Namespace resolution
  * Element recognition
  * Attribute parsing
  * Event binding detection

==== Phase 2: IR Generation ====

The AST is transformed into an Intermediate Representation (IR) - a JSON-based intermediate format.

<code json>
{
  "type": "Window",
  "properties": {
    "Title": { "value": "Demo", "type": "string" },
    "Width": { "value": 400, "type": "number" }
  },
  "children": [
    {
      "type": "Button",
      "properties": {
        "Content": { "value": "Click me", "type": "string" }
      },
      "events": {
        "Click": { "handler": "OnClick" }
      }
    }
  ]
}
</code>

**IR properties:**
  * Platform-independent
  * Serializable (JSON)
  * Diff-capable for hot reload
  * Type information preserved

==== Phase 3: Binding Resolution ====

Data bindings are analyzed and converted into executable structures.

<code xml>
<!-- PXAML with Binding -->
<TextBox Text="{Binding Path=UserName, Mode=TwoWay}"/>
</code>

<code json>
{
  "type": "TextBox",
  "properties": {
    "Text": {
      "type": "binding",
      "path": "UserName",
      "mode": "TwoWay"
    }
  }
}
</code>

==== Phase 4: Rendering ====

The IR is translated by the target-specific renderer into native UI elements.

^ Renderer ^ Output ^ Technology ^
| GUI | Native Controls | LCL/WinAPI |
| TUI | Terminal characters | ANSI/VT100 |
| Web | DOM Elements | HTML/CSS |

===== Components =====

==== TWvdSPxamlParser ====

<code pascal>
type
  TWvdSPxamlParser = class
  public
    function Parse(const ASource: string): TWvdSIRNode;
    function ParseFile(const APath: string): TWvdSIRNode;
  end;
</code>

==== TWvdSIRNode ====

<code pascal>
type
  TWvdSIRNode = class
    NodeType: string;
    Properties: TWvdSPropertyMap;
    Children: TWvdSIRNodeList;
    Events: TWvdSEventMap;
    Bindings: TWvdSBindingList;
  end;
</code>

==== TWvdSRenderer (Abstract) ====

<code pascal>
type
  TWvdSRenderer = class abstract
  public
    procedure Render(ARoot: TWvdSIRNode); virtual; abstract;
    procedure Update(AOldRoot, ANewRoot: TWvdSIRNode); virtual; abstract;
  end;
</code>

===== Hot Reload =====

The pipeline supports hot reload through IR differentiation:

<code>
1. New PXAML → Parser → New IR
2. Diff(Old IR, New IR) → Patch List
3. Renderer.ApplyPatches(Patch List)
</code>

**Benefits:**
  * Only changed elements are updated
  * State is preserved
  * Fast iteration during development

===== Error Handling =====

^ Error Type ^ Phase ^ Handling ^
| XML syntax error | Parsing | Position + message |
| Unknown element | Parsing | Warning + fallback |
| Invalid property type | IR | Type coercion + warning |
| Binding error | Binding | Fallback value |

===== See Also =====

  * [[.:architektur|Architecture Overview]]
  * [[.:targets|Build Targets]]
  * [[..:p:designer|UI Designer]]