====== Control Development ======

Workflow for creating new UI controls for the WvdS FPC RAD Suite.

<note>Controls must work for **design-time** (VS Code Designer) and **runtime** (Desktop/TUI/Web).</note>

===== Overview =====

A control consists of multiple layers:

^ Layer ^ Purpose ^ Path ^
| Runtime Model | Target-neutral logic | ''~/sources/common/ui/controls/{category}/'' |
| Target Renderer | Target-specific rendering | ''~/sources/common/ui/targets/{target}/renderers/'' |
| Pack Manifest | PXAML tag → class mapping | ''~/packs/controls/{control_id}/'' |
| Designer Metadata | Toolbox, Properties, Events | ''~/sources/extensions/wvds.vscode.ui.meta/'' |

===== Variables =====

When creating a control, define these variables:

^ Variable ^ Example ^ Description ^
| ''{CONTROL_ID}'' | ''dateedit'' | Unique identifier (lowercase) |
| ''{CONTROL_CLASS}'' | ''TWvdSDateEdit'' | Pascal class name |
| ''{PXAML_TAG}'' | ''DateEdit'' | Tag name in PXAML |
| ''{PXAML_NS}'' | ''wvds'' | Namespace (wvds for internal controls) |
| ''{TARGETS}'' | ''tui,desktop,web'' | Supported targets |

===== Workflow (7 Steps) =====

==== Step 1: Contract Freeze ====

Define the public API of the control:

**Properties:**
<code pascal>
(* Minimal set of public properties *)
property Value: TDateTime read FValue write SetValue;
property Format: string read FFormat write SetFormat;
property MinDate: TDateTime read FMinDate write FMinDate;
property MaxDate: TDateTime read FMaxDate write FMaxDate;
property ReadOnly: Boolean read FReadOnly write FReadOnly;
</code>

**Events:**
<code pascal>
(* Required events *)
property OnValueChanged: TWvdSNotifyEvent read FOnValueChanged write FOnValueChanged;
property OnValidating: TWvdSValidateEvent read FOnValidating write FOnValidating;
</code>

**TargetCaps:**

^ Capability ^ TUI ^ Desktop ^ Web ^
| Keyboard | Required | Required | Required |
| Mouse | Optional | Required | Required |
| Touch | N/A | Optional | Optional |
| Popup | Optional | Required | Required |

==== Step 2: Runtime Model Unit ====

Create the target-neutral model unit:

**Path:** ''~/sources/common/ui/controls/{category}/WvdS.UI.Controls.{Category}.{ControlId}.pas''

<code pascal>
unit WvdS.UI.Controls.Editors.DateEdit;

{$mode objfpc}{$H+}

interface

uses
  WvdS.UI.Core.Base,
  WvdS.UI.Core.Events;

type
  (*
    @abstract(Date input field with calendar popup)

    Target-neutral model for DateEdit.
    Contains NO rendering or host dependencies.
  *)
  TWvdSDateEdit = class(TWvdSControl)
  private
    FValue: TDateTime;
    FFormat: string;
    FOnValueChanged: TWvdSNotifyEvent;
    procedure SetValue(AValue: TDateTime);
  protected
    procedure DoValueChanged; virtual;
  public
    constructor Create(AOwner: TWvdSComponent); override;
    property Value: TDateTime read FValue write SetValue;
    property Format: string read FFormat write FFormat;
    property OnValueChanged: TWvdSNotifyEvent read FOnValueChanged write FOnValueChanged;
  end;

implementation

(* Implementation without target-specific code *)

end.
</code>

<note warning>**No target-specific dependencies!** No DOM, no terminal I/O, no LCL units.</note>

==== Step 3: Target Renderer Units ====

Create a renderer for each target in ''{TARGETS}'':

=== TUI Renderer ===

**Path:** ''~/sources/common/ui/targets/tui/renderers/WvdS.UI.TUI.Renderers.DateEdit.pas''

<code pascal>
unit WvdS.UI.TUI.Renderers.DateEdit;

{$mode objfpc}{$H+}

interface

uses
  WvdS.UI.TUI.Renderer.Base,
  WvdS.UI.Controls.Editors.DateEdit;

type
  TWvdSTUIDateEditRenderer = class(TWvdSTUIRenderer)
  public
    procedure Measure(AControl: TWvdSControl; out AWidth, AHeight: Integer); override;
    procedure Paint(AControl: TWvdSControl; ACanvas: TWvdSTUICanvas); override;
    procedure HandleInput(AControl: TWvdSControl; AEvent: TWvdSInputEvent); override;
  end;

implementation

procedure TWvdSTUIDateEditRenderer.Measure(AControl: TWvdSControl; out AWidth, AHeight: Integer);
begin
  AWidth := 12;  (* [YYYY-MM-DD] *)
  AHeight := 1;
end;

procedure TWvdSTUIDateEditRenderer.Paint(AControl: TWvdSControl; ACanvas: TWvdSTUICanvas);
var
  DateEdit: TWvdSDateEdit;
begin
  DateEdit := AControl as TWvdSDateEdit;
  ACanvas.DrawText(0, 0, FormatDateTime(DateEdit.Format, DateEdit.Value));
end;

procedure TWvdSTUIDateEditRenderer.HandleInput(AControl: TWvdSControl; AEvent: TWvdSInputEvent);
begin
  (* Keyboard handling for date changes *)
end;

end.
</code>

=== Desktop Renderer ===

**Path:** ''~/sources/common/ui/targets/gui/renderers/WvdS.UI.Desktop.Renderers.DateEdit.pas''

=== Web Renderer ===

**Path:** ''~/sources/common/ui/targets/web/renderers/WvdS.UI.Web.Renderers.DateEdit.pas''

==== Step 4: Pack Manifest ====

Create the pack manifest for the PXAML resolver:

**Path:** ''~/packs/controls/{control_id}/pack.wvds.json''

<code javascript>
{
  "id": "dateedit",
  "vendor": "wvds",
  "version": "0.1.0",
  "xml": {
    "namespace": "wvds",
    "tag": "DateEdit"
  },
  "model": {
    "unit": "WvdS.UI.Controls.Editors.DateEdit",
    "class": "TWvdSDateEdit"
  },
  "renderers": {
    "tui": {
      "unit": "WvdS.UI.TUI.Renderers.DateEdit",
      "class": "TWvdSTUIDateEditRenderer"
    },
    "desktop": {
      "unit": "WvdS.UI.Desktop.Renderers.DateEdit",
      "class": "TWvdSDesktopDateEditRenderer"
    },
    "web": {
      "unit": "WvdS.UI.Web.Renderers.DateEdit",
      "class": "TWvdSWebDateEditRenderer"
    }
  },
  "targetCaps": {
    "requires": ["keyboard"],
    "optional": ["mouse", "popup"]
  }
}
</code>

==== Step 5: Designer Metadata ====

Create designer metadata for Toolbox and Properties:

**Add descriptor to:** ''~/sources/common/core/meta/WvdS.Meta.Controls.Editors.pas''

<code pascal>
procedure RegisterDateEditMeta(ARegistry: TMetaRegistry);
var
  TypeMeta: TTypeMeta;
begin
  TypeMeta := CreateTypeMeta('DateEdit', 'TWvdSDateEdit', 'Editors');
  TypeMeta.Description := 'Date input field with calendar popup';
  TypeMeta.Icon := 'calendar';

  (* Properties *)
  TypeMeta.AddProperty(CreatePropertyMeta('Value', pkDateTime, 'Current date value'));
  TypeMeta.AddProperty(CreatePropertyMeta('Format', pkString, 'Display format (e.g. yyyy-mm-dd)'));
  TypeMeta.AddProperty(CreatePropertyMeta('MinDate', pkDateTime, 'Earliest allowed date'));
  TypeMeta.AddProperty(CreatePropertyMeta('MaxDate', pkDateTime, 'Latest allowed date'));
  TypeMeta.AddProperty(CreatePropertyMeta('ReadOnly', pkBoolean, 'Read-only mode'));

  (* Events *)
  TypeMeta.AddEvent(CreateEventMeta('OnValueChanged', 'Fired when Value changes'));
  TypeMeta.AddEvent(CreateEventMeta('OnValidating', 'Fired before value change'));

  ARegistry.RegisterType(TypeMeta);
end;
</code>

==== Step 6: Registry Registration ====

Register the control in the runtime registries:

=== PXAML Resolver ===

The ''pxamlc'' compiler reads ''pack.wvds.json'' automatically from ''~/packs/''.

=== Target Runtime Registry ===

Update the renderer registry for each target:

<code pascal>
(* In WvdS.UI.TUI.Render.Registry.pas *)
procedure RegisterTUIRenderers;
begin
  (* ... other renderers ... *)
  RegisterRenderer(TWvdSDateEdit, TWvdSTUIDateEditRenderer);
end;
</code>

==== Step 7: Documentation ====

Create API documentation for the control:

**Path:** ''~/docs/api/controls/dateedit.md''

<code markdown>
# TWvdSDateEdit

Date input field with optional calendar popup.

## When to Use

- User needs to enter a date
- Restrict date range (MinDate/MaxDate)
- Formatted date display required

## Properties

| Property | Type | Description |
|----------|------|-------------|
| Value | TDateTime | Current date value |
| Format | string | Display format |
| MinDate | TDateTime | Earliest allowed date |
| MaxDate | TDateTime | Latest allowed date |
| ReadOnly | Boolean | Read-only mode |

## Events

| Event | Description |
|-------|-------------|
| OnValueChanged | Fired when Value changes |
| OnValidating | Allows validation before value change |

## Example

```xml
<DateEdit Value="{Binding BirthDate}"
          Format="dd.MM.yyyy"
          MinDate="1900-01-01"
          MaxDate="2100-12-31" />
```
</code>

===== Completion Criteria =====

A control is complete when:

<code>
[ ] VS Code Designer can place {PXAML_NS}:{PXAML_TAG}
[ ] Properties editable in Designer
[ ] Preview in Designer works
[ ] Target build (tui/desktop/web) compiles successfully
[ ] Pack manifest present and recognized by resolver
[ ] API documentation written
</code>

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

  * [[.:pxaml-pipeline|PXAML Pipeline]]
  * [[.:pack-struktur|Pack Structure]]
  * [[.:targets|Build Targets]]
  * [[.:meta-api|Meta API]]