TRender

Base class for all custom rendering shapes in TeeGrid

Overview

TRender is the base class for all custom rendering shapes in TeeGrid. It provides the foundation for painting cells, headers, and other grid elements with custom visual representations.

The rendering system in TeeGrid includes specialized renderers like TFormatRender, TTextRender, TBooleanRender, TExpanderRender, and TProgressRender.

Unit: Tee.Renders.pas

Class Hierarchy

TPersistentChange
└── TRender
    └── TFormatRender
        ├── TTextRender
        │   ├── TVisibleTextRender
        │   │   ├── TCellRender
        │   │   └── THover
        │   ├── TBoxRender
        │   │   ├── TBooleanRender
        │   │   └── TExpanderRender
        │   └── TPasswordRender
        └── TProgressRender

TRender Base Class

Methods

Paint

procedure Paint(var AData: TRenderData); virtual;

Renders the visual representation of the cell or element.

Parameters:

• AData: Rendering data containing bounds, painter, data value, and row index

Example:

var
  Render: TRender;
  Data: TRenderData;
begin
  Render := TTextRender.Create(nil);
  try
    Data.Bounds := RectF(0, 0, 100, 25);
    Data.Data := 'Hello World';
    Data.Painter := MyPainter;
    Data.Row := 0;
    
    Render.Paint(Data);
  finally
    Render.Free;
  end;
end;

Hit

function Hit(const R: TRectF; const X, Y: Single): Boolean; virtual;

Determines if a point (X, Y) is within the renderable area.

Parameters:

• R: Rectangle bounds
• X, Y: Point coordinates

Returns: True if the point hits the render area

TRenderData Record

The TRenderData record contains all information needed for rendering:

type
  TRenderData = record
    Bounds: TRectF;      // Rectangle to paint within
    Data: String;        // Cell data (as string)
    Painter: TPainter;   // Painter instance for drawing
    Row: Integer;        // Row index
    
    function AsBoolean: Boolean;
    procedure ClearData;
    function IsEmpty: Boolean;
  end;

Methods

• AsBoolean: Converts data to boolean value
• ClearData: Clears the data string
• IsEmpty: Checks if data is empty

TFormatRender

Rectangle shape renderer with borders and format support.

Properties

Borders

property Borders: TBorders read GetBorders write SetBorders;

Left, top, right, and bottom border strokes.

Example:

Render.Borders.Left.Visible := True;
Render.Borders.Left.Color := clBlue;
Render.Borders.Left.Size := 2;

Format

property Format: TTextFormat read GetFormat write SetFormat;

Background and stroke formatting.

Methods

HasFormat

function HasFormat: Boolean;

Returns True if format properties are assigned.

StrokeHeight

function StrokeHeight: Single;

Calculates the total height of all border strokes.

TTextRender

Rectangle renderer with text, margins, and alignment support.

Properties

Margins

property Margins: TMargins read GetMargins write SetMargins;

Left, top, right, bottom margins (pixels or %).

Example:

Render.Margins.Left.Value := 4;
Render.Margins.Top.Value := 2;
Render.Margins.Right.Value := 4;
Render.Margins.Bottom.Value := 2;

TextAlign

property TextAlign: TTextAlign read FAlign write SetAlign;

Horizontal and vertical text alignment.

Example:

Render.TextAlign.Horizontal := THorizontalAlign.Center;
Render.TextAlign.Vertical := TVerticalAlign.Center;

Trimming

property Trimming: TTextTrimming read GetTrimming write SetTrimming;

Text trimming mode and ellipsis settings.

Example:

Render.Trimming.Mode := TTrimmingMode.Character;
Render.Trimming.Ellipsi := True;

Methods

CalcHeight

function CalcHeight(const APainter: TPainter): Single; overload;
function CalcHeight(const APainter: TPainter; const AText: String): Single; overload;

Calculates the required height for rendering text.

Parameters:

• APainter: Painter instance for text measurement
• AText: Text to measure (optional)

Returns: Required height in pixels

TBooleanRender

Checkbox-style renderer for boolean values.

Properties

Style

property Style: TBooleanRenderStyle read FStyle write SetStyle;

Values:

• TBooleanRenderStyle.Check: Checkbox with checkmark
• TBooleanRenderStyle.Text: Text representation (“True”/“False”)

CheckFormat

property CheckFormat: TFormat read FCheckFormat write SetCheckFormat;

Format for the check mark itself.

Example:

var
  BoolRender: TBooleanRender;
begin
  BoolRender := TBooleanRender.Create(nil);
  BoolRender.Style := TBooleanRenderStyle.Check;
  BoolRender.CheckFormat.Stroke.Color := clGreen;
  BoolRender.CheckFormat.Stroke.Size := 2;
end;

TExpanderRender

Expander renderer with plus/minus, triangle, or arrow styles.

Properties

Style

property Style: TExpanderStyle read FStyle write SetStyle;

Values:

• TExpanderStyle.PlusMinus: Plus/minus symbols
• TExpanderStyle.Triangle: Triangle shapes
• TExpanderStyle.Arrow: Arrow symbols

AlwaysExpand

property AlwaysExpand: Boolean read FAlwaysExpand write FAlwaysExpand;

Always show expand indicator, even if no children.

ExpandFormat

property ExpandFormat: TFormat read FExpandFormat write SetExpandFormat;

Format for the expand symbol background.

ExpandLine

property ExpandLine: TStroke read FExpandLine write SetExpandLine;

Stroke for drawing the expand symbol lines.

Events

OnCanExpand

property OnCanExpand: TExpanderEvent read FOnCanExpand write FOnCanExpand;

Determines if a row can be expanded.

type
  TExpanderEvent = function(const Sender: TRender; const ARow: Integer): Boolean of object;

OnExpand

property OnExpand: TExpanderEvent read FOnExpand write FOnExpand;

Fired when expanding/collapsing a row.

OnGetExpanded

property OnGetExpanded: TExpanderEvent read FOnGetExpanded write FOnGetExpanded;

Gets the current expanded state.

Example:

function TForm1.ExpanderCanExpand(const Sender: TRender; const ARow: Integer): Boolean;
begin
  Result := HasChildren(ARow);
end;

function TForm1.ExpanderGetExpanded(const Sender: TRender; const ARow: Integer): Boolean;
begin
  Result := FExpandedRows.Contains(ARow);
end;

procedure TForm1.SetupExpander;
begin
  Expander.Style := TExpanderStyle.Triangle;
  Expander.OnCanExpand := ExpanderCanExpand;
  Expander.OnGetExpanded := ExpanderGetExpanded;
end;

Methods

Expand

procedure Expand(const ARow: Integer);

Toggles the expanded state of a row.

PaintLines

procedure PaintLines(var AData: TRenderData);

Paints hierarchical connection lines.

TProgressRender

Progress bar renderer showing percentage completion.

Properties

Minimum

property Minimum: Single read FMin write SetMin;

Minimum value (default: 0).

Maximum

property Maximum: Single read FMax write SetMax;

Maximum value (default: 100).

Orientation

property Orientation: TOrientation read FOrientation write SetOrientation;

Values:

• TOrientation.Horizontal: Left to right fill
• TOrientation.Vertical: Bottom to top fill

Example:

var
  ProgressRender: TProgressRender;
begin
  ProgressRender := TProgressRender.Create(nil);
  ProgressRender.Minimum := 0;
  ProgressRender.Maximum := 100;
  ProgressRender.Orientation := TOrientation.Horizontal;
  ProgressRender.Format.Brush.Color := clGreen;
end;

TPasswordRender

Text renderer that masks password characters.

Example:

var
  PassRender: TPasswordRender;
begin
  PassRender := TPasswordRender.Create(nil);
  // Automatically masks text as '***'
end;

TShapePainter Helper

Utility class for painting common shapes.

Methods

Check

class procedure Check(const APainter: TPainter; const ARect: TRectF); static;

Draws a checkmark symbol.

PlusMinus

class procedure PlusMinus(const APainter: TPainter; const ARect: TRectF; const IsExpanded: Boolean); static;

Draws plus or minus symbol.

Arrow.Down / Arrow.Right

class procedure TArrow.Down(const APainter: TPainter; const ARect: TRectF); static;
class procedure TArrow.Right(const APainter: TPainter; const ARect: TRectF); static;

Draws arrow symbols.

Triangle.LeftRight / Triangle.TopBottom

class procedure TTriangle.LeftRight(const APainter: TPainter; const ARect: TRectF); static;
class procedure TTriangle.TopBottom(const APainter: TPainter; const ARect: TRectF); static;

Draws triangle symbols.

Creating Custom Renderers

To create a custom renderer, inherit from TRender or one of its descendants:

type
  TMyCustomRender = class(TTextRender)
  public
    procedure Paint(var AData: TRenderData); override;
  end;

procedure TMyCustomRender.Paint(var AData: TRenderData);
begin
  // Custom painting logic
  inherited; // Call base class if needed
  
  // Additional custom drawing
  AData.Painter.SetBrush(Format.Brush);
  AData.Painter.FillEllipse(AData.Bounds);
end;

See Also

• TPainter - Abstract painter class for rendering
• TFormat - Formatting classes for styles and colors
• Custom Renderers Guide - How to create custom renderers