TImageEnView.OnDrawLayerGrip

Declaration

property OnDrawLayerGrip: TIEDrawLayerGrip;

Description

Occurs when a layer grip is painted. If you handle this event the default behavior is disabled.
ABitmap is the destination bitmap and LayerIndex is the layer we are drawing.
Grip is in the range 0-9 as follows:
Rect specifies the actual grip rectangle.

See the LayerEditing\Layers demo for more details.

ImageEnView Paint Events

The main paint events of TImageEnView are OnDrawBackBuffer which occurs when the back buffer is painted and OnDrawCanvas which occurs every time the canvas is painted. Generally OnDrawBackBuffer is used for better performance, because the back buffer painting only occurs after the content is updated. If you need constant custom drawing (e.g. to draw a marker at the current cursor position) then use OnDrawCanvas.

In layer applications, OnBeforeDrawLayer and OnDrawLayer will occur while painting each individual layer. Use these methods if you need easy custom drawing upon each individual layer (e.g. a layer title). Generally OnBeforeDrawLayer is best, unless you need to paint to the whole image (i.e. outside the area of the layer).

Other drawing events:
◼OnDrawBackground occurs when the background (area behind the image is painted) is painted to allow custom background styling
◼OnDrawLayerBox occurs when the box around a layer is painted to allow custom styling of the box
◼OnDrawLayerGrip occurs when the grips of the selected layer are drawn to allow custom grip styling
◼OnTransitionPaint occurs while transitioning from one image to the next
◼OnPaint notifies whenever there is a paint event. It is not used for custom drawing
◼OnDrawPolygon notifies whenever a point of a polygonal selection is drawn

Examples

// Draw custom style grips
procedure TForm1.ImageEnView1DrawLayerGrip(Sender: TObject;
  ABitmap: TBitmap; layer, grip: Integer; rect: TRect);
begin
  with ABitmap.Canvas do
  begin
    Pen.Style := psSolid;
    Pen.Mode  := pmCopy;
    Pen.Color := clGreen;
    Brush.Style := bsSolid;
    Brush.Color := $0000FF00;
    with rect do
      Ellipse(Left-1, Top-1, Right+1, Bottom+1);
  end;
end;

// Only draw corner grips
procedure TForm1.ImageEnView1DrawLayerGrip(Sender: TObject;
  ABitmap: TBitmap; layer, grip: Integer; rect: TRect);
var
  iec: TIECanvas;
begin
  if grip in [0,1,2,3] then
  begin
    iec := TIECanvas.Create( ABitmap.Canvas );
    IEDrawGrip( iec, rect,  ImageEnView1.GetLayersGripStyle() );
    iec.Free();
  end;
end;

See Also

◼GetLayersGripStyle
◼SetLayersBoxStyle
◼SetLayersGripStyle
◼LayersDrawBox
◼TIELayer.VisibleBox
◼OnDrawLayerBox

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