macOS Gestures

This article applies to macOS only.

See also: Multiplatform Programming Guide

Overview

The Gestures unit provides convenient Free Pascal classes for handling macOS gestures.

Currently only the magnification gesture is implemented, but others can be implemented easily in a similar way.

Usage Example

Let's assume your scalable control has a Scale property and you want to allow an end user to scale it by using the typical trackpad gesture. Here is the code:

uses
  Gestures;

type
  TForm_Main = class(TForm)
  private
    Gesture: TMagnificationGesture;
    InitialScale: Double;
  end;

procedure TForm_Main.FormCreate(Sender: TObject);
begin
  Gesture := TMagnificationGesture.Create(Self);
  Gesture.Control := MyScalableControl;
  Gesture.OnGesture := @MagnificationGestureGesture;
end;

procedure TForm_Main.MagnificationGestureGesture(Sender: TMagnificationGesture;
  State: TGestureState; Magnification: Double);
begin
  case State of
    gsBegan:
      InitialScale := MyScalableControl.Scale;

    gsChanged:
      if Magnification > 0 then
        MyScalableControl.Scale := InitialScale * (1 + Magnification)
      else
        MyScalableControl.Scale := InitialScale / (1 - Magnification);
  end;
end;

Author

Yuri Plashenkov

License

This package is licensed under the MIT license.

Download

The Gestures unit may be downloaded from GitHub.

External links

• Apple: Trackpad gestures
• Apple: Gestures