Working with Scrolling Content

Pixel based scrolling tables and scrolling layers provide the ability to scroll content in a smooth and uniform fashion. Configuring table's for scrolling is covered in the chapter Creating Lists and Tables. Scrolling layers are based entirely on the bounds of their child group and control content and require a simple property enablement Enable layer scrolling behaviour within the Properties View.

scrolling_layers.png

When scrolling is enabled the object that is being scrolled, be it a layer or a table, is being moved as if it were positioned virtually and the object bounds provide the viewport into that virtual position. To track and measure this virtual positioning there are two internal Storyboard variables grd_xoffset and grd_yoffset that can be used to determine the virtual object position relative to the it's actual position. Considering the y offset value, when it is at 0 the content is aligned with the top of the control. When the y offset value is negative the content appears to be moving down.

When scrolling is enabled in the properties for an object the Storyboard Engine will start automatically tracking any press, release and motion events targeted at the object. While a press is active, the object will track exactly to the user motion. Once the press turns to a release, then the object will scroll automatically based on the scrolling properties configured.

Orientation

Vertical or Horizontal scrolling

Bounce

Number of pixels for the scrolling object to bounce when reaching the edge of the contents within the object

Top/Bottom Padding

Additional pixels at the top (left) or bottom (right) to allow scrolling past the edge of the contents within the object

Flick Gesture

If enabled, the object will continue to scroll after a drag and release based on the momentum of the gesture

Decay

Maximum time in milliseconds the scrolling object will scroll after a flick

Friction

A number from 0 to 100 to determine the friction level of the scrolling object. With higher friction it becomes more resistant to moving when swiped and more inclined to slowing down when released

Snap

If enabled, a scrolling table will automatically have its cell boundaries snap to the specified pixel offset after a flick gesture is triggered. A scrolling layer will have its offset snap to the nearest multiple of the specified offset

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