Visual LANSA Layout Managers
|Product/Release:||LANSA for Windows|
|Abstract:||Layout Managers automatically manage the layout of a form. (Layout Managers is part of LANSA for Windows release 7.84)|
|Submitted By:||LANSA Amsterdam|
Using VL it's possible to arrange visual components such as push buttons and list views on forms by positioning and sizing them in the Component Editor. When the form is compiled and executed the form's visual components are initially arranged according to the position and size values set by the Component Editor.
This style of user interface management has a few restrictions:
When a form is executed, the application user may be able to maximize/minimize/restore the form or drag a border of the form. All these actions change the size of the form but the visual components on the form do not change their position or size. A technique using the Tick event of a Timer can be used to re-position and/or re-size the visual components but this is somewhat laborious and complex process.
Positioning a number of fields on a form or a page of a tabbed folder so that they follow a particular layout (like all aligned on the left side and appear evenly spaced down the screen) is time consuming. Adding another field causes the process to be manually repeated.
Reusable Parts are static when placed and sized in a form. Reusable Parts need to be designed so that their user interface components re-act when the size of the part changes.
There is no way to ensure visual components remain in view as a Form or Reusable Part is re-sized. A facility to enforce a minimum size is required.
In order to address these issues Visual LANSA provides a selection of Layout Managers.
Layout Managers control the way in which visual components are laid out within a container (ie: the visual component's parent) and how that layout changes when the container's size is changed.
Each type of layout manager implements a different layout policy.