Canvas is a surface inside a window on which visual objects can be placed. A canvas is assigned to a window. Each item in a form must refer to not more than one canvas.
Types of Canvases:
- Content Canvas
- Stacked Canvas
- Toolbar Canvas
- Vertical Toolbar
- Horizontal toolbar
- Tab Canvas
Content Canvas is a base canvas and is a default canvas type. Content canvas occupies the entire content area of the window. More than one content canvas can be assigned to the same window but only one content canvas can be displayed on a window at a time. To display more than one content canvas at the same time, assign each content canvas to a different window.
Stacked Canvas is displayed on top of the content canvas and is usually small in size then that of content canvas in the same window. To convert an existing content canvas to a stacked canvas, simply change its canvas type property from content to stack. To show and hide canvases programmatically, use the SHOW_VIEW, HIDE_VIEW and SET_VIEW_PROPERTY built-ins. stacked canvas is useful to display additional information, for hiding information and can act as a scrolling view.
Toolbar Canvas is used to create toolbar for individual window. Toolbar canvas is of two types: Vertical and Horizontal toolbar canvases.
Vertical Toolbar canvas is displayed to the left of a content canvas.
Horizontal Toolbar canvas is displayed at the top of a content canvas.
Toolbar canvas is used to hold buttons and other frequently used GUI elements. Toolbar canvas increases application usability and decrease form module maintenance Time. Object Navigator window has both horizontal and vertical toolbars where as Property Palette has a horizontal toolbar only. You can also create more than one toolbar for the same window.
MDI Toolbar: Attaching a Toolbar to a form provides a MDI toolbar, so that there is no need to create more than one toolbar for a form application that uses multiple windows. Toolbar can be attached to individual windows or to the form itself.
(MDI-Multiple Document Interface is a parent window through which multiple documents can be accessed and browsed).
Tab Canvas enables the user to organize and display data on separate Tabs. Tab canvas is displayed on top of the Content Canvas. Each Tab canvas is made up of one or more Tab pages and must have at least one. Each Tab page occupies an equal amount of space on Tab canvas. Any Item you place on a Tab canvas has a Canvas property as well as Tab page Property. The ordering of Tab pages in the object navigator determines the left-to-right or Top-To-bottom order of the Tabs at runtime. Tab canvas provides easy access to data and displays large amount of data on a single canvas and is also used to hide information.
Frame, Item and Block
Frame is used to arrange data block items.
Item are Members of data block. Items grouped into Records.
Block provides a mechanism for grouping related items into a functional unit for storing, displaying and manipulating Records.
Window and View Port
Window is a container for all visual objects that make up a form application. Window performs functionality such as scrolling, moving and resizing. A single form may include several windows. Each window should have at least one content canvas. Each new form module has one predefined window which is called Window1 and is a modeless window.
View port is a visible portion of canvas.