Roku SDK Documentation : ifImageCanvas

Implemented By

• roImageCanvas

Supported Methods

Description of Methods

AllowUpdates(updatesEnabled as Boolean) as Void

Turn updates on or off. Surrounding changes to several layers with AllowUpdates(false) and AllowUpdates(true) calls makes complex display modification atomic. Gives the application protection against the image canvas trying to render a partial update.

SetLayer(zOrder as Integer, contentMetaData as Object) as Void

zOrder is a z-order specifier with higher z-orders closer to the viewer. Negative z-orders are "behind the display" and are thus invisible. Each call to SetLayer replaces the previous content metadata that previously existed at that z-order layer. The caller passes an roAssociativeArray (Content Meta-Data objects) representing the information for each image to be displayed on the roImageCanvas.

The screen is redrawn when SetLayer()is called.

SetLayer(zOrder as Integer, contentList as Object) as Void

Works like the previous SetLayer(), except passes an roArray of roAssociativeArrays instead of just a single roAssociativeArray of Content Meta-Data.

SwapLayers(zOrderA as Integer, zOrderB as Integer) as Void

Swap the content Meta-Data stored in zOrderA with the content Meta-Data stored in zOrderB.

Enables the developer to change which layer is displayed "On Top"

It is possible to SwapLayers with empty (unspecified) layers.

SetRequireAllImagesToDraw(requireAllImages as Boolean) as Void

If true, wait till all images in the content-meta-data array are downloaded, decoded, and loaded into memory before drawing the screen.

There is a large performance penalty for setting this to true.

PurgeCachedImages() as Void

This is a convenience method that will purge the internal cache of all images related to urls in the current content list. If the content list is empty, then this method will do nothing.

GetCanvasRect() as Object

Returns an roAssociativeArray with names w for width and h for height.

ClearLayer(zOrder as Integer) as Void

Clear all content from a layer (see SetLayer for the layer definition)

Clear() as Void

Clear all content from all layers.

Show() as Boolean

Display or refresh the screen after initial creation or state changes.

Note that screen update times can vary significantly depending on how much of the screen needs to be redrawn, and how many different images and layers you are using.

Close() as Void

Close the screen and delete the associated object. Useful for avoiding screen flicker when the display order of your screens does not resemble a stack.

AddButton(id as Integer, title as String) as Boolean

Adds a button to the screen identified by the title and ID provided. The buttons are displayed in a standard location on the screen and appear in the order added. The ID is defined by the developer and used to uniquely identify the button instance. When the button is pressed, the script will receive an event from the application containing the ID of the button pressed and allowing the script to perform the desired action for that case.

ClearButtons() as Void

Clears all of the buttons from the screen and resets the array of buttons back to default with no buttons set.