[Spec] ImageSourceHandler

[ImageSource]

Create a service that handles the ImageSource logic on shared code based on this discussion between me, @PureWeen, and @mattleibow.

The general idea is to have an ImageSource handler class that will handle all ImageSource updates in the shared layer and reflects them to the Control.

API

[ IImageSourceHandler]

interface IImageSourceHandler
{
    ImageSource Current {get;}
    ImageSource LoadingPlaceholder {get;}
    ImageSource ErrorPlaceholder {get;}
    ImageSource Desired {get;}

    // Those can be internals

    Action OnLoadingStarted {get;}
    Action OnSourceChanged {get;}
    Action OnLoadingFailed {get;}
    Action OnLoadingCompleted {get;}
}

Properties

API	Description
Current	This will be the current ImageSource for displayed Image.
LoadingPlaceholder	ImageSource that will be presented while we load/download the Desired ImageSource
ErrorPlaceholder	ImageSource that will be presented if something goes wrong with the Desired ImageSource
Desired	The ImageSource that the user wants to present in the control

Events

API	Description
OnLoadingStarted	Action that will be fired when we start to load the Desired ImageSource
OnSourceChanged	Action that will be fired when Current value changes
OnLoadingFailed	Action that will be fired when something goes wrong during the Loading process
OnLoadingCompleted	Action that will be fired when we loaded the Desired ImageSource successfully

Scenarios

<Image Desired="ImageThatIWant"
       LoadingPlaceholder="LoadingTheDesiredSource"
       ErrorPlaceholder="ImageIfSomethingGoesWrong" />

Backward Compatibility

Minimum API levels? Breaking changes? Unsupported platforms?

Difficulty: medium

[pictos]

@mattleibow, thinking aloud here.

If inside the ImageSource we have a Stream or byte array that stores the current Bitmap (but could be any image file), and if the dev uses it in more than one place all they will see the same Image File and the same state (Loading, Loaded, Error, etc).

With this approach, we need to care about disposing of that Stream, not sure if this easy to do. Also, making it immutable can reduce the complexity (?)

[karthikraja-arumugam]

Do we have any workaround for this? We need a notification when the image has been successfully loaded into view.