Align GC behavior on init calls on all platforms

[karolszafranski]

Problem description

You can call init on GC instance multiple times. We have to align what should happen if you call it for the second time with different dimensions or without any parameters at all.

Currently, iOS uses 0 for the dimension which is undefined and all drawings are removed on each init call.

Expected behavior

We expect that all platforms are consistent :-)

Environment

• Tabris.js version: 3.0.0-beta
• Device: any
• OS: any

[mpost]

As you pointed out calling getContext and thereby the internal init() call again should reset the context with the newly given dimensions. The Android client does so and reinitializes the context.

[karolszafranski]

What about the case when init is called without width and height parameters?

[mpost]

Than it should be assumed that the canvas has 0 width and height but the context is reinitialized as expected.

[karolszafranski]

This means that we have to update the test in run-all.js

@tbuschto

[tbuschto]

Actually calling getContext without parameters may cause errors and even crashes on both platforms. This should simply not be allowed. Calling getImageData with values that are out of bounds also behaves inconsistently.