Bug 18920 - ISpannable does not include the constants included in the Android Spannable Interface.
Summary: ISpannable does not include the constants included in the Android Spannable I...
Status: RESOLVED FEATURE
Alias: None
Product: Android
Classification: Xamarin
Component: BCL Class Libraries ()
Version: 4.2.x
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: ---
Assignee: Jonathan Pryor
URL:
Depends on:
Blocks:
 
Reported: 2014-04-09 23:42 UTC by Dustin Graham
Modified: 2014-04-10 11:25 UTC (History)
1 user (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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RESOLVED FEATURE

Description Dustin Graham 2014-04-09 23:42:19 UTC
The Android Spannable interface includes several very important constants which are used to define the styling behavior of SpannableStrings. The Android documentation details these constants:

http://developer.android.com/reference/android/text/Spanned.html#SPAN_EXCLUSIVE_EXCLUSIVE

I believe these should be added to the ISpannable interface to match Android functionality?
Comment 1 Jonathan Pryor 2014-04-10 11:25:11 UTC
This is unfortunately By Design.

The way binding works is we take a .jar (e.g. android.jar), generate an API description via jar2xml, then generate C# source from the API description, then compile the C# source into the binding assembly.

All of the glue code is thus represented in C#, and thus must be valid C#.

Unfortunately, C#'s definition of what's valid within an interface doesn't match Java's: C# interfaces can only contain method, property, and event declarations. No fields, no constants, no nested types, no static methods, etc.

Consequently, the C# ISpannable binding CANNOT contain an ISpannable.SpanExclusiveExclusive member, not without changing the language. (IL should allow this, but who wants to hand-write IL?)

Instead, one of two things is done:

1. The interface constants are mapped to enumerations.

In the case of android.text.Spannable, the constants are present on the SpanTypes enum: http://androidapi.xamarin.com/?link=T%3aAndroid.Text.SpanTypes

2. When the interface constants don't map to an enumeration
http://docs.xamarin.com/guides/android/advanced_topics/api_design/#Interfaces

In this case, e.g. the android.os.Parcelable interface, the interface methods are moved to a normal C# interface -- IParcelable -- while the interface constants are moved to a type with the same name as the Java interface, in this case Android.OS.Parcelable.

For the same 'C# is our glue" reason, nested types such as android.os.Parcelable.Creator are not nested types, and android.os.Parcelable.Creator is bound as IParcelableCreator: http://androidapi.xamarin.com/?link=T%3aAndroid.OS.IParcelableCreator