add enums to distinguish different constructors for matrix44

add enums to distinguish different constructors for matrix44

[reed1, 2012-12-05 14:29:01]

This CL is just for show, to get a feel for this style of constructor-specialization and ways to name it.

[bsalomon, 2012-12-05 14:32:08]

On 2012/12/05 14:29:01, reed1 wrote: > This CL is just for show, to get a feel for this style of > constructor-specialization and ways to name it. I like the idea... would you get rid of the existing default constructor? Whatever we do I think we should keep SkMatrix and SkMatrix44 in sync. It would kinda irk me to type kUninitializedConstructor every time I want a matrix, though.

[reed1, 2012-12-05 14:36:29]

I agree on both counts. I like the empty/default constructor to be uninitialized. I think we might keep it hidden initially, to explicitly catch all of our current callers in chrome, which are today relying on it calling setIdent. After that phase, I would like to re-introduce the empty guy. Given all that, I bet we could start to use this pattern in SkMatrix now: to add helper constructors w/ enums as we see the value at call-sites. (in a separate cl)

[shawnsingh, 2012-12-05 18:41:18]

I'm against re-introducing the default constructor. I don't feel it adds any expressive power or efficiency to how we use the matrix class. But on the other hand it does risk additional obscurity and error-proneness. For chrome in particular, many of us have it baked in our minds that default constructor will initialize to identity. In general I would expect that its very common for people to assume a class is correctly initialized and ready to use after its default constructor...