gfxContext needs to have a valid draw target to be constructed. Don't attempt to make one of those if the target is invalid, and make it obvious to the callers they will not get a gfxContext if the draw target is invalid, by removing direct access to the constructor, and instead having a utility function that can return failure.

Review commit: https://reviewboard.mozilla.org/r/42243/diff/#index_header See other reviews: https://reviewboard.mozilla.org/r/42243/

Would it make more sense to just have the constructor crash and make the users check the drawtarget before constructing the gfxContext?

That's what we do today, and it hasn't worked. I'm hoping that having an explicit method that looks like it can fail, instead of a constructor, which people assume does not, would help this.

Comment on attachment 8734451 [details] MozReview Request: Bug 1259513: Make gfxContext constructor private, use a utility function that can return nullptr. r?lsalzman Review request updated; see interdiff: https://reviewboard.mozilla.org/r/42243/diff/1-2/

Comment on attachment 8734451 [details] MozReview Request: Bug 1259513: Make gfxContext constructor private, use a utility function that can return nullptr. r?lsalzman Critical note if the arguments aren't checked, just to make some more noise and a few places where the calling code wasn't consistent.

Comment on attachment 8734451 [details] MozReview Request: Bug 1259513: Make gfxContext constructor private, use a utility function that can return nullptr. r?lsalzman https://reviewboard.mozilla.org/r/42243/#review38841 With the caveat that we must now make sure that we check the result of gfxContext::ForDrawTarget when we use it, r+.

Comment on attachment 8734451 [details] MozReview Request: Bug 1259513: Make gfxContext constructor private, use a utility function that can return nullptr. r?lsalzman https://reviewboard.mozilla.org/r/42243/#review39213

Comment on attachment 8734451 [details] MozReview Request: Bug 1259513: Make gfxContext constructor private, use a utility function that can return nullptr. r?lsalzman Review request updated; see interdiff: https://reviewboard.mozilla.org/r/42243/diff/2-3/

(In reply to Milan Sreckovic [:milan] from comment #8) > Comment on attachment 8734451 [details] > MozReview Request: Bug 1259513: Make gfxContext constructor private, use a > utility function that can return nullptr. r?lsalzman > > Review request updated; see interdiff: > https://reviewboard.mozilla.org/r/42243/diff/2-3/ This is just a rebase.

Comment on attachment 8734451 [details] MozReview Request: Bug 1259513: Make gfxContext constructor private, use a utility function that can return nullptr. r?lsalzman Review request updated; see interdiff: https://reviewboard.mozilla.org/r/42243/diff/3-4/

Comment on attachment 8734451 [details] MozReview Request: Bug 1259513: Make gfxContext constructor private, use a utility function that can return nullptr. r?lsalzman Review request updated; see interdiff: https://reviewboard.mozilla.org/r/42243/diff/4-5/