The caret movement code already handles unselectable text frames if we
happen to land in the middle of one in nsTextFrame::PeekOffsetCharacter/Word.
However, when performing frame traversal to find the next frame to jump
to, we don't remember if we skipped over an unselectable frame, which causes
us to jump one offset too much when the caret is on the boundary of
selectable and unselectable content. The test cases demonstrate the
scenario. Note that an <img alt=foo> is implemented by adding a
generated content to the inline frame representing it, so as far as
the caret movement code is concerned, both test cases are treated similarly.
Note that we need to do this only when moving the selection, and not
when extending it. We are adding an aExtend argument to
nsPeekOffsetStruct's constructor in order to be able to special case
that.
This patch started an attempt to remove nsFrameSelection.h from nsCaret.h
and metastasized into a rather large refactoring patch that removed it
from some other header files as well, and changed nsFrameSelection::HINT
into a global-scope enum with better names. I also converted bools
into CaretAssociationHint in a few places where that was appropriate,
but there are still some more places (GetChildFrameContainingOffset)
where bools need to be converted. I figured this patch was big enough already.
GetGeometry is used in two different ways. Sometimes it's used to get
information about a particular caret. Sometimes it's used to get
information about a particular selection that's not associated with
a caret. Splitting GetGeometry into a non-static version for the former
and a static version for the latter makes this more clear. Also it saves
code since for the latter version we don't have to get an nsCaret first.
