Everything that goes in a PLDHashtable (and its derivatives, like
nsTHashtable) needs to inherit from PLDHashEntryHdr. But through a lack
of enforcement, copy constructors for these derived classes didn't
explicitly invoke the copy constructor for PLDHashEntryHdr (and the
compiler didn't invoke the copy constructor for us). Instead,
PLDHashTable explicitly copied around the bits that the copy constructor
would have.
The current setup has two problems:
1) Derived classes should be using move construction, not copy
construction, since anything that's shuffling hash table keys/entries
around will be using move construction.
2) Derived classes should take responsibility for transferring bits of
superclass state around, and not rely on something else to handle that.
The second point is not a huge problem for PLDHashTable (PLDHashTable
only has to copy PLDHashEntryHdr's bits in a single place), but future
hash table implementations that might move entries around more
aggressively would have to insert compensation code all over the
place. Additionally, if moving entries is implemented via memcpy (which
is quite common), PLDHashTable copying around bits *again* is
inefficient.
Let's fix all these problems in one go, by:
1) Explicitly declaring the set of constructors that PLDHashEntryHdr
implements (and does not implement). In particular, the copy
constructor is deleted, so any derived classes that attempt to make
themselves copyable will be detected at compile time: the compiler
will complain that the superclass type is not copyable.
This change on its own will result in many compiler errors, so...
2) Change any derived classes to implement move constructors instead of
copy constructors. Note that some of these move constructors are,
strictly speaking, unnecessary, since the relevant classes are moved
via memcpy in nsTHashtable and its derivatives.
One thing to note here is that the Scale function on gfxRect has a
different implementation than that in gfx::Rect which is replacing it.
The former just scales the width/height directly whereas the latter
scales the XMost/YMost and recomputes the width/height.
MozReview-Commit-ID: 5FImdIaNfC3
--HG--
extra : rebase_source : 98662d2a52ff9652ec60b066641a07c6d5ee8e08
AutoTextRun now only needs a DrawTarget instead of an nsRenderingContext, and
similar nsRenderingContext/gfxContext-to-DrawTarget replacements can be
propagated a long way up the call graph. This patch replaces 93 occurrences of
nsRenderingContext and 135 occurrences of gfxContext with DrawTarget; that's
13% of them.
The patch is mostly plumbing changes. A couple of not-entirely-plumbing
changes:
- It adds a comment about the null check in
gfxGlyphExtents::GetTightGlyphExtentsAppUnits().
- A couple of functions simply had an unused gfxContext or nsRenderingContext
parameter removed, e.g. SetLineBreaks().
--HG--
extra : rebase_source : 8f56994bb4d254a86788b17ab2864ebc758a7e6b
Tooru Fujisawa
Sylvestre Ledru
Nathan Froyd
Andi-Bogdan Postelnicu
Sebastian Hengst
Tristan Bourvon
Kartikaya Gupta
David Anderson
Nicholas Nethercote
Jonathan Kew
Ehsan Akhgari