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To prepare for color management, we have to make the device colorspaces
per-context and able to be overridden by users.
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This requires a slight change to the device interface.
Callers that use fz_begin_tile will see no change (and no caching
will be done). We add a new fz_begin_tile_id function that takes an
extra 'id' parameter, and returns 0 or 1. If the id is 0 then the
function behaves exactly as fz_being_tile does, and always returns 0.
The PDF and XPS code continues to call the old (uncached) version.
The display list code however generates a unique id for every
BEGIN_TILE node, and passes this in.
If the id is non zero, then it is taken to be a unique identifier
for this tile; the implementer of the fz_begin_tile_id entry point
can choose to use this to implement caching. If it chooses to ignore
the id (and do no caching), it returns 0.
If the device implements caching, then it can check on entry for a
previously rendered tile with the appropriate matrix and a matching id.
If it finds one, then it returns 1. It is the callers responsibility
to then skip over all the device calls that would usually happen to
render the tiles (i.e. to skip forward to the matching 'END_TILE'
operation).
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Thanks to zeniko.
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When cloning, ensure the locks are done on the new context, not the
old one; this makes no difference except to suppress some spurious
debugging messages.
Also ensure that DEBUG is predefined for Makefile based debug and memento
builds.
Thanks to Bas Weelinck.
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Make fz_clone_context copy existing AA settings.
Add accessor function for fz_bitmap.
Add more documentation for various functions/types.
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Attempt to separate public API from internal functions.
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Add docs for fz_store, fz_image, fz_halftones.
Move fz_item definition into res_store.c as it does not need to be
external.
Rename fz_store_context to fz_keep_store_context to be consistent.
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Currently, we are in the slightly strange position of having
the PDF specific object types as part of fitz. Here we pull
them out into the pdf layer instead. This has been made possible
by the recent changes to make the store no longer be tied to
having fz_obj's as keys.
Most of this work is a simple huge rename; to help customers who
may have code that use such functions we have provided a sed
script to do the renaming; scripts/rename2.sed.
Various other small tweaks are required; the store used to have
some debugging code that still required knowledge of fz_obj
types - we extract that into a nicer 'type' based function
pointer. Also, the type 3 font handling used to have an fz_obj
pointer for type 3 resources, and therefore needed to know how
to free this; this has become a void * with a function to free
it.
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All in one command line replacement for muxpsdraw and mupdfdraw.
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We only open one instance of freetype per document. We therefore
have to ensure that only 1 call to it takes place at a time. We
introduce a lock for this purpose (FZ_LOCK_FREETYPE), and arrange
to take/release it as required.
We also update the font context so it is properly shared.
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This is a significant change to the use of locks in MuPDF.
Previously, the user had the option of passing us lock/unlock
functions for a single mutex as part of the allocation struct.
Now we remove these entries from the allocation struct, and
make a separate 'locks' struct. This enables people to use
fz_alloc_default with locking.
If multithreaded operation is required, then the user is
required to create FZ_LOCK_MAX mutexes, which will be locked
or unlocked by MuPDF calling the lock/unlock functions within
the new fz_locks_context structure passed in at context creation.
These mutexes are not required to be recursive (they may be, but
MuPDF should never call them in this way). MuPDF avoids deadlocks
by imposing a locking ordering on itself; a thread will never take
lock n, if it already holds any lock i for which 0 <= i <= n.
Currently, there are 4 locks used within MuPDF.
Lock 0: The alloc lock; taken around all calls to user supplied
(or default) allocation functions. Also taken around all accesses
to the refs field of storable items.
Lock 1: The store lock; taken whenever the store data structures
(specifically the linked list pointers) are accessed.
Lock 2: The file lock; taken whenever a thread is accessing the raw
file. We use the debugging macros to insist that this is held
whenever we do a file based seek or read. We also insist that this
is never held when we resolve an indirect reference, as this can
have the effect of moving the file pointer.
Lock 3: The glyphcache lock; taken whenever a thread calls freetype,
or accesses the glyphcache data structures. This introduces some
complexities w.r.t type3 fonts.
Locking can be hugely problematic, so to ease our minds as to
the correctness of this code, we introduce some debugging macros.
These compile away to nothing unless FITZ_DEBUG_LOCKING is defined.
fz_assert_lock_held(ctx, lock) checks that we hold lock.
fz_assert_lock_not_held(ctx, lock) checks that we do not hold lock.
In addition fz_lock_debug_lock and fz_lock_debug_unlock are used
on every fz_lock/fz_unlock to check the validity of the operation
we are performing - in particular it checks that we do/do not already
hold the lock we are trying to take/drop, and that by taking this
lock we are not violating our defined locking order.
The RESOLVE macro (used throughout the code to check whether we need
to resolve an indirect reference) calls fz_assert_lock_not_held to
ensure that we aren't about to resolve an indirect reference (and
hence move the stream pointer) when the file is locked.
In order to implement the file locking properly, pdf_open_stream
(and friends) now lock the file as a side effect (because they
fz_seek to the start of the stream). The lock is automatically
dropped on an fz_close of such streams.
Previously, the glyph cache was created in a context when it was first
required; this presents problems as it can be shared between several
contexts or not, depending on whether it is created before the
contexts are cloned. We now always create it at startup, so it is
always shared.
This means that we need reference counting for the glyph caches.
Added here.
In fz_render_glyph, we take the glyph cache lock, and check to see
whether the glyph is in the cache. If it is, we bump the refcount,
drop the lock and returned the cached character. If it is not, we
need to render the character.
For freetype based fonts we keep the lock throughout the rendering
process, thus ensuring that freetype is only called in a single
threaded manner.
For type3 fonts, however, we need to invoke the interpreter again
to render the glyph streams. This can require reentrance to this
routine. We therefore drop the glyph cache lock, call the
interpreter to render us our pixmap, and take the lock again.
This dropping and retaking of the lock introduces a possible race
condition; 2 threads may try to render the same character at the
same time. We therefore modify our hash table insert routines to
behave differently if it comes to insert an entry only to find
that an entry with the same key is already there.
We spot this case; if we have just rendered a type3 glyph and when
we try to insert it into the cache discover that someone has beaten
us to it, we just discard our entry and use the cached one.
Hopefully this will seldom be a problem in practise; to solve it
properly would require greater complexity (probably involving
spotting that another thread is already working on the desired
rendering, and sleeping on a semaphore until it completes).
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When cloning a context, it's generally best to return your new
context, rather than the one you cloned from.
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When we moved over to a context based system, we laid the foundation
for a thread-safe mupdf. This commit should complete that process.
Firstly, fz_clone_context is properly implemented so that it
makes a new context, but shares certain sections (currently
just the allocator, and the store).
Secondly, we add locking (to parts of the code that have
previously just had placeholder LOCK/UNLOCK comments). Functions
to lock and unlock a mutex are added to the allocator structure;
omit these (as is the case today) and no multithreading is
(safely) possible. The context will refuse to clone if these are
not provided.
Finally we flesh out the LOCK/UNLOCK comments to be real calls of
the functions - unfortunately this requires us to plumb fz_context
into the fz_keep_storable function (and all the fz_keep_xxx
functions that call it). This is the largest section of the patch.
No changes expected to any test files.
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Change the fz_store to be limited to 256 Megs. Remove the soft limit
for pixmaps; the store will automatically throw old resources away
to stay below the limit.
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Firstly, we rename pdf_store to fz_store, reflecting the fact that
there are no pdf specific dependencies on it.
Next, we rework it so that all the objects that can be stored in
the store start with an fz_storable structure. This consists of
a reference count, and a function used to free the object when
the reference count reaches zero.
All the keep/drop functions are then reimplemented by calling
fz_keep_sharable/fz_drop_sharable. The 'drop' functions as supplied
by the callers are thus now 'free' functions, only called if
the reference count drops to 0.
The store changes to keep all the items in the store in the linked
list (which becomes a doubly linked one). We still make use of
the hashtable to index into this list quickly, but we now have
the objects in an LRU ordering within the list.
Every object is put into the store, with a size record; this is
an estimate of how much memory would be freed by freeing that
object.
The store is moved into the context and given a maximum size;
when new things are inserted into the store, care is taken to
ensure that we do not expand beyond this size. We evict any
stored items (that are not in use) starting from the least
recently used.
Finding an object in the store now takes a reference to it already.
LOCK and UNLOCK comments are used to indicate where locks need to
be taken and released to ensure thread safety.
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Also: use 'cannot' instead of 'failed to' in error messages.
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Remove use of 'die', in place of proper exception handling.
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In builds that support configurable layers of antialiasing, move
the variables that control this into the context. This makes it
possible to safely use different levels of antialiasing in different
threads.
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Freetype globals are not shared between threads currently - to do that
we'll need to introduce a lock.
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This was removed during a previous commit to make the editing easier.
Now added back in.
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