mirror of
https://gitlab.gnome.org/GNOME/gtk.git
synced 2024-12-26 05:31:07 +00:00
3eacf8bd39
The documented icon flags didn't match the actual constants used by GTK when reading and updating icon theme cache files. Fix the values of flags in the documentation. Closes: https://gitlab.gnome.org/GNOME/gtk/-/issues/6489
164 lines
4.2 KiB
Plaintext
164 lines
4.2 KiB
Plaintext
Information about the icon theme cache format used by GTK
|
|
for more information, see the mailing list threads at
|
|
|
|
http://mail.gnome.org/archives/gtk-devel-list/2004-April/msg00065.html
|
|
http://lists.freedesktop.org/archives/xdg/2004-October/005140.html
|
|
|
|
|
|
Back in May, Owen Taylor proposed [1] caching scheme for icon theme
|
|
information, to reduce the amount of stating and disk seeking at
|
|
application startup, and to reduce the memory overhead if each app
|
|
allocates all the icon theme data separately.
|
|
|
|
The proposal is to keep the information about the icons in the
|
|
directory tree below each icon theme directory in an mmap()able
|
|
cache file (There is basically one cache file per index.theme file).
|
|
|
|
The cache doesn't try to hold all information from the index.theme files
|
|
that you would need to do lookups; it turns out that with the icon theme
|
|
specification, this isn't even sensible - you can install a
|
|
|
|
$HOME/.local/share/icons/Bluecurve/index.theme
|
|
|
|
That overrides
|
|
|
|
/usr/share/icons/Bluecurve/index.theme
|
|
|
|
and chances how lookup happens for icons in /usr/share/icons/Bluecurve.
|
|
|
|
We would like to propose the cache file format as an appendix to the
|
|
icon theme specification. One thing which still needs to be investigated
|
|
is caching of the actual image data; the file format is has an
|
|
IMAGE_DATA_OFFSET member to allow adding that compatibly. An
|
|
implementation of the caching scheme for GTK can be found at [2]. The
|
|
cache generator which is included in the patch depends only on glib, and
|
|
it may be a good idea to move it to freedesktop.org as well.
|
|
|
|
|
|
Regards, Matthias Clasen
|
|
|
|
|
|
The cache file format:
|
|
|
|
Header:
|
|
2 CARD16 MAJOR_VERSION 1
|
|
2 CARD16 MINOR_VERSION 0
|
|
4 CARD32 HASH_OFFSET
|
|
4 CARD32 DIRECTORY_LIST_OFFSET
|
|
|
|
DirectoryList:
|
|
4 CARD32 N_DIRECTORIES
|
|
4*N_DIRECTORIES CARD32 DIRECTORY_OFFSET
|
|
|
|
Hash:
|
|
4 CARD32 N_BUCKETS
|
|
4*N_BUCKETS CARD32 ICON_OFFSET
|
|
|
|
Icon:
|
|
4 CARD32 CHAIN_OFFSET
|
|
4 CARD32 NAME_OFFSET
|
|
4 CARD32 IMAGE_LIST_OFFSET
|
|
|
|
ImageList:
|
|
4 CARD32 N_IMAGES
|
|
8*N_IMAGES Image IMAGES
|
|
|
|
Image:
|
|
2 CARD16 DIRECTORY_INDEX
|
|
2 ICON_FLAGS FLAGS
|
|
4 CARD32 IMAGE_DATA_OFFSET
|
|
|
|
ICON_FLAGS
|
|
HAS_SUFFIX_XPM 1
|
|
HAS_SUFFIX_SVG 2
|
|
HAS_SUFFIX_PNG 4
|
|
HAS_ICON_FILE 8
|
|
|
|
ImageData:
|
|
4 CARD32 IMAGE_PIXEL_DATA_OFFSET
|
|
4 CARD32 IMAGE_META_DATA_OFFSET
|
|
|
|
4 CARD32 IMAGE_PIXEL_DATA_TYPE
|
|
4 CARD32 IMAGE_PIXEL_DATA_LENGTH
|
|
N/A N/A PIXEL_DATA
|
|
|
|
IMAGE_PIXEL_DATA_TYPE
|
|
0 GdkPixdata format
|
|
|
|
MetaData:
|
|
4 CARD32 EMBEDDED_RECT_OFFSET
|
|
4 CARD32 ATTACH_POINT_LIST_OFFSET
|
|
4 CARD32 DISPLAY_NAME_LIST_OFFSET
|
|
|
|
EmbeddedRect:
|
|
2 CARD16 X0
|
|
2 CARD16 Y0
|
|
2 CARD16 X1
|
|
2 CARD16 Y1
|
|
|
|
AttachPointList:
|
|
4 CARD32 N_ATTACH_POINTS
|
|
4*N_ATTACH_POINTS AttachPoint
|
|
|
|
AttachPoint:
|
|
2 CARD16 X
|
|
2 CARD16 Y
|
|
|
|
DisplayNameList:
|
|
4 CARD32 N_DISPLAY_NAMES
|
|
4*N_DISPLAY_NAMES DisplayName
|
|
|
|
DisplayName:
|
|
4 CARD32 DISPLAY_LANG_OFFSET
|
|
4 CARD32 DISPLAY_NAME_OFFSET
|
|
|
|
|
|
Notes:
|
|
|
|
* All offsets are from in bytes from the beginning of the file
|
|
|
|
* Strings are zero-terminated
|
|
|
|
* Directories are stored as relative paths.
|
|
|
|
* All numbers are in network (big-endian) order. This is
|
|
necessary because the data will be stored in arch-independent
|
|
directories like /usr/share/icons or even in user's
|
|
home directories.
|
|
|
|
* The hash function is that used by g_str_hash()
|
|
|
|
unsigned int
|
|
icon_str_hash (gconstpointer key)
|
|
{
|
|
const char *p = key;
|
|
unsigned int h = *p;
|
|
|
|
if (h)
|
|
for (p += 1; *p != '\0'; p++)
|
|
h = (h << 5) - h + *p;
|
|
|
|
return h;
|
|
}
|
|
|
|
This should not be implemented by calling g_str_hash(). For
|
|
optimal results, N_BUCKETS should be typically be prime.
|
|
|
|
* The same file format is used for icon themes (e.g.,
|
|
/usr/share/icons/Bluecurve) and for unthemed icon directories
|
|
(e.g., /usr/share/pixmaps)
|
|
|
|
For an unthemed directory, N_DIRECTORIES==0 and each
|
|
image has a DIRECTORY_INDEX field of 0xFFFF.
|
|
|
|
* Up-to-dateness of a cache file is determined simply:
|
|
|
|
If the mod-time on the directory where the cache file
|
|
lives is newer than the mod-time of the cache file,
|
|
the cache file is out of date.
|
|
|
|
* Cache files have to be written atomically - write to a
|
|
temporary name, then move over the old file - so that
|
|
clients that have the old cache file open and mmap'ed
|
|
won't get corrupt data.
|