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GetBitmap.3
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1994-09-20
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Tk_GetBitmap(3) Tk Library Procedures
_________________________________________________________________
NAME
Tk_GetBitmap, Tk_DefineBitmap, Tk_NameOfBitmap,
Tk_SizeOfBitmap, Tk_FreeBitmap, Tk_GetBitmapFromData - main-
tain database of single-plane pixmaps
SYNOPSIS
#include <tk.h>
Pixmap
Tk_GetBitmap(_i_n_t_e_r_p, _t_k_w_i_n, _i_d)
int |
Tk_DefineBitmap(_i_n_t_e_r_p, _n_a_m_e_I_d, _s_o_u_r_c_e, _w_i_d_t_h, _h_e_i_g_h_t) |
Tk_Uid
Tk_NameOfBitmap(_d_i_s_p_l_a_y, _b_i_t_m_a_p) |
Tk_SizeOfBitmap(_d_i_s_p_l_a_y, _b_i_t_m_a_p, _w_i_d_t_h_P_t_r, _h_e_i_g_h_t_P_t_r) |
Tk_FreeBitmap(_d_i_s_p_l_a_y, _b_i_t_m_a_p) |
ARGUMENTS
Tcl_Interp *_i_n_t_e_r_p (in) Interpreter to use for
error reporting.
Tk_Window _t_k_w_i_n (in) Token for window in
which the bitmap will
be used.
Tk_Uid _i_d (in) Description of bitmap;
see below for possible
values.
Tk_Uid *_n_a_m_e_I_d (in) Name for new bitmap to
be defined.
char *_s_o_u_r_c_e (in) Data for bitmap, in
standard bitmap for-
mat. Must be stored
in static memory whose
value will never
change.
unsigned int _w_i_d_t_h (in) Width of bitmap.
unsigned int _h_e_i_g_h_t (in) Height of bitmap.
unsigned int *_w_i_d_t_h_P_t_r (out) Pointer to word to
fill in with _b_i_t_m_a_p's
width.
Tk 1
Tk_GetBitmap(3) Tk Library Procedures
unsigned int *_h_e_i_g_h_t_P_t_r (out) Pointer to word to
fill in with _b_i_t_m_a_p's
height.
Display *_d_i_s_p_l_a_y (in) Display for which _b_i_t_-
_m_a_p was allocated. |
Pixmap _b_i_t_m_a_p (in) Identifier for a bit-
map allocated by
Tk_GetBitmap.
_________________________________________________________________
DESCRIPTION
These procedures manage a collection of bitmaps (one-plane
pixmaps) being used by an application. The procedures allow
bitmaps to be re-used efficiently, thereby avoiding server
overhead, and also allow bitmaps to be named with character
strings.
Tk_GetBitmap takes as argument a Tk_Uid describing a bitmap.
It returns a Pixmap identifier for a bitmap corresponding to
the description. It re-uses an existing bitmap, if possi-
ble, and creates a new one otherwise. At present, _i_d must
have one of the following forms:
@_f_i_l_e_N_a_m_e _F_i_l_e_N_a_m_e must be the name of a file con-
taining a bitmap description in the
standard X11 or X10 format.
_n_a_m_e _N_a_m_e must be the name of a bitmap
defined previously with a call to
Tk_DefineBitmap. The following names
are pre-defined by Tk:
error The international "don't" |
symbol: a circle with a |
diagonal line across it.
gray50 50% gray: a checkerboard
pattern where every other
bit is on.
gray25 25% gray: a pattern where
25% of the bits are on, con-
sisting of all the bit posi-
tions that can be reached by
a chess knight starting at
(0,0).
hourglass An hourglass symbol. |
Tk 2
Tk_GetBitmap(3) Tk Library Procedures
info ||
A large letter ``i''. |
quest- |
head ||
The silhouette of a human |
head, with a question mark |
in it. |
ques- |
tion ||
A large question-mark. |
warn- |
ing ||
A large exclamation point.
Under normal conditions, Tk_GetBitmap returns an identifier
for the requested bitmap. If an error occurs in creating
the bitmap, such as when _i_d refers to a non-existent file,
then None is returned and an error message is left in
_i_n_t_e_r_p->_r_e_s_u_l_t.
Tk_DefineBitmap associates a name with in-memory bitmap data |
so that the name can be used in later calls to Tk_GetBitmap. |
The _n_a_m_e_I_d argument gives a name for the bitmap; it must |
not previously have been used in a call to Tk_DefineBitmap. |
The arguments _s_o_u_r_c_e, _w_i_d_t_h, and _h_e_i_g_h_t describe the bitmap. |
Tk_DefineBitmap normally returns TCL_OK; if an error occurs |
(e.g. a bitmap named _n_a_m_e_I_d has already been defined) then |
TCL_ERROR is returned and an error message is left in |
_i_n_t_e_r_p->_r_e_s_u_l_t. Note: Tk_DefineBitmap expects the memory |
pointed to by _s_o_u_r_c_e to be static: Tk_DefineBitmap doesn't |
make a private copy of this memory, but uses the bytes |
pointed to by _s_o_u_r_c_e later in calls to Tk_GetBitmap.
Typically Tk_DefineBitmap is used by #include-ing a bitmap
file directly into a C program and then referencing the
variables defined by the file. For example, suppose there
exists a file stip.bitmap, which was created by the bitmap
program and contains a stipple pattern. The following code
uses Tk_DefineBitmap to define a new bitmap named foo:
Pixmap bitmap;
#include "stip.bitmap"
Tk_DefineBitmap(interp, Tk_GetUid("foo"), stip_bits,
stip_width, stip_height);
...
bitmap = Tk_GetBitmap(interp, tkwin, Tk_GetUid("foo"));
This code causes the bitmap file to be read at compile-time
and incorporates the bitmap information into the program's
executable image. The same bitmap file could be read at
Tk 3
Tk_GetBitmap(3) Tk Library Procedures
run-time using Tk_GetBitmap:
Pixmap bitmap;
bitmap = Tk_GetBitmap(interp, tkwin, Tk_GetUid("@stip.bitmap"));
The second form is a bit more flexible (the file could be
modified after the program has been compiled, or a different
string could be provided to read a different file), but it
is a little slower and requires the bitmap file to exist
separately from the program.
Tk_GetBitmap maintains a database of all the bitmaps that
have been created. Whenever possible, it will return an
existing bitmap rather than creating a new one. This
approach can substantially reduce server overhead, so
Tk_GetBitmap should generally be used in preference to Xlib
procedures like XReadBitmapFile.
The bitmaps returned by Tk_GetBitmap are shared, so callers
should never modify them. If a bitmap must be modified
dynamically, then it should be created by calling Xlib pro-
cedures such as XReadBitmapFile or XCreatePixmap directly.
The procedure Tk_NameOfBitmap is roughly the inverse of
Tk_GetBitmap. Given an X Pixmap argument, it returns the _i_d
that was passed to Tk_GetBitmap when the bitmap was created. |
_B_i_t_m_a_p must have been the return value from a previous call |
to Tk_GetBitmap.
Tk_SizeOfBitmap returns the dimensions of its _b_i_t_m_a_p argu- |
ment in the words pointed to by the _w_i_d_t_h_P_t_r and _h_e_i_g_h_t_P_t_r |
arguments. As with Tk_NameOfBitmap, _b_i_t_m_a_p must have been |
created by Tk_GetBitmap.
When a bitmap returned by Tk_GetBitmap is no longer needed,
Tk_FreeBitmap should be called to release it. There should
be exactly one call to Tk_FreeBitmap for each call to
Tk_GetBitmap. When a bitmap is no longer in use anywhere
(i.e. it has been freed as many times as it has been gotten)
Tk_FreeBitmap will release it to the X server and delete it
from the database.
BUGS
In determining whether an existing bitmap can be used to
satisfy a new request, Tk_GetBitmap considers only the
immediate value of its _i_d argument. For example, when a
file name is passed to Tk_GetBitmap, Tk_GetBitmap will
assume it is safe to re-use an existing bitmap created from
the same file name: it will not check to see whether the
file itself has changed, or whether the current directory
has changed, thereby causing the name to refer to a dif-
ferent file.
Tk 4
Tk_GetBitmap(3) Tk Library Procedures
KEYWORDS
bitmap, pixmap
Tk 5
