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- '\" $Header: /user6/ouster/wish/man/RCS/GetBitmap.3,v 1.11 93/04/01 09:41:24 ouster Exp $ SPRITE (Berkeley)
- '\"
- .\" The definitions below are for supplemental macros used in Tcl/Tk
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- .HS Tk_GetBitmap tkc
- .BS
- .SH NAME
- Tk_GetBitmap, Tk_DefineBitmap, Tk_NameOfBitmap, Tk_SizeOfBitmap, Tk_FreeBitmap, Tk_GetBitmapFromData \- maintain database of single-plane pixmaps
- .SH SYNOPSIS
- .nf
- \fB#include <tk.h>\fR
- .sp
- Pixmap
- \fBTk_GetBitmap(\fIinterp, tkwin, id\fB)\fR
- .sp
- .VS
- int
- \fBTk_DefineBitmap(\fIinterp, nameId, source, width, height\fR)\fR
- .VE
- .sp
- Tk_Uid
- .VS
- \fBTk_NameOfBitmap(\fIdisplay, bitmap\fB)\fR
- .sp
- \fBTk_SizeOfBitmap(\fIdisplay, bitmap, widthPtr, heightPtr\fB)\fR
- .sp
- \fBTk_FreeBitmap(\fIdisplay, bitmap\fB)\fR
- .VE
- .SH ARGUMENTS
- .AS "unsigned long" *pixelPtr
- .AP Tcl_Interp *interp in
- Interpreter to use for error reporting.
- .AP Tk_Window tkwin in
- Token for window in which the bitmap will be used.
- .AP Tk_Uid id in
- Description of bitmap; see below for possible values.
- .AP Tk_Uid *nameId in
- Name for new bitmap to be defined.
- .AP char *source in
- Data for bitmap, in standard bitmap format.
- Must be stored in static memory whose value will never change.
- .AP "unsigned int" width in
- Width of bitmap.
- .AP "unsigned int" height in
- Height of bitmap.
- .AP "unsigned int" *widthPtr out
- Pointer to word to fill in with \fIbitmap\fR's width.
- .AP "unsigned int" *heightPtr out
- Pointer to word to fill in with \fIbitmap\fR's height.
- .AP Display *display in
- Display for which \fIbitmap\fR was allocated.
- .VS
- .VE
- .AP Pixmap bitmap in
- Identifier for a bitmap allocated by \fBTk_GetBitmap\fR.
- .BE
-
- .SH DESCRIPTION
- .PP
- 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.
- .PP
- \fBTk_GetBitmap\fR 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 possible, and
- creates a new one otherwise. At present, \fIid\fR must have
- one of the following forms:
- .TP 20
- \fB@\fIfileName\fR
- \fIFileName\fR must be the name of a file containing a bitmap
- description in the standard X11 or X10 format.
- .TP 20
- \fIname\fR
- \fIName\fR must be the name of a bitmap defined previously with
- a call to \fBTk_DefineBitmap\fR. The following names are pre-defined
- by Tk:
- .RS
- .TP 12
- \fBerror\fR
- .VS
- The international "don't" symbol: a circle with a diagonal line
- across it.
- .VE
- .TP 12
- \fBgray50\fR
- 50% gray: a checkerboard pattern where every other bit is on.
- .TP 12
- \fBgray25\fR
- 25% gray: a pattern where 25% of the bits are on, consisting of all the
- bit positions that can be reached by a chess knight starting at (0,0).
- .TP 12
- \fBhourglass\fR
- .VS
- An hourglass symbol.
- .TP 12
- \fBinfo\fR
- A large letter ``i''.
- .TP 12
- \fBquesthead\fR
- The silhouette of a human head, with a question mark in it.
- .TP 12
- \fBquestion\fR
- A large question-mark.
- .TP 12
- \fBwarning\fR
- A large exclamation point.
- .VE
- \fB
- .RE
- .LP
- Under normal conditions, \fBTk_GetBitmap\fR
- returns an identifier for the requested bitmap. If an error
- occurs in creating the bitmap, such as when \fIid\fR refers
- to a non-existent file, then \fBNone\fR is returned and an error
- message is left in \fIinterp->result\fR.
- .PP
- \fBTk_DefineBitmap\fR associates a name with
- .VS
- in-memory bitmap data so that the name can be used in later
- calls to \fBTk_GetBitmap\fR. The \fInameId\fR
- argument gives a name for the bitmap; it must not previously
- have been used in a call to \fBTk_DefineBitmap\fR.
- The arguments \fIsource\fR, \fIwidth\fR, and \fIheight\fR
- describe the bitmap.
- \fBTk_DefineBitmap\fR normally returns TCL_OK; if an error occurs
- (e.g. a bitmap named \fInameId\fR has already been defined) then
- TCL_ERROR is returned and an error message is left in
- \fIinterp->result\fR.
- Note: \fBTk_DefineBitmap\fR expects the memory pointed to by
- \fIsource\fR to be static: \fBTk_DefineBitmap\fR doesn't make
- a private copy of this memory, but uses the bytes pointed to
- by \fIsource\fR later in calls to \fBTk_GetBitmap\fR.
- .VE
- .PP
- Typically \fBTk_DefineBitmap\fR is used by \fB#include\fR-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 \fBstip.bitmap\fR,
- which was created by the \fBbitmap\fR program and contains
- a stipple pattern.
- The following code uses \fBTk_DefineBitmap\fR to define a
- new bitmap named \fBfoo\fR:
- .nf
- .RS
- \fCPixmap bitmap;
- #include "stip.bitmap"
- Tk_DefineBitmap(interp, Tk_GetUid("foo"), stip_bits,
- stip_width, stip_height);
- \&...
- bitmap = Tk_GetBitmap(interp, tkwin, Tk_GetUid("foo"));\fR
- .RE
- .fi
- 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 run-time using \fBTk_GetBitmap\fR:
- .nf
- .RS
- \fCPixmap bitmap;
- bitmap = Tk_GetBitmap(interp, tkwin, Tk_GetUid("@stip.bitmap"));\fR
- .RE
- .fi
- 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.
- .PP
- \fBTk_GetBitmap\fR 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
- \fBTk_GetBitmap\fR should generally be used in preference to Xlib
- procedures like \fBXReadBitmapFile\fR.
- .PP
- The bitmaps returned by \fBTk_GetBitmap\fR
- are shared, so callers should never modify them.
- If a bitmap must be modified dynamically, then it should be
- created by calling Xlib procedures such as \fBXReadBitmapFile\fR
- or \fBXCreatePixmap\fR directly.
- .PP
- The procedure \fBTk_NameOfBitmap\fR is roughly the inverse of
- \fBTk_GetBitmap\fR.
- Given an X Pixmap argument, it returns the \fIid\fR that was
- passed to \fBTk_GetBitmap\fR when the bitmap was created.
- .VS
- \fIBitmap\fR must have been the return value from a previous
- call to \fBTk_GetBitmap\fR.
- .VE
- .PP
- \fBTk_SizeOfBitmap\fR returns the dimensions of its \fIbitmap\fR
- .VS
- argument in the words pointed to by the \fIwidthPtr\fR and
- \fIheightPtr\fR arguments. As with \fBTk_NameOfBitmap\fR,
- \fIbitmap\fR must have been created by \fBTk_GetBitmap\fR.
- .VE
- .PP
- When a bitmap returned by \fBTk_GetBitmap\fR
- is no longer needed, \fBTk_FreeBitmap\fR should be called to release it.
- There should be exactly one call to \fBTk_FreeBitmap\fR for
- each call to \fBTk_GetBitmap\fR.
- When a bitmap is no longer in use anywhere (i.e. it has been freed as
- many times as it has been gotten) \fBTk_FreeBitmap\fR will release
- it to the X server and delete it from the database.
-
- .SH BUGS
- In determining whether an existing bitmap can be used to satisfy
- a new request, \fBTk_GetBitmap\fR
- considers only the immediate value of its \fIid\fR argument. For
- example, when a file name is passed to \fBTk_GetBitmap\fR,
- \fBTk_GetBitmap\fR 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 different file.
-
- .SH KEYWORDS
- bitmap, pixmap
-