tkCursor.c

/* 
 * tkCursor.c --
 *
 *	This file maintains a database of read-only cursors for the Tk
 *	toolkit.  This allows cursors to be shared between widgets and
 *	also avoids round-trips to the X server.
 *
 * Copyright (c) 1990-1994 The Regents of the University of California.
 * Copyright (c) 1994-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

#include "tkPort.h"
#include "tkInt.h"

/*
 * A TkCursor structure exists for each cursor that is currently
 * active.  Each structure is indexed with two hash tables defined
 * below.  One of the tables is cursorIdTable, and the other is either
 * cursorNameTable or cursorDataTable, each of which are stored in the
 * TkDisplay structure for the current thread.
 */

typedef struct {
    CONST char *source;		/* Cursor bits. */
    CONST char *mask;		/* Mask bits. */
    int width, height;		/* Dimensions of cursor (and data
				 * and mask). */
    int xHot, yHot;		/* Location of cursor hot-spot. */
    Tk_Uid fg, bg;		/* Colors for cursor. */
    Display *display;		/* Display on which cursor will be used. */
} DataKey;

/*
 * Forward declarations for procedures defined in this file:
 */

static void		CursorInit _ANSI_ARGS_((TkDisplay *dispPtr));
static void		DupCursorObjProc _ANSI_ARGS_((Tcl_Obj *srcObjPtr,
			    Tcl_Obj *dupObjPtr));
static void		FreeCursor _ANSI_ARGS_((TkCursor *cursorPtr));
static void		FreeCursorObjProc _ANSI_ARGS_((Tcl_Obj *objPtr));
static TkCursor *	TkcGetCursor _ANSI_ARGS_((Tcl_Interp *interp,
			    Tk_Window tkwin, CONST char *name));
static TkCursor *	GetCursorFromObj _ANSI_ARGS_((Tk_Window tkwin,
			    Tcl_Obj *objPtr));
static void		InitCursorObj _ANSI_ARGS_((Tcl_Obj *objPtr));

/*
 * The following structure defines the implementation of the "cursor" Tcl
 * object, used for drawing. The color object remembers the hash table
 * entry associated with a color. The actual allocation and deallocation
 * of the color should be done by the configuration package when the cursor
 * option is set.
 */

Tcl_ObjType tkCursorObjType = {
    "cursor",			/* name */
    FreeCursorObjProc,		/* freeIntRepProc */
    DupCursorObjProc,		/* dupIntRepProc */
    NULL,			/* updateStringProc */
    NULL			/* setFromAnyProc */
};

/*
 *----------------------------------------------------------------------
 *
 * Tk_AllocCursorFromObj --
 *
 *	Given a Tcl_Obj *, map the value to a corresponding
 *	Tk_Cursor structure based on the tkwin given.
 *
 * Results:
 *	The return value is the X identifer for the desired cursor,
 *	unless objPtr couldn't be parsed correctly.  In this case,
 *	None is returned and an error message is left in the interp's result.
 *	The caller should never modify the cursor that is returned, and
 *	should eventually call Tk_FreeCursorFromObj when the cursor is no 
 *	longer needed.
 *
 * Side effects:
 *	The cursor is added to an internal database with a reference count.
 *	For each call to this procedure, there should eventually be a call
 *	to Tk_FreeCursorFromObj, so that the database can be cleaned up 
 *	when cursors aren't needed anymore.
 *
 *----------------------------------------------------------------------
 */

Tk_Cursor
Tk_AllocCursorFromObj(interp, tkwin, objPtr)
    Tcl_Interp *interp;		/* Interp for error results. */
    Tk_Window tkwin;		/* Window in which the cursor will be used.*/
    Tcl_Obj *objPtr;		/* Object describing cursor; see manual
				 * entry for description of legal
				 * syntax of this obj's string rep. */
{
    TkCursor *cursorPtr;

    if (objPtr->typePtr != &tkCursorObjType) {
	InitCursorObj(objPtr);
    }
    cursorPtr = (TkCursor *) objPtr->internalRep.twoPtrValue.ptr1;

    /*
     * If the object currently points to a TkCursor, see if it's the
     * one we want.  If so, increment its reference count and return.
     */

    if (cursorPtr != NULL) {
	if (cursorPtr->resourceRefCount == 0) {
	    /*
	     * This is a stale reference: it refers to a TkCursor that's
	     * no longer in use.  Clear the reference.
	     */
	    FreeCursorObjProc(objPtr);
	    cursorPtr = NULL;
	} else if (Tk_Display(tkwin) == cursorPtr->display) {
	    cursorPtr->resourceRefCount++;
	    return cursorPtr->cursor;
	}
    }

    /*
     * The object didn't point to the TkCursor that we wanted.  Search
     * the list of TkCursors with the same name to see if one of the
     * other TkCursors is the right one.
     */

    if (cursorPtr != NULL) {
	TkCursor *firstCursorPtr =
		(TkCursor *) Tcl_GetHashValue(cursorPtr->hashPtr);
	FreeCursorObjProc(objPtr);
	for (cursorPtr = firstCursorPtr;  cursorPtr != NULL;
		cursorPtr = cursorPtr->nextPtr) {
	    if (Tk_Display(tkwin) == cursorPtr->display) {
		cursorPtr->resourceRefCount++;
		cursorPtr->objRefCount++;
		objPtr->internalRep.twoPtrValue.ptr1 = (VOID *) cursorPtr;
		return cursorPtr->cursor;
	    }
	}
    }

    /*
     * Still no luck.  Call TkcGetCursor to allocate a new TkCursor object.
     */

    cursorPtr = TkcGetCursor(interp, tkwin, Tcl_GetString(objPtr));
    objPtr->internalRep.twoPtrValue.ptr1 = (VOID *) cursorPtr;
    if (cursorPtr == NULL) {
	return None;
    } else {
	cursorPtr->objRefCount++;
	return cursorPtr->cursor;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tk_GetCursor --
 *
 *	Given a string describing a cursor, locate (or create if necessary)
 *	a cursor that fits the description.
 *
 * Results:
 *	The return value is the X identifer for the desired cursor,
 *	unless string couldn't be parsed correctly.  In this case,
 *	None is returned and an error message is left in the interp's result.
 *	The caller should never modify the cursor that is returned, and
 *	should eventually call Tk_FreeCursor when the cursor is no longer
 *	needed.
 *
 * Side effects:
 *	The cursor is added to an internal database with a reference count.
 *	For each call to this procedure, there should eventually be a call
 *	to Tk_FreeCursor, so that the database can be cleaned up when cursors
 *	aren't needed anymore.
 *
 *----------------------------------------------------------------------
 */

Tk_Cursor
Tk_GetCursor(interp, tkwin, string)
    Tcl_Interp *interp;		/* Interpreter to use for error reporting. */
    Tk_Window tkwin;		/* Window in which cursor will be used. */
    Tk_Uid string;		/* Description of cursor.  See manual entry
				 * for details on legal syntax. */
{
    TkCursor *cursorPtr = TkcGetCursor(interp, tkwin, string);
    if (cursorPtr == NULL) {
	return None;
    }
    return cursorPtr->cursor;
}

/*
 *----------------------------------------------------------------------
 *
 * TkcGetCursor --
 *
 *	Given a string describing a cursor, locate (or create if necessary)
 *	a cursor that fits the description. This routine returns the
 *	internal data structure for the cursor, which avoids extra
 *	hash table lookups in Tk_AllocCursorFromObj.
 *
 * Results:
 *	The return value is a pointer to the TkCursor for the desired
 *	cursor, unless string couldn't be parsed correctly.  In this
 *	case, NULL is returned and an error message is left in the
 *	interp's result. The caller should never modify the cursor that
 *	is returned, and should eventually call Tk_FreeCursor when the
 *	cursor is no longer needed.
 *
 * Side effects:
 *	The cursor is added to an internal database with a reference count.
 *	For each call to this procedure, there should eventually be a call
 *	to Tk_FreeCursor, so that the database can be cleaned up when cursors
 *	aren't needed anymore.
 *
 *----------------------------------------------------------------------
 */

static TkCursor *
TkcGetCursor(interp, tkwin, string)
    Tcl_Interp *interp;		/* Interpreter to use for error reporting. */
    Tk_Window tkwin;		/* Window in which cursor will be used. */
    CONST char *string;		/* Description of cursor.  See manual entry
				 * for details on legal syntax. */
{
    Tcl_HashEntry *nameHashPtr;
    register TkCursor *cursorPtr;
    TkCursor *existingCursorPtr = NULL;
    int new;
    TkDisplay *dispPtr = ((TkWindow *) tkwin)->dispPtr;

    if (!dispPtr->cursorInit) {
	CursorInit(dispPtr);
    }

    nameHashPtr = Tcl_CreateHashEntry(&dispPtr->cursorNameTable, 
            string, &new);
    if (!new) {
	existingCursorPtr = (TkCursor *) Tcl_GetHashValue(nameHashPtr);
	for (cursorPtr = existingCursorPtr; cursorPtr != NULL;
		cursorPtr = cursorPtr->nextPtr) {
	    if (Tk_Display(tkwin) == cursorPtr->display) {
		cursorPtr->resourceRefCount++;
		return cursorPtr;
	    }
	}
    } else {
	existingCursorPtr = NULL;
    }

    cursorPtr = TkGetCursorByName(interp, tkwin, string);

    if (cursorPtr == NULL) {
	if (new) {
	    Tcl_DeleteHashEntry(nameHashPtr);
	}
	return NULL;
    }

    /*
     * Add information about this cursor to our database.
     */

    cursorPtr->display = Tk_Display(tkwin);
    cursorPtr->resourceRefCount = 1;
    cursorPtr->objRefCount = 0;
    cursorPtr->otherTable = &dispPtr->cursorNameTable;
    cursorPtr->hashPtr = nameHashPtr;
    cursorPtr->nextPtr = existingCursorPtr;
    cursorPtr->idHashPtr = Tcl_CreateHashEntry(&dispPtr->cursorIdTable, 
            (char *) cursorPtr->cursor, &new);
    if (!new) {
	panic("cursor already registered in Tk_GetCursor");
    }
    Tcl_SetHashValue(nameHashPtr, cursorPtr);
    Tcl_SetHashValue(cursorPtr->idHashPtr, cursorPtr);

    return cursorPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tk_GetCursorFromData --
 *
 *	Given a description of the bits and colors for a cursor,
 *	make a cursor that has the given properties.
 *
 * Results:
 *	The return value is the X identifer for the desired cursor,
 *	unless it couldn't be created properly.  In this case, None is
 *	returned and an error message is left in the interp's result.  The
 *	caller should never modify the cursor that is returned, and
 *	should eventually call Tk_FreeCursor when the cursor is no
 *	longer needed.
 *
 * Side effects:
 *	The cursor is added to an internal database with a reference count.
 *	For each call to this procedure, there should eventually be a call
 *	to Tk_FreeCursor, so that the database can be cleaned up when cursors
 *	aren't needed anymore.
 *
 *----------------------------------------------------------------------
 */

Tk_Cursor
Tk_GetCursorFromData(interp, tkwin, source, mask, width, height,
	xHot, yHot, fg, bg)
    Tcl_Interp *interp;		/* Interpreter to use for error reporting. */
    Tk_Window tkwin;		/* Window in which cursor will be used. */
    CONST char *source;		/* Bitmap data for cursor shape. */
    CONST char *mask;		/* Bitmap data for cursor mask. */
    int width, height;		/* Dimensions of cursor. */
    int xHot, yHot;		/* Location of hot-spot in cursor. */
    Tk_Uid fg;			/* Foreground color for cursor. */
    Tk_Uid bg;			/* Background color for cursor. */
{
    DataKey dataKey;
    Tcl_HashEntry *dataHashPtr;
    register TkCursor *cursorPtr;
    int new;
    XColor fgColor, bgColor;
    TkDisplay *dispPtr = ((TkWindow *) tkwin)->dispPtr;


    if (!dispPtr->cursorInit) {
	CursorInit(dispPtr);
    }

    dataKey.source = source;
    dataKey.mask = mask;
    dataKey.width = width;
    dataKey.height = height;
    dataKey.xHot = xHot;
    dataKey.yHot = yHot;
    dataKey.fg = fg;
    dataKey.bg = bg;
    dataKey.display = Tk_Display(tkwin);
    dataHashPtr = Tcl_CreateHashEntry(&dispPtr->cursorDataTable, 
            (char *) &dataKey, &new);
    if (!new) {
	cursorPtr = (TkCursor *) Tcl_GetHashValue(dataHashPtr);
	cursorPtr->resourceRefCount++;
	return cursorPtr->cursor;
    }

    /*
     * No suitable cursor exists yet.  Make one using the data
     * available and add it to the database.
     */

    if (TkParseColor(dataKey.display, Tk_Colormap(tkwin), fg, &fgColor) == 0) {
	Tcl_AppendResult(interp, "invalid color name \"", fg, "\"",
		(char *) NULL);
	goto error;
    }
    if (TkParseColor(dataKey.display, Tk_Colormap(tkwin), bg, &bgColor) == 0) {
	Tcl_AppendResult(interp, "invalid color name \"", bg, "\"",
		(char *) NULL);
	goto error;
    }

    cursorPtr = TkCreateCursorFromData(tkwin, source, mask, width, height,
	    xHot, yHot, fgColor, bgColor);

    if (cursorPtr == NULL) {
	goto error;
    }

    cursorPtr->resourceRefCount = 1;
    cursorPtr->otherTable = &dispPtr->cursorDataTable;
    cursorPtr->hashPtr = dataHashPtr;
    cursorPtr->objRefCount = 0;
    cursorPtr->idHashPtr = Tcl_CreateHashEntry(&dispPtr->cursorIdTable, 
            (char *) cursorPtr->cursor, &new);
    cursorPtr->nextPtr = NULL;

    if (!new) {
	panic("cursor already registered in Tk_GetCursorFromData");
    }
    Tcl_SetHashValue(dataHashPtr, cursorPtr);
    Tcl_SetHashValue(cursorPtr->idHashPtr, cursorPtr);
    return cursorPtr->cursor;

    error:
    Tcl_DeleteHashEntry(dataHashPtr);
    return None;
}

/*
 *--------------------------------------------------------------
 *
 * Tk_NameOfCursor --
 *
 *	Given a cursor, return a textual string identifying it.
 *
 * Results:
 *	If cursor was created by Tk_GetCursor, then the return
 *	value is the "string" that was used to create it.
 *	Otherwise the return value is a string giving the X
 *	identifier for the cursor.  The storage for the returned
 *	string is only guaranteed to persist up until the next
 *	call to this procedure.
 *
 * Side effects:
 *	None.
 *
 *--------------------------------------------------------------
 */

CONST char *
Tk_NameOfCursor(display, cursor)
    Display *display;		/* Display for which cursor was allocated. */
    Tk_Cursor cursor;		/* Identifier for cursor whose name is
				 * wanted. */
{
    Tcl_HashEntry *idHashPtr;
    TkCursor *cursorPtr;
    TkDisplay *dispPtr;

    dispPtr = TkGetDisplay(display);

    if (!dispPtr->cursorInit) {
	printid:
	sprintf(dispPtr->cursorString, "cursor id 0x%x", 
                (unsigned int) cursor);
	return dispPtr->cursorString;
    }
    idHashPtr = Tcl_FindHashEntry(&dispPtr->cursorIdTable, (char *) cursor);
    if (idHashPtr == NULL) {
	goto printid;
    }
    cursorPtr = (TkCursor *) Tcl_GetHashValue(idHashPtr);
    if (cursorPtr->otherTable != &dispPtr->cursorNameTable) {
	goto printid;
    }
    return cursorPtr->hashPtr->key.string;
}

/*
 *----------------------------------------------------------------------
 *
 * FreeCursor --
 *
 *	This procedure is invoked by both Tk_FreeCursor and
 *	Tk_FreeCursorFromObj; it does all the real work of deallocating
 *	a cursor.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The reference count associated with cursor is decremented, and
 *	it is officially deallocated if no-one is using it anymore.
 *
 *----------------------------------------------------------------------
 */

static void
FreeCursor(cursorPtr)
    TkCursor *cursorPtr;	/* Cursor to be released. */
{
    TkCursor *prevPtr;

    cursorPtr->resourceRefCount--;
    if (cursorPtr->resourceRefCount > 0) {
	return;
    }

    Tcl_DeleteHashEntry(cursorPtr->idHashPtr);
    prevPtr = (TkCursor *) Tcl_GetHashValue(cursorPtr->hashPtr);
    if (prevPtr == cursorPtr) {
	if (cursorPtr->nextPtr == NULL) {
	    Tcl_DeleteHashEntry(cursorPtr->hashPtr);
	} else {
	    Tcl_SetHashValue(cursorPtr->hashPtr, cursorPtr->nextPtr);
	}
    } else {
	while (prevPtr->nextPtr != cursorPtr) {
	    prevPtr = prevPtr->nextPtr;
	}
	prevPtr->nextPtr = cursorPtr->nextPtr;
    }
    TkpFreeCursor(cursorPtr);
    if (cursorPtr->objRefCount == 0) {
	ckfree((char *) cursorPtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tk_FreeCursor --
 *
 *	This procedure is called to release a cursor allocated by
 *	Tk_GetCursor or TkGetCursorFromData.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The reference count associated with cursor is decremented, and
 *	it is officially deallocated if no-one is using it anymore.
 *
 *----------------------------------------------------------------------
 */

void
Tk_FreeCursor(display, cursor)
    Display *display;		/* Display for which cursor was allocated. */
    Tk_Cursor cursor;		/* Identifier for cursor to be released. */
{
    Tcl_HashEntry *idHashPtr;
    TkDisplay *dispPtr = TkGetDisplay(display);

    if (!dispPtr->cursorInit) {
	panic("Tk_FreeCursor called before Tk_GetCursor");
    }

    idHashPtr = Tcl_FindHashEntry(&dispPtr->cursorIdTable, (char *) cursor);
    if (idHashPtr == NULL) {
	panic("Tk_FreeCursor received unknown cursor argument");
    }
    FreeCursor((TkCursor *) Tcl_GetHashValue(idHashPtr));
}

/*
 *----------------------------------------------------------------------
 *
 * Tk_FreeCursorFromObj --
 *
 *	This procedure is called to release a cursor allocated by
 *	Tk_AllocCursorFromObj. It does not throw away the Tcl_Obj *;
 *	it only gets rid of the hash table entry for this cursor
 *	and clears the cached value that is normally stored in the object.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The reference count associated with the cursor represented by
 *	objPtr is decremented, and the cursor is released to X if there are 
 *	no remaining uses for it.
 *
 *----------------------------------------------------------------------
 */

void
Tk_FreeCursorFromObj(tkwin, objPtr)
    Tk_Window tkwin;		/* The window this cursor lives in. Needed
				 * for the display value. */
    Tcl_Obj *objPtr;		/* The Tcl_Obj * to be freed. */
{
    FreeCursor(GetCursorFromObj(tkwin, objPtr));
    FreeCursorObjProc(objPtr);
}

/*
 *---------------------------------------------------------------------------
 *
 * FreeCursorFromObjProc -- 
 *
 *	This proc is called to release an object reference to a cursor.
 *	Called when the object's internal rep is released or when
 *	the cached tkColPtr needs to be changed.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The object reference count is decremented. When both it
 *	and the hash ref count go to zero, the color's resources
 *	are released.
 *
 *---------------------------------------------------------------------------
 */

static void
FreeCursorObjProc(objPtr)
    Tcl_Obj *objPtr;		/* The object we are releasing. */
{
    TkCursor *cursorPtr = (TkCursor *) objPtr->internalRep.twoPtrValue.ptr1;

    if (cursorPtr != NULL) {
	cursorPtr->objRefCount--;
	if ((cursorPtr->objRefCount == 0) 
		&& (cursorPtr->resourceRefCount == 0)) {
	    ckfree((char *) cursorPtr);
	}
	objPtr->internalRep.twoPtrValue.ptr1 = (VOID *) NULL;
    }
}

/*
 *---------------------------------------------------------------------------
 *
 * DupCursorObjProc -- 
 *
 *	When a cached cursor object is duplicated, this is called to
 *	update the internal reps.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The color's objRefCount is incremented and the internal rep
 *	of the copy is set to point to it.
 *
 *---------------------------------------------------------------------------
 */

static void
DupCursorObjProc(srcObjPtr, dupObjPtr)
    Tcl_Obj *srcObjPtr;		/* The object we are copying from. */
    Tcl_Obj *dupObjPtr;		/* The object we are copying to. */
{
    TkCursor *cursorPtr = (TkCursor *) srcObjPtr->internalRep.twoPtrValue.ptr1;
    
    dupObjPtr->typePtr = srcObjPtr->typePtr;
    dupObjPtr->internalRep.twoPtrValue.ptr1 = (VOID *) cursorPtr;

    if (cursorPtr != NULL) {
	cursorPtr->objRefCount++;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tk_GetCursorFromObj --
 *
 *	Returns the cursor referred to buy a Tcl object. The cursor must
 *	already have been allocated via a call to Tk_AllocCursorFromObj or 
 *	Tk_GetCursor.
 *
 * Results:
 *	Returns the Tk_Cursor that matches the tkwin and the string rep
 *	of the name of the cursor given in objPtr.
 *
 * Side effects:
 *	If the object is not already a cursor, the conversion will free
 *	any old internal representation. 
 *
 *----------------------------------------------------------------------
 */

Tk_Cursor
Tk_GetCursorFromObj(tkwin, objPtr)
    Tk_Window tkwin;
    Tcl_Obj *objPtr;		/* The object from which to get pixels. */
{
    TkCursor *cursorPtr = GetCursorFromObj(tkwin, objPtr);
    /* GetCursorFromObj should never return NULL */
    return cursorPtr->cursor;
}

/*
 *----------------------------------------------------------------------
 *
 * GetCursorFromObj --
 *
 *	Returns the cursor referred to by a Tcl object.  The cursor must
 *	already have been allocated via a call to Tk_AllocCursorFromObj
 *	or Tk_GetCursor.
 *
 * Results:
 *	Returns the TkCursor * that matches the tkwin and the string rep
 *	of the name of the cursor given in objPtr.
 *
 * Side effects:
 *	If the object is not already a cursor, the conversion will free
 *	any old internal representation. 
 *
 *----------------------------------------------------------------------
 */

static TkCursor *
GetCursorFromObj(tkwin, objPtr)
    Tk_Window tkwin;		/* Window in which the cursor will be used. */
    Tcl_Obj *objPtr;		/* The object that describes the desired
				 * cursor. */
{
    TkCursor *cursorPtr;
    Tcl_HashEntry *hashPtr;
    TkDisplay *dispPtr = ((TkWindow *) tkwin)->dispPtr;

    if (objPtr->typePtr != &tkCursorObjType) {
	InitCursorObj(objPtr);
    }

    /*
     * The internal representation is a cache of the last cursor used
     * with the given name.  But there can be lots different cursors
     * for each cursor name; one cursor for each display.  Check to
     * see if the cursor we have cached is the one that is needed.
     */
    cursorPtr = (TkCursor *) objPtr->internalRep.twoPtrValue.ptr1;
    if ((cursorPtr != NULL) && (Tk_Display(tkwin) == cursorPtr->display)) {
	return cursorPtr;
    }

    /*
     * If we get to here, it means the cursor we need is not in the cache.
     * Try to look up the cursor in the TkDisplay structure of the window.
     */

    hashPtr = Tcl_FindHashEntry(&dispPtr->cursorNameTable,
	    Tcl_GetString(objPtr));
    if (hashPtr == NULL) {
	goto error;
    }
    for (cursorPtr = (TkCursor *) Tcl_GetHashValue(hashPtr);
	    cursorPtr != NULL; cursorPtr = cursorPtr->nextPtr) {
	if (Tk_Display(tkwin) == cursorPtr->display) {
	    FreeCursorObjProc(objPtr);
	    objPtr->internalRep.twoPtrValue.ptr1 = (VOID *) cursorPtr;
	    cursorPtr->objRefCount++;
	    return cursorPtr;
	}
    }

    error:
    panic("GetCursorFromObj called with non-existent cursor!");
    /*
     * The following code isn't reached; it's just there to please compilers.
     */
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * InitCursorObj --
 *
 *	Bookeeping procedure to change an objPtr to a cursor type.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The old internal rep of the object is freed. The internal
 *	rep is cleared. The final form of the object is set
 *	by either Tk_AllocCursorFromObj or GetCursorFromObj.
 *
 *----------------------------------------------------------------------
 */

static void
InitCursorObj(objPtr)
    Tcl_Obj *objPtr;		/* The object to convert. */
{
    Tcl_ObjType *typePtr;

    /*
     * Free the old internalRep before setting the new one. 
     */

    Tcl_GetString(objPtr);
    typePtr = objPtr->typePtr;
    if ((typePtr != NULL) && (typePtr->freeIntRepProc != NULL)) {
	(*typePtr->freeIntRepProc)(objPtr);
    }
    objPtr->typePtr = &tkCursorObjType;
    objPtr->internalRep.twoPtrValue.ptr1 = (VOID *) NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * CursorInit --
 *
 *	Initialize the structures used for cursor management.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Read the code.
 *
 *----------------------------------------------------------------------
 */

static void
CursorInit(dispPtr)
    TkDisplay *dispPtr;   /* Display used to store thread-specific data. */
{
    Tcl_InitHashTable(&dispPtr->cursorNameTable, TCL_STRING_KEYS);
    Tcl_InitHashTable(&dispPtr->cursorDataTable, sizeof(DataKey)/sizeof(int));

    /*
     * The call below is tricky:  can't use sizeof(IdKey) because it
     * gets padded with extra unpredictable bytes on some 64-bit
     * machines.
     */

    /* 
     *  Old code....
     *     Tcl_InitHashTable(&dispPtr->cursorIdTable, sizeof(Display *) 
     *                       /sizeof(int));
     *
     * The comment above doesn't make sense.
     * However, XIDs should only be 32 bits, by the definition of X,
     * so the code above causes Tk to crash.  Here is the real code:
     */

    Tcl_InitHashTable(&dispPtr->cursorIdTable, TCL_ONE_WORD_KEYS);

    dispPtr->cursorInit = 1;
}

/*
 *----------------------------------------------------------------------
 *
 * TkDebugCursor --
 *
 *	This procedure returns debugging information about a cursor.
 *
 * Results:
 *	The return value is a list with one sublist for each TkCursor
 *	corresponding to "name".  Each sublist has two elements that
 *	contain the resourceRefCount and objRefCount fields from the
 *	TkCursor structure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TkDebugCursor(tkwin, name)
    Tk_Window tkwin;		/* The window in which the cursor will be
				 * used (not currently used). */
    char *name;			/* Name of the desired color. */
{
    TkCursor *cursorPtr;
    Tcl_HashEntry *hashPtr;
    Tcl_Obj *resultPtr, *objPtr;
    TkDisplay *dispPtr = ((TkWindow *) tkwin)->dispPtr;

    if (!dispPtr->cursorInit) {
	CursorInit(dispPtr);
    }
    resultPtr = Tcl_NewObj();
    hashPtr = Tcl_FindHashEntry(&dispPtr->cursorNameTable, name);
    if (hashPtr != NULL) {
	cursorPtr = (TkCursor *) Tcl_GetHashValue(hashPtr);
	if (cursorPtr == NULL) {
	    panic("TkDebugCursor found empty hash table entry");
	}
	for ( ; (cursorPtr != NULL); cursorPtr = cursorPtr->nextPtr) {
	    objPtr = Tcl_NewObj();
	    Tcl_ListObjAppendElement(NULL, objPtr,
		    Tcl_NewIntObj(cursorPtr->resourceRefCount));
	    Tcl_ListObjAppendElement(NULL, objPtr,
		    Tcl_NewIntObj(cursorPtr->objRefCount)); 
	    Tcl_ListObjAppendElement(NULL, resultPtr, objPtr);
	}
    }
    return resultPtr;
}