generic/ttk/ttkPanedwindow.c

/* $Id$
 *
 * Copyright (c) 2005, Joe English.  Freely redistributable.
 *
 * ttk::panedwindow widget implementation.
 *
 * TODO: track active/pressed sash.
 */

#include <string.h>
#include <tk.h>
#include "ttkManager.h"
#include "ttkTheme.h"
#include "ttkWidget.h"

/*------------------------------------------------------------------------
 * +++ Layout algorithm.
 *
 * (pos=x/y, size=width/height, depending on -orient=horizontal/vertical)
 *
 * Each pane carries two pieces of state: the request size and the
 * position of the following sash.  (The final pane has no sash,
 * its sash position is used as a sentinel value).
 *
 * Pane geometry is determined by the sash positions.
 * When resizing, sash positions are computed from the request sizes,
 * the available space, and pane weights (see PlaceSashes()).
 * This ensures continuous resize behavior (that is: changing
 * the size by X pixels then changing the size by Y pixels
 * gives the same result as changing the size by X+Y pixels
 * in one step).
 *
 * The request size is initially set to the slave window's requested size.
 * When the user drags a sash, each pane's request size is set to its
 * actual size.  This ensures that panes "stay put" on the next resize.
 *
 * If reqSize == 0, use 0 for the weight as well.  This ensures that
 * "collapsed" panes stay collapsed during a resize, regardless of
 * their nominal -weight.
 *
 * +++ Invariants.
 *
 * #sash 		=  #pane - 1
 * pos(pane[0]) 	=  0
 * pos(sash[i]) 	=  pos(pane[i]) + size(pane[i]), 0 <= i <= #sash
 * pos(pane[i+1]) 	=  pos(sash[i]) + size(sash[i]), 0 <= i <  #sash
 * pos(sash[#sash])	=  size(pw)   // sentinel value, constraint
 *
 * size(pw) 		=  sum(size(pane(0..#pane))) + sum(size(sash(0..#sash)))
 * size(pane[i]) 	>= 0,  for 0 <= i < #pane
 * size(sash[i]) 	>= 0,  for 0 <= i < #sash
 * ==> pos(pane[i]) <= pos(sash[i]) <= pos(pane[i+1]), for 0 <= i < #sash
 *
 * Assumption: all sashes are the same size.
 */

/*------------------------------------------------------------------------
 * +++ Widget record.
 */

typedef struct {
    Tcl_Obj	*orientObj;
    int 	orient;
    int 	width;
    int 	height;
    Ttk_Manager	*mgr;
    Tk_OptionTable paneOptionTable;
    Ttk_Layout	sashLayout;
    int 	sashThickness;
} PanedPart;

typedef struct {
    WidgetCore	core;
    PanedPart	paned;
} Paned;

/* @@@ NOTE: -orient is readonly 'cause dynamic oriention changes NYI
 */
static Tk_OptionSpec PanedOptionSpecs[] = {
    {TK_OPTION_STRING_TABLE, "-orient", "orient", "Orient", "vertical",
	Tk_Offset(Paned,paned.orientObj), Tk_Offset(Paned,paned.orient),
	0,(ClientData)ttkOrientStrings,READONLY_OPTION|STYLE_CHANGED },
    {TK_OPTION_INT, "-width", "width", "Width", "0",
	-1,Tk_Offset(Paned,paned.width),
	0,0,GEOMETRY_CHANGED },
    {TK_OPTION_INT, "-height", "height", "Height", "0",
	-1,Tk_Offset(Paned,paned.height),
	0,0,GEOMETRY_CHANGED },

    WIDGET_INHERIT_OPTIONS(ttkCoreOptionSpecs)
};

/*------------------------------------------------------------------------
 * +++ Slave pane record.
 */
typedef struct {
    int 	reqSize;		/* Pane request size */
    int 	sashPos;		/* Folowing sash position */
    int 	weight; 		/* Pane -weight, for resizing */
} Pane;

static Tk_OptionSpec PaneOptionSpecs[] = {
    {TK_OPTION_INT, "-weight", "weight", "Weight", "0",
	-1,Tk_Offset(Pane,weight), 0,0,GEOMETRY_CHANGED },
    {TK_OPTION_END, 0,0,0, NULL, -1,-1, 0,0,0}
};

/* CreatePane --
 * 	Create a new pane record.
 */
static Pane *CreatePane(Tcl_Interp *interp, Paned *pw, Tk_Window slaveWindow)
{
    Tk_OptionTable optionTable = pw->paned.paneOptionTable;
    void *record = ckalloc(sizeof(Pane));
    Pane *pane = record;

    memset(record, 0, sizeof(Pane));
    if (Tk_InitOptions(interp, record, optionTable, slaveWindow) != TCL_OK) {
	ckfree(record);
	return NULL;
    }

    pane->reqSize
	= pw->paned.orient == TTK_ORIENT_HORIZONTAL
	? Tk_ReqWidth(slaveWindow) : Tk_ReqHeight(slaveWindow);

    return pane;
}

/* DestroyPane --
 * 	Free pane record.
 */
static void DestroyPane(Paned *pw, Pane *pane)
{
    void *record = pane;
    Tk_FreeConfigOptions(record, pw->paned.paneOptionTable, pw->core.tkwin);
    ckfree(record);
}

/* ConfigurePane --
 * 	Set pane options.
 */
static int ConfigurePane(
    Tcl_Interp *interp, Paned *pw, Pane *pane, Tk_Window slaveWindow,
    int objc, Tcl_Obj *const objv[])
{
    Ttk_Manager *mgr = pw->paned.mgr;
    Tk_SavedOptions savedOptions;
    int mask = 0;

    if (Tk_SetOptions(interp, (void*)pane, pw->paned.paneOptionTable,
	    objc, objv, slaveWindow, &savedOptions, &mask) != TCL_OK)
    {
	return TCL_ERROR;
    }

    /* Sanity-check:
     */
    if (pane->weight < 0) {
	Tcl_AppendResult(interp, "-weight must be nonnegative", NULL);
	goto error;
    }

    /* Done.
     */
    Tk_FreeSavedOptions(&savedOptions);
    Ttk_ManagerSizeChanged(mgr);
    return TCL_OK;

error:
    Tk_RestoreSavedOptions(&savedOptions);
    return TCL_ERROR;
}


/*------------------------------------------------------------------------
 * +++ Sash adjustment.
 */

/* ShoveUp --
 * 	Place sash i at specified position, recursively shoving
 * 	previous sashes upwards as needed, until hitting the top
 * 	of the window.  If that happens, shove back down.
 *
 * 	Returns: final position of sash i.
 */

static int ShoveUp(Paned *pw, int i, int pos)
{
    Pane *pane = Ttk_SlaveData(pw->paned.mgr, i);
    int sashThickness = pw->paned.sashThickness;

    if (i == 0) {
	if (pos < 0)
	    pos = 0;
    } else {
	Pane *prevPane = Ttk_SlaveData(pw->paned.mgr, i-1);
	if (pos < prevPane->sashPos + sashThickness)
	    pos = ShoveUp(pw, i-1, pos - sashThickness) + sashThickness;
    }
    return pane->sashPos = pos;
}

/* ShoveDown --
 * 	Same as ShoveUp, but going in the opposite direction
 * 	and stopping at the sentinel sash.
 */
static int ShoveDown(Paned *pw, int i, int pos)
{
    Pane *pane = Ttk_SlaveData(pw->paned.mgr,i);
    int sashThickness = pw->paned.sashThickness;

    if (i == Ttk_NumberSlaves(pw->paned.mgr) - 1) {
	pos = pane->sashPos; /* Sentinel value == master window size */
    } else {
	Pane *nextPane = Ttk_SlaveData(pw->paned.mgr,i+1);
	if (pos + sashThickness > nextPane->sashPos)
	    pos = ShoveDown(pw, i+1, pos + sashThickness) - sashThickness;
    }
    return pane->sashPos = pos;
}

/* PanedSize --
 * 	Compute the requested size of the paned widget
 * 	from the individual pane request sizes.
 *
 * 	Used as the WidgetSpec sizeProc and the ManagerSpec sizeProc.
 */
static int PanedSize(void *recordPtr, int *widthPtr, int *heightPtr)
{
    Paned *pw = recordPtr;
    int nPanes = Ttk_NumberSlaves(pw->paned.mgr);
    int nSashes = nPanes - 1;
    int sashThickness = pw->paned.sashThickness;
    int width = 0, height = 0;
    int index;

    if (pw->paned.orient == TTK_ORIENT_HORIZONTAL) {
	for (index = 0; index < nPanes; ++index) {
	    Pane *pane = Ttk_SlaveData(pw->paned.mgr, index);
	    Tk_Window slaveWindow = Ttk_SlaveWindow(pw->paned.mgr, index);

	    if (height < Tk_ReqHeight(slaveWindow))
		height = Tk_ReqHeight(slaveWindow);
	    width += pane->reqSize;
	}
	width += nSashes * sashThickness;
    } else {
	for (index = 0; index < nPanes; ++index) {
	    Pane *pane = Ttk_SlaveData(pw->paned.mgr, index);
	    Tk_Window slaveWindow = Ttk_SlaveWindow(pw->paned.mgr, index);

	    if (width < Tk_ReqWidth(slaveWindow))
		width = Tk_ReqWidth(slaveWindow);
	    height += pane->reqSize;
	}
	height += nSashes * sashThickness;
    }

    *widthPtr = pw->paned.width > 0 ? pw->paned.width : width;
    *heightPtr = pw->paned.height > 0 ? pw->paned.height : height;
    return 1;
}

/* AdjustPanes --
 * 	Set pane request sizes from sash positions.
 *
 * NOTE:
 * 	AdjustPanes followed by PlaceSashes (called during relayout)
 * 	will leave the sashes in the same place, as long as available size
 * 	remains contant.
 */
static void AdjustPanes(Paned *pw)
{
    int sashThickness = pw->paned.sashThickness;
    int pos = 0;
    int index;

    for (index = 0; index < Ttk_NumberSlaves(pw->paned.mgr); ++index) {
	Pane *pane = Ttk_SlaveData(pw->paned.mgr, index);
	int size = pane->sashPos - pos;
	pane->reqSize = size >= 0 ? size : 0;
	pos = pane->sashPos + sashThickness;
    }
}

/* PlaceSashes --
 *	Set sash positions from pane request sizes and available space.
 *	The sentinel sash position is set to the available space.
 *
 *	Allocate pane->reqSize pixels to each pane, and distribute
 *	the difference = available size - requested size according
 *	to pane->weight.
 *
 *	If there's still some left over, squeeze panes from the bottom up
 *	(This can happen if all weights are zero, or if one or more panes
 *	are too small to absorb the required shrinkage).
 *
 * Notes:
 * 	This doesn't distribute the remainder pixels as evenly as it could
 * 	when more than one pane has weight > 1.
 */
static void PlaceSashes(Paned *pw, int width, int height)
{
    Ttk_Manager *mgr = pw->paned.mgr;
    int nPanes = Ttk_NumberSlaves(mgr);
    int sashThickness = pw->paned.sashThickness;
    int available = pw->paned.orient == TTK_ORIENT_HORIZONTAL ? width : height;
    int reqSize = 0, totalWeight = 0;
    int difference, delta, remainder, pos, i;

    if (nPanes == 0)
	return;

    /* Compute total required size and total available weight:
     */
    for (i = 0; i < nPanes; ++i) {
	Pane *pane = Ttk_SlaveData(mgr, i);
	reqSize += pane->reqSize;
	totalWeight += pane->weight * (pane->reqSize != 0);
    }

    /* Compute difference to be redistributed:
     */
    difference = available - reqSize - sashThickness*(nPanes-1);
    if (totalWeight != 0) {
	delta = difference / totalWeight;
	remainder = difference % totalWeight;
	if (remainder < 0) {
	    --delta;
	    remainder += totalWeight;
	}
    } else {
	delta = remainder = 0;
    }
    /* ASSERT: 0 <= remainder < totalWeight */

    /* Place sashes:
     */
    pos = 0;
    for (i = 0; i < nPanes; ++i) {
	Pane *pane = Ttk_SlaveData(mgr, i);
	int weight = pane->weight * (pane->reqSize != 0);
	int size = pane->reqSize + delta * weight;

	if (weight > remainder)
	    weight = remainder;
	remainder -= weight;
	size += weight;

	if (size < 0)
	    size = 0;

	pane->sashPos = (pos += size);
	pos += sashThickness;
    }

    /* Handle emergency shrink/emergency stretch:
     * Set sentinel sash position to end of widget,
     * shove preceding sashes up.
     */
    ShoveUp(pw, nPanes - 1, available);
}

/* PlacePanes --
 *	Places slave panes based on sash positions.
 */
static void PlacePanes(Paned *pw)
{
    int horizontal = pw->paned.orient == TTK_ORIENT_HORIZONTAL;
    int width = Tk_Width(pw->core.tkwin), height = Tk_Height(pw->core.tkwin);
    int sashThickness = pw->paned.sashThickness;
    int pos = 0;
    int index;

    for (index = 0; index < Ttk_NumberSlaves(pw->paned.mgr); ++index) {
	Pane *pane = Ttk_SlaveData(pw->paned.mgr, index);
	int size = pane->sashPos - pos;

	if (size > 0) {
	    if (horizontal) {
		Ttk_PlaceSlave(pw->paned.mgr, index, pos, 0, size, height);
	    } else {
		Ttk_PlaceSlave(pw->paned.mgr, index, 0, pos, width, size);
	    }
	} else {
	    Ttk_UnmapSlave(pw->paned.mgr, index);
	}

	pos = pane->sashPos + sashThickness;
    }
}

/*------------------------------------------------------------------------
 * +++ Manager specification.
 */

static void PanedPlaceSlaves(void *managerData)
{
    Paned *pw = managerData;
    PlaceSashes(pw, Tk_Width(pw->core.tkwin), Tk_Height(pw->core.tkwin));
    PlacePanes(pw);
}

static void PaneRemoved(void *managerData, int index)
{
    Paned *pw = managerData;
    Pane *pane = Ttk_SlaveData(pw->paned.mgr, index);
    DestroyPane(pw, pane);
}

static int AddPane(
    Tcl_Interp *interp, Paned *pw,
    int destIndex, Tk_Window slaveWindow,
    int objc, Tcl_Obj *const objv[])
{
    Pane *pane;
    if (!Ttk_Maintainable(interp, slaveWindow, pw->core.tkwin)) {
	return TCL_ERROR;
    }
    if (Ttk_SlaveIndex(pw->paned.mgr, slaveWindow) >= 0) {
	Tcl_AppendResult(interp,
	    Tk_PathName(slaveWindow), " already added",
	    NULL);
	return TCL_ERROR;
    }

    pane = CreatePane(interp, pw, slaveWindow);
    if (!pane) {
	return TCL_ERROR;
    }
    if (ConfigurePane(interp, pw, pane, slaveWindow, objc, objv) != TCL_OK) {
	DestroyPane(pw, pane);
	return TCL_ERROR;
    }

    Ttk_InsertSlave(pw->paned.mgr, destIndex, slaveWindow, pane);
    return TCL_OK;
}

/* PaneRequest --
 * 	Only update pane request size if slave is currently unmapped.
 * 	Geometry requests from mapped slaves are not directly honored
 * 	in order to avoid unexpected pane resizes (esp. while the
 * 	user is dragging a sash [#1325286]).
 */
static int PaneRequest(void *managerData, int index, int width, int height)
{
    Paned *pw = managerData;
    Pane *pane = Ttk_SlaveData(pw->paned.mgr, index);
    Tk_Window slaveWindow = Ttk_SlaveWindow(pw->paned.mgr, index);
    int horizontal = pw->paned.orient == TTK_ORIENT_HORIZONTAL;

    if (!Tk_IsMapped(slaveWindow)) {
	pane->reqSize = horizontal ? width : height;
    }
    return 1;
}

static Ttk_ManagerSpec PanedManagerSpec = {
    { "panedwindow", Ttk_GeometryRequestProc, Ttk_LostSlaveProc },
    PanedSize,
    PanedPlaceSlaves,
    PaneRequest,
    PaneRemoved
};

/*------------------------------------------------------------------------
 * +++ Event handler.
 *
 * <<NOTE-PW-LEAVE-NOTIFYINFERIOR>>
 * Tk does not execute binding scripts for <Leave> events when
 * the pointer crosses from a parent to a child.  This widget
 * needs to know when that happens, though, so it can reset
 * the cursor.
 *
 * This event handler generates an <<EnteredChild>> virtual event
 * on LeaveNotify/NotifyInferior.
 */

static const unsigned PanedEventMask = LeaveWindowMask;
static void PanedEventProc(ClientData clientData, XEvent *eventPtr)
{
    WidgetCore *corePtr = clientData;
    if (   eventPtr->type == LeaveNotify
	&& eventPtr->xcrossing.detail == NotifyInferior)
    {
	TtkSendVirtualEvent(corePtr->tkwin, "EnteredChild");
    }
}

/*------------------------------------------------------------------------
 * +++ Initialization and cleanup hooks.
 */

static void PanedInitialize(Tcl_Interp *interp, void *recordPtr)
{
    Paned *pw = recordPtr;

    Tk_CreateEventHandler(pw->core.tkwin,
	PanedEventMask, PanedEventProc, recordPtr);
    pw->paned.mgr = Ttk_CreateManager(&PanedManagerSpec, pw, pw->core.tkwin);
    pw->paned.paneOptionTable = Tk_CreateOptionTable(interp,PaneOptionSpecs);
    pw->paned.sashLayout = 0;
    pw->paned.sashThickness = 1;
}

static void PanedCleanup(void *recordPtr)
{
    Paned *pw = recordPtr;

    if (pw->paned.sashLayout)
	Ttk_FreeLayout(pw->paned.sashLayout);
    Tk_DeleteEventHandler(pw->core.tkwin,
	PanedEventMask, PanedEventProc, recordPtr);
    Ttk_DeleteManager(pw->paned.mgr);
}

/* Post-configuration hook.
 */
static int PanedPostConfigure(Tcl_Interp *interp, void *clientData, int mask)
{
    Paned *pw = clientData;

    if (mask & GEOMETRY_CHANGED) {
	/* User has changed -width or -height.
	 * Recalculate sash positions based on requested size.
	 */
	Tk_Window tkwin = pw->core.tkwin;
	PlaceSashes(pw,
	    pw->paned.width > 0 ? pw->paned.width : Tk_Width(tkwin),
	    pw->paned.height > 0 ? pw->paned.height : Tk_Height(tkwin));
    }

    return TCL_OK;
}

/*------------------------------------------------------------------------
 * +++ Layout management hooks.
 */
static Ttk_Layout PanedGetLayout(
    Tcl_Interp *interp, Ttk_Theme themePtr, void *recordPtr)
{
    Paned *pw = recordPtr;
    Ttk_Layout panedLayout = TtkWidgetGetLayout(interp, themePtr, recordPtr);

    if (panedLayout) {
	int horizontal = pw->paned.orient == TTK_ORIENT_HORIZONTAL;
	const char *layoutName =
	    horizontal ? ".Vertical.Sash" : ".Horizontal.Sash";
	Ttk_Layout sashLayout = Ttk_CreateSublayout(
	    interp, themePtr, panedLayout, layoutName, pw->core.optionTable);

	if (sashLayout) {
	    int sashWidth, sashHeight;

	    Ttk_LayoutSize(sashLayout, 0, &sashWidth, &sashHeight);
	    pw->paned.sashThickness = horizontal ? sashWidth : sashHeight;

	    if (pw->paned.sashLayout)
		Ttk_FreeLayout(pw->paned.sashLayout);
	    pw->paned.sashLayout = sashLayout;
	} else {
	    Ttk_FreeLayout(panedLayout);
	    return 0;
	}
    }

    return panedLayout;
}

/*------------------------------------------------------------------------
 * +++ Drawing routines.
 */

/* SashLayout --
 * 	Place the sash sublayout after the specified pane,
 * 	in preparation for drawing.
 */
static Ttk_Layout SashLayout(Paned *pw, int index)
{
    Pane *pane = Ttk_SlaveData(pw->paned.mgr, index);
    int thickness = pw->paned.sashThickness,
	height = Tk_Height(pw->core.tkwin),
	width = Tk_Width(pw->core.tkwin),
	sashPos = pane->sashPos;

    Ttk_PlaceLayout(
	pw->paned.sashLayout, pw->core.state,
	pw->paned.orient == TTK_ORIENT_HORIZONTAL
	    ? Ttk_MakeBox(sashPos, 0, thickness, height)
	    : Ttk_MakeBox(0, sashPos, width, thickness));

    return pw->paned.sashLayout;
}

static void DrawSash(Paned *pw, int index, Drawable d)
{
    Ttk_DrawLayout(SashLayout(pw, index), pw->core.state, d);
}

static void PanedDisplay(void *recordPtr, Drawable d)
{
    Paned *pw = recordPtr;
    int i, nSashes = Ttk_NumberSlaves(pw->paned.mgr) - 1;

    TtkWidgetDisplay(recordPtr, d);
    for (i = 0; i < nSashes; ++i) {
	DrawSash(pw, i, d);
    }
}

/*------------------------------------------------------------------------
 * +++ Widget commands.
 */

/* $pw add window [ options ... ]
 */
static int PanedAddCommand(
    void *recordPtr, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[])
{
    Paned *pw = recordPtr;
    Tk_Window slaveWindow;

    if (objc < 3) {
	Tcl_WrongNumArgs(interp, 2, objv, "window");
	return TCL_ERROR;
    }

    slaveWindow = Tk_NameToWindow(
	interp, Tcl_GetString(objv[2]), pw->core.tkwin);

    if (!slaveWindow) {
	return TCL_ERROR;
    }

    return AddPane(interp, pw, Ttk_NumberSlaves(pw->paned.mgr), slaveWindow,
	    objc - 3, objv + 3);
}

/* $pw insert $index $slave ?-option value ...?
 * 	Insert new slave, or move existing one.
 */
static int PanedInsertCommand(
    void *recordPtr, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[])
{
    Paned *pw = recordPtr;
    int nSlaves = Ttk_NumberSlaves(pw->paned.mgr);
    int srcIndex, destIndex;
    Tk_Window slaveWindow;

    if (objc < 4) {
	Tcl_WrongNumArgs(interp, 2,objv, "index slave ?-option value ...?");
	return TCL_ERROR;
    }

    slaveWindow = Tk_NameToWindow(
	interp, Tcl_GetString(objv[3]), pw->core.tkwin);
    if (!slaveWindow) {
	return TCL_ERROR;
    }

    if (!strcmp(Tcl_GetString(objv[2]), "end")) {
	destIndex = Ttk_NumberSlaves(pw->paned.mgr);
    } else if (TCL_OK != Ttk_GetSlaveIndexFromObj(
		interp,pw->paned.mgr,objv[2],&destIndex))
    {
	return TCL_ERROR;
    }

    srcIndex = Ttk_SlaveIndex(pw->paned.mgr, slaveWindow);
    if (srcIndex < 0) { /* New slave: */
	return AddPane(interp, pw, destIndex, slaveWindow, objc-4, objv+4);
    } /* else -- move existing slave: */

    if (destIndex >= nSlaves)
	destIndex  = nSlaves - 1;
    Ttk_ReorderSlave(pw->paned.mgr, srcIndex, destIndex);

    return objc == 4 ? TCL_OK :
	ConfigurePane(interp, pw,
		Ttk_SlaveData(pw->paned.mgr, destIndex),
		Ttk_SlaveWindow(pw->paned.mgr, destIndex),
		objc-4,objv+4);
}

/* $pw forget $pane
 */
static int PanedForgetCommand(
    void *recordPtr, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[])
{
    Paned *pw = recordPtr;
    int paneIndex;

    if (objc != 3) {
	Tcl_WrongNumArgs(interp, 2,objv, "pane");
	return TCL_ERROR;
    }

    if (TCL_OK != Ttk_GetSlaveIndexFromObj(
		    interp, pw->paned.mgr, objv[2], &paneIndex))
    {
	return TCL_ERROR;
    }
    Ttk_ForgetSlave(pw->paned.mgr, paneIndex);

    return TCL_OK;
}

/* $pw identify ?what? $x $y --
 * 	Return index of sash at $x,$y
 */
static int PanedIdentifyCommand(
    void *recordPtr, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[])
{
    const char *whatTable[] = { "element", "sash", NULL };
    enum { IDENTIFY_ELEMENT, IDENTIFY_SASH };
    int what = IDENTIFY_SASH;
    Paned *pw = recordPtr;
    int sashThickness = pw->paned.sashThickness;
    int nSashes = Ttk_NumberSlaves(pw->paned.mgr) - 1;
    int x, y, pos;
    int index;

    if (objc < 4 || objc > 5) {
	Tcl_WrongNumArgs(interp, 2,objv, "?what? x y");
	return TCL_ERROR;
    }

    if (   Tcl_GetIntFromObj(interp, objv[objc-2], &x) != TCL_OK
	|| Tcl_GetIntFromObj(interp, objv[objc-1], &y) != TCL_OK
	|| (objc == 5 &&
	    Tcl_GetIndexFromObj(interp, objv[2], whatTable, "option", 0, &what)
		!= TCL_OK)
    ) {
	return TCL_ERROR;
    }

    pos = pw->paned.orient == TTK_ORIENT_HORIZONTAL ? x : y;
    for (index = 0; index < nSashes; ++index) {
	Pane *pane = Ttk_SlaveData(pw->paned.mgr, index);
	if (pane->sashPos <= pos && pos <= pane->sashPos + sashThickness) {
	    /* Found it. */
	    switch (what) {
		case IDENTIFY_SASH:
		    Tcl_SetObjResult(interp, Tcl_NewIntObj(index));
		    return TCL_OK;
		case IDENTIFY_ELEMENT:
		{
		    Ttk_Element element =
			Ttk_IdentifyElement(SashLayout(pw, index), x, y);
		    if (element) {
			Tcl_SetObjResult(interp,
			    Tcl_NewStringObj(Ttk_ElementName(element), -1));
		    }
		    return TCL_OK;
		}
	    }
	}
    }

    return TCL_OK; /* nothing found - return empty string */
}

/* $pw pane $pane ?-option ?value -option value ...??
 * 	Query/modify pane options.
 */
static int PanedPaneCommand(
    void *recordPtr, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[])
{
    Paned *pw = recordPtr;
    int paneIndex;
    Tk_Window slaveWindow;
    Pane *pane;

    if (objc < 3) {
	Tcl_WrongNumArgs(interp, 2,objv, "pane ?-option value ...?");
	return TCL_ERROR;
    }

    if (TCL_OK != Ttk_GetSlaveIndexFromObj(
		    interp,pw->paned.mgr,objv[2],&paneIndex))
    {
	return TCL_ERROR;
    }

    pane = Ttk_SlaveData(pw->paned.mgr, paneIndex);
    slaveWindow = Ttk_SlaveWindow(pw->paned.mgr, paneIndex);

    switch (objc) {
	case 3:
	    return TtkEnumerateOptions(interp, pane, PaneOptionSpecs,
			pw->paned.paneOptionTable, slaveWindow);
	case 4:
	    return TtkGetOptionValue(interp, pane, objv[3],
			pw->paned.paneOptionTable, slaveWindow);
	default:
	    return ConfigurePane(interp, pw, pane, slaveWindow, objc-3,objv+3);
    }
}

/* $pw panes --
 * 	Return list of managed panes.
 */
static int PanedPanesCommand(
    void *recordPtr, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[])
{
    Paned *pw = recordPtr;
    Ttk_Manager *mgr = pw->paned.mgr;
    Tcl_Obj *panes;
    int i;

    if (objc != 2) {
	Tcl_WrongNumArgs(interp, 2, objv, "");
	return TCL_ERROR;
    }

    panes = Tcl_NewListObj(0, NULL);
    for (i = 0; i < Ttk_NumberSlaves(mgr); ++i) {
	const char *pathName = Tk_PathName(Ttk_SlaveWindow(mgr,i));
	Tcl_ListObjAppendElement(interp, panes, Tcl_NewStringObj(pathName,-1));
    }
    Tcl_SetObjResult(interp, panes);

    return TCL_OK;
}


/* $pw sashpos $index ?$newpos?
 * 	Query or modify sash position.
 */
static int PanedSashposCommand(
    void *recordPtr, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[])
{
    Paned *pw = recordPtr;
    int sashIndex, position = -1;
    Pane *pane;

    if (objc < 3 || objc > 4) {
	Tcl_WrongNumArgs(interp, 2,objv, "index ?newpos?");
	return TCL_ERROR;
    }
    if (Tcl_GetIntFromObj(interp, objv[2], &sashIndex) != TCL_OK) {
	return TCL_ERROR;
    }
    if (sashIndex < 0 || sashIndex >= Ttk_NumberSlaves(pw->paned.mgr) - 1) {
	Tcl_AppendResult(interp,
	    "sash index ", Tcl_GetString(objv[2]), " out of range",
	    NULL);
	return TCL_ERROR;
    }

    pane = Ttk_SlaveData(pw->paned.mgr, sashIndex);

    if (objc == 3) {
	Tcl_SetObjResult(interp, Tcl_NewIntObj(pane->sashPos));
	return TCL_OK;
    }
    /* else -- set new sash position */

    if (Tcl_GetIntFromObj(interp, objv[3], &position) != TCL_OK) {
	return TCL_ERROR;
    }

    if (position < pane->sashPos) {
	ShoveUp(pw, sashIndex, position);
    } else {
	ShoveDown(pw, sashIndex, position);
    }

    AdjustPanes(pw);
    Ttk_ManagerLayoutChanged(pw->paned.mgr);

    Tcl_SetObjResult(interp, Tcl_NewIntObj(pane->sashPos));
    return TCL_OK;
}

static const Ttk_Ensemble PanedCommands[] = {
    { "add", 		PanedAddCommand,0 },
    { "configure",	TtkWidgetConfigureCommand,0 },
    { "cget",		TtkWidgetCgetCommand,0 },
    { "forget", 	PanedForgetCommand,0 },
    { "identify", 	PanedIdentifyCommand,0 },
    { "insert", 	PanedInsertCommand,0 },
    { "instate",	TtkWidgetInstateCommand,0 },
    { "pane",   	PanedPaneCommand,0 },
    { "panes",   	PanedPanesCommand,0 },
    { "sashpos",  	PanedSashposCommand,0 },
    { "state",  	TtkWidgetStateCommand,0 },
    { 0,0,0 }
};

/*------------------------------------------------------------------------
 * +++ Widget specification.
 */

static WidgetSpec PanedWidgetSpec =
{
    "TPanedwindow",		/* className */
    sizeof(Paned),		/* recordSize */
    PanedOptionSpecs,		/* optionSpecs */
    PanedCommands,		/* subcommands */
    PanedInitialize,		/* initializeProc */
    PanedCleanup,		/* cleanupProc */
    TtkCoreConfigure,		/* configureProc */
    PanedPostConfigure, 	/* postConfigureProc */
    PanedGetLayout,		/* getLayoutProc */
    PanedSize, 			/* sizeProc */
    TtkWidgetDoLayout,		/* layoutProc */
    PanedDisplay		/* displayProc */
};

/*------------------------------------------------------------------------
 * +++ Elements and layouts.
 */

static const int DEFAULT_SASH_THICKNESS = 5;

typedef struct {
    Tcl_Obj *thicknessObj;
} SashElement;

static Ttk_ElementOptionSpec SashElementOptions[] = {
    { "-sashthickness", TK_OPTION_INT,
	    Tk_Offset(SashElement,thicknessObj), "5" },
    { NULL, 0, 0, NULL }
};

static void SashElementSize(
    void *clientData, void *elementRecord, Tk_Window tkwin,
    int *widthPtr, int *heightPtr, Ttk_Padding *paddingPtr)
{
    SashElement *sash = elementRecord;
    int thickness = DEFAULT_SASH_THICKNESS;
    Tcl_GetIntFromObj(NULL, sash->thicknessObj, &thickness);
    *widthPtr = *heightPtr = thickness;
}

static Ttk_ElementSpec SashElementSpec = {
    TK_STYLE_VERSION_2,
    sizeof(SashElement),
    SashElementOptions,
    SashElementSize,
    TtkNullElementDraw
};

TTK_BEGIN_LAYOUT(PanedLayout)
    TTK_NODE("Panedwindow.background", 0)/* @@@ BUG: empty layouts don't work */
TTK_END_LAYOUT

TTK_BEGIN_LAYOUT(HorizontalSashLayout)
    TTK_NODE("Sash.hsash", TTK_FILL_X)
TTK_END_LAYOUT

TTK_BEGIN_LAYOUT(VerticalSashLayout)
    TTK_NODE("Sash.vsash", TTK_FILL_Y)
TTK_END_LAYOUT

/*------------------------------------------------------------------------
 * +++ Registration routine.
 */
MODULE_SCOPE
void TtkPanedwindow_Init(Tcl_Interp *interp)
{
    Ttk_Theme themePtr = Ttk_GetDefaultTheme(interp);
    RegisterWidget(interp, "ttk::panedwindow", &PanedWidgetSpec);

    Ttk_RegisterElement(interp, themePtr, "hsash", &SashElementSpec, 0);
    Ttk_RegisterElement(interp, themePtr, "vsash", &SashElementSpec, 0);

    Ttk_RegisterLayout(themePtr, "TPanedwindow", PanedLayout);
    Ttk_RegisterLayout(themePtr, "Horizontal.Sash", HorizontalSashLayout);
    Ttk_RegisterLayout(themePtr, "Vertical.Sash", VerticalSashLayout);
}