Import Micropolis from http://www.donhopkins.com/home/micropolis/

[micropolis] / src / tk / tkcvtext.c

/* 
 * tkCanvText.c --
 *
 *      This file implements text items for canvas widgets.
 *
 * Copyright 1991-1992 Regents of the University of California.
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  The University of California
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */

#ifndef lint
static char rcsid[] = "$Header: /user6/ouster/wish/RCS/tkCanvText.c,v 1.12 92/08/19 08:34:12 ouster Exp $ SPRITE (Berkeley)";
#endif

#include <stdio.h>
#include "tkint.h"
#include "tkcanvas.h"
#include "tkconfig.h"

/*
 * One of the following structures is kept for each line of text
 * in a text item.  It contains geometry and display information
 * for that line.
 */

typedef struct TextLine {
    char *firstChar;            /* Pointer to the first character in this
                                 * line (in the "text" field of enclosing
                                 * text item). */
    int numChars;               /* Number of characters displayed in this
                                 * line. */
    int totalChars;             /* Total number of characters included as
                                 * part of this line (may include an extra
                                 * space character at the end that isn't
                                 * displayed). */
    int x, y;                   /* Origin at which to draw line on screen
                                 * (in integer pixel units, but in canvas
                                 * coordinates, not screen coordinates). */
    int x1, y1;                 /* Upper-left pixel that is part of text
                                 * line on screen (again, in integer canvas
                                 * pixel units). */
    int x2, y2;                 /* Lower-left pixel that is part of text
                                 * line on screen (again, in integer canvas
                                 * pixel units). */
} TextLine;

/*
 * The structure below defines the record for each text item.
 */

typedef struct TextItem  {
    Tk_Item header;             /* Generic stuff that's the same for all
                                 * types.  MUST BE FIRST IN STRUCTURE. */
    char *text;                 /* Text for item (malloc-ed). */
    int numChars;               /* Number of non-NULL characters in text. */
    double x, y;                /* Positioning point for text. */
    Tk_Anchor anchor;           /* Where to anchor text relative to (x,y). */
    int width;                  /* Width of lines for word-wrap, pixels.
                                 * Zero means no word-wrap. */
    Tk_Justify justify;         /* Justification mode for text. */
    int rightEdge;              /* Pixel just to right of right edge of
                                 * area of text item.  Used for selecting
                                 * up to end of line. */
    XFontStruct *fontPtr;       /* Font for drawing text. */
    XColor *color;              /* Color for text. */
    Pixmap stipple;             /* Stipple bitmap for text, or None. */
    GC gc;                      /* Graphics context for drawing text. */
    TextLine *linePtr;          /* Pointer to array of structures describing
                                 * individual lines of text item (malloc-ed). */
    int numLines;               /* Number of structs at *linePtr. */
    int cursorPos;              /* Insertion cursor is displayed just to left
                                 * of character with this index. */
    GC selTextGC;               /* Graphics context for selected text. */
} TextItem;

/*
 * Information used for parsing configuration specs:
 */

static Tk_ConfigSpec configSpecs[] = {
    {TK_CONFIG_ANCHOR, "-anchor", (char *) NULL, (char *) NULL,
        "center", Tk_Offset(TextItem, anchor),
        TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_COLOR, "-fill", (char *) NULL, (char *) NULL,
        "black", Tk_Offset(TextItem, color), 0},
    {TK_CONFIG_FONT, "-font", (char *) NULL, (char *) NULL,
        "-Adobe-Helvetica-Bold-R-Normal-*-120-*",
        Tk_Offset(TextItem, fontPtr), 0},
    {TK_CONFIG_JUSTIFY, "-justify", (char *) NULL, (char *) NULL,
        "left", Tk_Offset(TextItem, justify),
        TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_BITMAP, "-stipple", (char *) NULL, (char *) NULL,
        (char *) NULL, Tk_Offset(TextItem, stipple), TK_CONFIG_NULL_OK},
    {TK_CONFIG_CUSTOM, "-tags", (char *) NULL, (char *) NULL,
        (char *) NULL, 0, TK_CONFIG_NULL_OK, &tkCanvasTagsOption},
    {TK_CONFIG_STRING, "-text", (char *) NULL, (char *) NULL,
        "", Tk_Offset(TextItem, text), 0},
    {TK_CONFIG_PIXELS, "-width", (char *) NULL, (char *) NULL,
        "0", Tk_Offset(TextItem, width), TK_CONFIG_DONT_SET_DEFAULT},
    {TK_CONFIG_END, (char *) NULL, (char *) NULL, (char *) NULL,
        (char *) NULL, 0, 0}
};

/*
 * Prototypes for procedures defined in this file:
 */

static void             ComputeTextBbox _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            TextItem *textPtr));
static int              ConfigureText _ANSI_ARGS_((
                            Tk_Canvas *canvasPtr, Tk_Item *itemPtr, int argc,
                            char **argv, int flags));
static int              CreateText _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            struct Tk_Item *itemPtr, int argc, char **argv));
static void             DeleteText _ANSI_ARGS_((Tk_Item *itemPtr));
static void             DisplayText _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, Drawable dst));
static int              GetSelText _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, int offset, char *buffer,
                            int maxBytes));
static int              GetTextIndex _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, char *indexString,
                            int *indexPtr));
static void             ScaleText _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double originX, double originY,
                            double scaleX, double scaleY));
static void             SetTextCursor _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, int index));
static int              TextCoords _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, int argc, char **argv));
static int              TextDeleteChars _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, int first, int last));
static int              TextInsert _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, int beforeThis, char *string));
static int              TextToArea _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double *rectPtr));
static double           TextToPoint _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double *pointPtr));
static void             TranslateText _ANSI_ARGS_((Tk_Canvas *canvasPtr,
                            Tk_Item *itemPtr, double deltaX, double deltaY));

/*
 * The structures below defines the rectangle and oval item types
 * by means of procedures that can be invoked by generic item code.
 */

Tk_ItemType TkTextType = {
    "text",                             /* name */
    sizeof(TextItem),                   /* itemSize */
    CreateText,                         /* createProc */
    configSpecs,                        /* configSpecs */
    ConfigureText,                      /* configureProc */
    TextCoords,                         /* coordProc */
    DeleteText,                         /* deleteProc */
    DisplayText,                        /* displayProc */
    0,                                  /* alwaysRedraw */
    TextToPoint,                        /* pointProc */
    TextToArea,                         /* areaProc */
    (Tk_ItemPostscriptProc *) NULL,     /* postscriptProc */
    ScaleText,                          /* scaleProc */
    TranslateText,                      /* translateProc */
    GetTextIndex,                       /* indexProc */
    SetTextCursor,                      /* cursorProc */
    GetSelText,                         /* selectionProc */
    TextInsert,                         /* insertProc */
    TextDeleteChars,                    /* dTextProc */
    (Tk_ItemType *) NULL                /* nextPtr */
};
\f
/*
 *--------------------------------------------------------------
 *
 * CreateText --
 *
 *      This procedure is invoked to create a new text item
 *      in a canvas.
 *
 * Results:
 *      A standard Tcl return value.  If an error occurred in
 *      creating the item then an error message is left in
 *      canvasPtr->interp->result;  in this case itemPtr is
 *      left uninitialized so it can be safely freed by the
 *      caller.
 *
 * Side effects:
 *      A new text item is created.
 *
 *--------------------------------------------------------------
 */

static int
CreateText(canvasPtr, itemPtr, argc, argv)
    register Tk_Canvas *canvasPtr;      /* Canvas to hold new item. */
    Tk_Item *itemPtr;                   /* Record to hold new item;  header
                                         * has been initialized by caller. */
    int argc;                           /* Number of arguments in argv. */
    char **argv;                        /* Arguments describing rectangle. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;

    if (argc < 2) {
        Tcl_AppendResult(canvasPtr->interp, "wrong # args:  should be \"",
                Tk_PathName(canvasPtr->tkwin),
                "\" create text x y [options]", (char *) NULL);
        return TCL_ERROR;
    }

    /*
     * Carry out initialization that is needed in order to clean
     * up after errors during the the remainder of this procedure.
     */

    textPtr->text = NULL;
    textPtr->anchor = TK_ANCHOR_CENTER;
    textPtr->width = 0;
    textPtr->justify = TK_JUSTIFY_LEFT;
    textPtr->fontPtr = NULL;
    textPtr->color = NULL;
    textPtr->stipple = None;
    textPtr->gc = None;
    textPtr->linePtr = NULL;
    textPtr->numLines = 0;
    textPtr->cursorPos = 0;
    textPtr->selTextGC = None;

    /*
     * Process the arguments to fill in the item record.
     */

    if ((TkGetCanvasCoord(canvasPtr, argv[0], &textPtr->x) != TCL_OK)
            || (TkGetCanvasCoord(canvasPtr, argv[1], &textPtr->y) != TCL_OK)) {
        return TCL_ERROR;
    }

    if (ConfigureText(canvasPtr, itemPtr, argc-2, argv+2, 0) != TCL_OK) {
        DeleteText(itemPtr);
        return TCL_ERROR;
    }
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * TextCoords --
 *
 *      This procedure is invoked to process the "coords" widget
 *      command on text items.  See the user documentation for
 *      details on what it does.
 *
 * Results:
 *      Returns TCL_OK or TCL_ERROR, and sets canvasPtr->interp->result.
 *
 * Side effects:
 *      The coordinates for the given item may be changed.
 *
 *--------------------------------------------------------------
 */

static int
TextCoords(canvasPtr, itemPtr, argc, argv)
    register Tk_Canvas *canvasPtr;      /* Canvas containing item. */
    Tk_Item *itemPtr;                   /* Item whose coordinates are to be
                                         * read or modified. */
    int argc;                           /* Number of coordinates supplied in
                                         * argv. */
    char **argv;                        /* Array of coordinates: x1, y1,
                                         * x2, y2, ... */
{
    register TextItem *textPtr = (TextItem *) itemPtr;

    if (argc == 0) {
        sprintf(canvasPtr->interp->result, "%g %g", textPtr->x, textPtr->y);
    } else if (argc == 2) {
        if ((TkGetCanvasCoord(canvasPtr, argv[0], &textPtr->x) != TCL_OK)
                || (TkGetCanvasCoord(canvasPtr, argv[1],
                    &textPtr->y) != TCL_OK)) {
            return TCL_ERROR;
        }
        ComputeTextBbox(canvasPtr, textPtr);
    } else {
        sprintf(canvasPtr->interp->result,
                "wrong # coordinates:  expected 0 or 2, got %d",
                argc);
        return TCL_ERROR;
    }
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * ConfigureText --
 *
 *      This procedure is invoked to configure various aspects
 *      of a text item, such as its border and background colors.
 *
 * Results:
 *      A standard Tcl result code.  If an error occurs, then
 *      an error message is left in canvasPtr->interp->result.
 *
 * Side effects:
 *      Configuration information, such as colors and stipple
 *      patterns, may be set for itemPtr.
 *
 *--------------------------------------------------------------
 */

static int
ConfigureText(canvasPtr, itemPtr, argc, argv, flags)
    Tk_Canvas *canvasPtr;       /* Canvas containing itemPtr. */
    Tk_Item *itemPtr;           /* Rectangle item to reconfigure. */
    int argc;                   /* Number of elements in argv.  */
    char **argv;                /* Arguments describing things to configure. */
    int flags;                  /* Flags to pass to Tk_ConfigureWidget. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;
    XGCValues gcValues;
    GC newGC, newSelGC;
    unsigned long mask;

    if (Tk_ConfigureWidget(canvasPtr->interp, canvasPtr->tkwin,
            configSpecs, argc, argv, (char *) textPtr, flags) != TCL_OK) {
        return TCL_ERROR;
    }

    /*
     * A few of the options require additional processing, such as
     * graphics contexts.
     */

    textPtr->numChars = strlen(textPtr->text);
    newGC = newSelGC = None;
    if ((textPtr->color != NULL) && (textPtr->fontPtr != NULL)) {
        gcValues.foreground = textPtr->color->pixel;
        gcValues.font = textPtr->fontPtr->fid;
        mask = GCForeground|GCFont;
        if (textPtr->stipple != None) {
            gcValues.stipple = textPtr->stipple;
            gcValues.fill_style = FillStippled;
            mask |= GCForeground|GCStipple|GCFillStyle;
        }
        newGC = Tk_GetGC(canvasPtr->tkwin, mask, &gcValues);
        gcValues.foreground = canvasPtr->selFgColorPtr->pixel;
        newSelGC = Tk_GetGC(canvasPtr->tkwin, mask, &gcValues);
    }
    if (textPtr->gc != None) {
        Tk_FreeGC(textPtr->gc);
    }
    textPtr->gc = newGC;
    if (textPtr->selTextGC != None) {
        Tk_FreeGC(textPtr->selTextGC);
    }
    textPtr->selTextGC = newSelGC;

    /*
     * If the text was changed, move the selection and insertion indices
     * to keep them inside the item.
     */

    if (canvasPtr->selItemPtr == itemPtr) {
        if (canvasPtr->selectFirst >= textPtr->numChars) {
            canvasPtr->selItemPtr = NULL;
        } else {
            if (canvasPtr->selectLast >= textPtr->numChars) {
                canvasPtr->selectLast = textPtr->numChars-1;
            }
            if ((canvasPtr->anchorItemPtr == itemPtr)
                    && (canvasPtr->selectAnchor >= textPtr->numChars)) {
                canvasPtr->selectAnchor = textPtr->numChars-1;
            }
        }
    }
    if (textPtr->cursorPos >= textPtr->numChars) {
        textPtr->cursorPos = textPtr->numChars;
    }

    ComputeTextBbox(canvasPtr, textPtr);
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * DeleteText --
 *
 *      This procedure is called to clean up the data structure
 *      associated with a text item.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Resources associated with itemPtr are released.
 *
 *--------------------------------------------------------------
 */

static void
DeleteText(itemPtr)
    Tk_Item *itemPtr;                   /* Item that is being deleted. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;

    if (textPtr->text != NULL) {
        ckfree(textPtr->text);
    }
    if (textPtr->fontPtr != NULL) {
        Tk_FreeFontStruct(textPtr->fontPtr);
    }
    if (textPtr->color != NULL) {
        Tk_FreeColor(textPtr->color);
    }
    if (textPtr->stipple != None) {
        Tk_FreeBitmap(textPtr->stipple);
    }
    if (textPtr->gc != None) {
        Tk_FreeGC(textPtr->gc);
    }
    if (textPtr->linePtr != NULL) {
        ckfree((char *) textPtr->linePtr);
    }
    if (textPtr->selTextGC != None) {
        Tk_FreeGC(textPtr->selTextGC);
    }
}
\f
/*
 *--------------------------------------------------------------
 *
 * ComputeTextBbox --
 *
 *      This procedure is invoked to compute the bounding box of
 *      all the pixels that may be drawn as part of a text item.
 *      In addition, it recomputes all of the geometry information
 *      used to display a text item or check for mouse hits.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The fields x1, y1, x2, and y2 are updated in the header
 *      for itemPtr, and the linePtr structure is regenerated
 *      for itemPtr.
 *
 *--------------------------------------------------------------
 */

static void
ComputeTextBbox(canvasPtr, textPtr)
    register Tk_Canvas *canvasPtr;      /* Canvas that contains item. */
    register TextItem *textPtr;         /* Item whose bbos is to be
                                         * recomputed. */
{
    register TextLine *linePtr;
#define MAX_LINES 100
    char *lineStart[MAX_LINES];
    int lineChars[MAX_LINES];
    int linePixels[MAX_LINES];
    int numLines, wrapPixels, maxLinePixels, leftX, topY, y;
    int lineHeight, i, fudge;
    char *p;
    XCharStruct *maxBoundsPtr = &textPtr->fontPtr->max_bounds;

    if (textPtr->linePtr != NULL) {
        ckfree((char *) textPtr->linePtr);
        textPtr->linePtr = NULL;
    }

    /*
     * Work through the text computing the starting point, number of
     * characters, and number of pixels in each line.
     */

    p = textPtr->text;
    if (textPtr->width > 0) {
        wrapPixels = maxLinePixels = textPtr->width;
    } else {
        wrapPixels = 10000000;
        maxLinePixels = 0;
    }
    for (numLines = 0; (numLines < MAX_LINES) && (*p != 0);
            numLines++) {
        int numChars, numPixels;
        numChars = TkMeasureChars(textPtr->fontPtr, p,
                (textPtr->text + textPtr->numChars) - p, 0,
                wrapPixels, TK_WHOLE_WORDS|TK_AT_LEAST_ONE, &numPixels);
        if (numPixels > maxLinePixels) {
            maxLinePixels = numPixels;
        }
        lineStart[numLines] = p;
        lineChars[numLines] = numChars;
        linePixels[numLines] = numPixels;
        p += numChars;

        /*
         * Skip space character that terminates a line, if there is one.
         * In the case of multiple spaces, all but one will be displayed.
         * This is important to make sure the insertion cursor gets
         * displayed when it is in the middle of a multi-space.
         */

        if (isspace(*p)) {
            p++;
        }
    }

    /*
     * Use overall geometry information to compute the top-left corner
     * of the bounding box for the text item.
     */

    leftX = textPtr->x + 0.5;
    topY = textPtr->y + 0.5;
    lineHeight = textPtr->fontPtr->ascent + textPtr->fontPtr->descent;
    switch (textPtr->anchor) {
        case TK_ANCHOR_NW:
        case TK_ANCHOR_N:
        case TK_ANCHOR_NE:
            break;

        case TK_ANCHOR_W:
        case TK_ANCHOR_CENTER:
        case TK_ANCHOR_E:
            topY -= (lineHeight * numLines)/2;
            break;

        case TK_ANCHOR_SW:
        case TK_ANCHOR_S:
        case TK_ANCHOR_SE:
            topY -= lineHeight * numLines;
            break;
    }
    switch (textPtr->anchor) {
        case TK_ANCHOR_NW:
        case TK_ANCHOR_W:
        case TK_ANCHOR_SW:
            break;

        case TK_ANCHOR_N:
        case TK_ANCHOR_CENTER:
        case TK_ANCHOR_S:
            leftX -= maxLinePixels/2;
            break;

        case TK_ANCHOR_NE:
        case TK_ANCHOR_E:
        case TK_ANCHOR_SE:
            leftX -= maxLinePixels;
            break;
    }
    textPtr->rightEdge = leftX + maxLinePixels;

    /*
     * Create the new TextLine array and fill it in using the geometry
     * information gathered already.
     */

    if (numLines > 0) {
        textPtr->linePtr = (TextLine *) ckalloc((unsigned)
                (numLines * sizeof(TextLine)));
    } else {
        textPtr->linePtr = NULL;
    }
    textPtr->numLines = numLines;
    for (i = 0, linePtr = textPtr->linePtr, y = topY;
            i < numLines; i++, linePtr++, y += lineHeight) {
        linePtr->firstChar = lineStart[i];
        linePtr->numChars = lineChars[i];
        if (i == (numLines-1)) {
            linePtr->totalChars = linePtr->numChars;
        } else {
            linePtr->totalChars = lineStart[i+1] - lineStart[i];
        }
        switch (textPtr->justify) {
            case TK_JUSTIFY_LEFT:
            case TK_JUSTIFY_FILL:
                linePtr->x = leftX;
                break;
            case TK_JUSTIFY_CENTER:
                linePtr->x = leftX + maxLinePixels/2 - linePixels[i]/2;
                break;
            case TK_JUSTIFY_RIGHT:
                linePtr->x = leftX + maxLinePixels - linePixels[i];
                break;
        }
        linePtr->y = y + textPtr->fontPtr->ascent;
        linePtr->x1 = linePtr->x - maxBoundsPtr->lbearing;
        linePtr->y1 = y;
        linePtr->x2 = linePtr->x + linePixels[i] + maxBoundsPtr->rbearing
                - textPtr->fontPtr->min_bounds.rbearing;
        linePtr->y2 = linePtr->y + textPtr->fontPtr->descent - 1;
    }

    /*
     * Last of all, update the bounding box for the item.  The item's
     * bounding box includes the bounding box of all its lines, plus
     * an extra fudge factor for the cursor border (which could
     * potentially be quite large).
     */

    linePtr = textPtr->linePtr;
    textPtr->header.x1 = textPtr->header.x2 = leftX;
    textPtr->header.y1 = topY;
    textPtr->header.y2 = topY + numLines*lineHeight;
    for (linePtr = textPtr->linePtr, i = textPtr->numLines; i > 0;
            i--, linePtr++) {
        if (linePtr->x1 < textPtr->header.x1) {
            textPtr->header.x1 = linePtr->x1;
        }
        if (linePtr->x2 >= textPtr->header.x2) {
            textPtr->header.x2 = linePtr->x2 + 1;
        }
    }

    fudge = canvasPtr->cursorWidth/2;
    if (canvasPtr->selBorderWidth > fudge) {
        fudge = canvasPtr->selBorderWidth;
    }
    textPtr->header.x1 -= fudge;
    textPtr->header.x2 += fudge;
}
\f
/*
 *--------------------------------------------------------------
 *
 * DisplayText --
 *
 *      This procedure is invoked to draw a text item in a given
 *      drawable.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      ItemPtr is drawn in drawable using the transformation
 *      information in canvasPtr.
 *
 *--------------------------------------------------------------
 */

static void
DisplayText(canvasPtr, itemPtr, drawable)
    register Tk_Canvas *canvasPtr;      /* Canvas that contains item. */
    Tk_Item *itemPtr;                   /* Item to be displayed. */
    Drawable drawable;                  /* Pixmap or window in which to draw
                                         * item. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;
    Display *display = Tk_Display(canvasPtr->tkwin);
    register TextLine *linePtr;
    int i, focusHere, cursorX, cursorIndex, lineIndex;
    int beforeSelect, inSelect, afterSelect, selStartX, selEndX;

    if (textPtr->gc == None) {
        return;
    }
    focusHere = (canvasPtr->focusItemPtr == itemPtr) &&
            (canvasPtr->flags & GOT_FOCUS);
    for (linePtr = textPtr->linePtr, i = textPtr->numLines;
            i > 0; linePtr++, i--) {

        /*
         * If part or all of this line is selected, then draw a special
         * background under the selected part of the line.
         */

        lineIndex = linePtr->firstChar - textPtr->text;
        if ((canvasPtr->selItemPtr != itemPtr)
                || (canvasPtr->selectLast < lineIndex)
                || (canvasPtr->selectFirst >= (lineIndex
                        + linePtr->totalChars))) {
            beforeSelect = linePtr->numChars;
            inSelect = 0;
        } else {
            beforeSelect = canvasPtr->selectFirst - lineIndex;
            if (beforeSelect <= 0) {
                beforeSelect = 0;
                selStartX = linePtr->x;
            } else {
                (void) TkMeasureChars(textPtr->fontPtr,
                        linePtr->firstChar, beforeSelect, 0,
                        (int) 1000000, TK_PARTIAL_OK, &selStartX);
                selStartX += linePtr->x;
            }
            inSelect = canvasPtr->selectLast + 1 - (lineIndex + beforeSelect);

            /*
             * If the selection spans the end of this line, then display
             * selection background all the way to the end of the line.
             * However, for the last line we only want to display up to
             * the last character, not the end of the line, hence the
             * "i != 1" check.
             */

            if (inSelect >= (linePtr->totalChars - beforeSelect)) {
                inSelect = linePtr->numChars - beforeSelect;
                if (i != 1) {
                    selEndX = textPtr->rightEdge;
                    goto fillSelectBackground;
                }
            }
            (void) TkMeasureChars(textPtr->fontPtr,
                    linePtr->firstChar + beforeSelect, inSelect,
                    selStartX-linePtr->x, (int) 1000000, TK_PARTIAL_OK,
                    &selEndX);
            selEndX += linePtr->x;
            fillSelectBackground:
            Tk_Fill3DRectangle(display, drawable, canvasPtr->selBorder,
                    selStartX - canvasPtr->drawableXOrigin
                        - canvasPtr->selBorderWidth,
                    linePtr->y - canvasPtr->drawableYOrigin
                        - textPtr->fontPtr->ascent,
                    selEndX - selStartX + 2*canvasPtr->selBorderWidth,
                    textPtr->fontPtr->ascent + textPtr->fontPtr->descent,
                    canvasPtr->selBorderWidth, TK_RELIEF_RAISED);
        }

        /*
         * If the insertion cursor is in this line, then draw a special
         * background for the cursor before drawing the text.  Note:
         * if we're the cursor item but the cursor is turned off, then
         * redraw background over the area of the cursor.  This guarantees
         * that the selection won't make the cursor invisible on mono
         * displays, where both are drawn in the same color.
         */

        if (focusHere) {
            cursorIndex = textPtr->cursorPos
                    - (linePtr->firstChar - textPtr->text);
            if ((cursorIndex >= 0) && (cursorIndex <= linePtr->numChars)) {
                (void) TkMeasureChars(textPtr->fontPtr, linePtr->firstChar,
                    cursorIndex, 0, (int) 1000000, TK_PARTIAL_OK, &cursorX);
                if (canvasPtr->flags & CURSOR_ON) {
                    Tk_Fill3DRectangle(display, drawable,
                            canvasPtr->cursorBorder,
                            linePtr->x - canvasPtr->drawableXOrigin
                                + cursorX  - (canvasPtr->cursorWidth)/2,
                            linePtr->y - canvasPtr->drawableYOrigin
                                - textPtr->fontPtr->ascent,
                            canvasPtr->cursorWidth,
                            textPtr->fontPtr->ascent
                                + textPtr->fontPtr->descent,
                            canvasPtr->cursorBorderWidth, TK_RELIEF_RAISED);
                } else if (Tk_DefaultDepth(
                        Tk_Screen(canvasPtr->tkwin)) == 1){
                    Tk_Fill3DRectangle(display, drawable,
                            canvasPtr->bgBorder,
                            linePtr->x - canvasPtr->drawableXOrigin
                                + cursorX  - (canvasPtr->cursorWidth)/2,
                            linePtr->y - canvasPtr->drawableYOrigin
                                - textPtr->fontPtr->ascent,
                            canvasPtr->cursorWidth,
                            textPtr->fontPtr->ascent
                                + textPtr->fontPtr->descent,
                            0, TK_RELIEF_FLAT);
                }
            }
        }

        /*
         * Display the text in three pieces:  the part before the
         * selection, the selected part (which needs a different graphics
         * context), and the part after the selection.
         */

        if (beforeSelect != 0) {
            TkDisplayChars(display, drawable, textPtr->gc, textPtr->fontPtr,
                    linePtr->firstChar, beforeSelect,
                    linePtr->x - canvasPtr->drawableXOrigin,
                    linePtr->y - canvasPtr->drawableYOrigin, 0);
        }
        if (inSelect != 0) {
            TkDisplayChars(display, drawable, textPtr->selTextGC,
                    textPtr->fontPtr, linePtr->firstChar + beforeSelect,
                    inSelect, selStartX - canvasPtr->drawableXOrigin,
                    linePtr->y - canvasPtr->drawableYOrigin, 0);
        }
        afterSelect = linePtr->numChars - beforeSelect - inSelect;
        if (afterSelect > 0) {
            TkDisplayChars(display, drawable, textPtr->gc, textPtr->fontPtr,
                    linePtr->firstChar + beforeSelect + inSelect,
                    afterSelect, selEndX - canvasPtr->drawableXOrigin,
                    linePtr->y - canvasPtr->drawableYOrigin, 0);
        }
    }
}
\f
/*
 *--------------------------------------------------------------
 *
 * TextInsert --
 *
 *      Insert characters into a text item at a given position.
 *
 * Results:
 *      Always returns TCL_OK.
 *
 * Side effects:
 *      The text in the given item is modified.  The cursor and
 *      selection positions are also modified to reflect the
 *      insertion.
 *
 *--------------------------------------------------------------
 */

static int
TextInsert(canvasPtr, itemPtr, beforeThis, string)
    Tk_Canvas *canvasPtr;       /* Canvas containing text item. */
    Tk_Item *itemPtr;           /* Text item to be modified. */
    int beforeThis;             /* Index of character before which text is
                                 * to be inserted. */
    char *string;               /* New characters to be inserted. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;
    int length;
    char *new;

    length = strlen(string);
    if (length == 0) {
        return TCL_OK;
    }
    if (beforeThis < 0) {
        beforeThis = 0;
    }
    if (beforeThis > textPtr->numChars) {
        beforeThis = textPtr->numChars;
    }

    new = (char *) ckalloc((unsigned) (textPtr->numChars + length + 1));
    strncpy(new, textPtr->text, beforeThis);
    strcpy(new+beforeThis, string);
    strcpy(new+beforeThis+length, textPtr->text+beforeThis);
    ckfree(textPtr->text);
    textPtr->text = new;
    textPtr->numChars += length;

    /*
     * Inserting characters invalidates indices such as those for the
     * selection and cursor.  Update the indices appropriately.
     */

    if (canvasPtr->selItemPtr == itemPtr) {
        if (canvasPtr->selectFirst >= beforeThis) {
            canvasPtr->selectFirst += length;
        }
        if (canvasPtr->selectLast >= beforeThis) {
            canvasPtr->selectLast += length;
        }
        if ((canvasPtr->anchorItemPtr == itemPtr)
                && (canvasPtr->selectAnchor >= beforeThis)) {
            canvasPtr->selectAnchor += length;
        }
    }
    if (textPtr->cursorPos >= beforeThis) {
        textPtr->cursorPos += length;
    }
    ComputeTextBbox(canvasPtr, textPtr);
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * TextDeleteChars --
 *
 *      Delete one or more characters from a text item.
 *
 * Results:
 *      Always returns TCL_OK.
 *
 * Side effects:
 *      Characters between "first" and "last", inclusive, get
 *      deleted from itemPtr, and things like the selection
 *      position get updated.
 *
 *--------------------------------------------------------------
 */

static int
TextDeleteChars(canvasPtr, itemPtr, first, last)
    Tk_Canvas *canvasPtr;       /* Canvas containing itemPtr. */
    Tk_Item *itemPtr;           /* Item in which to delete characters. */
    int first;                  /* Index of first character to delete. */
    int last;                   /* Index of last character to delete. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;
    int count;
    char *new;

    if (first < 0) {
        first = 0;
    }
    if (last >= textPtr->numChars) {
        last = textPtr->numChars-1;
    }
    if (first > last) {
        return TCL_OK;
    }
    count = last + 1 - first;

    new = ckalloc((unsigned) (textPtr->numChars + 1 - count));
    strncpy(new, textPtr->text, first);
    strcpy(new+first, textPtr->text+last+1);
    ckfree(textPtr->text);
    textPtr->text = new;
    textPtr->numChars -= count;

    /*
     * Update indexes for the selection and cursor to reflect the
     * renumbering of the remaining characters.
     */

    if (canvasPtr->selItemPtr == itemPtr) {
        if (canvasPtr->selectFirst > first) {
            canvasPtr->selectFirst -= count;
            if (canvasPtr->selectFirst < first) {
                canvasPtr->selectFirst = first;
            }
        }
        if (canvasPtr->selectLast >= first) {
            canvasPtr->selectLast -= count;
            if (canvasPtr->selectLast < (first-1)) {
                canvasPtr->selectLast = (first-1);
            }
        }
        if (canvasPtr->selectFirst > canvasPtr->selectLast) {
            canvasPtr->selItemPtr = NULL;
        }
        if ((canvasPtr->anchorItemPtr == itemPtr)
                && (canvasPtr->selectAnchor > first)) {
            canvasPtr->selectAnchor -= count;
            if (canvasPtr->selectAnchor < first) {
                canvasPtr->selectAnchor = first;
            }
        }
    }
    if (textPtr->cursorPos > first) {
        textPtr->cursorPos -= count;
        if (textPtr->cursorPos < first) {
            textPtr->cursorPos = first;
        }
    }
    ComputeTextBbox(canvasPtr, textPtr);
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * TextToPoint --
 *
 *      Computes the distance from a given point to a given
 *      text item, in canvas units.
 *
 * Results:
 *      The return value is 0 if the point whose x and y coordinates
 *      are pointPtr[0] and pointPtr[1] is inside the arc.  If the
 *      point isn't inside the arc then the return value is the
 *      distance from the point to the arc.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static double
TextToPoint(canvasPtr, itemPtr, pointPtr)
    Tk_Canvas *canvasPtr;       /* Canvas containing itemPtr. */
    Tk_Item *itemPtr;           /* Item to check against point. */
    double *pointPtr;           /* Pointer to x and y coordinates. */
{
    TextItem *textPtr = (TextItem *) itemPtr;
    register TextLine *linePtr;
    int i;
    double xDiff, yDiff, dist, minDist;

    /*
     * Treat each line in the text item as a rectangle, compute the
     * distance to that rectangle, and take the minimum of these
     * distances.  Perform most of the calculations in integer pixel
     * units, since that's how the dimensions of the text are defined.
     */

    minDist = -1.0;
    for (linePtr = textPtr->linePtr, i = textPtr->numLines;
            i > 0; linePtr++, i--) {

        /*
         * If the point is inside the line's rectangle, then can
         * return immediately.
         */
    
        if ((pointPtr[0] >= linePtr->x1)
                && (pointPtr[0] <= linePtr->x2)
                && (pointPtr[1] >= linePtr->y1)
                && (pointPtr[1] <= linePtr->y2)) {
            return 0.0;
        }
    
        /*
         * Point is outside line's rectangle; compute distance to nearest
         * side.
         */
    
        if (pointPtr[0] < linePtr->x1) {
            xDiff = linePtr->x1 - pointPtr[0];
        } else if (pointPtr[0] > linePtr->x2)  {
            xDiff = pointPtr[0] - linePtr->x2;
        } else {
            xDiff = 0;
        }
    
        if (pointPtr[1] < linePtr->y1) {
            yDiff = linePtr->y1 - pointPtr[1];
        } else if (pointPtr[1] > linePtr->y2)  {
            yDiff = pointPtr[1] - linePtr->y2;
        } else {
            yDiff = 0;
        }

        dist = hypot((float) xDiff, (float) yDiff);
        if ((dist < minDist) || (minDist < 0.0)) {
            minDist = dist;
        }
    }
    return minDist;
}
\f
/*
 *--------------------------------------------------------------
 *
 * TextToArea --
 *
 *      This procedure is called to determine whether an item
 *      lies entirely inside, entirely outside, or overlapping
 *      a given rectangle.
 *
 * Results:
 *      -1 is returned if the item is entirely outside the area
 *      given by rectPtr, 0 if it overlaps, and 1 if it is entirely
 *      inside the given area.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static int
TextToArea(canvasPtr, itemPtr, rectPtr)
    Tk_Canvas *canvasPtr;       /* Canvas containing itemPtr. */
    Tk_Item *itemPtr;           /* Item to check against rectangle. */
    double *rectPtr;            /* Pointer to array of four coordinates
                                 * (x1, y1, x2, y2) describing rectangular
                                 * area.  */
{
    TextItem *textPtr = (TextItem *) itemPtr;
    register TextLine *linePtr;
    int i, result;

    /*
     * Scan the lines one at a time, seeing whether each line is
     * entirely in, entirely out, or overlapping the rectangle.  If
     * an overlap is detected, return immediately;  otherwise wait
     * until all lines have been processed and see if they were all
     * inside or all outside.
     */

    result = 0;
    for (linePtr = textPtr->linePtr, i = textPtr->numLines;
            i > 0; linePtr++, i--) {
        if ((rectPtr[2] < linePtr->x1) || (rectPtr[0] > linePtr->x2)
                || (rectPtr[3] < linePtr->y1) || (rectPtr[1] > linePtr->y2)) {
            if (result == 1) {
                return 0;
            }
            result = -1;
            continue;
        }
        if ((linePtr->x1 < rectPtr[0]) || (linePtr->x2 > rectPtr[2])
                || (linePtr->y1 < rectPtr[1]) || (linePtr->y2 > rectPtr[3])) {
            return 0;
        }
        if (result == -1) {
            return 0;
        }
        result = 1;
    }
    return result;
}
\f
/*
 *--------------------------------------------------------------
 *
 * ScaleText --
 *
 *      This procedure is invoked to rescale a text item.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Scales the position of the text, but not the size
 *      of the font for the text.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static void
ScaleText(canvasPtr, itemPtr, originX, originY, scaleX, scaleY)
    Tk_Canvas *canvasPtr;               /* Canvas containing rectangle. */
    Tk_Item *itemPtr;                   /* Rectangle to be scaled. */
    double originX, originY;            /* Origin about which to scale rect. */
    double scaleX;                      /* Amount to scale in X direction. */
    double scaleY;                      /* Amount to scale in Y direction. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;

    textPtr->x = originX + scaleX*(textPtr->x - originX);
    textPtr->y = originY + scaleY*(textPtr->y - originY);
    ComputeTextBbox(canvasPtr, textPtr);
    return;
}
\f
/*
 *--------------------------------------------------------------
 *
 * TranslateText --
 *
 *      This procedure is called to move a text item by a
 *      given amount.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The position of the text item is offset by (xDelta, yDelta),
 *      and the bounding box is updated in the generic part of the
 *      item structure.
 *
 *--------------------------------------------------------------
 */

static void
TranslateText(canvasPtr, itemPtr, deltaX, deltaY)
    Tk_Canvas *canvasPtr;               /* Canvas containing item. */
    Tk_Item *itemPtr;                   /* Item that is being moved. */
    double deltaX, deltaY;              /* Amount by which item is to be
                                         * moved. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;

    textPtr->x += deltaX;
    textPtr->y += deltaY;
    ComputeTextBbox(canvasPtr, textPtr);
}
\f
/*
 *--------------------------------------------------------------
 *
 * GetTextIndex --
 *
 *      Parse an index into a text item and return either its value
 *      or an error.
 *
 * Results:
 *      A standard Tcl result.  If all went well, then *indexPtr is
 *      filled in with the index (into itemPtr) corresponding to
 *      string.  Otherwise an error message is left in
 *      canvasPtr->interp->result.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

static int
GetTextIndex(canvasPtr, itemPtr, string, indexPtr)
    Tk_Canvas *canvasPtr;       /* Canvas containing item. */
    Tk_Item *itemPtr;           /* Item for which the index is being
                                 * specified. */
    char *string;               /* Specification of a particular character
                                 * in itemPtr's text. */
    int *indexPtr;              /* Where to store converted index. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;
    int length;

    length = strlen(string);

    if (string[0] == 'e') {
        if (strncmp(string, "end", length) == 0) {
            *indexPtr = textPtr->numChars;
        } else {
            badIndex:

            /*
             * Some of the paths here leave messages in
             * canvasPtr->interp->result, so we have to clear it out
             * before storing our own message.
             */

            Tcl_SetResult(canvasPtr->interp, (char *) NULL, TCL_STATIC);
            Tcl_AppendResult(canvasPtr->interp, "bad index \"", string,
                    "\"", (char *) NULL);
            return TCL_ERROR;
        }
    } else if (string[0] == 'c') {
        if (strncmp(string, "cursor", length) == 0) {
            *indexPtr = textPtr->cursorPos;
        } else {
            goto badIndex;
        }
    } else if (string[0] == 's') {
        if (canvasPtr->selItemPtr != itemPtr) {
            canvasPtr->interp->result = "selection isn't in item";
            return TCL_ERROR;
        }
        if (length < 5) {
            goto badIndex;
        }
        if (strncmp(string, "sel.first", length) == 0) {
            *indexPtr = canvasPtr->selectFirst;
        } else if (strncmp(string, "sel.last", length) == 0) {
            *indexPtr = canvasPtr->selectLast;
        } else {
            goto badIndex;
        }
    } else if (string[0] == '@') {
        int x, y, dummy, i;
        char *end, *p;
        register TextLine *linePtr;

        p = string+1;
        x = strtol(p, &end, 0);
        if ((end == p) || (*end != ',')) {
            goto badIndex;
        }
        p = end+1;
        y = strtol(p, &end, 0);
        if ((end == p) || (*end != 0)) {
            goto badIndex;
        }
        if ((textPtr->numChars == 0) || (y < textPtr->linePtr[0].y1)) {
            *indexPtr = 0;
            return TCL_OK;
        }
        for (i = 0, linePtr = textPtr->linePtr; ; i++, linePtr++) {
            if (i >= textPtr->numLines) {
                *indexPtr = textPtr->numChars;
                return TCL_OK;
            }
            if (y <= linePtr->y2) {
                break;
            }
        }
        *indexPtr = TkMeasureChars(textPtr->fontPtr, linePtr->firstChar,
                linePtr->numChars, linePtr->x, x, 0, &dummy);
        *indexPtr += linePtr->firstChar - textPtr->text;
    } else {
        if (Tcl_GetInt(canvasPtr->interp, string, indexPtr) != TCL_OK) {
            goto badIndex;
        }
        if (*indexPtr < 0){
            *indexPtr = 0;
        } else if (*indexPtr > textPtr->numChars) {
            *indexPtr = textPtr->numChars;
        }
    }
    return TCL_OK;
}
\f
/*
 *--------------------------------------------------------------
 *
 * SetTextCursor --
 *
 *      Set the position of the insertion cursor in this item.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The cursor position will change.
 *
 *--------------------------------------------------------------
 */

        /* ARGSUSED */
static void
SetTextCursor(canvasPtr, itemPtr, index)
    Tk_Canvas *canvasPtr;               /* Record describing canvas widget. */
    Tk_Item *itemPtr;                   /* Text item in which cursor position
                                         * is to be set. */
    int index;                          /* Index of character just before which
                                         * cursor is to be positioned. */
{
    register TextItem *textPtr = (TextItem *) itemPtr;

    if (index < 0) {
        textPtr->cursorPos = 0;
    } else  if (index > textPtr->numChars) {
        textPtr->cursorPos = textPtr->numChars;
    } else {
        textPtr->cursorPos = index;
    }
}
\f
/*
 *--------------------------------------------------------------
 *
 * GetSelText --
 *
 *      This procedure is invoked to return the selected portion
 *      of a text item.  It is only called when this item has
 *      the selection.
 *
 * Results:
 *      The return value is the number of non-NULL bytes stored
 *      at buffer.  Buffer is filled (or partially filled) with a
 *      NULL-terminated string containing part or all of the selection,
 *      as given by offset and maxBytes.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

static int
GetSelText(canvasPtr, itemPtr, offset, buffer, maxBytes)
    Tk_Canvas *canvasPtr;               /* Canvas containing selection. */
    Tk_Item *itemPtr;                   /* Text item containing selection. */
    int offset;                         /* Offset within selection of first
                                         * character to be returned. */
    char *buffer;                       /* Location in which to place
                                         * selection. */
    int maxBytes;                       /* Maximum number of bytes to place
                                         * at buffer, not including terminating
                                         * NULL character. */
{
    TextItem *textPtr = (TextItem *) itemPtr;
    int count;

    count = canvasPtr->selectLast + 1 - canvasPtr->selectFirst - offset;
    if (canvasPtr->selectLast == textPtr->numChars) {
        count -= 1;
    }
    if (count > maxBytes) {
        count = maxBytes;
    }
    if (count <= 0) {
        return 0;
    }
    strncpy(buffer, textPtr->text + canvasPtr->selectFirst + offset, count);
    buffer[count] = '\0';
    return count;
}