/*
 * tscroll.c
 *
 * standard table class.
 *
 * scrolling and selection routines
 *
 * see table.h for interface description
 *
 * This implementation currently only supports TM_SINGLE, not TM_MANY
 * modes of selection.
 */

#include "windows.h"
#include "commdlg.h"
#include "gutils.h"

#include "table.h"
#include "tpriv.h"


VOID
gtab_extendsel(
    HWND hwnd,
    lpTable ptab,
    long startrow,
    long startcell,
    BOOL bNotify
);


/* handle a vscroll message */
void
gtab_msg_vscroll(HWND hwnd, lpTable ptab, int opcode, int pos)
{
        long change;

        switch(opcode) {
        case SB_THUMBPOSITION:
                change = (pos * ptab->scrollscale) - ptab->toprow;
                break;

        case SB_LINEUP:
                change = -1;
                break;

        case SB_LINEDOWN:
                change = 1;
                break;

        case SB_PAGEUP:
                change = - (ptab->nlines - 3);
                if (change>=0) change = -1;  // consider nlines <=3!
                break;

        case SB_PAGEDOWN:
                change = (ptab->nlines - 3);
                if (change<=0) change = 1;  // consider nlines <=3!
                break;

        default:
                return;
        }
        gtab_dovscroll(hwnd, ptab, change);
}

/* handle a hscroll message */
void
gtab_msg_hscroll(HWND hwnd, lpTable ptab, int opcode, int pos)
{
        int change;

        switch(opcode) {
        case SB_THUMBPOSITION:
                change = pos - ptab->scroll_dx;
                break;

        case SB_LINEUP:
                change = -(ptab->avewidth);
                break;

        case SB_LINEDOWN:
                change = ptab->avewidth;
                break;

        case SB_PAGEUP:
                change = - (ptab->winwidth * 2 / 3);
                break;

        case SB_PAGEDOWN:
                change = (ptab->winwidth * 2 / 3);
                break;

        default:
                return;
        }
        gtab_dohscroll(hwnd, ptab, change);
}



/*
 * set new vertical scroll pos,
 * adjust linedata array
 * set line win-relative start posns & clip top/bottom posns
 * revise display.
 */
void
gtab_dovscroll(HWND hwnd, lpTable ptab, long change)
{
        int cury, i;
        long ncopy;
        lpCellPos cp;
        LineData ldtemp;
        RECT rc, rcpaint;
        long range;
        long newtop;
        int newpos;


        range = ptab->hdr.nrows - (ptab->nlines - 1);
        newtop = ptab->toprow + change;
        if (range < 0) {
                range = 0;
        }
        if (newtop > range) {
                change = range - ptab->toprow;
        } else if (newtop < 0) {
                change = -(ptab->toprow);
        }
        ptab->toprow += change;

        newpos = (int) (newtop / ptab->scrollscale);
        SetScrollPos(hwnd, SB_VERT, newpos, TRUE);

        if (ptab->hdr.sendscroll) {
                gtab_sendtq(hwnd, TQ_SCROLL, ptab->toprow);
        }

        /* adjust data ptrs rather than invalidate, to retain the
         * data we know is still valid
         */
        if (abs(change) >= ptab->nlines) {
                gtab_invallines(hwnd, ptab, ptab->hdr.fixedrows,
                        ptab->nlines - ptab->hdr.fixedrows);
                InvalidateRect(hwnd, NULL, TRUE);
                change = 0;
        } else if (change < 0) {
                /* copy data down */
                ncopy = (ptab->nlines - ptab->hdr.fixedrows) - abs(change);
                for (i =  ptab->nlines - 1;
                  i >= (ptab->hdr.fixedrows + abs(change)); i--) {
                        ldtemp = ptab->pdata[i - abs(change)];
                        ptab->pdata[i - abs(change)] = ptab->pdata[i];
                        ptab->pdata[i] = ldtemp;
                }
                gtab_invallines(hwnd, ptab,
                        ptab->hdr.fixedrows, (int) abs(change));
        } else if (change > 0) {
                ncopy = (ptab->nlines - ptab->hdr.fixedrows) - change;
                for (i = ptab->hdr.fixedrows;
                  i < (ncopy + ptab->hdr.fixedrows); i++) {
                        ldtemp = ptab->pdata[i + change];
                        ptab->pdata[i + change] = ptab->pdata[i];
                        ptab->pdata[i] = ldtemp;
                }
                gtab_invallines(hwnd, ptab,
                        (int) ncopy + ptab->hdr.fixedrows, (int) change);
        }

        /* scroll window */
        GetClientRect(hwnd, &rc);
        rcpaint = rc;
        if (change > 0) {
                rc.top += (int) (change + ptab->hdr.fixedrows) * ptab->rowheight;
                rcpaint.top = (ptab->hdr.fixedrows * ptab->rowheight);
                rcpaint.top += rc.bottom - rc.top;
        } else if (change < 0) {
                rc.top += (ptab->hdr.fixedrows * ptab->rowheight);
                rc.bottom -= (int) (change * ptab->rowheight);
                rcpaint.bottom -= rc.bottom - rc.top;
        }

        /* loop through each line setting relative posn and clipping */

        /* set up all rows  - the fixed/moveable difference for
         * rows is made at fetch-time during painting, when we remember
         * which absolute row nr to ask for, for a given screen line
         */
        cury = 0;
        for (i = 0; i < ptab->nlines; i++) {
                cp = &ptab->pdata[i].linepos;
                cp->start = cury;
                cp->clipstart = cury;
                cp->clipend = cury + cp->size;
                cury += cp->size;
        }

        /* now move and repaint the window */
        if (change != 0) {
                if (rc.top < rc.bottom) {
                        ScrollWindow(hwnd, 0, (int) -(change * ptab->rowheight),
                                &rc, NULL);

                }

                /* force repaint now, not just post message for later,
                 * since we want to repaint that line before the next
                 * scroll down occurs
                 */
                RedrawWindow(hwnd, &rcpaint, NULL,
                        RDW_ERASE | RDW_INVALIDATE|RDW_UPDATENOW);
        }
}

/*
 * set new horizontal scroll pos,
 * set col win-relative start posns & clip left/right posns
 * revise display.
 */
void
gtab_dohscroll(HWND hwnd, lpTable ptab, long change)
{
        int curx, i;
        int moveable;
        lpCellPos cp;
        int newdx, range;


        /* check that the new scroll pos is still within the valid range */
        range = ptab->rowwidth - ptab->winwidth;
        newdx = ptab->scroll_dx + (int) change;
        if (range < 0) {
                range = 0;
        }
        if (newdx > range) {
                change = range - ptab->scroll_dx;
        } else if (newdx < 0) {
                change = -(ptab->scroll_dx);
        }
        ptab->scroll_dx += (int) change;

        SetScrollPos(hwnd, SB_HORZ, ptab->scroll_dx, TRUE);
        InvalidateRect(hwnd, NULL, TRUE);

        /* loop through each col setting relative posn and clipping */
        /* clip off 1 pixel left and right (we added 2 on to size for this) */

        /* first set up fixed columns */
        curx = 0;
        for (i = 0; i < ptab->hdr.fixedcols; i++) {
                cp = &ptab->pcellpos[i];
                cp->start = curx + 1;
                cp->clipstart = cp->start;
                cp->clipend = cp->start + cp->size - 2;
                curx += cp->size;
        }

        /* now moveable columns. remember start of moveable cols */
        moveable = curx;
        curx = - ptab->scroll_dx;       /* rel. pos of col */
        for (i = ptab->hdr.fixedcols; i < ptab->hdr.ncols; i++) {
                cp = &ptab->pcellpos[i];
                cp->start = curx + moveable + 1;
                cp->clipstart = max(moveable+1, cp->start);
                cp->clipend = cp->start + cp->size - 2;
                curx += cp->size;
        }
}

/*
 * convert screen line nr to table row nr
 */
long
gtab_linetorow(HWND hwnd, lpTable ptab, int line)
{
        if (line < ptab->hdr.fixedrows) {
                return(line);
        }

        return (line + ptab->toprow);
}

/*
 * convert table row nr to screen line nr or -1 if not on screen
 */
int
gtab_rowtoline(HWND hwnd, lpTable ptab, long row)
{
        if (row < ptab->hdr.fixedrows) {
                return( (int) row);
        }

        row -= ptab->toprow;
        if ((row >= ptab->hdr.fixedrows) && (row < ptab->nlines)) {
                return ( (int) row);
        }
        return(-1);
}


/*
 * check if a given location is within the current selection.
 * Returns true if it is inside the current selection, or false if
 * either there is no selection, or the row, cell passed is outside it.
 */
BOOL
gtab_insideselection(
    lpTable ptab,
    long row,
    long cell)
{
    long startrow, endrow;
    long startcell, endcell;

    if (0 == ptab->select.nrows) {
	// no selection
	return FALSE;
    }

    // selection maintains anchor point as startrow,
    // so the selection can extend forwards or backwards from there.
    // need to convert to forward only for comparison
    startrow = ptab->select.startrow;
    if (ptab->select.nrows < 0) {
	endrow = startrow;
	startrow += ptab->select.nrows + 1;
    } else {
	endrow = startrow + ptab->select.nrows - 1;
    }
    if ((row < startrow) || (row > endrow)) {
	return FALSE;
    }

    // if we are in row-select mode, then that's it - its inside
    if (ptab->hdr.selectmode & TM_ROW) {
	return TRUE;
    }

    // same calculation for cells
    startcell = ptab->select.startcell;
    if (ptab->select.ncells < 0) {
	endcell = startcell;
	startcell += ptab->select.ncells + 1;
    } else {
	endcell = startcell + ptab->select.ncells - 1;
    }
    if ((cell < startcell) || (cell > endcell)) {
	return FALSE;
    }

    return TRUE;
}



/*
 * replace old selection with new. Notify owner if bNotify. Change
 * display to reflect new display.
 */
void
gtab_select(
        HWND hwnd,
        lpTable ptab,
        long row,
        long col,
        long nrows,
        long ncells,
        BOOL bNotify)
{

        /* if in ROW mode, force col and ncells to reflect the entire row. */
        if (ptab->hdr.selectmode & TM_ROW) {
                col = 0;
                ncells = ptab->hdr.ncols;
        }

        /* clear existing sel if valid and visible */
        if ((ptab->select.nrows != 0) && (ptab->selvisible == TRUE)) {

                /* only clear sel if it is different from the new one */
                if ((ptab->select.startrow != row) ||
                    (ptab->select.startcell != col) ||
                    (ptab->select.nrows != nrows) ||
                    (ptab->select.ncells != ncells)) {

                        gtab_invertsel(hwnd, ptab, NULL);
                        ptab->selvisible = FALSE;
                }
        }

        /* set select fields and send TQ_SELECT */
        if (row < ptab->hdr.nrows) {
                ptab->select.startrow = row;
                ptab->select.startcell = col;
                ptab->select.nrows = nrows;
                ptab->select.ncells = ncells;
        } else {
                ptab->select.nrows = 0;
                ptab->select.startrow = 0;
                ptab->select.startcell = 0;
                ptab->select.ncells = 0;
        }

        if (bNotify) {
                gtab_sendtq(hwnd, TQ_SELECT, (long) (LPSTR) &ptab->select);
        }

        /* paint in selection */
        if (nrows != 0) {
                if (!ptab->selvisible) {
                        gtab_invertsel(hwnd, ptab, NULL);
                        ptab->selvisible = TRUE;
                }
        } else {
                if (ptab->selvisible) {
                        gtab_invertsel(hwnd, ptab, NULL);
                        ptab->selvisible = FALSE;
                }
                ptab->selvisible = FALSE;
        }
}

/*
 * convert window y co-ord to a line nr
 */
int
gtab_ytoline(HWND hwnd, lpTable ptab, int y)
{
        return(y / ptab->rowheight);
}

/*
 * convert window x co-ord to a cell nr
 */
int
gtab_xtocol(HWND hwnd, lpTable ptab, int x)
{
        int i;
        lpCellPos ppos;

        for (i = 0; i < ptab->hdr.ncols; i++) {
                ppos = &ptab->pcellpos[i];
                if (ppos->clipstart < ppos->clipend) {
                        if ( (x >= ppos->clipstart) && (x < ppos->clipend)) {
                                return(i);
                        }
                }
        }
        return(-1);
}


/*
 * check if x co-ord is 'near' (+- 2 pixels) the right border of given cell
 */
BOOL
gtab_isborder(HWND hwnd, lpTable ptab, long x, long col)
{

        if (abs(ptab->pcellpos[col].clipend - x) < 2) {
                return(TRUE);
        } else {
                return(FALSE);
        }
}


/*
 * set selection and send 'TQ_ENTER' event to owner
 */
void
gtab_enter(HWND hwnd, lpTable ptab, long row, long col, long nrows,
        long ncells)
{
        /* clear existing sel if valid and visible */
        if ((ptab->select.nrows != 0) && (ptab->selvisible == TRUE)) {

                /* only clear sel if it is different from the new one */
                if ((ptab->select.startrow != row) ||
                    (ptab->select.startcell != col) ||
                    (ptab->select.nrows != nrows) ||
                    (ptab->select.ncells != ncells)) {
                        gtab_invertsel(hwnd, ptab, NULL);
                        ptab->selvisible = FALSE;
                }
        }

        /* set select fields and send TQ_ENTER */
        if (row < ptab->hdr.nrows) {
                ptab->select.startrow = row;
                ptab->select.startcell = col;
                ptab->select.nrows = nrows;
                ptab->select.ncells = ncells;
        } else {
                ptab->select.nrows = 0;
                ptab->select.startrow = 0;
                ptab->select.startcell = 0;
                ptab->select.ncells = 0;
        }

        /* paint in selection */
        if (nrows != 0) {
                if (!ptab->selvisible) {
                        gtab_invertsel(hwnd, ptab, NULL);
                        ptab->selvisible = TRUE;
                }
                /* do this at end because it could cause a layout-change */
                gtab_sendtq(hwnd, TQ_ENTER, (long) (LPSTR) &ptab->select);
        } else {
                if (ptab->selvisible) {
                        gtab_invertsel(hwnd, ptab, NULL);
                }
                ptab->selvisible = FALSE;
        }
}


/*
 * start re-sizing a column
 */
void
gtab_trackcol(HWND hwnd, lpTable ptab, long col, long x)
{

        /* ensure we see the mouse-up */
        SetCapture(hwnd);
        ptab->trackmode = TRACK_COLUMN;
#ifdef WIN32
	ptab->tracknr = col;
        ptab->trackline1 = x;
#else
	// maximum 32767 columns is a reasonable limit!
        ptab->tracknr = (int) (col & 0x7fff);
        ptab->trackline1 = (int) (x & 0x7fff);
#endif

        /* if line at other side of cell is visible, draw that too */
        if (ptab->pcellpos[col].start >= ptab->pcellpos[col].clipstart) {
                ptab->trackline2 = ptab->pcellpos[col].start;
        } else {
                ptab->trackline2 = -1;
        }
        gtab_drawvertline(hwnd, ptab);
}


/*
 * called on right-click events. Select the cell clicked on, and if
 * valid, send on to owner for any context-menu type operation
 */
void
gtab_rightclick(HWND hwnd, lpTable ptab, int x, int y)
{
        long cell, ncells;
        long row;
        HWND hOwner;

        /* find which col, row he selected */
        cell = gtab_xtocol(hwnd, ptab, x);
        if (cell == -1) {
                return;
        }
        row = gtab_linetorow(hwnd, ptab, gtab_ytoline(hwnd, ptab, y));

	/* is he selecting a disabled fixed area ? */
        if ( (row < ptab->hdr.fixedrows) || (cell < ptab->hdr.fixedcols)) {
                if (ptab->hdr.fixedselectable == FALSE) {
                        return;
                }
        }

	// ignore if beyond data
	if ((row >= ptab->hdr.nrows) ||
	    (cell >= ptab->hdr.ncols)) {
		return;
	}

	/* is this within the already-selected area? */
	if (!gtab_insideselection(ptab, row, cell)) {
	    // no selection, or clicked outside the selection - make new selection
	    // before sending the right-click

	    // if shift is down, extend selection
	    if (GetKeyState(VK_SHIFT) & 0x8000) {
		gtab_extendsel(hwnd, ptab, row, cell, TRUE);
	    } else {
		/* record and paint new selection */
		
		if (ptab->hdr.selectmode & TM_ROW) {
			cell = 0;
			ncells = ptab->hdr.ncols;
		} else {
			ncells = 1;
		}
		gtab_select(hwnd, ptab, row, cell, 1, ncells, TRUE);
	    }
	}

        // now we have sent the selection, pass the message onto him
        hOwner = (HANDLE) GetWindowHandle(hwnd, WW_OWNER);
        SendMessage(hOwner, WM_RBUTTONDOWN, 0, MAKELONG( (short)x, (short)y));
}


/*
 * called on mouse-down events. decide what to start tracking.
 */
void
gtab_press(HWND hwnd, lpTable ptab, int x, int y)
{
        long cell, ncells;
        long row;

        if (ptab->trackmode != TRACK_NONE) {
                return;
        }

        /* has he grabbed a cell-edge to resize ? */
        cell = gtab_xtocol(hwnd, ptab, x);
        if (cell == -1) {
                return;
        }
        if (gtab_isborder(hwnd, ptab, x, cell)) {
                gtab_trackcol(hwnd, ptab, cell, x);
                return;
        }
        if ( (cell > 0) && gtab_isborder(hwnd, ptab, x, cell-1)) {
                gtab_trackcol(hwnd, ptab, cell, x);
                return;
        }

        /* find which line he selected */
        row = gtab_linetorow(hwnd, ptab, gtab_ytoline(hwnd, ptab, y));

        /* is he selecting a disabled fixed area ? */
        if ( (row < ptab->hdr.fixedrows) || (cell < ptab->hdr.fixedcols)) {
                if (ptab->hdr.fixedselectable == FALSE) {
                        return;
                }
        }

	// ignore if beyond data
	if ((row >= ptab->hdr.nrows) ||
	    (cell >= ptab->hdr.ncols)) {
		return;
	}


        /* ok, start cell selection */
        ptab->trackmode = TRACK_CELL;
        SetCapture(hwnd);

        /* record and paint new selection */
	
        if (ptab->hdr.selectmode & TM_ROW) {
		cell = 0;
		ncells = ptab->hdr.ncols;
	} else {
		ncells = 1;
	}

	/*
	 * if the shift key is down, then extend the selection to this
	 * new anchor point, rather than create a new selection
	 */
	if (GetKeyState(VK_SHIFT) & 0x8000) {
	    gtab_extendsel(hwnd, ptab, row, cell, FALSE);
	} else {
            gtab_select(hwnd, ptab, row, cell, 1, ncells, FALSE);
        }
        return;
}

/*
 * called on mouse-up. complete any tracking that was happening
 */
void
gtab_release(HWND hwnd, lpTable ptab, int x, int y)
{
        lpCellPos ppos;
        lpProps pprop;
        long row, cell;
        int cx;

        switch(ptab->trackmode) {

        case TRACK_NONE:
                return;

        case TRACK_COLUMN:
                /* erase marker lines */
                gtab_drawvertline(hwnd, ptab);
                ReleaseCapture();
                ptab->trackmode = TRACK_NONE;

                /* adjust cell width */
                ppos = &ptab->pcellpos[ptab->tracknr];
                cx = ptab->trackline1 - ppos->start;
                pprop = &ptab->pcolhdr[ptab->tracknr].props;
                pprop->valid |= P_WIDTH;
                pprop->width = cx;
                gtab_calcwidths(hwnd, ptab);
                gtab_setsize(hwnd, ptab);
                InvalidateRect(hwnd, NULL, TRUE);
                return;

        case TRACK_CELL:
                row = gtab_linetorow(hwnd, ptab, gtab_ytoline(hwnd, ptab, y));
		cell = gtab_xtocol(hwnd, ptab, x);

                ReleaseCapture();
                ptab->trackmode = TRACK_NONE;

		// ignore if before or beyond data
                if ( (row < ptab->hdr.fixedrows) ||
                     (cell < ptab->hdr.fixedcols)) {
                    if (ptab->hdr.fixedselectable == FALSE) {
                        gtab_select(
                            hwnd,
                            ptab,
                            ptab->select.startrow,
                            ptab->select.startcell,
                            ptab->select.nrows,
                            ptab->select.ncells,
                            TRUE);

                        return;
                    }
                }

		if ((row >= ptab->hdr.nrows) ||
		    (cell >= ptab->hdr.ncols)) {
                        gtab_select(
                            hwnd,
                            ptab,
                            ptab->select.startrow,
                            ptab->select.startcell,
                            ptab->select.nrows,
                            ptab->select.ncells,
                            TRUE);
		        return;
		}

		/*
		 * Extend to this new selection end point
		 * we used to only do this if shift key pressed, but that
		 * is not a good UI.
		 */
		gtab_extendsel(hwnd, ptab, row, cell, TRUE);
                return;
        }
}


/* called on mouse-move. if tracking - adjust position, if not,
 * set correct cursor
 */
void
gtab_move(HWND hwnd, lpTable ptab, int x, int y)
{
        BOOL fOK;
	int line;
        long row;
        int col;
        lpCellPos ppos;

        switch(ptab->trackmode) {

        case TRACK_NONE:
                col = gtab_xtocol(hwnd, ptab, x);
                if (col == -1) {
                        SetCursor(hNormCurs);
                        return;
                }
                if (gtab_isborder(hwnd, ptab, x, col)) {
                        SetCursor(hVertCurs);
                        return;
                }
                if ( (col > 0) && gtab_isborder(hwnd, ptab, x, col-1)) {
                        SetCursor(hVertCurs);
                        return;
                }
                SetCursor(hNormCurs);
                return;

        case TRACK_CELL:
    		line = gtab_ytoline(hwnd, ptab, y);

		// we used to only allow drag to extend
		// the selection if the shift key was down.
		// this doesn't seem to work as a UI - you expect
		// to drag and extend.

		/* if extending selection then
		 * allow scrolling by dragging off window
		 */
		if (line < 0) {
		    gtab_dovscroll(hwnd, ptab, -1);
		    line = gtab_ytoline(hwnd, ptab, y);
		} else if (line >=  ptab->nlines) {
		    gtab_dovscroll(hwnd, ptab, 1);
    		    line = gtab_ytoline(hwnd, ptab, y);
		}
	

                row = gtab_linetorow(hwnd, ptab, line);
		col = gtab_xtocol(hwnd, ptab, x);

		// ignore if before or beyond data
                if ( (row < ptab->hdr.fixedrows) || (col < ptab->hdr.fixedcols)) {
                    if (ptab->hdr.fixedselectable == FALSE) {
                        return;
                    }
                }

		if ((row >= ptab->hdr.nrows) ||
		    (col >= ptab->hdr.ncols)) {
		    return;
		}

		/*
		 * extend to this new selection end point
		 */
		gtab_extendsel(hwnd, ptab, row, col, FALSE);
                return;

        case TRACK_COLUMN:
                /* check that new x is still visible/valid */
                ppos = &ptab->pcellpos[ptab->tracknr];
                fOK = FALSE;

                if (ptab->tracknr < ptab->hdr.fixedcols)  {
                        if ((x > ppos->start) && (x < ptab->winwidth)) {
                                fOK = TRUE;
                        }
                } else {
                        if ((x > ppos->clipstart) && (x < ptab->winwidth)) {
                                fOK = TRUE;
                        }
                }
                if (fOK == TRUE) {
                        gtab_drawvertline(hwnd, ptab);
                        ptab->trackline1 = x;
                        gtab_drawvertline(hwnd, ptab);
                }
                return;
        }
}

/* dbl-click - send an TQ_ENTER event to the owner (if valid) */
void
gtab_dblclick(HWND hwnd, lpTable ptab, int x, int y)
{
        int cell, line;
        long row;

        line = gtab_ytoline(hwnd, ptab, y);
        cell = gtab_xtocol(hwnd, ptab, x);
        if ( (line < ptab->hdr.fixedrows) || (cell < ptab->hdr.fixedcols) ) {
                if (!ptab->hdr.fixedselectable) {
                        return;
                }
        }
        row = gtab_linetorow(hwnd, ptab, line);

        if (ptab->hdr.selectmode & TM_ROW) {
                gtab_enter(hwnd, ptab, row, 0, 1, ptab->hdr.ncols);
        } else {
                gtab_enter(hwnd, ptab, row, cell, 1, 1);
        }
}

/*
 * move selection area to visible part of window. argument bToBottom
 * indicates whether to move the line onto the bottom or the top of the
 * window if not visible - this affects the smoothness of scrolling
 * line-by-line.
 */
void
gtab_showsel(HWND hwnd, lpTable ptab, BOOL bToBottom)
{
        int line;
        long change;

        line = gtab_rowtoline(hwnd, ptab, ptab->select.startrow);

        /* move up if last line or not at all visible */
        if ( (line < 0) || line == (ptab->nlines - 1)) {
                change = ptab->select.startrow - ptab->toprow;
                if (bToBottom) {
                        /* change to bottom of window. subtract 2 not 1
                         * since nlines includes one line that is only
                         * partly visible
                         */
                        change -= (ptab->nlines - 2);
                }
                change -= ptab->hdr.fixedrows;
                gtab_dovscroll(hwnd, ptab, change);
        }
        /* add support for TM_CELL here! */
}

/*
 * scroll the window so that if possible, the selected row is in the
 * middle 60% of the screen so that context around it is visible.
 */
void
gtab_showsel_middle(HWND hwnd, lpTable ptab)
{
        int line;
        long change;
        int mid_top, mid_end;

        line = gtab_rowtoline(hwnd, ptab, ptab->select.startrow);


        /* is this within the middle 60 % ?  */
        mid_top = ptab->nlines * 20 / 100;
        mid_end = ptab->nlines * 80 / 100;
        if ((line < mid_top) || (line > mid_end)) {

                /* no - scroll so that selected line is at
                 * the 20% mark
                 */
                change = (ptab->select.startrow - mid_top) - ptab->toprow;
                change -= ptab->hdr.fixedrows;
                gtab_dovscroll(hwnd, ptab, change);
        }
        /* again - need code here for TM_CELL mode to ensure that
         * active cell is horizontally scrolled correctly
         */
}


/*
 * extend the selection to set the new anchor point as startrow, startcell.
 *
 * nrows and ncells will then be set to include the end row of the previous
 * selection. nrows, ncells < 0 indicate left and up. -1 and +1 both indicate
 * just one cell or row selected.
 */
VOID
gtab_extendsel(
    HWND hwnd,
    lpTable ptab,
    long startrow,
    long startcell,
    BOOL bNotify
)
{
    long endrow, endcell, nrows, ncells;

    /*
     * if no current selection, then just select the new anchor point
     */
    if (ptab->select.nrows == 0) {
	gtab_select(hwnd, ptab, startrow, startcell, 1,
    	    (ptab->hdr.selectmode & TM_ROW) ? ptab->hdr.ncols:1,
	    bNotify);
	return;
    }

    if (startrow >= ptab->hdr.nrows) {
	startrow = ptab->hdr.nrows -1;
    } else if (startrow < 0) {
	startrow = 0;
    }
    if (startcell >= ptab->hdr.ncols) {
	startcell = ptab->hdr.ncols-1;
    } else if (startcell < 0) {
	startcell = 0;
    }



    /* calculate the row just beyond the selection
     * this is one above for upwards sels, and one below for
     * downard-extending sels. Then adjust down or up one
     * to be the actual (inclusive) last row.
     */
    endrow = ptab->select.startrow + ptab->select.nrows;
    if (ptab->select.nrows < 0) {
	endrow++;
    } else {
	endrow--;
    }

    if (endrow >= ptab->hdr.nrows) {
	endrow = ptab->hdr.nrows-1;
    }
    nrows = endrow - startrow;

    if (nrows >= 0) {
	// convert from exclusive to inclusive
	nrows++;
    } else {
	// convert from exclusive to inclusive
	nrows--;
    }

    /* same calculation for cells */
    endcell = ptab->select.startcell + ptab->select.ncells;
    if (ptab->select.ncells < 0) {
	endcell++;
    } else {
	endcell--;
    }
    ncells = endcell - startcell;
    if (ncells >= 0) {
	ncells++;
    } else {
	ncells--;
    }
    gtab_select(hwnd, ptab, startrow, startcell, nrows, ncells, bNotify);
}



/* move the selection a specified nr of rows or cells
 * if no selection, select first visible unit
 *
 * if bExtend is true and there is a current selection, then extend it rather than
 * replace it. Note that (startrow, startcell) will always be set to the newly
 * selected position - this is the anchor point. nrows or ncells may be negative
 * if the selection extends upwards above the anchor. nrows == -1 is the same
 * as nrows == 1, meaning only the current row is visible. Similarly
 * (in TM_CELL mode), ncells may be negative.
 *
 * Move the selection (ie anchor point) to make it visible. bToBottom
 * indicates whether it should be moved to the bottom or the top
 * of the window.
 */
VOID
gtab_changesel(
    HWND hwnd,
    lpTable ptab,
    long rowincr,
    int cellincr,
    BOOL bToBottom,
    BOOL bExtend
)
{
        long row, col, ncols;

        /* is there a selection ? */
        if (ptab->select.nrows == 0) {

                /* no selection - force a selection
                 * at the first visible unit
                 */
                if (ptab->hdr.fixedselectable) {
                        row = 0;
                        col = 0;
                } else {
                        row = gtab_linetorow(hwnd, ptab, ptab->hdr.fixedrows);
                        /* should really check for first visible cell */
                        col = ptab->hdr.fixedcols;
                }
                ncols = 1;
                if (ptab->hdr.selectmode & TM_ROW) {
                        col = 0;
                        ncols = ptab->hdr.ncols;
                }
		gtab_select(hwnd, ptab, row, col, 1, ncols, TRUE);

        } else {
    		/* move the anchor point by rowincr, cellincr */
		row = ptab->select.startrow + rowincr;
		col = ptab->select.startcell + cellincr;


		/*
		 * ensure that new anchor point is in a valid position
		 */

                while (col >= ptab->hdr.ncols) {
                        col -= ptab->hdr.ncols;
                        row++;
                }
                while (col < 0) {
                        col += ptab->hdr.ncols;
                        row--;
                }
                if (row < 0) {
                        row = 0;
                }
                if (row >= ptab->hdr.nrows) {
                        row = ptab->hdr.nrows-1;
                }
                /* check we haven't moved into non-selectable region */
                if ((row < ptab->hdr.fixedrows) &&
                        (!ptab->hdr.fixedselectable)) {
                                row = ptab->hdr.fixedrows;
                }

		if (bExtend) {
		    gtab_extendsel(hwnd, ptab, row, col, TRUE);
		} else {
		    gtab_select(
			hwnd,
			ptab,
			row,
			col,
			1,
			(ptab->hdr.selectmode & TM_ROW) ? ptab->hdr.ncols : 1,
			TRUE);
		}
        }

        /* ensure selection visible */
        gtab_showsel(hwnd, ptab, bToBottom);
}

/*
 * set the topmost selectable unit in window as the selection
 *
 * if bExtend is TRUE, then extend the selection to include this, rather
 * than replacing the existing selection. Note that (startrow, startcell)
 * is always the anchor point - ie most recently selected end, and the
 * (nrows, ncells) can be + or - to extend the selection downwards or upwards.
 */
void
gtab_selhome(HWND hwnd, lpTable ptab, BOOL bExtend)
{
        long startrow, startcell, ncells;

	if (ptab->hdr.selectmode & TM_ROW) {
	    ncells = ptab->hdr.ncols;
	} else {
	    ncells = 1;
	}
	startcell = 0;


        if (ptab->hdr.fixedselectable) {
                startrow = gtab_linetorow(hwnd, ptab, 0);
	} else {
    		startrow = gtab_linetorow(hwnd, ptab, ptab->hdr.fixedrows);
		if (!(ptab->hdr.selectmode & TM_ROW)) {
		    startcell = ptab->hdr.fixedcols;
		}
	}
	
	if (bExtend) {
	    gtab_extendsel(hwnd, ptab, startrow, startcell, TRUE);
	} else {
	    gtab_select(hwnd, ptab, startrow, startcell, 1, ncells, TRUE);
	}
}


/* handle key-down events - scroll windows and/or move selection */
int
gtab_key(HWND hwnd, lpTable ptab, int vkey)
{
        long startrow, ncells, startcell;
        BOOL bControl = FALSE;
	BOOL bShift = FALSE;

        if (GetKeyState(VK_CONTROL) & 0x8000) {
            bControl = TRUE;
        }
	if (GetKeyState(VK_SHIFT) & 0x8000) {
	    /* ignore shift key here if TM_MANY -multiple selection flag- is
	     * not selected
	     */
	    if (ptab->hdr.selectmode & TM_MANY) {
		bShift = TRUE;
	    }
	}

        switch(vkey) {

        case VK_UP:
                if (bControl) {
                        /* control-uparrow scrolls window without selection.
                         * the selection is de-selected (to avoid surprises
                         * moving back to it).
                         */
                        gtab_select(hwnd, ptab, 0, 0, 0, 0, TRUE);
                        gtab_dovscroll(hwnd, ptab, -1);
                } else {
                        /* uparrow moves selection up one line */
                        gtab_changesel(hwnd, ptab, -1, 0, FALSE, bShift);
                }
                return(0);

        case VK_DOWN:
                if (bControl) {
                        /* control downarrow scrolls window without
                         * a selection.
                         */
                        gtab_select(hwnd, ptab, 0, 0, 0, 0, TRUE);
                        gtab_dovscroll(hwnd, ptab, 1);
                } else {
                        /* the normal gtab_changesel behaviour is
                         * that if the selected line is not visible now,
                         * we scroll it to the top of the window. This is fine
                         * in most cases but causes unacceptable jumps when
                         * repeatedly scrolling down with the down key.
                         *
                         * Thus we now have an argument to changesel to say
                         * that in this case, if you need to move the line onto
                         * the window, move it to the bottom and not the top
                         */
                        gtab_changesel(hwnd, ptab, 1, 0, TRUE, bShift);
                }
                return(0);

        case VK_LEFT:
                /* if cell-selection mode, move left one cell.
                 * otherwise the whole row is selected - scroll
                 * the line left a little
                 */

                if (ptab->hdr.selectmode & TM_ROW) {
                        if (bControl) {
                                /* ctrl-left moves to start of line */
                                gtab_dohscroll(hwnd, ptab, -(ptab->scroll_dx));
                        } else {
                                gtab_dohscroll(hwnd, ptab, -(ptab->avewidth));
                        }
                } else {
                        gtab_changesel(hwnd, ptab, 0, -1, FALSE, bShift);
                }
                return(0);

        case VK_RIGHT:
                /* if cell-selection mode, move right one cell.
                 * otherwise the whole row is selected - scroll
                 * the line right a little
                 */
                if (ptab->hdr.selectmode & TM_ROW) {
                        if (bControl) {
                                /* control-right moves to right end of line */
                                gtab_dohscroll(hwnd, ptab, ptab->rowwidth -
                                                ptab->winwidth);
                        } else {
                                gtab_dohscroll(hwnd, ptab, ptab->avewidth);
                        }
                } else {
                        gtab_changesel(hwnd, ptab, 0, 1, TRUE, bShift);
                }
                return(0);

        case VK_HOME:
                if (bControl) {
                        /* control-home == top of file */
                        gtab_dovscroll(hwnd, ptab, -(ptab->toprow));
                }
                /* top of window */
                gtab_selhome(hwnd, ptab, bShift);
                gtab_showsel(hwnd, ptab, FALSE);

                return(0);

        case VK_END:
                if (bControl) {
                        /* control-end -> end of file */
                        startrow = ptab->hdr.nrows-1;
                } else {
                        startrow = gtab_linetorow(hwnd, ptab, ptab->nlines - 1);
                        if (startrow >= ptab->hdr.nrows) {
                                startrow = ptab->hdr.nrows-1;
                        }
                }

		startcell = 0;
		ncells = ptab->hdr.ncols;
		if (!(ptab->hdr.selectmode & TM_ROW)) {
		    startcell = ptab->hdr.ncols-1;
		    ncells = 1;
		}

		if (bShift) {
		    gtab_extendsel(hwnd, ptab, startrow, startcell, TRUE);
		} else {
		    gtab_select(hwnd, ptab, startrow, startcell, 1, ncells, TRUE);
		}

                /* we have selected the bottom line. We don't want to
                 * move it up into the window, since the intended
                 * effect is to select the lowest line. This doesn't
                 * apply to the ctrl-end behaviour (move to bottom of
                 * buffer.
                 */
                if (bControl) {
                        /* move the selection to make it visible - but move it
                         * to the bottom and not to the top of the window
                         */
                        gtab_showsel(hwnd, ptab, TRUE);
                }
                return(0);

        case VK_RETURN:
                if (ptab->select.nrows != 0) {
                        gtab_showsel(hwnd, ptab, FALSE);
                        gtab_enter(hwnd, ptab, ptab->select.startrow,
                                ptab->select.startcell,
                                ptab->select.nrows, ptab->select.ncells);
                }
                return(0);

        case VK_SPACE:
                /* toggle the selection */
                if (ptab->select.nrows == 0) {
                        /* no selection - make one */
                        gtab_changesel(hwnd, ptab, 0, 0, TRUE, FALSE);
                } else {
                        /* there is a selection - deselect it */
                        gtab_select(hwnd, ptab, 0, 0, 0, 0, TRUE);
                }
                return(0);

        case VK_PRIOR:          /* page up */

    		if (ptab->nlines > 3) {
		    gtab_dovscroll(hwnd, ptab, -(ptab->nlines - 3));
		}
                gtab_selhome(hwnd, ptab, bShift);
                return(0);

        case VK_NEXT:           /* page down */

                /* scroll down one page */
		if (ptab->nlines > 3) {
		    gtab_dovscroll(hwnd, ptab, (ptab->nlines - 3));
		}

                /* select new bottom line */
                startrow = gtab_linetorow(hwnd, ptab, ptab->nlines - 1);
                if (startrow >= ptab->hdr.nrows) {
                        startrow = ptab->hdr.nrows-1;
                }
		startcell = 0;
		ncells = ptab->hdr.ncols;
		if (!(ptab->hdr.selectmode & TM_ROW)) {
		    startcell = ptab->hdr.ncols-1;
		    ncells = 1;
		}

                /* select bottom line, but don't call showsel
                 * since we don't want to adjust it's position - we
                 * want it to remain at the bottom of the window
                 */
		if (bShift) {
		    gtab_extendsel(hwnd, ptab, startrow, startcell, TRUE);
		} else {
		    gtab_select(hwnd, ptab, startrow, startcell, 1, ncells, TRUE);
		}
                return(0);

        default:
                return(1);
        }
}