/*
 * bc_scrn.c
 *
 * Borland C interface, screen manipulation
 *
 */

#include <dos.h>
#include <mem.h>
#include "bc_frotz.h"

/*
 * get_scrnptr
 *
 * Return a pointer to the given line in video RAM.
 *
 */

byte far *get_scrnptr (int y)
{

    if (display == _CGA_)
	return MK_FP ((y & 1) ? 0xba00 : 0xb800, 40 * (y & ~1));
    else if (display == _MCGA_)
	return MK_FP (0xa000, 320 * y);
    else
	return MK_FP (0xa000, 80 * y);

}/* get_scrnptr */

/*
 * clear_byte
 *
 * Helper function for clear_line.
 *
 */

static void clear_byte (byte far *scrn, word mask)
{

    if (display == _CGA_)

	if (scrn_attr == 0)
	    *scrn &= ~mask;
	else
	    *scrn |= mask;

    else {

	outport (0x03ce, 0x0205);

	outportb (0x03ce, 0x08);
	outportb (0x03cf, mask);

	asm les bx,scrn
	asm mov al,es:[bx]
	asm mov al,scrn_attr
	asm mov es:[bx],al

    }

}/* clear_byte */

/*
 * clear_line
 *
 * Helper function for os_erase_area.
 *
 */

static void clear_line (int y, int left, int right)
{
    byte far *scrn = get_scrnptr (y);

    if (display == _MCGA_)

	_fmemset (scrn + left, scrn_attr, right - left + 1);

    else {

	word mask1 = 0x00ff >> (left & 7);
	word mask2 = 0xff80 >> (right & 7);

	int x = right / 8 - left / 8;

	scrn += left / 8;

	if (x == 0) {
	    mask1 &= mask2;
	    mask2 &= mask1;
	}

	/* Clear first byte */

	clear_byte (scrn++, mask1);

	/* Clear middle bytes */

	if (display >= _EGA_)
	    outport (0x03ce, 0xff08);

	while (--x > 0)
	    *scrn++ = scrn_attr;

	/* Clear last byte */

	clear_byte (scrn, mask2);
    }

}/* clear_line */

/*
 * os_erase_area
 *
 * Fill a rectangular area of the screen with the current background
 * colour. Top left coordinates are (1,1). The cursor does not move.
 *
 */

void os_erase_area (int top, int left, int bottom, int right)
{
    int y;

    top--;
    left--;
    bottom--;
    right--;

    if (display <= _TEXT_) {

	asm mov ax,0x0600
	asm mov ch,byte ptr top
	asm mov cl,byte ptr left
	asm mov dh,byte ptr bottom
	asm mov dl,byte ptr right
	asm mov bh,scrn_attr
	asm int 0x10

    } else

	for (y = top; y <= bottom; y++)
	    clear_line (y, left, right);

}/* os_erase_area */

/*
 * copy_byte
 *
 * Helper function for copy_line.
 *
 */

static void copy_byte (byte far *scrn1, byte far *scrn2, byte mask)
{
    int i;

    if (display == _CGA_)

	*scrn1 = (*scrn1 & ~mask) | (*scrn2 & mask);

    else {

	outport (0x03ce, 0x0005);

	outportb (0x03ce, 0x08);
	outportb (0x03cf, mask);

	outportb (0x03ce, 0x04);
	outportb (0x03c4, 0x02);

	for (i = 0; i < 4; i++) {

	    outportb (0x03cf, i);
	    outportb (0x03c5, 1 << i);

	    asm les bx,scrn2
	    asm mov ah,es:[bx]
	    asm les bx,scrn1
	    asm mov al,es:[bx]
	    asm mov es:[bx],ah

	}

	outportb (0x03c5, 0x0f);
    }

}/* copy_byte */

/*
 * copy_line
 *
 * Helper function for os_scroll_area.
 *
 */

static void copy_line (int y1, int y2, int left, int right)
{
    byte far *scrn1 = get_scrnptr (y1);
    byte far *scrn2 = get_scrnptr (y2);

    if (display == _MCGA_)

	_fmemcpy (scrn1 + left, scrn2 + left, right - left + 1);

    else {

	word mask1 = 0x00ff >> (left & 7);
	word mask2 = 0xff80 >> (right & 7);

	int x = right / 8 - left / 8;

	scrn1 += left / 8;
	scrn2 += left / 8;

	if (x == 0) {
	    mask1 &= mask2;
	    mask2 &= mask1;
	}

	/* Copy first byte */

	copy_byte (scrn1++, scrn2++, mask1);

	/* Copy middle bytes */

	if (display >= _EGA_)
	    outport (0x03ce, 0x0105);

	while (--x > 0)
	    *scrn1++ = *scrn2++;

	/* Copy last byte */

	copy_byte (scrn1, scrn2, mask2);
    }

}/* copy_line */

/*
 * os_scroll_area
 *
 * Scroll a rectangular area of the screen up (units > 0) or down
 * (units < 0) and fill the empty space with the current background
 * colour. Top left coordinates are (1,1). The cursor stays put.
 *
 */

void os_scroll_area (int top, int left, int bottom, int right, int units)
{
    int y;

    top--;
    left--;
    bottom--;
    right--;

    if (display <= _TEXT_) {

	asm mov ah,6
	asm mov bx,units
	asm cmp bx,0
	asm jg scroll
	asm mov ah,7
	asm neg bx
    scroll:
	asm mov al,bl
	asm mov ch,byte ptr top
	asm mov cl,byte ptr left
	asm mov dh,byte ptr bottom
	asm mov dl,byte ptr right
	asm mov bh,scrn_attr
	asm int 0x10

    } else

	if (units > 0)

	    for (y = top; y <= bottom; y++)

		if (y <= bottom - units)
		    copy_line (y, y + units, left, right);
		else
		    clear_line (y, left, right);

	else

	    for (y = bottom; y >= top; y--)

		if (y >= top - units)
		    copy_line (y, y + units, left, right);
		else
		    clear_line (y, left, right);

}/* os_scroll_area */
