helos1/extlib/libvterm/screen.c

#include "vterm_internal.h"

#include <stdio.h>
#include <string.h>

#include "rect.h"
#include "utf8.h"

#define UNICODE_SPACE    0x20
#define UNICODE_LINEFEED 0x0a

/* State of the pen at some moment in time, also used in a cell */
typedef struct
{
	/* After the bitfield */
	VTermColor fg, bg;

	unsigned int bold : 1;
	unsigned int underline : 2;
	unsigned int italic : 1;
	unsigned int blink : 1;
	unsigned int reverse : 1;
	unsigned int strike : 1;
	unsigned int font : 4; /* 0 to 9 */

	/* Extra state storage that isn't strictly pen-related */
	unsigned int protected_cell : 1;
	unsigned int dwl : 1; /* on a DECDWL or DECDHL line */
	unsigned int dhl : 2; /* on a DECDHL line (1=top 2=bottom) */
} ScreenPen;

/* Internal representation of a screen cell */
typedef struct
{
	uint32_t  chars[VTERM_MAX_CHARS_PER_CELL];
	ScreenPen pen;
} ScreenCell;

static int vterm_screen_set_cell(VTermScreen *screen, VTermPos pos, const VTermScreenCell *cell);

struct VTermScreen {
	VTerm *     vt;
	VTermState *state;

	const VTermScreenCallbacks *callbacks;
	void *                      cbdata;

	VTermDamageSize damage_merge;
	/* start_row == -1 => no damage */
	VTermRect damaged;
	VTermRect pending_scrollrect;
	int       pending_scroll_downward, pending_scroll_rightward;

	int rows;
	int cols;
	int global_reverse;

	/* Primary and Altscreen. buffers[1] is lazily allocated as needed */
	ScreenCell *buffers[2];

	/* buffer will == buffers[0] or buffers[1], depending on altscreen */
	ScreenCell *buffer;

	/* buffer for a single screen row used in scrollback storage callbacks */
	VTermScreenCell *sb_buffer;

	ScreenPen pen;
};

static inline ScreenCell *getcell(const VTermScreen *screen, int row, int col) {
	if (row < 0 || row >= screen->rows)
		return NULL;
	if (col < 0 || col >= screen->cols)
		return NULL;
	return screen->buffer + (screen->cols * row) + col;
}

static ScreenCell *realloc_buffer(VTermScreen *screen, ScreenCell *buffer, int new_rows, int new_cols) {
	ScreenCell *new_buffer = vterm_allocator_malloc(screen->vt, sizeof(ScreenCell) * new_rows * new_cols);

	for (int row = 0; row < new_rows; row++) {
		for (int col = 0; col < new_cols; col++) {
			ScreenCell *new_cell = new_buffer + row * new_cols + col;

			if (buffer && row < screen->rows && col < screen->cols)
				*new_cell = buffer[row * screen->cols + col];
			else {
				new_cell->chars[0] = 0;
				new_cell->pen      = screen->pen;
			}
		}
	}

	if (buffer)
		vterm_allocator_free(screen->vt, buffer);

	return new_buffer;
}

static void damagerect(VTermScreen *screen, VTermRect rect) {
	VTermRect emit;

	switch (screen->damage_merge) {
		case VTERM_DAMAGE_CELL:
			/* Always emit damage event */
			emit = rect;
			break;

		case VTERM_DAMAGE_ROW:
			/* Emit damage longer than one row. Try to merge with existing damage in
     * the same row */
			if (rect.end_row > rect.start_row + 1) {
				// Bigger than 1 line - flush existing, emit this
				vterm_screen_flush_damage(screen);
				emit = rect;
			} else if (screen->damaged.start_row == -1) {
				// None stored yet
				screen->damaged = rect;
				return;
			} else if (rect.start_row == screen->damaged.start_row) {
				// Merge with the stored line
				if (screen->damaged.start_col > rect.start_col)
					screen->damaged.start_col = rect.start_col;
				if (screen->damaged.end_col < rect.end_col)
					screen->damaged.end_col = rect.end_col;
				return;
			} else {
				// Emit the currently stored line, store a new one
				emit            = screen->damaged;
				screen->damaged = rect;
			}
			break;

		case VTERM_DAMAGE_SCREEN:
		case VTERM_DAMAGE_SCROLL:
			/* Never emit damage event */
			if (screen->damaged.start_row == -1)
				screen->damaged = rect;
			else {
				rect_expand(&screen->damaged, &rect);
			}
			return;

		default:
			DEBUG_LOG("TODO: Maybe merge damage for level %d\n", screen->damage_merge);
			return;
	}

	if (screen->callbacks && screen->callbacks->damage)
		(*screen->callbacks->damage)(emit, screen->cbdata);
}

static void damagescreen(VTermScreen *screen) {
	VTermRect rect = {
		.start_row = 0,
		.end_row   = screen->rows,
		.start_col = 0,
		.end_col   = screen->cols,
	};

	damagerect(screen, rect);
}

static int putglyph(VTermGlyphInfo *info, VTermPos pos, void *user) {
	VTermScreen *screen = user;
	ScreenCell * cell   = getcell(screen, pos.row, pos.col);

	if (!cell)
		return 0;

	int i;
	for (i = 0; i < VTERM_MAX_CHARS_PER_CELL && info->chars[i]; i++) {
		cell->chars[i] = info->chars[i];
		cell->pen      = screen->pen;
	}
	if (i < VTERM_MAX_CHARS_PER_CELL)
		cell->chars[i] = 0;

	for (int col = 1; col < info->width; col++)
		getcell(screen, pos.row, pos.col + col)->chars[0] = (uint32_t)-1;

	VTermRect rect = {
		.start_row = pos.row,
		.end_row   = pos.row + 1,
		.start_col = pos.col,
		.end_col   = pos.col + info->width,
	};

	cell->pen.protected_cell = info->protected_cell;
	cell->pen.dwl            = info->dwl;
	cell->pen.dhl            = info->dhl;

	damagerect(screen, rect);

	return 1;
}

static int moverect_internal(VTermRect dest, VTermRect src, void *user) {
	VTermScreen *screen = user;

	if (screen->callbacks && screen->callbacks->sb_pushline &&
		dest.start_row == 0 && dest.start_col == 0 && // starts top-left corner
		dest.end_col == screen->cols &&               // full width
		screen->buffer == screen->buffers[0]) {       // not altscreen
		VTermPos pos;
		for (pos.row = 0; pos.row < src.start_row; pos.row++) {
			for (pos.col = 0; pos.col < screen->cols; pos.col++)
				vterm_screen_get_cell(screen, pos, screen->sb_buffer + pos.col);

			(screen->callbacks->sb_pushline)(screen->cols, screen->sb_buffer, screen->cbdata);
		}
	}

	int cols     = src.end_col - src.start_col;
	int downward = src.start_row - dest.start_row;

	int init_row, test_row, inc_row;
	if (downward < 0) {
		init_row = dest.end_row - 1;
		test_row = dest.start_row - 1;
		inc_row  = -1;
	} else {
		init_row = dest.start_row;
		test_row = dest.end_row;
		inc_row  = +1;
	}

	for (int row = init_row; row != test_row; row += inc_row)
		memmove(getcell(screen, row, dest.start_col), getcell(screen, row + downward, src.start_col), cols * sizeof(ScreenCell));

	return 1;
}

static int moverect_user(VTermRect dest, VTermRect src, void *user) {
	VTermScreen *screen = user;

	if (screen->callbacks && screen->callbacks->moverect) {
		if (screen->damage_merge != VTERM_DAMAGE_SCROLL)
			// Avoid an infinite loop
			vterm_screen_flush_damage(screen);

		if ((*screen->callbacks->moverect)(dest, src, screen->cbdata))
			return 1;
	}

	damagerect(screen, dest);

	return 1;
}

static int erase_internal(VTermRect rect, int selective, void *user) {
	VTermScreen *screen = user;

	for (int row = rect.start_row; row < screen->state->rows && row < rect.end_row; row++) {
		const VTermLineInfo *info = vterm_state_get_lineinfo(screen->state, row);

		for (int col = rect.start_col; col < rect.end_col; col++) {
			ScreenCell *cell = getcell(screen, row, col);

			if (selective && cell->pen.protected_cell)
				continue;

			cell->chars[0] = 0;
			cell->pen      = screen->pen;
			cell->pen.dwl  = info->doublewidth;
			cell->pen.dhl  = info->doubleheight;
		}
	}

	return 1;
}

static int erase_user(VTermRect rect, int selective, void *user) {
	VTermScreen *screen = user;

	damagerect(screen, rect);

	return 1;
}

static int erase(VTermRect rect, int selective, void *user) {
	erase_internal(rect, selective, user);
	return erase_user(rect, 0, user);
}

static int scrollrect(VTermRect rect, int downward, int rightward, void *user) {
	VTermScreen *screen = user;

	if (screen->damage_merge != VTERM_DAMAGE_SCROLL) {
		vterm_scroll_rect(rect, downward, rightward, moverect_internal, erase_internal, screen);

		vterm_screen_flush_damage(screen);

		vterm_scroll_rect(rect, downward, rightward, moverect_user, erase_user, screen);

		return 1;
	}

	if (screen->damaged.start_row != -1 &&
		!rect_intersects(&rect, &screen->damaged)) {
		vterm_screen_flush_damage(screen);
	}

	if (screen->pending_scrollrect.start_row == -1) {
		screen->pending_scrollrect       = rect;
		screen->pending_scroll_downward  = downward;
		screen->pending_scroll_rightward = rightward;
	} else if (rect_equal(&screen->pending_scrollrect, &rect) && ((screen->pending_scroll_downward == 0 && downward == 0) || (screen->pending_scroll_rightward == 0 && rightward == 0))) {
		screen->pending_scroll_downward += downward;
		screen->pending_scroll_rightward += rightward;
	} else {
		vterm_screen_flush_damage(screen);

		screen->pending_scrollrect       = rect;
		screen->pending_scroll_downward  = downward;
		screen->pending_scroll_rightward = rightward;
	}

	vterm_scroll_rect(rect, downward, rightward, moverect_internal, erase_internal, screen);

	if (screen->damaged.start_row == -1)
		return 1;

	if (rect_contains(&rect, &screen->damaged)) {
		/* Scroll region entirely contains the damage; just move it */
		vterm_rect_move(&screen->damaged, -downward, -rightward);
		rect_clip(&screen->damaged, &rect);
	}
	/* There are a number of possible cases here, but lets restrict this to only
   * the common case where we might actually gain some performance by
   * optimising it. Namely, a vertical scroll that neatly cuts the damage
   * region in half.
   */
	else if (rect.start_col <= screen->damaged.start_col && rect.end_col >= screen->damaged.end_col && rightward == 0) {
		if (screen->damaged.start_row >= rect.start_row &&
			screen->damaged.start_row < rect.end_row) {
			screen->damaged.start_row -= downward;
			if (screen->damaged.start_row < rect.start_row)
				screen->damaged.start_row = rect.start_row;
			if (screen->damaged.start_row > rect.end_row)
				screen->damaged.start_row = rect.end_row;
		}
		if (screen->damaged.end_row >= rect.start_row &&
			screen->damaged.end_row < rect.end_row) {
			screen->damaged.end_row -= downward;
			if (screen->damaged.end_row < rect.start_row)
				screen->damaged.end_row = rect.start_row;
			if (screen->damaged.end_row > rect.end_row)
				screen->damaged.end_row = rect.end_row;
		}
	} else {
		DEBUG_LOG("TODO: Just flush and redo damaged=" STRFrect " rect=" STRFrect "\n", ARGSrect(screen->damaged), ARGSrect(rect));
	}

	return 1;
}

static int movecursor(VTermPos pos, VTermPos oldpos, int visible, void *user) {
	VTermScreen *screen = user;

	if (screen->callbacks && screen->callbacks->movecursor)
		return (*screen->callbacks->movecursor)(pos, oldpos, visible, screen->cbdata);

	return 0;
}

static int setpenattr(VTermAttr attr, VTermValue *val, void *user) {
	VTermScreen *screen = user;

	switch (attr) {
		case VTERM_ATTR_BOLD:
			screen->pen.bold = val->boolean;
			return 1;
		case VTERM_ATTR_UNDERLINE:
			screen->pen.underline = val->number;
			return 1;
		case VTERM_ATTR_ITALIC:
			screen->pen.italic = val->boolean;
			return 1;
		case VTERM_ATTR_BLINK:
			screen->pen.blink = val->boolean;
			return 1;
		case VTERM_ATTR_REVERSE:
			screen->pen.reverse = val->boolean;
			return 1;
		case VTERM_ATTR_STRIKE:
			screen->pen.strike = val->boolean;
			return 1;
		case VTERM_ATTR_FONT:
			screen->pen.font = val->number;
			return 1;
		case VTERM_ATTR_FOREGROUND:
			screen->pen.fg = val->color;
			return 1;
		case VTERM_ATTR_BACKGROUND:
			screen->pen.bg = val->color;
			return 1;

		case VTERM_N_ATTRS:
			return 0;
	}

	return 0;
}

static int settermprop(VTermProp prop, VTermValue *val, void *user) {
	VTermScreen *screen = user;

	switch (prop) {
		case VTERM_PROP_ALTSCREEN:
			if (val->boolean && !screen->buffers[1])
				return 0;

			screen->buffer = val->boolean ? screen->buffers[1] : screen->buffers[0];
			/* only send a damage event on disable; because during enable there's an
     * erase that sends a damage anyway
     */
			if (!val->boolean)
				damagescreen(screen);
			break;
		case VTERM_PROP_REVERSE:
			screen->global_reverse = val->boolean;
			damagescreen(screen);
			break;
		default:; /* ignore */
	}

	if (screen->callbacks && screen->callbacks->settermprop)
		return (*screen->callbacks->settermprop)(prop, val, screen->cbdata);

	return 1;
}

static int bell(void *user) {
	VTermScreen *screen = user;

	if (screen->callbacks && screen->callbacks->bell)
		return (*screen->callbacks->bell)(screen->cbdata);

	return 0;
}

static int resize(int new_rows, int new_cols, VTermPos *delta, void *user) {
	VTermScreen *screen = user;

	int is_altscreen = (screen->buffers[1] && screen->buffer == screen->buffers[1]);

	int old_rows = screen->rows;
	int old_cols = screen->cols;

	if (!is_altscreen && new_rows < old_rows) {
		// Fewer rows - determine if we're going to scroll at all, and if so, push
		// those lines to scrollback
		VTermPos pos    = {0, 0};
		VTermPos cursor = screen->state->pos;
		// Find the first blank row after the cursor.
		for (pos.row = old_rows - 1; pos.row >= new_rows; pos.row--)
			if (!vterm_screen_is_eol(screen, pos) || cursor.row == pos.row)
				break;

		int first_blank_row = pos.row + 1;
		if (first_blank_row > new_rows) {
			VTermRect rect = {
				.start_row = 0,
				.end_row   = old_rows,
				.start_col = 0,
				.end_col   = old_cols,
			};
			scrollrect(rect, first_blank_row - new_rows, 0, user);
			vterm_screen_flush_damage(screen);

			delta->row -= first_blank_row - new_rows;
		}
	}

	screen->buffers[0] = realloc_buffer(screen, screen->buffers[0], new_rows, new_cols);
	if (screen->buffers[1])
		screen->buffers[1] = realloc_buffer(screen, screen->buffers[1], new_rows, new_cols);

	screen->buffer = is_altscreen ? screen->buffers[1] : screen->buffers[0];

	screen->rows = new_rows;
	screen->cols = new_cols;

	if (screen->sb_buffer)
		vterm_allocator_free(screen->vt, screen->sb_buffer);

	screen->sb_buffer = vterm_allocator_malloc(screen->vt, sizeof(VTermScreenCell) * new_cols);

	if (new_cols > old_cols) {
		VTermRect rect = {
			.start_row = 0,
			.end_row   = old_rows,
			.start_col = old_cols,
			.end_col   = new_cols,
		};
		damagerect(screen, rect);
	}

	if (new_rows > old_rows) {
		if (!is_altscreen && screen->callbacks && screen->callbacks->sb_popline) {
			int rows = new_rows - old_rows;
			while (rows) {
				if (!(screen->callbacks->sb_popline(screen->cols, screen->sb_buffer, screen->cbdata)))
					break;

				VTermRect rect = {
					.start_row = 0,
					.end_row   = screen->rows,
					.start_col = 0,
					.end_col   = screen->cols,
				};
				scrollrect(rect, -1, 0, user);

				VTermPos pos = {0, 0};
				for (pos.col = 0; pos.col < screen->cols; pos.col += screen->sb_buffer[pos.col].width)
					vterm_screen_set_cell(screen, pos, screen->sb_buffer + pos.col);

				rect.end_row = 1;
				damagerect(screen, rect);

				vterm_screen_flush_damage(screen);

				rows--;
				delta->row++;
			}
		}

		VTermRect rect = {
			.start_row = old_rows,
			.end_row   = new_rows,
			.start_col = 0,
			.end_col   = new_cols,
		};
		damagerect(screen, rect);
	}

	if (screen->callbacks && screen->callbacks->resize)
		return (*screen->callbacks->resize)(new_rows, new_cols, screen->cbdata);

	return 1;
}

static int setlineinfo(int row, const VTermLineInfo *newinfo, const VTermLineInfo *oldinfo, void *user) {
	VTermScreen *screen = user;

	if (newinfo->doublewidth != oldinfo->doublewidth ||
		newinfo->doubleheight != oldinfo->doubleheight) {
		for (int col = 0; col < screen->cols; col++) {
			ScreenCell *cell = getcell(screen, row, col);
			cell->pen.dwl    = newinfo->doublewidth;
			cell->pen.dhl    = newinfo->doubleheight;
		}

		VTermRect rect = {
			.start_row = row,
			.end_row   = row + 1,
			.start_col = 0,
			.end_col   = newinfo->doublewidth ? screen->cols / 2 : screen->cols,
		};
		damagerect(screen, rect);

		if (newinfo->doublewidth) {
			rect.start_col = screen->cols / 2;
			rect.end_col   = screen->cols;

			erase_internal(rect, 0, user);
		}
	}

	return 1;
}

static VTermStateCallbacks state_cbs = {
	.putglyph    = &putglyph,
	.movecursor  = &movecursor,
	.scrollrect  = &scrollrect,
	.erase       = &erase,
	.setpenattr  = &setpenattr,
	.settermprop = &settermprop,
	.bell        = &bell,
	.resize      = &resize,
	.setlineinfo = &setlineinfo,
};

static VTermScreen *screen_new(VTerm *vt) {
	VTermState *state = vterm_obtain_state(vt);
	if (!state)
		return NULL;

	VTermScreen *screen = vterm_allocator_malloc(vt, sizeof(VTermScreen));
	int          rows, cols;

	vterm_get_size(vt, &rows, &cols);

	screen->vt    = vt;
	screen->state = state;

	screen->damage_merge                 = VTERM_DAMAGE_CELL;
	screen->damaged.start_row            = -1;
	screen->pending_scrollrect.start_row = -1;

	screen->rows = rows;
	screen->cols = cols;

	screen->callbacks = NULL;
	screen->cbdata    = NULL;

	screen->buffers[0] = realloc_buffer(screen, NULL, rows, cols);

	screen->buffer = screen->buffers[0];

	screen->sb_buffer = vterm_allocator_malloc(screen->vt, sizeof(VTermScreenCell) * cols);

	vterm_state_set_callbacks(screen->state, &state_cbs, screen);

	return screen;
}

INTERNAL void vterm_screen_free(VTermScreen *screen) {
	vterm_allocator_free(screen->vt, screen->buffers[0]);
	if (screen->buffers[1])
		vterm_allocator_free(screen->vt, screen->buffers[1]);

	vterm_allocator_free(screen->vt, screen->sb_buffer);

	vterm_allocator_free(screen->vt, screen);
}

void vterm_screen_reset(VTermScreen *screen, int hard) {
	screen->damaged.start_row            = -1;
	screen->pending_scrollrect.start_row = -1;
	vterm_state_reset(screen->state, hard);
	vterm_screen_flush_damage(screen);
}

static size_t _get_chars(const VTermScreen *screen, const int utf8, void *buffer, size_t len, const VTermRect rect) {
	size_t outpos  = 0;
	int    padding = 0;

#define PUT(c)                                                 \
	if (utf8) {                                                \
		size_t thislen = utf8_seqlen(c);                       \
		if (buffer && outpos + thislen <= len)                 \
			outpos += fill_utf8((c), (char *)buffer + outpos); \
		else                                                   \
			outpos += thislen;                                 \
	} else {                                                   \
		if (buffer && outpos + 1 <= len)                       \
			((uint32_t *)buffer)[outpos++] = (c);              \
		else                                                   \
			outpos++;                                          \
	}

	for (int row = rect.start_row; row < rect.end_row; row++) {
		for (int col = rect.start_col; col < rect.end_col; col++) {
			ScreenCell *cell = getcell(screen, row, col);

			if (cell->chars[0] == 0)
				// Erased cell, might need a space
				padding++;
			else if (cell->chars[0] == (uint32_t)-1)
				// Gap behind a double-width char, do nothing
				;
			else {
				while (padding) {
					PUT(UNICODE_SPACE);
					padding--;
				}
				for (int i = 0; i < VTERM_MAX_CHARS_PER_CELL && cell->chars[i]; i++) {
					PUT(cell->chars[i]);
				}
			}
		}

		if (row < rect.end_row - 1) {
			PUT(UNICODE_LINEFEED);
			padding = 0;
		}
	}

	return outpos;
}

size_t vterm_screen_get_chars(const VTermScreen *screen, uint32_t *chars, size_t len, const VTermRect rect) {
	return _get_chars(screen, 0, chars, len, rect);
}

size_t vterm_screen_get_text(const VTermScreen *screen, char *str, size_t len, const VTermRect rect) {
	return _get_chars(screen, 1, str, len, rect);
}

/* Copy internal to external representation of a screen cell */
int vterm_screen_get_cell(const VTermScreen *screen, VTermPos pos, VTermScreenCell *cell) {
	ScreenCell *intcell = getcell(screen, pos.row, pos.col);
	if (!intcell)
		return 0;

	for (int i = 0; i < VTERM_MAX_CHARS_PER_CELL; i++) {
		cell->chars[i] = intcell->chars[i];
		if (!intcell->chars[i])
			break;
	}

	cell->attrs.bold      = intcell->pen.bold;
	cell->attrs.underline = intcell->pen.underline;
	cell->attrs.italic    = intcell->pen.italic;
	cell->attrs.blink     = intcell->pen.blink;
	cell->attrs.reverse   = intcell->pen.reverse ^ screen->global_reverse;
	cell->attrs.strike    = intcell->pen.strike;
	cell->attrs.font      = intcell->pen.font;

	cell->attrs.dwl = intcell->pen.dwl;
	cell->attrs.dhl = intcell->pen.dhl;

	cell->fg = intcell->pen.fg;
	cell->bg = intcell->pen.bg;

	if (pos.col < (screen->cols - 1) &&
		getcell(screen, pos.row, pos.col + 1)->chars[0] == (uint32_t)-1)
		cell->width = 2;
	else
		cell->width = 1;

	return 1;
}

/* Copy external to internal representation of a screen cell */
/* static because it's only used internally for sb_popline during resize */
static int vterm_screen_set_cell(VTermScreen *screen, VTermPos pos, const VTermScreenCell *cell) {
	ScreenCell *intcell = getcell(screen, pos.row, pos.col);
	if (!intcell)
		return 0;

	for (int i = 0; i < VTERM_MAX_CHARS_PER_CELL; i++) {
		intcell->chars[i] = cell->chars[i];
		if (!cell->chars[i])
			break;
	}

	intcell->pen.bold      = cell->attrs.bold;
	intcell->pen.underline = cell->attrs.underline;
	intcell->pen.italic    = cell->attrs.italic;
	intcell->pen.blink     = cell->attrs.blink;
	intcell->pen.reverse   = cell->attrs.reverse ^ screen->global_reverse;
	intcell->pen.strike    = cell->attrs.strike;
	intcell->pen.font      = cell->attrs.font;

	intcell->pen.fg = cell->fg;
	intcell->pen.bg = cell->bg;

	if (cell->width == 2)
		getcell(screen, pos.row, pos.col + 1)->chars[0] = (uint32_t)-1;

	return 1;
}

int vterm_screen_is_eol(const VTermScreen *screen, VTermPos pos) {
	/* This cell is EOL if this and every cell to the right is black */
	for (; pos.col < screen->cols; pos.col++) {
		ScreenCell *cell = getcell(screen, pos.row, pos.col);
		if (cell->chars[0] != 0)
			return 0;
	}

	return 1;
}

VTermScreen *vterm_obtain_screen(VTerm *vt) {
	if (vt->screen)
		return vt->screen;

	VTermScreen *screen = screen_new(vt);
	vt->screen          = screen;

	return screen;
}

void vterm_screen_enable_altscreen(VTermScreen *screen, int altscreen) {
	if (!screen->buffers[1] && altscreen) {
		int rows, cols;
		vterm_get_size(screen->vt, &rows, &cols);

		screen->buffers[1] = realloc_buffer(screen, NULL, rows, cols);
	}
}

void vterm_screen_set_callbacks(VTermScreen *screen, const VTermScreenCallbacks *callbacks, void *user) {
	screen->callbacks = callbacks;
	screen->cbdata    = user;
}

void *vterm_screen_get_cbdata(VTermScreen *screen) {
	return screen->cbdata;
}

void vterm_screen_set_unrecognised_fallbacks(VTermScreen *screen, const VTermParserCallbacks *fallbacks, void *user) {
	vterm_state_set_unrecognised_fallbacks(screen->state, fallbacks, user);
}

void *vterm_screen_get_unrecognised_fbdata(VTermScreen *screen) {
	return vterm_state_get_unrecognised_fbdata(screen->state);
}

void vterm_screen_flush_damage(VTermScreen *screen) {
	if (screen->pending_scrollrect.start_row != -1) {
		vterm_scroll_rect(screen->pending_scrollrect, screen->pending_scroll_downward, screen->pending_scroll_rightward, moverect_user, erase_user, screen);

		screen->pending_scrollrect.start_row = -1;
	}

	if (screen->damaged.start_row != -1) {
		if (screen->callbacks && screen->callbacks->damage)
			(*screen->callbacks->damage)(screen->damaged, screen->cbdata);

		screen->damaged.start_row = -1;
	}
}

void vterm_screen_set_damage_merge(VTermScreen *screen, VTermDamageSize size) {
	vterm_screen_flush_damage(screen);
	screen->damage_merge = size;
}

static int attrs_differ(VTermAttrMask attrs, ScreenCell *a, ScreenCell *b) {
	if ((attrs & VTERM_ATTR_BOLD_MASK) && (a->pen.bold != b->pen.bold))
		return 1;
	if ((attrs & VTERM_ATTR_UNDERLINE_MASK) && (a->pen.underline != b->pen.underline))
		return 1;
	if ((attrs & VTERM_ATTR_ITALIC_MASK) && (a->pen.italic != b->pen.italic))
		return 1;
	if ((attrs & VTERM_ATTR_BLINK_MASK) && (a->pen.blink != b->pen.blink))
		return 1;
	if ((attrs & VTERM_ATTR_REVERSE_MASK) && (a->pen.reverse != b->pen.reverse))
		return 1;
	if ((attrs & VTERM_ATTR_STRIKE_MASK) && (a->pen.strike != b->pen.strike))
		return 1;
	if ((attrs & VTERM_ATTR_FONT_MASK) && (a->pen.font != b->pen.font))
		return 1;
	if ((attrs & VTERM_ATTR_FOREGROUND_MASK) && !vterm_color_is_equal(&a->pen.fg, &b->pen.fg))
		return 1;
	if ((attrs & VTERM_ATTR_BACKGROUND_MASK) && !vterm_color_is_equal(&a->pen.bg, &b->pen.bg))
		return 1;

	return 0;
}

int vterm_screen_get_attrs_extent(const VTermScreen *screen, VTermRect *extent, VTermPos pos, VTermAttrMask attrs) {
	ScreenCell *target = getcell(screen, pos.row, pos.col);

	// TODO: bounds check
	extent->start_row = pos.row;
	extent->end_row   = pos.row + 1;

	if (extent->start_col < 0)
		extent->start_col = 0;
	if (extent->end_col < 0)
		extent->end_col = screen->cols;

	int col;

	for (col = pos.col - 1; col >= extent->start_col; col--)
		if (attrs_differ(attrs, target, getcell(screen, pos.row, col)))
			break;
	extent->start_col = col + 1;

	for (col = pos.col + 1; col < extent->end_col; col++)
		if (attrs_differ(attrs, target, getcell(screen, pos.row, col)))
			break;
	extent->end_col = col - 1;

	return 1;
}

void vterm_screen_convert_color_to_rgb(const VTermScreen *screen, VTermColor *col) {
	vterm_state_convert_color_to_rgb(screen->state, col);
}