#| -*-Scheme-*-

Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
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    2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016,
    2017, 2018, 2019, 2020, 2021, 2022 Massachusetts Institute of
    Technology

This file is part of MIT/GNU Scheme.

MIT/GNU Scheme is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.

MIT/GNU Scheme is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with MIT/GNU Scheme; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
USA.

|#

;;;; Screen Abstraction

(declare (usual-integrations))

(define-structure (screen
		   (constructor make-screen
				(state
				 operation/beep
				 operation/clear-line!
				 operation/clear-rectangle!
				 operation/clear-screen!
				 operation/discard!
				 operation/enter!
				 operation/exit!
				 operation/flush!
				 operation/modeline-event!
				 operation/discretionary-flush
				 operation/scroll-lines-down!
				 operation/scroll-lines-up!
				 operation/wrap-update!
				 operation/write-char!
				 operation/write-cursor!
				 operation/write-substring!
				 preemption-modulus
				 x-size
				 y-size)))
  (state false read-only true)
  (operation/beep false read-only true)
  (operation/clear-line! false read-only true)
  (operation/clear-rectangle! false read-only true)
  (operation/clear-screen! false read-only true)
  (operation/discard! false read-only true)
  (operation/enter! false read-only true)
  (operation/exit! false read-only true)
  (operation/flush! false read-only true)
  (operation/modeline-event! false read-only true)
  (operation/discretionary-flush false read-only true)
  (operation/scroll-lines-down! false read-only true)
  (operation/scroll-lines-up! false read-only true)
  (operation/wrap-update! false read-only true)
  (operation/write-char! false read-only true)
  (operation/write-cursor! false read-only true)
  (operation/write-substring! false read-only true)
  (preemption-modulus false read-only true)
  (root-window false)
  ;; Visibility is one of the following:
  ;; VISIBLE PARTIALLY-OBSCURED OBSCURED UNMAPPED DELETED
  (visibility 'VISIBLE)
  (needs-update? false)
  (in-update? false)
  (x-size false)
  (y-size false)

  ;; Description of actual screen contents.
  current-matrix

  ;; Description of desired screen contents.
  new-matrix

  ;; Set this variable in the debugger to trace interesting events.
  (debug-trace false))

(define (guarantee-screen object procedure)
  (if (not (screen? object))
      (error:wrong-type-argument object "screen" procedure)))

(define (initialize-screen-root-window! screen bufferset buffer)
  (set-screen-root-window!
   screen
   (make-editor-frame
    screen
    buffer
    (bufferset-find-or-create-buffer bufferset (make-typein-buffer-name -1))))
  (set-screen-current-matrix! screen (make-matrix screen))
  (set-screen-new-matrix! screen (make-matrix screen)))

(define (screen-beep screen)
  ((screen-operation/beep screen) screen))

(define (screen-enter! screen)
  ((screen-operation/enter! screen) screen)
  (screen-modeline-event! screen
			  (screen-selected-window screen)
			  'SELECT-SCREEN))

(define (screen-exit! screen)
  ((screen-operation/exit! screen) screen)
  (screen-modeline-event! screen
			  (screen-selected-window screen)
			  'DESELECT-SCREEN))

(define (screen-discard! screen)
  (if (not (screen-deleted? screen))
      (begin
	(set-screen-visibility! screen 'DELETED)
	(for-each (lambda (window) (send window ':kill!))
		  (screen-window-list screen))
	((screen-operation/discard! screen) screen))))

(define (screen-modeline-event! screen window type)
  ((screen-operation/modeline-event! screen) screen window type))

(define-integrable (screen-selected-window screen)
  (editor-frame-selected-window (screen-root-window screen)))

(define (screen-select-window! screen window)
  (editor-frame-select-window! (screen-root-window screen) window)
  (screen-modeline-event! screen window 'SELECT-WINDOW))

(define-integrable (screen-cursor-window screen)
  (editor-frame-cursor-window (screen-root-window screen)))

(define-integrable (screen-select-cursor! screen window)
  (editor-frame-select-cursor! (screen-root-window screen) window))

(define-integrable (screen-window-list screen)
  (editor-frame-windows (screen-root-window screen)))

(define-integrable (screen-window0 screen)
  (editor-frame-window0 (screen-root-window screen)))

(define-integrable (screen-typein-window screen)
  (editor-frame-typein-window (screen-root-window screen)))

(define (window-screen window)
  (editor-frame-screen (window-root-window window)))

(define (screen-visible? screen)
  (not (or (screen-deleted? screen)
	   (eq? 'UNMAPPED (screen-visibility screen)))))

(define-integrable (screen-deleted? screen)
  (eq? 'DELETED (screen-visibility screen)))

(define (update-screen! screen display-style)
  (if (display-style/discard-screen-contents? display-style)
      (screen-force-update screen))
  (let ((finished?
	 (with-screen-in-update screen display-style
	   (lambda ()
	     (editor-frame-update-display! (screen-root-window screen)
					   display-style)))))
    (if (eq? finished? #t)
	(set-screen-needs-update?! screen #f))
    finished?))

;;; Interface from update optimizer to terminal:

(define-integrable (terminal-scroll-lines-down screen xl xu yl yu amount)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'terminal screen 'scroll-lines-down
				   xl xu yl yu amount))
  ((screen-operation/scroll-lines-down! screen) screen xl xu yl yu amount))

(define-integrable (terminal-scroll-lines-up screen xl xu yl yu amount)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'terminal screen 'scroll-lines-up
				   xl xu yl yu amount))
  ((screen-operation/scroll-lines-up! screen) screen xl xu yl yu amount))

(define-integrable (terminal-flush screen)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'terminal screen 'flush))
  ((screen-operation/flush! screen) screen))

(define-integrable (terminal-move-cursor screen x y)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'terminal screen 'move-cursor x y))
  ((screen-operation/write-cursor! screen) screen x y))

(define-integrable (terminal-clear-screen screen)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'terminal screen 'clear-screen))
  ((screen-operation/clear-screen! screen) screen))

(define-integrable (terminal-clear-line screen x y first-unused-x)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'terminal screen 'clear-line
				   x y first-unused-x))
  ((screen-operation/clear-line! screen) screen x y first-unused-x))

(define-integrable (terminal-output-char screen x y char face)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'terminal screen 'output-char
				   x y char face))
  ((screen-operation/write-char! screen) screen x y char face))

(define-integrable (terminal-output-substring screen x y string start end face)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'terminal screen 'output-substring
				   x y (string-copy string) start end face))
  ((screen-operation/write-substring! screen) screen x y string start end
					      face))

;;;; Update Optimization

(define-structure (matrix (constructor %make-matrix ()))
  ;; Vector of line contents.
  ;; (string-ref (vector-ref (matrix-contents m) y) x) is the
  ;; character at position X, Y.
  contents

  ;; Vector of line highlights.
  ;; (vector-ref (vector-ref (matrix-highlight m) y) x) is the
  ;; highlight at position X, Y.
  highlight

  ;; Boolean-vector indicating, for each line, whether its contents
  ;; mean anything.
  enable

  ;; Boolean-vector indicating, for each line, whether there is any
  ;; highlighting on the line.
  highlight-enable

  ;; Cursor position.
  (cursor-x #f)
  (cursor-y #f))

(define (make-matrix screen)
  (let ((matrix (%make-matrix))
	(x-size (screen-x-size screen))
	(y-size (screen-y-size screen)))
    (let ((contents (make-vector y-size))
	  (highlight (make-vector y-size))
	  (enable (make-boolean-vector y-size))
	  (highlight-enable (make-boolean-vector y-size)))
      (do ((i 0 (fix:1+ i)))
	  ((fix:= i y-size))
	(vector-set! contents i (make-string x-size))
	(vector-set! highlight i (make-vector x-size)))
      (boolean-vector-fill! enable false)
      (set-matrix-contents! matrix contents)
      (set-matrix-highlight! matrix highlight)
      (set-matrix-enable! matrix enable)
      (set-matrix-highlight-enable! matrix highlight-enable))
    matrix))

(define-integrable (highlight-ref matrix y x)
  (vector-ref (vector-ref (matrix-highlight matrix) y) x))

(define-integrable (highlight-set! matrix y x face)
  (vector-set! (vector-ref (matrix-highlight matrix) y) x face))

(define-integrable (set-line-highlights! matrix y face)
  (vector-fill! (vector-ref (matrix-highlight matrix) y) face))

(define-integrable (set-subline-highlights! matrix y xl xu face)
  (subvector-fill! (vector-ref (matrix-highlight matrix) y) xl xu face))

(define-integrable (clear-line-highlights! matrix y)
  (set-line-highlights! matrix y (default-face)))

(define-integrable (clear-subline-highlights! matrix y xl xu)
  (set-subline-highlights! matrix y xl xu (default-face)))

(define-integrable (copy-line-highlights! m1 y1 m2 y2)
  (vector-move! (vector-ref (matrix-highlight m1) y1)
		(vector-ref (matrix-highlight m2) y2)))

(define-integrable (copy-subline-highlights! m1 y1 xl1 xu1 m2 y2 xl2)
  (subvector-move-left! (vector-ref (matrix-highlight m1) y1) xl1 xu1
			(vector-ref (matrix-highlight m2) y2) xl2))

(define (line-highlights-cleared? matrix y)
  (vector-filled? (vector-ref (matrix-highlight matrix) y) (default-face)))

(define (swap-line-highlights! m1 y1 m2 y2)
  (let ((h (vector-ref (matrix-highlight m1) y1)))
    (vector-set! (matrix-highlight m1) y1
		 (vector-ref (matrix-highlight m2) y2))
    (vector-set! (matrix-highlight m2) y2 h)))

(define (subline-highlights-uniform? matrix y xl xu)
  (subvector-uniform? (vector-ref (matrix-highlight matrix) y) xl xu))

(define (find-subline-highlight-change matrix y xl xu face)
  (subvector-find-next-element-not (vector-ref (matrix-highlight matrix) y)
				   xl xu face))

(define-integrable (default-face? face)
  (not face))

(define-integrable (default-face)
  #f)

(define-integrable (highlight-face)
  #t)

(define-integrable (line-contents-enabled? matrix y)
  (boolean-vector-ref (matrix-enable matrix) y))

(define-integrable (enable-line-contents! matrix y)
  (boolean-vector-set! (matrix-enable matrix) y #t))

(define-integrable (disable-line-contents! matrix y)
  (boolean-vector-set! (matrix-enable matrix) y #f))

(define-integrable (multiple-line-contents-enabled? matrix yl yu)
  (boolean-subvector-all-elements? (matrix-enable matrix) yl yu #t))

(define-integrable (line-highlights-enabled? matrix y)
  (boolean-vector-ref (matrix-highlight-enable matrix) y))

(define-integrable (enable-line-highlights! matrix y)
  (boolean-vector-set! (matrix-highlight-enable matrix) y #t))

(define-integrable (disable-line-highlights! matrix y)
  (boolean-vector-set! (matrix-highlight-enable matrix) y #f))

(define (set-screen-size! screen x-size y-size)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'set-size! x-size y-size))
  (without-interrupts
   (lambda ()
     (set-screen-x-size! screen x-size)
     (set-screen-y-size! screen y-size)
     (set-screen-current-matrix! screen (make-matrix screen))
     (set-screen-new-matrix! screen (make-matrix screen))
     (send (screen-root-window screen) ':set-size! x-size y-size))))

(define (screen-move-cursor screen x y)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'move-cursor x y))
  (let ((new-matrix (screen-new-matrix screen)))
    (set-matrix-cursor-x! new-matrix x)
    (set-matrix-cursor-y! new-matrix y))
  ;; Kludge: forget current position of cursor in order to force it to
  ;; move.  Works around side-effects in terminal that move cursor.
  (let ((current-matrix (screen-current-matrix screen)))
    (set-matrix-cursor-x! current-matrix #f)
    (set-matrix-cursor-y! current-matrix #f)))

(define (screen-direct-output-move-cursor screen x y)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'direct-output-move-cursor
				   x y))
  (terminal-move-cursor screen x y)
  (terminal-flush screen)
  (let ((current-matrix (screen-current-matrix screen))
	(new-matrix (screen-new-matrix screen)))
    (set-matrix-cursor-x! current-matrix x)
    (set-matrix-cursor-y! current-matrix y)
    (set-matrix-cursor-x! new-matrix x)
    (set-matrix-cursor-y! new-matrix y)))

(define (screen-output-char screen x y char face)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'output-char x y char face))
  (let ((new-matrix (screen-new-matrix screen)))
    (cond ((not (line-contents-enabled? new-matrix y))
	   (enable-line-contents! new-matrix y)
	   (set-screen-needs-update?! screen true)
	   (initialize-new-line-contents screen y)
	   (if (not (default-face? face))
	       (begin
		 (enable-line-highlights! new-matrix y)
		 (initialize-new-line-highlight screen y)
		 (highlight-set! new-matrix y x face))))
	  ((line-highlights-enabled? new-matrix y)
	   (highlight-set! new-matrix y x face))
	  ((not (default-face? face))
	   (enable-line-highlights! new-matrix y)
	   (clear-line-highlights! new-matrix y)
	   (highlight-set! new-matrix y x face)))
    (string-set! (vector-ref (matrix-contents new-matrix) y) x char)))

(define (screen-get-output-line screen y xl xu face)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'output-line y xl xu face))
  (let ((new-matrix (screen-new-matrix screen)))
    (let ((full-line? (and (fix:= xl 0) (fix:= xu (screen-x-size screen)))))
      (cond ((not (line-contents-enabled? new-matrix y))
	     (enable-line-contents! new-matrix y)
	     (set-screen-needs-update?! screen true)
	     (if (not full-line?) (initialize-new-line-contents screen y))
	     (if (not (default-face? face))
		 (begin
		   (enable-line-highlights! new-matrix y)
		   (if (not full-line?)
		       (initialize-new-line-highlight screen y))
		   (set-subline-highlights! new-matrix y xl xu face))))
	    ((line-highlights-enabled? new-matrix y)
	     (if (and full-line? (not face))
		 (disable-line-highlights! new-matrix y)
		 (set-subline-highlights! new-matrix y xl xu face)))
	    ((not (default-face? face))
	     (enable-line-highlights! new-matrix y)
	     (if (not full-line?)
		 (set-line-highlights! new-matrix y (default-face)))
	     (set-subline-highlights! new-matrix y xl xu face))))
    (vector-ref (matrix-contents new-matrix) y)))

(define (screen-output-substring screen x y string start end face)
  (substring-move-left! string start end
			(screen-get-output-line screen y x
						(fix:+ x (fix:- end start))
						face)
			x))

(define-integrable (initialize-new-line-contents screen y)
  (if (line-contents-enabled? (screen-current-matrix screen) y)
      (string-move!
       (vector-ref (matrix-contents (screen-current-matrix screen)) y)
       (vector-ref (matrix-contents (screen-new-matrix screen)) y))
      (string-fill!
       (vector-ref (matrix-contents (screen-new-matrix screen)) y)
       #\space)))

(define-integrable (initialize-new-line-highlight screen y)
  (if (line-highlights-enabled? (screen-current-matrix screen) y)
      (copy-line-highlights! (screen-current-matrix screen) y
			     (screen-new-matrix screen) y)
      (clear-line-highlights! (screen-new-matrix screen) y)))

(define (screen-clear-rectangle screen xl xu yl yu face)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'clear-rectangle
				   xl xu yl yu face))
  (let ((new-matrix (screen-new-matrix screen)))
    (let ((new-contents (matrix-contents new-matrix)))
      (cond ((not (and (fix:= xl 0) (fix:= xu (screen-x-size screen))))
	     (let ((current-matrix (screen-current-matrix screen)))
	       (let ((current-contents (matrix-contents current-matrix)))
		 (do ((y yl (fix:1+ y)))
		     ((fix:= y yu))
		   (if (not (line-contents-enabled? new-matrix y))
		       (begin
			 (enable-line-contents! new-matrix y)
			 (if (line-contents-enabled? current-matrix y)
			     (begin
			       (string-move! (vector-ref current-contents y)
					     (vector-ref new-contents y))
			       (substring-fill! (vector-ref new-contents y)
						xl xu #\space))
			     (string-fill! (vector-ref new-contents y)
					   #\space)))
		       (substring-fill! (vector-ref new-contents y)
					xl xu #\space))
		   (cond ((line-highlights-enabled? new-matrix y)
			  (set-subline-highlights! new-matrix y xl xu face))
			 ((not (default-face? face))
			  (enable-line-highlights! new-matrix y)
			  (if (line-highlights-enabled? current-matrix y)
			      (copy-line-highlights! current-matrix y
						     new-matrix y)
			      (clear-line-highlights! new-matrix y))
			  (set-subline-highlights! new-matrix y xl xu face))
			 ((line-highlights-enabled? current-matrix y)
			  (copy-line-highlights! current-matrix y new-matrix y)
			  (clear-subline-highlights! new-matrix y xl xu)
			  (if (not (line-highlights-cleared? new-matrix y))
			      (enable-line-highlights! new-matrix y))))))))
	    ((not (default-face? face))
	     (do ((y yl (fix:1+ y)))
		 ((fix:= y yu))
	       (string-fill! (vector-ref new-contents y) #\space)
	       (enable-line-contents! new-matrix y)
	       (set-line-highlights! new-matrix y face)
	       (enable-line-highlights! new-matrix y)))
	    (else
	     (do ((y yl (fix:1+ y)))
		 ((fix:= y yu))
	       (string-fill! (vector-ref new-contents y) #\space)
	       (enable-line-contents! new-matrix y)
	       (disable-line-highlights! new-matrix y))))))
  (set-screen-needs-update?! screen true))

(define (screen-direct-output-char screen x y char face)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'direct-output-char
				   x y char face))
  (let ((cursor-x (fix:1+ x))
	(current-matrix (screen-current-matrix screen)))
    (terminal-output-char screen x y char face)
    (terminal-move-cursor screen cursor-x y)
    (terminal-flush screen)
    (string-set! (vector-ref (matrix-contents current-matrix) y) x char)
    (cond ((line-highlights-enabled? current-matrix y)
	   (highlight-set! current-matrix y x face))
	  ((not (default-face? face))
	   (enable-line-highlights! current-matrix y)
	   (highlight-set! current-matrix y x face)))
    (set-matrix-cursor-x! current-matrix cursor-x)
    (set-matrix-cursor-x! (screen-new-matrix screen) cursor-x)))

(define (screen-direct-output-substring screen x y string start end face)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'direct-output-substring
				   x y (string-copy string) start end face))
  (let ((cursor-x (fix:+ x (fix:- end start)))
	(current-matrix (screen-current-matrix screen)))
    (terminal-output-substring screen x y string start end face)
    (terminal-move-cursor screen cursor-x y)
    (terminal-flush screen)
    (substring-move-left! string start end
			  (vector-ref (matrix-contents current-matrix) y) x)
    (cond ((line-highlights-enabled? current-matrix y)
	   (set-subline-highlights! current-matrix y x cursor-x face))
	  ((not (default-face? face))
	   (enable-line-highlights! current-matrix y)
	   (set-subline-highlights! current-matrix y x cursor-x face)))
    (set-matrix-cursor-x! current-matrix cursor-x)
    (set-matrix-cursor-x! (screen-new-matrix screen) cursor-x)))

(define (screen-force-update screen)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'force-update))
  (let ((y-size (screen-y-size screen))
	(current-matrix (screen-current-matrix screen))
	(new-matrix (screen-new-matrix screen)))
    (terminal-clear-screen screen)
    (let ((current-contents (matrix-contents current-matrix))
	  (new-contents (matrix-contents new-matrix)))
      (do ((y 0 (fix:1+ y)))
	  ((fix:= y y-size))
	(if (not (line-contents-enabled? new-matrix y))
	    (begin
	      (let ((c (vector-ref new-contents y)))
		(vector-set! new-contents y (vector-ref current-contents y))
		(vector-set! current-contents y c))
	      (enable-line-contents! new-matrix y)
	      (if (line-highlights-enabled? current-matrix y)
		  (begin
		    (swap-line-highlights! new-matrix y current-matrix y)
		    (enable-line-highlights! new-matrix y)))))
	(string-fill! (vector-ref current-contents y) #\space)
	(enable-line-contents! current-matrix y)
	(disable-line-highlights! current-matrix y))))
  (invalidate-cursor screen)
  (set-screen-needs-update?! screen true))

(define (invalidate-cursor screen)
  (let ((current-matrix (screen-current-matrix screen))
	(new-matrix (screen-new-matrix screen)))
    (if (or (matrix-cursor-x current-matrix)
	    (matrix-cursor-y current-matrix))
	(begin
	  (set-matrix-cursor-x! new-matrix (matrix-cursor-x current-matrix))
	  (set-matrix-cursor-y! new-matrix (matrix-cursor-y current-matrix))
	  (set-matrix-cursor-x! current-matrix #f)
	  (set-matrix-cursor-y! current-matrix #f)))))

(define (screen-scroll-lines-down screen xl xu yl yu amount)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'scroll-lines-down
				   xl xu yl yu amount))
  (let ((current-matrix (screen-current-matrix screen)))
    (and (multiple-line-contents-enabled? current-matrix yl yu)
	 (not (screen-needs-update? screen))
	 (let ((scrolled?
		(terminal-scroll-lines-down screen xl xu yl yu amount)))
	   (and scrolled?
		(begin
		  (let ((contents (matrix-contents current-matrix)))
		    (do ((y (fix:-1+ (fix:- yu amount)) (fix:-1+ y))
			 (y* (fix:-1+ yu) (fix:-1+ y*)))
			((fix:< y yl))
		      (substring-move-left! (vector-ref contents y) xl xu
					    (vector-ref contents y*) xl)
		      (cond ((line-highlights-enabled? current-matrix y)
			     (enable-line-highlights! current-matrix y*)
			     (copy-subline-highlights! current-matrix y xl xu
						       current-matrix y* xl))
			    ((line-highlights-enabled? current-matrix y*)
			     (clear-subline-highlights! current-matrix y*
							xl xu))))
		    (case scrolled?
		      ((CLEARED)
		       (let ((yu (fix:+ yl amount)))
			 (if (and (fix:= xl 0)
				  (fix:= xu (screen-x-size screen)))
			     (do ((y yl (fix:1+ y)))
				 ((fix:= y yu))
			       (substring-fill! (vector-ref contents y) xl xu
						#\space)
			       (disable-line-highlights! current-matrix y))
			     (do ((y yl (fix:1+ y)))
				 ((fix:= y yu))
			       (substring-fill! (vector-ref contents y) xl xu
						#\space)
			       (if (line-highlights-enabled? current-matrix y)
				   (clear-subline-highlights! current-matrix y
							      xl xu))))))
		      ((CLOBBERED-CURSOR)
		       (invalidate-cursor screen))))
		  scrolled?))))))

(define (screen-scroll-lines-up screen xl xu yl yu amount)
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'scroll-lines-up
				   xl xu yl yu amount))
  (let ((current-matrix (screen-current-matrix screen)))
    (and (multiple-line-contents-enabled? current-matrix yl yu)
	 (not (screen-needs-update? screen))
	 (let ((scrolled?
		(terminal-scroll-lines-up screen xl xu yl yu amount)))
	   (and scrolled?
		(begin
		  (let ((contents (matrix-contents current-matrix)))
		    (do ((y yl (fix:1+ y))
			 (y* (fix:+ yl amount) (fix:1+ y*)))
			((fix:= y* yu))
		      (substring-move-left! (vector-ref contents y*) xl xu
					    (vector-ref contents y) xl)
		      (cond ((line-highlights-enabled? current-matrix y*)
			     (enable-line-highlights! current-matrix y)
			     (copy-subline-highlights! current-matrix y* xl xu
						       current-matrix y xl))
			    ((line-highlights-enabled? current-matrix y)
			     (clear-subline-highlights! current-matrix y
							xl xu))))
		    (case scrolled?
		      ((CLEARED)
		       (if (and (fix:= xl 0)
				(fix:= xu (screen-x-size screen)))
			   (do ((y (fix:- yu amount) (fix:1+ y)))
			       ((fix:= y yu))
			     (substring-fill! (vector-ref contents y) xl xu
					      #\space)
			     (disable-line-highlights! current-matrix y))
			   (do ((y (fix:- yu amount) (fix:1+ y)))
			       ((fix:= y yu))
			     (substring-fill! (vector-ref contents y) xl xu
					      #\space)
			     (if (line-highlights-enabled? current-matrix y)
				 (clear-subline-highlights! current-matrix y
							    xl xu)))))
		      ((CLOBBERED-CURSOR)
		       (invalidate-cursor screen))))
		  scrolled?))))))

(define (with-screen-in-update screen display-style thunk)
  (without-interrupts
   (lambda ()
     (let ((old-flag (screen-in-update? screen)))
       (set-screen-in-update?! screen true)
       (let ((finished?
	      ((screen-operation/wrap-update! screen)
	       screen
	       (lambda ()
		 (and (thunk)
		      (if (memq (screen-visibility screen)
				'(VISIBLE PARTIALLY-OBSCURED))
			  (and (or (not (screen-needs-update? screen))
				   (and (not (display-style/no-screen-output?
					      display-style))
					(screen-update screen display-style)))
			       (begin
				 (screen-update-cursor screen)
				 #t))
			  'INVISIBLE))))))
	 (set-screen-in-update?! screen old-flag)
	 finished?)))))

(define (screen-update-cursor screen)
  (let ((x (matrix-cursor-x (screen-new-matrix screen)))
	(y (matrix-cursor-y (screen-new-matrix screen))))
    (if (not (and (eqv? x (matrix-cursor-x (screen-current-matrix screen)))
		  (eqv? y (matrix-cursor-y (screen-current-matrix screen)))))
	(terminal-move-cursor screen x y))
    (set-matrix-cursor-x! (screen-current-matrix screen) x)
    (set-matrix-cursor-y! (screen-current-matrix screen) y)))

(define (screen-update screen force?)
  ;; Update the actual terminal screen based on the data in `new-matrix'.
  ;; Value is #F if redisplay stopped due to pending input.
  ;; FORCE? true means do not stop for pending input.
  (if (screen-debug-trace screen)
      ((screen-debug-trace screen) 'screen screen 'update force?))
  (let ((new-matrix (screen-new-matrix screen))
	(y-size (screen-y-size screen))
	(preemption-modulus (screen-preemption-modulus screen))
	(discretionary-flush (screen-operation/discretionary-flush screen))
	(halt-update? (editor-halt-update? current-editor)))
    (let loop ((y 0) (m 0))
      (cond ((fix:= y y-size)
	     true)
	    ((not (line-contents-enabled? new-matrix y))
	     (loop (fix:+ y 1) m))
	    ((not (fix:= 0 m))
	     (update-line screen y)
	     (loop (fix:+ y 1) (fix:- m 1)))
	    ((begin
	       (if discretionary-flush (discretionary-flush screen))
	       (and (not force?) (halt-update?)))
	     (if (screen-debug-trace screen)
		 ((screen-debug-trace screen) 'screen screen
					      'update-preemption y))
	     false)
	    (else
	     (update-line screen y)
	     (loop (fix:+ y 1) preemption-modulus))))))

(define (update-line screen y)
  (let ((current-matrix (screen-current-matrix screen))
	(new-matrix (screen-new-matrix screen))
	(x-size (screen-x-size screen)))
    (let ((current-contents (matrix-contents current-matrix))
	  (new-contents (matrix-contents new-matrix)))
      (let ((ccy (vector-ref current-contents y))
	    (ncy (vector-ref new-contents y))
	    (nhey (line-highlights-enabled? new-matrix y)))
	(cond ((or (not (line-contents-enabled? current-matrix y))
		   (if (line-highlights-enabled? current-matrix y)
		       (not nhey)
		       nhey))
	       (if nhey
		   (update-line-ignore-current screen y ncy new-matrix x-size)
		   (update-line-trivial screen y ncy x-size)))
	      (nhey
	       (update-line-highlight screen y
				      ccy current-matrix
				      ncy new-matrix
				      x-size))
	      (else
	       (update-line-no-highlight screen y ccy ncy x-size)))
	(vector-set! current-contents y ncy)
	(enable-line-contents! current-matrix y)
	(vector-set! new-contents y ccy)
	(disable-line-contents! new-matrix y)
	(if nhey
	    (begin
	      (swap-line-highlights! current-matrix y new-matrix y)
	      (enable-line-highlights! current-matrix y)
	      (disable-line-highlights! new-matrix y))
	    (disable-line-highlights! current-matrix y))))))

(define (update-line-ignore-current screen y nline matrix x-size)
  (cond ((not (subline-highlights-uniform? matrix y 0 x-size))
	 (let loop ((x 0))
	   (let ((face (highlight-ref matrix y x)))
	     (let ((x*
		    (find-subline-highlight-change matrix y (fix:1+ x) x-size
						   face)))
	       (if x*
		   (begin
		     (terminal-output-substring screen x y nline x x* face)
		     (loop x*))
		   (terminal-output-substring screen x y nline x x-size
					      face))))))
	((not (default-face? (highlight-ref matrix y 0)))
	 (terminal-output-substring screen 0 y nline 0 x-size
				    (highlight-ref matrix y 0)))
	(else
	 (update-line-trivial screen y nline x-size))))

(define (update-line-trivial screen y nline x-size)
  (let ((xe (substring-non-space-end nline 0 x-size)))
    (if (fix:< 0 xe)
	(terminal-output-substring screen 0 y nline 0 xe false))
    (if (fix:< xe x-size)
	(terminal-clear-line screen xe y x-size))))

(define (update-line-no-highlight screen y oline nline x-size)
  (let ((olen (substring-non-space-end oline 0 x-size))
	(nlen (substring-non-space-end nline 0 x-size)))
    (cond ((fix:= 0 olen)
	   (let ((nstart (substring-non-space-start nline 0 nlen)))
	     (if (fix:< nstart nlen)
		 (terminal-output-substring screen nstart y
					    nline nstart nlen false))))
	  ((fix:= 0 nlen)
	   (terminal-clear-line screen nlen y olen))
	  (else
	   (let ((len (fix:min olen nlen)))
	     (let find-mismatch ((x 0))
	       (cond ((fix:= x len)
		      (if (fix:< x nlen)
			  (terminal-output-substring screen x y
						     nline x nlen false)))
		     ((fix:= (vector-8b-ref oline x)
			     (vector-8b-ref nline x))
		      (find-mismatch (fix:+ x 1)))
		     (else
		      (let find-match ((x* (fix:+ x 1)))
			(cond ((fix:= x* len)
			       (terminal-output-substring
				screen x y nline x nlen false))
			      ((not (fix:= (vector-8b-ref oline x*)
					   (vector-8b-ref nline x*)))
			       (find-match (fix:+ x* 1)))
			      (else
			       ;; Ignore matches of 4 characters or less.
			       ;; The overhead of moving the cursor and
			       ;; drawing the characters is too much except
			       ;; for very slow terminals.
			       (let find-end-match ((x** (fix:+ x* 1)))
				 (cond ((fix:= x** len)
					(if (fix:< (fix:- x** x*) 5)
					    (terminal-output-substring
					     screen x y nline x nlen false)
					    (begin
					      (terminal-output-substring
					       screen x y nline x x* false)
					      (if (fix:< x** nlen)
						  (terminal-output-substring
						   screen x** y
						   nline x** nlen false)))))
				       ((fix:= (vector-8b-ref oline x**)
					       (vector-8b-ref nline x**))
					(find-end-match (fix:+ x** 1)))
				       ((fix:< (fix:- x** x*) 5)
					(find-match x**))
				       (else
					(terminal-output-substring
					 screen x y nline x x* false)
					(find-mismatch x**)))))))))))
	   (if (fix:< nlen olen)
	       (terminal-clear-line screen nlen y olen))))))

(define (screen-line-draw-cost screen y)
  (let ((line (vector-ref (matrix-contents (screen-current-matrix screen)) y)))
    (let ((end (substring-non-space-end line 0 (string-length line))))
      (if (fix:= 0 end)
	  0
	  (fix:- end (substring-non-space-start line 0 end))))))

(define (update-line-highlight screen y oline om nline nm x-size)
  (let find-mismatch ((x 0))
    (if (not (fix:= x x-size))
	(if (and (fix:= (vector-8b-ref oline x) (vector-8b-ref nline x))
		 (eqv? (highlight-ref om y x) (highlight-ref nm y x)))
	    (find-mismatch (fix:+ x 1))
	    (let ((face (highlight-ref nm y x)))
	      (let find-match ((x* (fix:+ x 1)))
		(cond ((fix:= x* x-size)
		       (terminal-output-substring screen x y nline x x* face))
		      ((not (eqv? face (highlight-ref nm y x*)))
		       (terminal-output-substring screen x y nline x x* face)
		       (find-mismatch x*))
		      ((not (and (eqv? face (highlight-ref om y x*))
				 (fix:= (vector-8b-ref oline x*)
					(vector-8b-ref nline x*))))
		       (find-match (fix:+ x* 1)))
		      (else
		       (let find-end-match ((x** (fix:+ x* 1)))
			 (cond ((fix:= x** x-size)
				(terminal-output-substring
				 screen x y nline x x* face))
			       ((and (eqv? face (highlight-ref om y x**))
				     (fix:= (vector-8b-ref oline x**)
					    (vector-8b-ref nline x**)))
				(find-end-match (fix:+ x** 1)))
			       ((fix:< (fix:- x** x*) 5)
				;; Ignore matches of 4 chars or less.
				(find-match x**))
			       (else
				(terminal-output-substring
				 screen x y nline x x* face)
				(find-mismatch x**))))))))))))

(define-integrable (substring-non-space-start string start end)
  (do ((index start (fix:+ index 1)))
      ((or (fix:= end index)
	   (not (fix:= (vector-8b-ref string index)
		       (char->integer #\space))))
       index)))

(define-integrable (substring-non-space-end string start end)
  (do ((index end (fix:- index 1)))
      ((or (fix:= start index)
	   (not (fix:= (vector-8b-ref string (fix:- index 1))
		       (char->integer #\space))))
       index)))

(define (string-move! x y)
  (substring-move-left! x 0 (string-length x) y 0))

(define-integrable (boolean-vector-ref vector index)
  (fix:= (char->integer #\t) (vector-8b-ref vector index)))

(define-integrable (boolean-vector-set! vector index value)
  (vector-8b-set! vector index (boolean->ascii value)))

(define (boolean-vector-all-elements? vector value)
  (boolean-subvector-all-elements? vector 0 (boolean-vector-length vector)
				   value))

(define (boolean-subvector-all-elements? vector start end value)
  (if (vector-8b-find-next-char vector start end (boolean->ascii (not value)))
      false
      true))

(define (boolean-subvector-uniform? vector start end)
  (if (and (fix:< start end)
	   (vector-8b-find-next-char
	    vector start end
	    (boolean->ascii (not (boolean-vector-ref vector start)))))
      false
      true))

(define-integrable (boolean-subvector-find-next vector start end value)
  (vector-8b-find-next-char vector start end (boolean->ascii value)))

(define-integrable make-boolean-vector string-allocate)
(define-integrable boolean-vector-length string-length)
(define-integrable boolean-vector=? string=?)
(define-integrable boolean-subvector-move-right! substring-move-right!)
(define-integrable boolean-subvector-move-left! substring-move-left!)
(define-integrable boolean-vector-move! string-move!)
(define-integrable boolean-vector-copy string-copy)

(define-integrable (boolean-subvector-fill! vector start end value)
  (vector-8b-fill! vector start end (boolean->ascii value)))

(define (boolean-vector-fill! vector value)
  (boolean-subvector-fill! vector 0 (boolean-vector-length vector) value))

(define-integrable (boolean->ascii boolean)
  (if boolean (char->integer #\t) (char->integer #\f)))