svn commit: r316636 - head/sys/dev/syscons

[Bruce Evans]

Author: bde
Date: Sat Apr  8 08:24:25 2017
New Revision: 316636
URL: https://svnweb.freebsd.org/changeset/base/316636

Log:
  Fix removal of the keyboard cursor image in text mode, especially
  in the vga renderer.  Removal used stale attributes and didn't try to
  merge with the current attribute for cut marking, so special rendering
  of cut marking was lost in many cases.  The gfb renderer is too broken
  to support special rendering of cut marking at all, so this change is
  supposed to be just a style fix for it.  Remove all traces of the
  saveunder method which was used to implement this bug.
  
  Fix drawing of the cursor image in text mode, only in the vga
  renderer.  This used a stale attribute from the frame buffer instead
  of from the saveunder, but did merge with the current attribute for
  cut marking so it caused less obvious bugs (subtle misrendering for
  the character under the cursor).
  
  The saveunder method may be good in simpler drivers, but in syscons
  the 'under' is already saved in a better way in the vtb.  Just redraw
  it from there, with visible complications for cut marking and
  invisible complications for mouse cursors.  Almost all drawing
  requests are passed a flag 'flip' which currently means to flip to
  reverse video for characters in the cut marking region, but should
  mean that the the characters are in the cut marking regions so should
  be rendered specially, preferably using something better than reverse
  video.  The gfb renderer always ignores this flag.  The vga renderer
  ignored it for removal of the text cursor -- the saveunder gave the
  stale rendering at the time the cursor was drawn.  Mouse cursors need
  even more complicated methods.  They are handled by drawing them last
  and removing them first.  Removing them usually redraws many other
  characters with the correct cut marking (but transiently loses the
  keyboard cursor, which is redrawn soon).  This tended to hide the
  saveunder bug for forward motions of the keyboard cursor.  But slow
  backward motions of the keyboard cursor always lost the cut marking,
  and fast backwards motions lost in for about 4 in every 5 characters,
  depending on races with the scrn_update() timeout handler.  This is
  because the forward motions are usually into the region redrawn for
  the mouse cursor, while backwards motions rarely are.
  
  Text cursor drawing in the vga renderer used also used a
  possibly-stale copy of the character and its attribute.  The vga
  render has the "optimization" of sometimes reading characters from the
  screen instead of from the vtb (this was not so good even in 1990 when
  main memory was only a few times faster than video RAM).  Due to care
  in update orders, the character is never stale, but its attribute
  might be (just the cut marking part, again due to care in order).
  
  gfb doesn't have the scp->scr pointer used for the "optimization", and
  vga only uses this pointer for text mode.  So most cases have to
  refresh from the vtb, and we can be sure that the ordering of vtb
  updates and drawing is as required for this to work.

Modified:
  head/sys/dev/syscons/scgfbrndr.c
  head/sys/dev/syscons/scvgarndr.c
  head/sys/dev/syscons/syscons.h

Modified: head/sys/dev/syscons/scgfbrndr.c
==============================================================================
--- head/sys/dev/syscons/scgfbrndr.c	Sat Apr  8 06:39:13 2017	(r316635)
+++ head/sys/dev/syscons/scgfbrndr.c	Sat Apr  8 08:24:25 2017	(r316636)
@@ -271,13 +271,11 @@ gfb_cursor(scr_stat *scp, int at, int bl
 			c = sc_vtb_getc(&scp->vtb, at);
 			vidd_putc(scp->sc->adp, at, c,
 			    (a >> 4) | ((a & 0xf) << 4));
-			scp->cursor_saveunder_attr = a;
-			scp->cursor_saveunder_char = c;
 		} else {
 			if (scp->status & VR_CURSOR_ON)
 				vidd_putc(scp->sc->adp, at,
-				    scp->cursor_saveunder_char,
-				    scp->cursor_saveunder_attr);
+				    sc_vtb_getc(&scp->vtb, at),
+				    sc_vtb_geta(&scp->vtb, at) >> 8);
 			scp->status &= ~VR_CURSOR_ON;
 		}
 	}

Modified: head/sys/dev/syscons/scvgarndr.c
==============================================================================
--- head/sys/dev/syscons/scvgarndr.c	Sat Apr  8 06:39:13 2017	(r316635)
+++ head/sys/dev/syscons/scvgarndr.c	Sat Apr  8 08:24:25 2017	(r316636)
@@ -294,8 +294,6 @@ draw_txtcharcursor(scr_stat *scp, int at
 	sc_softc_t *sc;
 
 	sc = scp->sc;
-	scp->cursor_saveunder_char = c;
-	scp->cursor_saveunder_attr = a;
 
 #ifndef SC_NO_FONT_LOADING
 	if (scp->curs_attr.flags & CONS_CHAR_CURSOR) {
@@ -372,18 +370,18 @@ vga_txtcursor(scr_stat *scp, int at, int
 		if (on) {
 			scp->status |= VR_CURSOR_ON;
 			draw_txtcharcursor(scp, at,
-					   sc_vtb_getc(&scp->scr, at),
-					   sc_vtb_geta(&scp->scr, at),
+					   sc_vtb_getc(&scp->vtb, at),
+					   sc_vtb_geta(&scp->vtb, at),
 					   flip);
 		} else {
-			cursor_attr = scp->cursor_saveunder_attr;
+			cursor_attr = sc_vtb_geta(&scp->vtb, at);
 			if (flip)
 				cursor_attr = (cursor_attr & 0x8800)
 					| ((cursor_attr & 0x7000) >> 4)
 					| ((cursor_attr & 0x0700) << 4);
 			if (scp->status & VR_CURSOR_ON)
 				sc_vtb_putc(&scp->scr, at,
-					    scp->cursor_saveunder_char,
+					    sc_vtb_getc(&scp->vtb, at),
 					    cursor_attr);
 			scp->status &= ~VR_CURSOR_ON;
 		}

Modified: head/sys/dev/syscons/syscons.h
==============================================================================
--- head/sys/dev/syscons/syscons.h	Sat Apr  8 06:39:13 2017	(r316635)
+++ head/sys/dev/syscons/syscons.h	Sat Apr  8 08:24:25 2017	(r316636)
@@ -312,8 +312,6 @@ typedef struct scr_stat {
 
 	int		cursor_pos;		/* cursor buffer position */
 	int		cursor_oldpos;		/* cursor old buffer position */
-	u_short		cursor_saveunder_char;	/* saved char under cursor */
-	u_short		cursor_saveunder_attr;	/* saved attr under cursor */
 	struct cursor_attr dflt_curs_attr;
 	struct cursor_attr curr_curs_attr;
 	struct cursor_attr curs_attr;