further improved monochrome terminal support: fixed reverse text on reverse backgrounds

* Unfortunately we cannot use `wbkgdset(win, A_REVERSE)` if we plan to
  use reverse text on this background, i.e. if we want to cancel out the background A_REVERSE.
* SciTECO therefore no longer uses background attributes, but only foreground attributes.
  When setting a reverse text, we XOR A_REVERSE into the previous attributes.
* This fixes control characters especially in the info line and popups, as well as rendering
  of the popup scroll bars.
* The command-line should now be rendered properly even on a dark-on-bright color theme
  (which does not yet exist).

4 files changed, 72 insertions, 28 deletions

diff --git a/src/interface-curses/curses-info-popup.c b/src/interface-curses/curses-info-popup.c
index dffbcf8..332d434 100644
--- a/src/interface-curses/curses-info-popup.c
+++ b/src/interface-curses/curses-info-popup.c
@@ -98,7 +98,13 @@ teco_curses_info_popup_init_pad(teco_curses_info_popup_t *ctx, attr_t attr)
 	 */
 	ctx->pad = newpad(pad_lines, cols - 2);
 
-	wbkgd(ctx->pad, ' ' | attr);
+	/*
+	 * NOTE: attr could contain A_REVERSE on monochrome terminals,
+	 * so we use foreground attributes instead of background attributes.
+	 * This way, we can cancel out the A_REVERSE if necessary.
+	 */
+	wattrset(ctx->pad, attr);
+	teco_curses_clrtobot(ctx->pad);
 
 	/*
 	 * cur_col is the row currently written.
@@ -113,7 +119,8 @@ teco_curses_info_popup_init_pad(teco_curses_info_popup_t *ctx, attr_t attr)
 		wmove(ctx->pad, cur_line-1,
 		      (cur_col % pad_cols)*pad_colwidth);
 
-		wattrset(ctx->pad, entry->highlight ? A_BOLD : A_NORMAL);
+		if (entry->highlight)
+			wattron(ctx->pad, A_BOLD);
 
 		switch (entry->type) {
 		case TECO_POPUP_FILE:
@@ -137,6 +144,8 @@ teco_curses_info_popup_init_pad(teco_curses_info_popup_t *ctx, attr_t attr)
 			break;
 		}
 
+		wattroff(ctx->pad, A_BOLD);
+
 		cur_col++;
 	}
 }
@@ -167,7 +176,7 @@ teco_curses_info_popup_show(teco_curses_info_popup_t *ctx, attr_t attr)
 	/* window covers message, scintilla and info windows */
 	ctx->window = newwin(popup_lines, 0, lines - 1 - popup_lines, 0);
 
-	wbkgdset(ctx->window, ' ' | attr);
+	wattrset(ctx->window, attr);
 
 	wborder(ctx->window,
 	        ACS_VLINE,
@@ -198,7 +207,7 @@ teco_curses_info_popup_show(teco_curses_info_popup_t *ctx, attr_t attr)
 	 * Instead, simply draw reverse blanks.
 	 */
 	wmove(ctx->window, bar_y, cols-1);
-	wattron(ctx->window, A_REVERSE);
+	wattrset(ctx->window, attr ^ A_REVERSE);
 	wvline(ctx->window, ' ', bar_height);
 }
 
diff --git a/src/interface-curses/curses-utils.c b/src/interface-curses/curses-utils.c
index 3fd680b..f94b6dc 100644
--- a/src/interface-curses/curses-utils.c
+++ b/src/interface-curses/curses-utils.c
@@ -48,9 +48,18 @@ guint
 teco_curses_format_str(WINDOW *win, const gchar *str, gsize len, gint max_width)
 {
 	gint truncate_len = teco_ed & TECO_ED_ICONS ? 1 : 3;
-	int old_x, old_y;
 	gint chars_added = 0;
 
+	/*
+	 * The entire background might be in reverse, especially
+	 * on monochrome terminals.
+	 * In those cases, we have to __remove__ the A_REVERSE flag.
+	 */
+	attr_t attrs = A_NORMAL;
+	short pair = 0;
+	wattr_get(win, &attrs, &pair, NULL);
+
+	int old_x, old_y;
 	getyx(win, old_y, old_x);
 
 	if (max_width < 0)
@@ -72,37 +81,38 @@ teco_curses_format_str(WINDOW *win, const gchar *str, gsize len, gint max_width)
 			chars_added++;
 			if (chars_added > max_width)
 				goto truncate;
-			waddch(win, '$' | A_REVERSE);
+			wattr_set(win, attrs ^ A_REVERSE, pair, NULL);
+			waddch(win, '$');
 			break;
 		case '\r':
 			chars_added += 2;
 			if (chars_added > max_width)
 				goto truncate;
-			waddch(win, 'C' | A_REVERSE);
-			waddch(win, 'R' | A_REVERSE);
+			wattr_set(win, attrs ^ A_REVERSE, pair, NULL);
+			waddstr(win, "CR");
 			break;
 		case '\n':
 			chars_added += 2;
 			if (chars_added > max_width)
 				goto truncate;
-			waddch(win, 'L' | A_REVERSE);
-			waddch(win, 'F' | A_REVERSE);
+			wattr_set(win, attrs ^ A_REVERSE, pair, NULL);
+			waddstr(win, "LF");
 			break;
 		case '\t':
 			chars_added += 3;
 			if (chars_added > max_width)
 				goto truncate;
-			waddch(win, 'T' | A_REVERSE);
-			waddch(win, 'A' | A_REVERSE);
-			waddch(win, 'B' | A_REVERSE);
+			wattr_set(win, attrs ^ A_REVERSE, pair, NULL);
+			waddstr(win, "TAB");
 			break;
 		default:
 			if (TECO_IS_CTL(*str)) {
 				chars_added += 2;
 				if (chars_added > max_width)
 					goto truncate;
-				waddch(win, '^' | A_REVERSE);
-				waddch(win, TECO_CTL_ECHO(*str) | A_REVERSE);
+				wattr_set(win, attrs ^ A_REVERSE, pair, NULL);
+				waddch(win, '^');
+				waddch(win, TECO_CTL_ECHO(*str));
 			} else {
 				chars_added++;
 				if (chars_added > max_width)
@@ -116,6 +126,8 @@ teco_curses_format_str(WINDOW *win, const gchar *str, gsize len, gint max_width)
 				waddnstr(win, str, clen);
 			}
 		}
+		/* restore original state of A_REVERSE */
+		wattr_set(win, attrs, pair, NULL);
 
 		str += clen;
 		len -= clen;
diff --git a/src/interface-curses/curses-utils.h b/src/interface-curses/curses-utils.h
index 9f2e8f3..18cdd3d 100644
--- a/src/interface-curses/curses-utils.h
+++ b/src/interface-curses/curses-utils.h
@@ -34,3 +34,20 @@ teco_curses_add_wc(WINDOW *win, gunichar chr)
 	gchar buf[6];
 	waddnstr(win, buf, g_unichar_to_utf8(chr, buf));
 }
+
+/**
+ * Clear from the current position until the end of the given
+ * curses window with the current \b foreground attributes.
+ * This is similar to wclrtobot(), but does not use the
+ * background attributes.
+ */
+static inline void
+teco_curses_clrtobot(WINDOW *win)
+{
+	int max_x, max_y;
+	getmaxyx(win, max_y, max_x);
+	if (getcurx(win)+1 < max_x)
+		whline(win, ' ', max_x - getcurx(win));
+	for (int y = getcury(win)+1; y <= max_y; y++)
+		mvwhline(win, y, 0, ' ', max_x);
+}
diff --git a/src/interface-curses/interface.c b/src/interface-curses/interface.c
index 2e87601..75ba036 100644
--- a/src/interface-curses/interface.c
+++ b/src/interface-curses/interface.c
@@ -899,8 +899,12 @@ teco_interface_vmsg(teco_msg_t type, const gchar *fmt, va_list ap)
 		break;
 	}
 
+	/*
+	 * NOTE: This is safe since we don't have to cancel out any A_REVERSE,
+	 * that could be set in the background attributes.
+	 */
 	wmove(teco_interface.msg_window, 0, 0);
-	wbkgdset(teco_interface.msg_window, ' ' | teco_color_attr(fg, bg));
+	wbkgdset(teco_interface.msg_window, teco_color_attr(fg, bg));
 	vw_printw(teco_interface.msg_window, fmt, ap);
 	wclrtoeol(teco_interface.msg_window);
 }
@@ -914,7 +918,7 @@ teco_interface_msg_clear(void)
 	short fg = teco_rgb2curses(teco_interface_ssm(SCI_STYLEGETBACK, STYLE_DEFAULT, 0));
 	short bg = teco_rgb2curses(teco_interface_ssm(SCI_STYLEGETFORE, STYLE_DEFAULT, 0));
 
-	wbkgdset(teco_interface.msg_window, ' ' | teco_color_attr(fg, bg));
+	wbkgdset(teco_interface.msg_window, teco_color_attr(fg, bg));
 	werase(teco_interface.msg_window);
 }
 
@@ -1026,7 +1030,7 @@ teco_interface_draw_info(void)
 	short bg = teco_rgb2curses(teco_interface_ssm(SCI_STYLEGETFORE, STYLE_DEFAULT, 0));
 
 	wmove(teco_interface.info_window, 0, 0);
-	wbkgdset(teco_interface.info_window, ' ' | teco_color_attr(fg, bg));
+	wattrset(teco_interface.info_window, teco_color_attr(fg, bg));
 
 	const gchar *info_type_str;
 
@@ -1061,7 +1065,7 @@ teco_interface_draw_info(void)
 		g_assert_not_reached();
 	}
 
-	wclrtoeol(teco_interface.info_window);
+	teco_curses_clrtobot(teco_interface.info_window);
 
 	/*
 	 * Make sure the title will consist only of printable characters.
@@ -1125,7 +1129,7 @@ teco_interface_cmdline_update(const teco_cmdline_t *cmdline)
 
 	short fg = teco_rgb2curses(teco_interface_ssm(SCI_STYLEGETFORE, STYLE_DEFAULT, 0));
 	short bg = teco_rgb2curses(teco_interface_ssm(SCI_STYLEGETBACK, STYLE_DEFAULT, 0));
-	wcolor_set(teco_interface.cmdline_pad, teco_color_pair(fg, bg), NULL);
+	wattrset(teco_interface.cmdline_pad, teco_color_attr(fg, bg));
 
 	/* format effective command line */
 	teco_interface.cmdline_len =
@@ -1141,6 +1145,8 @@ teco_interface_cmdline_update(const teco_cmdline_t *cmdline)
 	 * as command line, since we can then define a style
 	 * for rubbed out parts of the command line which will
 	 * be user-configurable.
+	 * The attributes, supported by the terminal can theoretically
+	 * be queried with term_attrs().
 	 */
 	wattron(teco_interface.cmdline_pad, A_UNDERLINE | A_BOLD);
 
@@ -1157,18 +1163,18 @@ teco_interface_cmdline_update(const teco_cmdline_t *cmdline)
 	 * Highlight cursor after effective command line
 	 * FIXME: This should use SCI_GETCARETFORE().
 	 */
+	attr_t attr = A_NORMAL;
+	short pair = 0;
 	if (teco_interface.cmdline_rubout_len) {
-		attr_t attr = 0;
-		short pair = 0;
-
 		wmove(teco_interface.cmdline_pad, 0, teco_interface.cmdline_len);
 		wattr_get(teco_interface.cmdline_pad, &attr, &pair, NULL);
 		wchgat(teco_interface.cmdline_pad, 1,
-		       (attr & A_UNDERLINE) | A_REVERSE, pair, NULL);
+		       (attr & (A_UNDERLINE | A_REVERSE)) ^ A_REVERSE, pair, NULL);
 	} else {
 		teco_interface.cmdline_len++;
-		wattroff(teco_interface.cmdline_pad, A_UNDERLINE | A_BOLD);
-		waddch(teco_interface.cmdline_pad, ' ' | A_REVERSE);
+		wattr_get(teco_interface.cmdline_pad, &attr, &pair, NULL);
+		wattr_set(teco_interface.cmdline_pad, (attr & ~(A_UNDERLINE | A_BOLD)) ^ A_REVERSE, pair, NULL);
+		waddch(teco_interface.cmdline_pad, ' ');
 	}
 
 	teco_interface_draw_cmdline();
@@ -1196,9 +1202,9 @@ teco_interface_draw_cmdline(void)
 	short fg = teco_rgb2curses(teco_interface_ssm(SCI_STYLEGETFORE, STYLE_DEFAULT, 0));
 	short bg = teco_rgb2curses(teco_interface_ssm(SCI_STYLEGETBACK, STYLE_DEFAULT, 0));
 
-	wbkgdset(teco_interface.cmdline_window, ' ' | teco_color_attr(fg, bg));
-	werase(teco_interface.cmdline_window);
+	wattrset(teco_interface.cmdline_window, teco_color_attr(fg, bg));
 	mvwaddch(teco_interface.cmdline_window, 0, 0, '*' | A_BOLD);
+	teco_curses_clrtobot(teco_interface.cmdline_window);
 	copywin(teco_interface.cmdline_pad, teco_interface.cmdline_window,
 	        0, disp_offset, 0, 1, 0, disp_len, FALSE);
 }