input: implement metaSendsEscape and eightBitMeta

csi.c

@@ -927,8 +927,16 @@ csi_dispatch(struct terminal *term, uint8_t final)
                     term->mouse_reporting = MOUSE_URXVT;
                     break;
 
+                case 1034:
+                    /* smm */
+                    LOG_DBG("enabling 8-bit meta mode");
+                    term->meta.eight_bit = true;
+                    break;
+
                 case 1036:
-                    /* metaSendsEscape - we always send escape */
+                    /* metaSendsEscape */
+                    LOG_DBG("enabling meta-sends-escape");
+                    term->meta.esc_prefix = true;
                     break;
 
 #if 0
@@ -1037,9 +1045,16 @@ csi_dispatch(struct terminal *term, uint8_t final)
                     term->alt_scrolling = false;
                     break;
 
+                case 1034:
+                    /* rmm */
+                    LOG_DBG("disabling 8-bit meta mode");
+                    term->meta.eight_bit = false;
+                    break;
+
                 case 1036:
-                    /* metaSendsEscape - we always send escape */
+                    /* metaSendsEscape */
-                    LOG_WARN("unimplemented: meta does *not* send escape");
+                    LOG_DBG("disabling  meta-sends-escape");
+                    term->meta.esc_prefix = false;
                     break;
 
 #if 0

foot.info

@@ -221,6 +221,7 @@ foot+base|foot base fragment,
     rmcup=\E[?1049l\E[23;0t,
     rmir=\E[4l,
     rmkx=\E[?1l\E>,
+    rmm=\E[?1034l,
     rmso=\E[27m,
     rmul=\E[24m,
     rmxx=\E[29m,
@@ -235,6 +236,7 @@ foot+base|foot base fragment,
     smcup=\E[?1049h\E[22;0t,
     smir=\E[4h,
     smkx=\E[?1h\E=,
+    smm=\E[?1034h,
     smso=\E[7m,
     smul=\E[4m,
     smxx=\E[9m,

input.c

@@ -484,9 +484,47 @@ keyboard_key(void *data, struct wl_keyboard *wl_keyboard, uint32_t serial,
     }
 
     else {
-                if (effective_mods & alt)
+        if (effective_mods & alt) {
+            /*
+             * When the alt modifier is pressed, we do one out of three things:
+             *
+             *  1. we prefix the output bytes with ESC
+             *  2. we set the 8:th bit in the output byte
+             *  3. we ignore the alt modifier
+             *
+             * #1 is configured with \E[?1036, and is on by default
+             *
+             * If #1 has been disabled, we use #2, *if* it's a single
+             * byte we're emitting. Since this is an UTF-8 terminal,
+             * we then UTF8-encode the 8-bit character. #2 is
+             * configured with \E[?1034, and is on by default.
+             *
+             * Lastly, if both #1 and #2 have been disabled, the alt
+             * modifier is ignored.
+             */
+            if (term->meta.esc_prefix) {
                 term_to_slave(term, "\x1b", 1);
+                term_to_slave(term, buf, count);
+            }
 
+            else if (term->meta.eight_bit && count == 1) {
+                const wchar_t wc = 0x80 | buf[0];
+
+                char utf8[8];
+                mbstate_t ps = {0};
+                size_t chars = wcrtomb(utf8, wc, &ps);
+
+                if (chars != (size_t)-1)
+                    term_to_slave(term, utf8, chars);
+                else
+                    term_to_slave(term, buf, count);
+            }
+
+            else {
+                /* Alt ignored */
+                term_to_slave(term, buf, count);
+            }
+        } else
             term_to_slave(term, buf, count);
     }
 

terminal.c

@@ -652,6 +652,10 @@ term_init(const struct config *conf, struct fdm *fdm, struct wayland *wayl,
         .normal = {.damage = tll_init(), .scroll_damage = tll_init()},
         .alt = {.damage = tll_init(), .scroll_damage = tll_init()},
         .grid = &term->normal,
+        .meta = {
+            .esc_prefix = true,
+            .eight_bit = true,
+        },
         .tab_stops = tll_init(),
         .wl = wayl,
         .render = {
@@ -1032,6 +1036,9 @@ term_reset(struct terminal *term, bool hard)
         selection_cancel(term);
     }
 
+    term->meta.esc_prefix = true;
+    term->meta.eight_bit = true;
+
     if (!hard)
         return;
 

terminal.h

@@ -283,6 +283,11 @@ struct terminal {
 
     struct font *fonts[4];
 
+    struct {
+        bool esc_prefix;
+        bool eight_bit;
+    } meta;
+
     tll(int) tab_stops;
 
     struct wayland *wl;