input: handle multi-combinations as key sequences

The input code always supported combinations of multiple keys (even in
MPlayer, although there the code was active really only for mouse
buttons). This was arcance and also made the code more complicated. I
only know of a single person who ever made use of this feature.

Remove this feature, and repurpose some of the support code (e.g.
parsing, display of key combinations, etc.) to handle such multi-
combinations as sequences, instead of keys to be pressed at the same
time. This is much simpler and implements the feature requested in
github issue #718.

This commit will probably cause a bunch of regressions, since the input
handling code has some weird corner cases. I couldn't find any problems
when testing, though.

2 files changed, 60 insertions, 64 deletions

diff --git a/DOCS/man/en/input.rst b/DOCS/man/en/input.rst
index 97c42ed811..36a19e9479 100644
--- a/DOCS/man/en/input.rst
+++ b/DOCS/man/en/input.rst
@@ -52,6 +52,16 @@ You can bind multiple commands to one key. For example:
 
 | a show_text "command 1" ; show_text "command 2"
 
+It's also possible to bind a command to a sequence of keys:
+
+| a-b-c show_text "command run after a, b, c have been pressed"
+
+(This is not shown in the general command syntax.)
+
+If ``a`` or ``a-b`` or ``b`` are already bound, this will run all commands. It
+doesn't delay key bindings, and it simply considers the past key history on
+any key press.
+
 List of Input Commands
 ----------------------
 
diff --git a/input/input.c b/input/input.c
index 91f9eecb33..39644fd723 100644
--- a/input/input.c
+++ b/input/input.c
@@ -137,6 +137,8 @@ struct input_ctx {
     // repeated slow commands piling up)
     int key_fifo_size;
 
+    // history of key downs - the newest is in position 0
+    int key_history[MP_MAX_KEY_DOWN];
     // these are the keys currently down
     int key_down[MP_MAX_KEY_DOWN];
     unsigned int num_key_down;
@@ -287,8 +289,6 @@ static struct mp_cmd *queue_peek_tail(struct cmd_queue *queue)
     return cur;
 }
 
-static bool bind_matches_key(struct cmd_bind *bind, int n, const int *keys);
-
 static void append_bind_info(struct input_ctx *ictx, char **pmsg,
                              struct cmd_bind *bind)
 {
@@ -309,9 +309,9 @@ static void append_bind_info(struct input_ctx *ictx, char **pmsg,
     *pmsg = msg;
 }
 
-static mp_cmd_t *handle_test(struct input_ctx *ictx, int n, int *keys)
+static mp_cmd_t *handle_test(struct input_ctx *ictx, int code)
 {
-    char *key_buf = mp_input_get_key_combo_name(keys, n);
+    char *key_buf = mp_input_get_key_combo_name(&code, 1);
     char *msg = talloc_asprintf(NULL, "Key %s is bound to:\n", key_buf);
     talloc_free(key_buf);
 
@@ -320,7 +320,7 @@ static mp_cmd_t *handle_test(struct input_ctx *ictx, int n, int *keys)
          bs; bs = bs->next)
     {
         for (int i = 0; i < bs->num_binds; i++) {
-            if (bind_matches_key(&bs->binds[i], n, keys)) {
+            if (bs->binds[i].num_keys && bs->binds[i].keys[0] == code) {
                 count++;
                 msg = talloc_asprintf_append(msg, "%d. ", count);
                 append_bind_info(ictx, &msg, &bs->binds[i]);
@@ -377,23 +377,41 @@ static struct cmd_bind_section *get_bind_section(struct input_ctx *ictx,
     return bind_section;
 }
 
+static void key_buf_add(int *buf, int code)
+{
+    for (int n = MP_MAX_KEY_DOWN - 1; n > 0; n--)
+        buf[n] = buf[n - 1];
+    buf[0] = code;
+}
+
 static struct cmd_bind *find_bind_for_key_section(struct input_ctx *ictx,
-                                                  char *section,
-                                                  int num_keys, int *keys)
+                                                  char *section, int code)
 {
     struct cmd_bind_section *bs = get_bind_section(ictx, bstr0(section));
 
-    if (!num_keys || !bs->num_binds)
+    if (!bs->num_binds)
         return NULL;
 
+    int keys[MP_MAX_KEY_DOWN];
+    memcpy(keys, ictx->key_history, sizeof(keys));
+    key_buf_add(keys, code);
+
     // Prefer user-defined keys over builtin bindings
     for (int builtin = 0; builtin < 2; builtin++) {
         if (builtin && !ictx->default_bindings)
             break;
         for (int n = 0; n < bs->num_binds; n++) {
-            if (bs->binds[n].is_builtin == (bool)builtin &&
-                bind_matches_key(&bs->binds[n], num_keys, keys))
-                return &bs->binds[n];
+            if (bs->binds[n].is_builtin == (bool)builtin) {
+                struct cmd_bind *b = &bs->binds[n];
+                // we have: keys=[key2 key1 keyX ...]
+                // and: b->keys=[key1 key2] (and may be just a prefix)
+                for (int i = 0; i < b->num_keys; i++) {
+                    if (b->keys[i] != keys[b->num_keys - 1 - i])
+                        goto skip;
+                }
+                return b;
+            skip: ;
+            }
         }
     }
     return NULL;
@@ -408,23 +426,13 @@ static bool any_mouse_buttons_down(int num_keys, int *keys)
     return false;
 }
 
-static bool depends_on_mouse_pos(int num_keys, int *keys)
-{
-    for (int n = 0; n < num_keys; n++) {
-        if (MP_KEY_DEPENDS_ON_MOUSE_POS(keys[n]))
-            return true;
-    }
-    return false;
-}
-
 static struct cmd_bind *find_any_bind_for_key(struct input_ctx *ictx,
-                                              char *force_section,
-                                              int n, int *keys)
+                                              char *force_section, int code)
 {
     if (force_section)
-        return find_bind_for_key_section(ictx, force_section, n, keys);
+        return find_bind_for_key_section(ictx, force_section, code);
 
-    bool use_mouse = depends_on_mouse_pos(n, keys);
+    bool use_mouse = MP_KEY_DEPENDS_ON_MOUSE_POS(code);
     // Check global state, because MOUSE_MOVE in particular does not include
     // the global state in n/keys.
     bool mouse_down = any_mouse_buttons_down(ictx->num_key_down, ictx->key_down);
@@ -433,7 +441,7 @@ static struct cmd_bind *find_any_bind_for_key(struct input_ctx *ictx,
     // exclusively (regardless of the active section stack order).
     if (use_mouse && mouse_down) {
         struct cmd_bind *bind =
-            find_bind_for_key_section(ictx, ictx->mouse_section, n, keys);
+            find_bind_for_key_section(ictx, ictx->mouse_section, code);
         if (bind)
             return bind;
     }
@@ -441,7 +449,7 @@ static struct cmd_bind *find_any_bind_for_key(struct input_ctx *ictx,
     struct cmd_bind *best_bind = NULL;
     for (int i = ictx->num_active_sections - 1; i >= 0; i--) {
         struct active_section *s = &ictx->active_sections[i];
-        struct cmd_bind *bind = find_bind_for_key_section(ictx, s->name, n, keys);
+        struct cmd_bind *bind = find_bind_for_key_section(ictx, s->name, code);
         if (bind) {
             struct cmd_bind_section *bs = bind->owner;
             if (!use_mouse || (bs->mouse_area_set && test_rect(&bs->mouse_area,
@@ -460,24 +468,17 @@ static struct cmd_bind *find_any_bind_for_key(struct input_ctx *ictx,
 }
 
 static mp_cmd_t *get_cmd_from_keys(struct input_ctx *ictx, char *force_section,
-                                   int n, int *keys)
+                                   int code)
 {
     if (ictx->test)
-        return handle_test(ictx, n, keys);
-
-    struct cmd_bind *cmd = find_any_bind_for_key(ictx, force_section, n, keys);
-    if (cmd == NULL && n > 1) {
-        // Hitting two keys at once, and if there's no binding for this
-        // combination, the key hit last should be checked.
-        cmd = find_any_bind_for_key(ictx, force_section, 1, (int[]){keys[n - 1]});
-    }
+        return handle_test(ictx, code);
 
+    struct cmd_bind *cmd = find_any_bind_for_key(ictx, force_section, code);
     if (cmd == NULL) {
         int msgl = MSGL_WARN;
-        if (n == 1 && (keys[0] == MP_KEY_MOUSE_MOVE ||
-                       keys[0] == MP_KEY_MOUSE_LEAVE))
+        if (code == MP_KEY_MOUSE_MOVE || code == MP_KEY_MOUSE_LEAVE)
             msgl = MSGL_DEBUG;
-        char *key_buf = mp_input_get_key_combo_name(keys, n);
+        char *key_buf = mp_input_get_key_combo_name(&code, 1);
         MP_MSG(ictx, msgl, "No bind found for key '%s'.\n", key_buf);
         talloc_free(key_buf);
         return NULL;
@@ -486,13 +487,13 @@ static mp_cmd_t *get_cmd_from_keys(struct input_ctx *ictx, char *force_section,
     if (ret) {
         ret->input_section = cmd->owner->section;
         if (mp_msg_test(ictx->log, MSGL_DEBUG)) {
-            char *keyname = mp_input_get_key_combo_name(keys, n);
+            char *keyname = mp_input_get_key_combo_name(&code, 1);
             MP_DBG(ictx, "key '%s' -> '%s' in '%s'\n",
                    keyname, cmd->cmd, ret->input_section);
             talloc_free(keyname);
         }
     } else {
-        char *key_buf = mp_input_get_key_combo_name(keys, n);
+        char *key_buf = mp_input_get_key_combo_name(&code, 1);
         MP_ERR(ictx, "Invalid command for bound key '%s': '%s'\n",
                key_buf, cmd->cmd);
         talloc_free(key_buf);
@@ -503,7 +504,7 @@ static mp_cmd_t *get_cmd_from_keys(struct input_ctx *ictx, char *force_section,
 static void update_mouse_section(struct input_ctx *ictx)
 {
     struct cmd_bind *bind =
-        find_any_bind_for_key(ictx, NULL, 1, (int[]){MP_KEY_MOUSE_MOVE});
+        find_any_bind_for_key(ictx, NULL, MP_KEY_MOUSE_MOVE);
 
     char *new_section = bind ? bind->owner->section : "default";
 
@@ -513,8 +514,7 @@ static void update_mouse_section(struct input_ctx *ictx)
     if (strcmp(old, ictx->mouse_section) != 0) {
         MP_DBG(ictx, "input: switch section %s -> %s\n",
                old, ictx->mouse_section);
-        struct mp_cmd *cmd =
-            get_cmd_from_keys(ictx, old, 1, (int[]){MP_KEY_MOUSE_LEAVE});
+        struct mp_cmd *cmd = get_cmd_from_keys(ictx, old, MP_KEY_MOUSE_LEAVE);
         if (cmd)
             queue_add_tail(&ictx->cmd_queue, cmd);
         ictx->got_new_events = true;
@@ -631,7 +631,8 @@ static void interpret_key(struct input_ctx *ictx, int code, double scale)
         update_mouse_section(ictx);
         ictx->last_key_down = mp_time_us();
         ictx->ar_state = 0;
-        cmd = get_cmd_from_keys(ictx, NULL, ictx->num_key_down, ictx->key_down);
+        cmd = get_cmd_from_keys(ictx, NULL, code & ~MP_KEY_STATE_DOWN);
+        key_buf_add(ictx->key_history, code & ~MP_KEY_STATE_DOWN);
         if (cmd && should_drop_cmd(ictx, cmd)) {
             ictx->num_key_down--;
             talloc_free(cmd);
@@ -643,7 +644,7 @@ static void interpret_key(struct input_ctx *ictx, int code, double scale)
         ictx->current_down_cmd_need_release = false;
     } else if (code & MP_KEY_STATE_UP) {
         if (key_was_down) {
-            remove_key_down(ictx, code);
+            remove_key_down(ictx, code & ~MP_KEY_STATE_DOWN);
             release_down_cmd(ictx, false);
         }
         update_mouse_section(ictx);
@@ -654,22 +655,8 @@ static void interpret_key(struct input_ctx *ictx, int code, double scale)
             MP_WARN(ictx, "Mixing key presses and up/down.\n");
         }
         update_mouse_section(ictx);
-        // Add temporarily (include ongoing down/up events)
-        int num_key_down = ictx->num_key_down;
-        int key_down[MP_MAX_KEY_DOWN];
-        memcpy(key_down, ictx->key_down, num_key_down * sizeof(int));
-        // Assume doubleclick events never use down/up, while button events do
-        if (MP_KEY_IS_MOUSE_BTN_DBL(code)) {
-            // Don't emit "MOUSE_BTN0+MOUSE_BTN0_DBL", just "MOUSE_BTN0_DBL"
-            int btn = code - MP_MOUSE_BTN0_DBL + MP_MOUSE_BTN0;
-            if (!num_key_down || key_down[num_key_down - 1] != btn)
-                return;
-            key_down[num_key_down - 1] = code;
-        } else {
-            key_down[num_key_down] = code;
-            num_key_down++;
-        }
-        cmd = get_cmd_from_keys(ictx, NULL, num_key_down, key_down);
+        cmd = get_cmd_from_keys(ictx, NULL, code);
+        key_buf_add(ictx->key_history, code);
         if (cmd && should_drop_cmd(ictx, cmd)) {
             talloc_free(cmd);
             return;
@@ -705,7 +692,7 @@ static void mp_input_feed_key(struct input_ctx *ictx, int code, double scale)
     }
     if (code == MP_KEY_MOUSE_LEAVE) {
         update_mouse_section(ictx);
-        struct mp_cmd *cmd = get_cmd_from_keys(ictx, NULL, 1, (int[]){code});
+        struct mp_cmd *cmd = get_cmd_from_keys(ictx, NULL, code);
         if (cmd)
             queue_add_tail(&ictx->cmd_queue, cmd);
         ictx->got_new_events = true;
@@ -767,8 +754,7 @@ void mp_input_set_mouse_pos(struct input_ctx *ictx, int x, int y)
     ictx->mouse_vo_y = y;
 
     update_mouse_section(ictx);
-    struct mp_cmd *cmd =
-        get_cmd_from_keys(ictx, NULL, 1, (int[]){MP_KEY_MOUSE_MOVE});
+    struct mp_cmd *cmd = get_cmd_from_keys(ictx, NULL, MP_KEY_MOUSE_MOVE);
     if (!cmd)
         cmd = mp_input_parse_cmd(ictx, bstr0("ignore"), "<internal>");