input: implement VO dragging deadzone

DOCS/interface-changes/input-builtin-dragging.txt

@@ -0,0 +1 @@
+add `--input-builtin-dragging` option

DOCS/interface-changes/input-dragging-deadzone.txt

@@ -0,0 +1 @@
+add `--input-dragging-deadzone` option

DOCS/man/options.rst

@@ -4139,6 +4139,12 @@ Input
     option is applied only during (lib)mpv initialization, and if disabled then it
     will not be not possible to enable them later. May be useful to libmpv clients.
 
+``--input-builtin-dragging=<yes|no>``
+    Enable the built-in window-dragging behavior (default: yes). Setting it to no
+    disables the built-in dragging behavior. Note that unlike the ``window-dragging``
+    option, this option only affects VOs which support the ``begin-vo-dragging``
+    command, and does not disable window dragging initialized with the command.
+
 ``--input-cmdlist``
     Prints all commands that can be bound to keys.
 
@@ -4236,8 +4242,7 @@ Input
 
 ``--input-cursor=<yes|no>``
     Permit mpv to receive pointer events reported by the video output
-    driver. Necessary to use the OSC, or to select the buttons in DVD menus.
-    Support depends on the VO in use.
+    driver. Necessary to use the OSC. Support depends on the VO in use.
 
 ``--input-cursor-passthrough=<yes|no>``
     Tell the backend windowing system to allow pointer events to passthrough
@@ -4304,6 +4309,11 @@ Input
     for mouse key bindings and scripts which read mouse positions for platforms
     which do not support ``--native-touch=no`` (e.g. Wayland).
 
+``--input-dragging-deadzone=<N>``
+    Begin the built-in window dragging when the mouse moves outside a deadzone of
+    ``N`` pixels while the mouse button is being held down (default: 3). This only
+    affects VOs which support the ``begin-vo-dragging`` command.
+
 OSD
 ---
 

input/input.c

@@ -120,6 +120,12 @@ struct input_ctx {
     int last_doubleclick_key_down;
     double last_doubleclick_time;
 
+    // VO dragging state
+    bool dragging_button_down;
+    int mouse_drag_x, mouse_drag_y;
+    // Raw mouse position before transform
+    int mouse_raw_x, mouse_raw_y;
+
     // Mouse position on the consumer side (as command.c sees it)
     int mouse_x, mouse_y;
     int mouse_hover;  // updated on mouse-enter/leave
@@ -175,11 +181,13 @@ struct input_opts {
     // Autorepeat config (be aware of mp_input_set_repeat_info())
     int ar_delay;
     int ar_rate;
+    int dragging_deadzone;
     bool use_alt_gr;
     bool use_gamepad;
     bool use_media_keys;
     bool default_bindings;
     bool builtin_bindings;
+    bool builtin_dragging;
     bool enable_mouse_movements;
     bool vo_key_input;
     bool test;
@@ -197,6 +205,7 @@ const struct m_sub_options input_config = {
         {"input-cmdlist", OPT_PRINT(mp_print_cmd_list)},
         {"input-default-bindings", OPT_BOOL(default_bindings)},
         {"input-builtin-bindings", OPT_BOOL(builtin_bindings)},
+        {"input-builtin-dragging", OPT_BOOL(builtin_dragging)},
         {"input-test", OPT_BOOL(test)},
         {"input-doubleclick-time", OPT_INT(doubleclick_time),
          M_RANGE(0, 1000)},
@@ -207,6 +216,7 @@ const struct m_sub_options input_config = {
         {"input-media-keys", OPT_BOOL(use_media_keys)},
         {"input-preprocess-wheel", OPT_BOOL(preprocess_wheel)},
         {"input-touch-emulate-mouse", OPT_BOOL(touch_emulate_mouse)},
+        {"input-dragging-deadzone", OPT_INT(dragging_deadzone)},
 #if HAVE_SDL2_GAMEPAD
         {"input-gamepad", OPT_BOOL(use_gamepad)},
 #endif
@@ -219,11 +229,13 @@ const struct m_sub_options input_config = {
         .doubleclick_time = 300,
         .ar_delay = 200,
         .ar_rate = 40,
+        .dragging_deadzone = 3,
         .use_alt_gr = true,
         .enable_mouse_movements = true,
         .use_media_keys = true,
         .default_bindings = true,
         .builtin_bindings = true,
+        .builtin_dragging = true,
         .vo_key_input = true,
         .allow_win_drag = true,
         .preprocess_wheel = true,
@@ -733,6 +745,7 @@ static void feed_key(struct input_ctx *ictx, int code, double scale,
     if (code == MP_INPUT_RELEASE_ALL) {
         MP_TRACE(ictx, "release all\n");
         release_down_cmd(ictx, false);
+        ictx->dragging_button_down = false;
         return;
     }
     if (code == MP_TOUCH_RELEASE_ALL) {
@@ -771,13 +784,22 @@ static void feed_key(struct input_ctx *ictx, int code, double scale,
                           1, 1);
         } else if (code == MP_MBTN_LEFT) {
             // This is a mouse left botton down event which isn't part of a doubleclick.
-            // Initialize vo dragging in this case.
-            mp_cmd_t *cmd = mp_input_parse_cmd(ictx, bstr0("begin-vo-dragging"), "<internal>");
-            queue_cmd(ictx, cmd);
+            // Mark the dragging mouse button down in this case.
+            ictx->dragging_button_down = true;
+            // Store the current mouse position for deadzone handling.
+            ictx->mouse_drag_x = ictx->mouse_raw_x;
+            ictx->mouse_drag_y = ictx->mouse_raw_y;
         }
         ictx->last_doubleclick_key_down = code;
         ictx->last_doubleclick_time = now;
     }
+    if (code & MP_KEY_STATE_UP) {
+        code &= ~MP_KEY_STATE_UP;
+        if (code == MP_MBTN_LEFT) {
+            // This is a mouse left botton up event. Mark the dragging mouse button up.
+            ictx->dragging_button_down = false;
+        }
+    }
 }
 
 void mp_input_put_key(struct input_ctx *ictx, int code)
@@ -853,9 +875,11 @@ static void set_mouse_pos(struct input_ctx *ictx, int x, int y)
 {
     MP_TRACE(ictx, "mouse move %d/%d\n", x, y);
 
-    if (ictx->mouse_vo_x == x && ictx->mouse_vo_y == y) {
+    if (ictx->mouse_raw_x == x && ictx->mouse_raw_y == y) {
         return;
     }
+    ictx->mouse_raw_x = x;
+    ictx->mouse_raw_y = y;
 
     if (ictx->mouse_mangle) {
         struct mp_rect *src = &ictx->mouse_src;
@@ -894,6 +918,22 @@ static void set_mouse_pos(struct input_ctx *ictx, int x, int y)
             queue_cmd(ictx, cmd);
         }
     }
+
+    bool mouse_outside_dragging_deadzone =
+        abs(ictx->mouse_raw_x - ictx->mouse_drag_x) >= ictx->opts->dragging_deadzone ||
+        abs(ictx->mouse_raw_y - ictx->mouse_drag_y) >= ictx->opts->dragging_deadzone;
+    if (ictx->dragging_button_down && mouse_outside_dragging_deadzone &&
+        ictx->opts->builtin_dragging)
+    {
+        // Begin built-in VO dragging if the mouse moves while the dragging button is down.
+        ictx->dragging_button_down = false;
+        // Prevent activation of MBTN_LEFT key binding if VO dragging begins.
+        release_down_cmd(ictx, true);
+        // Prevent activation of MBTN_LEFT_DBL if VO dragging begins.
+        ictx->last_doubleclick_time = 0;
+        mp_cmd_t *drag_cmd = mp_input_parse_cmd(ictx, bstr0("begin-vo-dragging"), "<internal>");
+        queue_cmd(ictx, drag_cmd);
+    }
 }
 
 void mp_input_set_mouse_pos_artificial(struct input_ctx *ictx, int x, int y)