command: add begin-vo-dragging command

This command initializes a vo dragging request for VOs that implement
the new VOCTRL_BEGIN_DRAGGING voctrl. This allows scripts to begin vo
dragging for any button press event.

4 files changed, 23 insertions, 0 deletions

diff --git a/DOCS/interface-changes.rst b/DOCS/interface-changes.rst
index 61a60d516a..2abf99ed93 100644
--- a/DOCS/interface-changes.rst
+++ b/DOCS/interface-changes.rst
@@ -27,6 +27,7 @@ Interface changes
 ::
 
  --- mpv 0.38.0 ---
+    - add `begin-vo-dragging` command
     - add `--volume-gain`, `--volume-gain-min`, and `--volume-gain-max` options
     - add `current-gpu-context` property
     - add `--secondary-sub-ass-override` option
diff --git a/DOCS/man/input.rst b/DOCS/man/input.rst
index 84f64cf5c7..f3e222d8c1 100644
--- a/DOCS/man/input.rst
+++ b/DOCS/man/input.rst
@@ -1478,6 +1478,13 @@ Input Commands that are Possibly Subject to Change
     This command has an even more uncertain future than ``ab-loop-dump-cache``
     and might disappear without replacement if the author decides it's useless.
 
+``begin-vo-dragging``
+    Begin window dragging if supported by the current VO. This command should
+    only be called while a mouse button is being pressed, otherwise it will
+    be ignored. The exact effect of this command depends on the VO implementation
+    of window dragging. For example, on Windows only the left mouse button can
+    begin window dragging, while X11 and Wayland allow other mouse buttons.
+
 Undocumented commands: ``ao-reload`` (experimental/internal).
 
 List of events
diff --git a/player/command.c b/player/command.c
index 2690fd4a27..e1de32be25 100644
--- a/player/command.c
+++ b/player/command.c
@@ -6502,6 +6502,16 @@ static void cmd_dump_cache_ab(void *p)
                  cmd->args[0].v.s);
 }
 
+static void cmd_begin_vo_dragging(void *p)
+{
+    struct mp_cmd_ctx *cmd = p;
+    struct MPContext *mpctx = cmd->mpctx;
+    struct vo *vo = mpctx->video_out;
+
+    if (vo)
+        vo_control(vo, VOCTRL_BEGIN_DRAGGING, NULL);
+}
+
 /* This array defines all known commands.
  * The first field the command name used in libmpv and input.conf.
  * The second field is the handler function (see mp_cmd_def.handler and
@@ -6970,6 +6980,8 @@ const struct mp_cmd_def mp_cmds[] = {
 
     { "ab-loop-align-cache", cmd_align_cache_ab },
 
+    { "begin-vo-dragging", cmd_begin_vo_dragging },
+
     {0}
 };
 
diff --git a/video/out/vo.h b/video/out/vo.h
index 2ed971c146..3879d024e7 100644
--- a/video/out/vo.h
+++ b/video/out/vo.h
@@ -122,6 +122,9 @@ enum mp_voctrl {
 
     /* private to vo_gpu and vo_gpu_next */
     VOCTRL_EXTERNAL_RESIZE,
+
+    // Begin VO dragging.
+    VOCTRL_BEGIN_DRAGGING,
 };
 
 // Helper to expose what kind of content is currently playing to the VO.