cocoa-cb: re-enable wid (NSView) embedding on macOS for libmpv use

In version 0.37, support for the old cocoa backend has been dropped,
which unfortunately also removed the ability of embedding mpv in
native applications by specifying a wid - which is still working for all
other platforms.

This PR aims to remedy that situation by leveraging the existing
cocoa-cb implementation which already had just about everything that it
takes and it has been merely about gluing loose ends together and
omitting those parts that are specific to standalone application use,
like NSApplication and NSWindow.

Author: softworkz

DOCS/man/options.rst

@@ -3763,6 +3763,21 @@ Window
     specially, and mpv will draw on top of the desktop wallpaper and below
     desktop icons.
 
+    On macOS/Cocoa, the ID is interpreted as ``NSView*``. Pass it as value cast
+    to ``intptr_t``. mpv will create its own sub-view.
+    The following constraints apply:
+      - This is only supported with libmpv. Specifying a wid with mpv cli will
+        and with an error
+      - The supplied NSView pointer must be from the same process into which
+        libmpv is loaded. Since macOS does not support cross-process window
+        access, attempts trying to do so will always crash
+      - The process needs to have an NSApplication with event loop running
+        on the main thread
+      - The wid must be set after mpv_create() and before mpv_initialize()
+        and cannot be changed afterwards
+      - The only supported vo is libmpv, which will be automatically set when
+        a wid is provided
+
     On Android, the ID is interpreted as ``android.view.Surface``. Pass it as a
     value cast to ``intptr_t``. Use with ``--vo=mediacodec_embed`` and
     ``--hwdec=mediacodec`` for direct rendering using MediaCodec, or with

osdep/mac/app_bridge.h

@@ -107,6 +107,7 @@ void cocoa_uninit_media_keys(void);
 void cocoa_set_input_context(struct input_ctx *input_context);
 void cocoa_set_mpv_handle(struct mpv_handle *ctx);
 void cocoa_init_cocoa_cb(void);
+void cocoa_init_embedded_view(int64_t wid);
 // multithreaded wrapper for mpv_main
 int cocoa_main(int argc, char *argv[]);
 

osdep/mac/app_bridge.m

@@ -161,6 +161,11 @@ void cocoa_init_cocoa_cb(void)
     [[AppHub shared] initCocoaCb];
 }
 
+void cocoa_init_embedded_view(int64_t wid)
+{
+[[AppHub shared] initCocoaCbWithView:(__bridge NSView *)(void *)wid];
+}
+
 int cocoa_main(int argc, char *argv[])
 {
     return [(Application *)[Application sharedApplication] main:argc :argv];

osdep/mac/app_hub.swift

@@ -51,10 +51,13 @@ class AppHub: NSObject {
     }
 
     @objc func initMpv(_ mpv: OpaquePointer) {
+
+        log.log = mp_log_new(nil, mp_client_get_log(mpv), "app")
+        log.verbose("AppHub: initMpv enter")
+
         event = EventHelper(self, mpv)
         if let mpv = event?.mpv {
             self.mpv = mpv
-            log.log = mp_log_new(nil, mp_client_get_log(mpv), "app")
             option = OptionHelper(UnsafeMutablePointer(mpv), mp_client_get_global(mpv))
             input.option = option
             DispatchQueue.main.sync { menu = MenuBar(self) }
@@ -76,6 +79,7 @@ class AppHub: NSObject {
     }
 
     @objc func initInput(_ input: OpaquePointer?) {
+        if !isApplication { return }
         log.verbose("Initialising Input")
         self.input.signal(input: input)
     }
@@ -90,6 +94,15 @@ class AppHub: NSObject {
 #endif
     }
 
+    @objc func initCocoaCbWithView(_ view: NSView) {
+#if HAVE_MACOS_COCOA_CB
+        log.verbose("Initialising CocoaCB (embedded view)")
+        DispatchQueue.main.sync {
+            self.cocoaCb = CocoaCB(mpv_create_client(mpv, "cocoacb"), view)
+        }
+#endif
+    }
+
     @objc func startRemote() {
 #if HAVE_MACOS_MEDIA_PLAYER
         log.verbose("Starting RemoteCommandCenter")

osdep/mac/event_helper.swift

@@ -71,11 +71,6 @@ class EventHelper {
     var events: [String: [Int: EventSubscriber]] = [:]
 
     init?(_ appHub: AppHub, _ mpv: OpaquePointer) {
-        if !appHub.isApplication {
-            mpv_destroy(mpv)
-            return nil
-        }
-
         self.appHub = appHub
         self.mpv = mpv
         mpv_set_wakeup_callback(mpv, wakeup, TypeHelper.bridge(obj: self))

player/main.c

@@ -42,6 +42,7 @@
 #include "common/codecs.h"
 #include "common/encode.h"
 #include "options/m_config.h"
+#include "options/m_config_frontend.h"
 #include "options/m_option.h"
 #include "options/m_property.h"
 #include "common/common.h"
@@ -366,6 +367,25 @@ int mp_initialize(struct MPContext *mpctx, char **options)
             return r == M_OPT_EXIT ? 1 : -1;
     }
 
+#if HAVE_COCOA
+
+    if (mpctx->is_cli && opts->vo->WinID > 0)
+    {
+        MP_FATAL(mpctx, "On macOS, window embedding via 'wid' parameter is not supported from the CLI.\n");
+        return -1;
+    }
+
+    if (!mpctx->is_cli && opts->vo->WinID > 0)
+    {
+        MP_INFO(mpctx, "A 'wid' for window embedding is specified. Setting vo=libmpv, which is the only supported way on macOS.\n");
+
+        int r = m_config_set_option_cli(mpctx->mconfig, bstr0("vo"), bstr0("libmpv"), 0);
+        if (r < 0) {
+            MP_WARN(mpctx, "Failed to force vo=libmpv for wid embedding (err=%d)\n", r);
+        }
+    }
+#endif
+
     if (opts->operation_mode == 1) {
         m_config_set_profile(mpctx->mconfig, "builtin-pseudo-gui",
                              M_SETOPT_NO_OVERWRITE);
@@ -410,8 +430,10 @@ int mp_initialize(struct MPContext *mpctx, char **options)
     MP_STATS(mpctx, "start init");
 
 #if HAVE_COCOA
-    mpv_handle *ctx = mp_new_client(mpctx->clients, "mac");
-    cocoa_set_mpv_handle(ctx);
+    if (mpctx->is_cli || opts->vo->WinID > 0) {
+        mpv_handle *ctx = mp_new_client(mpctx->clients, "mac");
+        cocoa_set_mpv_handle(ctx);
+    }
 #endif
 
 #if HAVE_WIN32_SMTC