MuMu 外壳在第一帧发布前照旧交出尺寸和黑图

README.md

@@ -46,13 +46,15 @@ if (modavd_open(&p, &h) == MODAVD_OK) {
     modavd_capture(h, 0, MODAVD_FMT_BGR, 0, NULL, 0, &info);          /* 先问尺寸 */
     void* buf = malloc((size_t)info.stride * info.height);
     int rc = modavd_capture(h, 0, MODAVD_FMT_BGR, 0, buf, (size_t)info.stride * info.height, &info);
-    /* rc: MODAVD_OK；MODAVD_E_NOT_READY 还没有画面；MODAVD_E_RESIZED 要重新 open */
+    /* rc: MODAVD_OK；MODAVD_E_NOT_READY 还没有画面（刚开流、第一帧没到时也是这样，稍后再调）；
+     *     MODAVD_E_RESIZED 要重新 open */
     free(buf);
     modavd_close(h);
 }
 ```
 
 - 所有函数返回 `MODAVD_OK`（0）或负的 `MODAVD_E_*`。
+- Linux、macOS 上 `modavd_open` 默认先经控制台开流（`screenrecord webrtc start`），所以控制台要连得上、鉴权要能过；模拟器退出后旧的共享内存可能还在，不开流会拿到上次的旧画面。确定映射属于当前实例而且已经在开流的，可以带 `MODAVD_OPEN_NO_START` 跳过控制台。
 - 结构体开头是 `size`，以后加字段不破坏旧的调用方。
 - `modavd_api_version()` 每加一个函数就加一，函数从不删。`modavd_capabilities()` 说明这个实例能做哪些事。
 - `modavd_frame_info` 里有帧号和时间戳：调用方可以据此跳过重复帧，也能分清「画面没变」和「模拟器卡住」。

shim/mumu_shim.c

@@ -203,11 +203,13 @@ EXPORT int nemu_capture_display(int handle, unsigned int display_id, int buffer_
     memset(&info, 0, sizeof(info));
     info.size = sizeof(info);
     size_t size = (buffer_size > 0 && pixels) ? (size_t)buffer_size : 0;
-    /* mx_copy_frame, not modavd_capture: when a new frame arrived during every
-     * copy, hand the last copy over as the DLL this replaces did, instead of
-     * failing (MaaCore would drop to its screencap speed test again). */
-    int rc = mx_copy_frame(&h->shm, MODAVD_FMT_RGBA, MODAVD_CAPTURE_BOTTOM_UP, h->simd, size ? pixels : NULL, size,
-                           &info);
+    /* mx_copy_frame, not modavd_capture: as the DLL this replaces did, report
+     * the size and a black frame before the first frame is published, and hand
+     * the last copy over when a new frame arrived during every copy, instead
+     * of failing (MaaCore would give up on this path at connect, or drop to its
+     * screencap speed test again). */
+    int rc = mx_copy_frame(&h->shm, MODAVD_FMT_RGBA, MODAVD_CAPTURE_BOTTOM_UP | MX_CAPTURE_UNPUBLISHED, h->simd,
+                           size ? pixels : NULL, size, &info);
     if (rc == MX_TORN) {
         rc = MODAVD_OK;
     }

src/core.c

@@ -311,7 +311,7 @@ int mx_copy_frame(const mx_shm* shm, uint32_t format, uint32_t flags, int simd,
     info->timestamp_us = vi->ts_us;
     /* Dimensions are set before the first frame is published. The counter
      * can wrap to zero, and a published static frame need not advance. */
-    if (w == 0 || h == 0 || info->timestamp_us == 0) {
+    if (w == 0 || h == 0 || (info->timestamp_us == 0 && !(flags & MX_CAPTURE_UNPUBLISHED))) {
         return MODAVD_E_NOT_READY;
     }
     if (MX_HEADER_SIZE + (uint64_t)w * h * 4 > shm->size) {
@@ -356,7 +356,7 @@ int modavd_capture(modavd_handle h, int display, uint32_t format, uint32_t flags
     if (display != 0) {
         return MODAVD_E_UNSUPPORTED;
     }
-    int rc = mx_copy_frame(&h->shm, format, flags, h->simd, buf, buf_size, info);
+    int rc = mx_copy_frame(&h->shm, format, flags & ~MX_CAPTURE_UNPUBLISHED, h->simd, buf, buf_size, info);
     if (rc == MX_TORN) {
         mx_log(MODAVD_LOG_WARN, "port=%d: a new frame arrived during each of %d copies", h->console_port,
                MX_MAX_COPY_ATTEMPTS);

src/mx_internal.h

@@ -38,6 +38,13 @@ typedef struct mx_video_info {
  * DLL it replaces did. */
 #define MX_TORN 1
 
+/* mx_copy_frame() flag, internal only (modavd_capture() clears it): copy the
+ * frame even if the emulator has not published one yet (timestamp 0). The
+ * region then holds the size and a black frame. The MuMu-shaped shim uses
+ * it, as the DLL it replaces did: a failed capture makes MaaCore give up on
+ * this path or rerun its screencap speed test. */
+#define MX_CAPTURE_UNPUBLISHED (1u << 31)
+
 /* ---- log.c ---- */
 void mx_log(int level, const char* fmt, ...)
 #if defined(__GNUC__)

tests/test_core.c

@@ -232,6 +232,13 @@ static void test_capture_before_first_frame(void)
                 CHECK_EQ(buf[i], 0xA5);
             }
         }
+        /* The shim's internal flag is not part of the public API. */
+        CHECK_EQ(modavd_capture(h, 0, MODAVD_FMT_BGRA, MX_CAPTURE_UNPUBLISHED, buf, sizeof(buf), &info),
+                 MODAVD_E_NOT_READY);
+        /* The shim's own call copies the unpublished frame. */
+        CHECK_EQ(mx_copy_frame(&h->shm, MODAVD_FMT_BGRA, MX_CAPTURE_UNPUBLISHED, 0, buf, sizeof(buf), &info),
+                 MODAVD_OK);
+        CHECK_EQ(info.timestamp_us, 0);
 
         /* A counter may wrap to zero. A published, unchanged black frame is valid. */
         vi->ts_us = 123456789ull;

tests/test_shim.c

@@ -96,6 +96,17 @@ int main(int argc, char** argv)
     CHECK(nemu_capture_display(handle, 0, (int)size, &cw, &ch, buf) == -2);
     fake_frame_set_size(&f, w, h);
 
+    /* Started but not published yet: the size and the frame as they are, like
+     * the DLL this replaces; MaaCore's connect asks for the size right away. */
+    mx_video_info* vi = (mx_video_info*)f.view;
+    uint64_t ts = vi->ts_us;
+    vi->ts_us = 0;
+    cw = ch = 0;
+    CHECK(nemu_capture_display(handle, 0, 0, &cw, &ch, NULL) == 0);
+    CHECK(cw == (int)w && ch == (int)h);
+    CHECK(nemu_capture_display(handle, 0, (int)size, &cw, &ch, buf) == 0);
+    vi->ts_us = ts;
+
     nemu_disconnect(handle);
     CHECK(nemu_capture_display(handle, 0, 0, &cw, &ch, NULL) == -1);
     free(buf);