Release GIL while calling WebPAnimDecoderGetNext

docs/releasenotes/10.3.0.rst

@@ -79,3 +79,9 @@ Portable FloatMap (PFM) images
 
 Support has been added for reading and writing grayscale (Pf format)
 Portable FloatMap (PFM) files containing ``F`` data.
+
+Release GIL when fetching WebP frames
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Python's Global Interpreter Lock is now released when fetching WebP frames from
+the libwebp decoder.

src/_webp.c

@@ -448,11 +448,16 @@ PyObject *
 _anim_decoder_get_next(PyObject *self) {
     uint8_t *buf;
     int timestamp;
+    int ok;
     PyObject *bytes;
     PyObject *ret;
+    ImagingSectionCookie cookie;
     WebPAnimDecoderObject *decp = (WebPAnimDecoderObject *)self;
 
-    if (!WebPAnimDecoderGetNext(decp->dec, &buf, &timestamp)) {
+    ImagingSectionEnter(&cookie);
+    ok = WebPAnimDecoderGetNext(decp->dec, &buf, &timestamp);
+    ImagingSectionLeave(&cookie);
+    if (!ok) {
         PyErr_SetString(PyExc_OSError, "failed to read next frame");
         return NULL;
     }