Update ANativeWindow_getNextFrameId docs to specify API contract
We rely on frame ids starting at 1, with 0 being invalid/uninitialize, and incrementing for each frame chronologically for as long as the underlying surface doesn't change.
Test: N/A
Change-Id: I90e9593b7ae852bcc90c5c17bc4969c7d827b2d9
diff --git a/libs/nativewindow/include/system/window.h b/libs/nativewindow/include/system/window.h
index 2038632..0bc2b5d 100644
--- a/libs/nativewindow/include/system/window.h
+++ b/libs/nativewindow/include/system/window.h
@@ -1089,7 +1089,10 @@
/**
* Retrieves an identifier for the next frame to be queued by this window.
*
- * \return the next frame id.
+ * Frame ids start at 1 and are incremented on each new frame until the underlying surface changes,
+ * in which case the frame id is reset to 1.
+ *
+ * \return the next frame id (0 being uninitialized).
*/
static inline uint64_t ANativeWindow_getNextFrameId(ANativeWindow* window) {
uint64_t value;