win32: UTF8 console input: don't spin the CPU

This is a regression from ec99f03ae which changed Read into Peek
in order to keep the record at the console queue.

However, it failed to take into account that as a result, if no input
is pending, that readConsoleInput_utf8 now returns immediately without
waiting for input - unlike ReadConsoleInput.

Other than incorrectly returning a FALSE value in such case, it also
caused a busy-wait loop of windows_read_key and high CPU usage.

Fix that by waiting till there's input before the peek. This should
make it just like ReadConsoleInput - which idles till there's input.

1 files changed, 5 insertions, 3 deletions

diff --git a/win32/winansi.c b/win32/winansi.c
index d85b6de23..67fcc17d3 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -1314,9 +1314,11 @@ BOOL readConsoleInput_utf8(HANDLE h, INPUT_RECORD *r, DWORD len, DWORD *got)
         if (u8pos == u8len) {
                 DWORD codepoint;
 
-                // peek rather than read to keep the last processed record at
-                // the console queue until we deliver all of its products, so
-                // that WaitForSingleObject(handle) shows there's data ready.
+                // wait-and-peek rather than read to keep the last processed record
+                // at the console queue until we deliver all of its products, so
+                // that external WaitForSingleObject(h) shows there's data ready.
+                if (WaitForSingleObject(h, INFINITE) != WAIT_OBJECT_0)
+                        return FALSE;
                 if (!PeekConsoleInputW(h, r, 1, got))
                         return FALSE;
                 if (*got == 0)