client/windows: fix SetClipboardViewer error handling rhbz#786554

MSDN says the following about SetClipboardViewer(): "If an error occurs or there
are no other windows in the clipboard viewer chain, the return value is NULL".
Seems like the buggy case was "no other windows in the clipboard viewer chain",
which explains the 3rd party clipboard manager workaround detailed in the bug
description.

It also seems like SetClipboardViewer() does not clear the error state on
succcess. Calling SetLastError(0) before SetClipboardViewer() seems to solves
this issue.

Since we could not reproduce the bug on our env, the customer has verified on
several of their systems that a private build resolved the issue.

1 files changed, 4 insertions, 3 deletions

diff --git a/client/windows/platform.cpp b/client/windows/platform.cpp
index 0f35a65f..223be1d7 100644
--- a/client/windows/platform.cpp
+++ b/client/windows/platform.cpp
@@ -236,6 +236,7 @@ static void create_message_wind()
 {
     WNDCLASSEX wclass;
     ATOM class_atom;
+    DWORD err;
 
     const LPCWSTR class_name = L"spicec_platform_wclass";
 
@@ -259,9 +260,9 @@ static void create_message_wind()
     if (!(platform_win = CreateWindow(class_name, L"", 0, 0, 0, 0, 0, NULL, NULL, instance, NULL))) {
         THROW("create message window failed");
     }
-
-    if (!(next_clipboard_viewer_win = SetClipboardViewer(platform_win)) && GetLastError()) {
-        THROW("set clipboard viewer failed");
+    SetLastError(0);
+    if (!(next_clipboard_viewer_win = SetClipboardViewer(platform_win)) && (err = GetLastError())) {
+        THROW("set clipboard viewer failed %u", err);
     }
     if (!(clipboard_event = CreateEvent(NULL, FALSE, FALSE, NULL))) {
         THROW("create clipboard event failed");