ui/win32-kbd-hook: handle AltGr in a hook procedure

Import win32 keyboard hooking code from project spice-gtk. This
patch removes the extra left control key up/down input events
inserted by Windows for the right alt key up/down input events
with international keyboard layouts. Additionally there's some
code to grab the keyboard.

The next patches will use this code.

Only Windows needs this.

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 20200516072014.7766-1-vr_qemu@t-online.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

include/ui/win32-kbd-hook.h

@@ -0,0 +1,14 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef UI_WIN32_KBD_HOOK_H
+#define UI_WIN32_KBD_HOOK_H
+
+void win32_kbd_set_window(void *hwnd);
+void win32_kbd_set_grab(bool grab);
+
+#endif

stubs/Makefile.objs

@@ -32,6 +32,7 @@ stub-obj-y += trace-control.o
 stub-obj-y += uuid.o
 stub-obj-y += vm-stop.o
 stub-obj-y += vmstate.o
+stub-obj-y += win32-kbd-hook.o
 stub-obj-y += fd-register.o
 stub-obj-y += qmp_memory_device.o
 stub-obj-y += target-monitor-defs.o

stubs/win32-kbd-hook.c

@@ -0,0 +1,18 @@
+/*
+ * Win32 keyboard hook stubs
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "ui/win32-kbd-hook.h"
+
+void win32_kbd_set_window(void *hwnd)
+{
+}
+
+void win32_kbd_set_grab(bool grab)
+{
+}

ui/Makefile.objs

@@ -15,6 +15,9 @@ common-obj-$(CONFIG_SPICE) += spice-core.o spice-input.o spice-display.o
 common-obj-$(CONFIG_COCOA) += cocoa.o
 common-obj-$(CONFIG_VNC) += $(vnc-obj-y)
 common-obj-$(call lnot,$(CONFIG_VNC)) += vnc-stubs.o
+ifneq (,$(findstring m,$(CONFIG_SDL)$(CONFIG_GTK)))
+common-obj-$(CONFIG_WIN32) += win32-kbd-hook.o
+endif
 
 # ui-sdl module
 common-obj-$(CONFIG_SDL) += sdl.mo

ui/win32-kbd-hook.c

@@ -0,0 +1,102 @@
+/*
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ *
+ * The win32 keyboard hooking code was imported from project spice-gtk.
+ */
+
+#include "qemu/osdep.h"
+#include "sysemu/sysemu.h"
+#include "ui/win32-kbd-hook.h"
+
+static Notifier win32_unhook_notifier;
+static HHOOK win32_keyboard_hook;
+static HWND win32_window;
+static DWORD win32_grab;
+
+static LRESULT CALLBACK keyboard_hook_cb(int code, WPARAM wparam, LPARAM lparam)
+{
+    if  (win32_window && code == HC_ACTION && win32_window == GetFocus()) {
+        KBDLLHOOKSTRUCT *hooked = (KBDLLHOOKSTRUCT *)lparam;
+
+        if (wparam != WM_KEYUP) {
+            DWORD dwmsg = (hooked->flags << 24) |
+                          ((hooked->scanCode & 0xff) << 16) | 1;
+
+            switch (hooked->vkCode) {
+            case VK_CAPITAL:
+                /* fall through */
+            case VK_SCROLL:
+                /* fall through */
+            case VK_NUMLOCK:
+                /* fall through */
+            case VK_LSHIFT:
+                /* fall through */
+            case VK_RSHIFT:
+                /* fall through */
+            case VK_RCONTROL:
+                /* fall through */
+            case VK_LMENU:
+                /* fall through */
+            case VK_RMENU:
+                break;
+
+            case VK_LCONTROL:
+                /*
+                 * When pressing AltGr, an extra VK_LCONTROL with a special
+                 * scancode with bit 9 set is sent. Let's ignore the extra
+                 * VK_LCONTROL, as that will make AltGr misbehave.
+                 */
+                if (hooked->scanCode & 0x200) {
+                    return 1;
+                }
+                break;
+
+            default:
+                if (win32_grab) {
+                    SendMessage(win32_window, wparam, hooked->vkCode, dwmsg);
+                    return 1;
+                }
+                break;
+            }
+
+        } else {
+            switch (hooked->vkCode) {
+            case VK_LCONTROL:
+                if (hooked->scanCode & 0x200) {
+                    return 1;
+                }
+                break;
+            }
+        }
+    }
+
+    return CallNextHookEx(NULL, code, wparam, lparam);
+}
+
+static void keyboard_hook_unhook(Notifier *n, void *data)
+{
+    UnhookWindowsHookEx(win32_keyboard_hook);
+    win32_keyboard_hook = NULL;
+}
+
+void win32_kbd_set_window(void *hwnd)
+{
+    if (hwnd && !win32_keyboard_hook) {
+        /* note: the installing thread must have a message loop */
+        win32_keyboard_hook = SetWindowsHookEx(WH_KEYBOARD_LL, keyboard_hook_cb,
+                                               GetModuleHandle(NULL), 0);
+        if (win32_keyboard_hook) {
+            win32_unhook_notifier.notify = keyboard_hook_unhook;
+            qemu_add_exit_notifier(&win32_unhook_notifier);
+        }
+    }
+
+    win32_window = hwnd;
+}
+
+void win32_kbd_set_grab(bool grab)
+{
+    win32_grab = grab;
+}