ActiveX控件在IE中不响应Backspace消息

1、操作输入法需要导入：

#include <imm.h>
#pragma comment(lib, "imm32")

2、定义变量：

//键盘钩子句柄
HHOOK g_hKeyboardHook = NULL;
//是否拦截Backspace
bool g_bInterceptBackspace = true;

3、定义键盘钩子回调函数：

LRESULT CALLBACK KeyboardHookProc(int nCode, WPARAM wParam, LPARAM lParam)
{
	if (nCode > -1)
	{
		BOOL bRet = FALSE;
		LPKBDLLHOOKSTRUCT lpKeyboard = (LPKBDLLHOOKSTRUCT)lParam;
		HWND hCurWnd = ::GetFocus();
		HIMC hImc = ImmGetContext(hCurWnd);
		LONG nSize = ImmGetCompositionString(hImc, GCS_COMPSTR, NULL, 0);

		ImmReleaseContext(hCurWnd, hImc);
		if (hImc)
		{
			if (nSize > 0)
			{
				//如果按键组合窗口字符串长度大于0，则表明显示了按键组合窗口，交给系统默认处理
				g_bInterceptBackspace = false;
				bRet = TRUE;
			}
			else if (nSize == 0)
			{
				if (!g_bInterceptBackspace)
				{
					//如果按键组合框窗口字符串等于0，且上次显示了按键组合框窗口，则表明是删除最后一个字符后，交给系统默认处理
					g_bInterceptBackspace = true;
					bRet = TRUE;
				}
			}
		}

		if (VK_BACK == wParam)
		{
			if (!bRet)
			{
				if (lParam & 0x80000000)
				{
					::SendMessage(::GetFocus(), WM_KEYUP, VK_BACK, 0);
				}
				else
				{
					::SendMessage(hCurWnd, WM_KEYDOWN, VK_BACK, 0);
					::SendMessage(hCurWnd, WM_CHAR, VK_BACK, 0);
				}
				return 1;
			}
		}
	}

	return CallNextHookEx(g_hKeyboardHook, nCode, wParam, lParam);
}

4、安装钩子

g_hKeyboardHook = ::SetWindowsHookEx(WH_KEYBOARD, (HOOKPROC)KeyboardHookProc, 0, GetCurrentThreadId());

5、卸载钩子

::UnhookWindowsHookEx(g_hKeyboardHook);