Windows Mobile系统弹出输入法时，自动调整窗口显示

windows mobile系统自带的输入法没有标题栏，用户没有办法移动它的显示位置。如果对话框的底部，有需要输入的编辑框，就会被弹出的输入法遮挡住，这样用户无法实时看到自己输入的内容。

参考mobile自带的系统程序，一般可以做成下面这种效果。也就是弹出输入法时，自动给窗口添加一个滚动条。用户可以通过滚动条调整界面的显示。当关闭输入法时，将滚动条去掉，同时窗口恢复到弹出输入法之前的默认显示。

  

下面介绍如何实现这种功能。首先需要在系统“弹出输入法”和“关闭输入法”时，能够获得一个通知。这可以通过响应WM_SETTINGCHANGE消息来完成。

当执行到自定义的WM_SETTINGCHANGE消息响应函数时，需要判断“输入法”是被“弹出”还是被“关闭”了？这可以通过如下代码获得：

SIPINFO sip_info = {0};   
sip_info.cbSize = sizeof(sip_info);
SHSipInfo(SPI_GETSIPINFO, 0, &sip_info, 0);
bool sipf_on = sip_info.fdwFlags & SIPF_ON;

当sipf_on为true时，表示“弹出输入法”，此时可以调整窗口显示，比如添加一个垂直滚动条，并将窗体初始滚到一个合适的位置，将最想让用户见到的部分显示出来。

SCROLLINFO scroll_info = {0}; 
scroll_info.cbSize = sizeof(SCROLLINFO); 
scroll_info.fMask = SIF_RANGE | SIF_PAGE | SIF_POS;

scroll_info.nMin = 0;
scroll_info.nMax = 90;
scroll_info.nPage = 10;
vert_scroll_pos_ = 80;
scroll_info.nPos = vert_scroll_pos_;

SetScrollInfo(SB_VERT, &scroll_info);
ScrollWindowEx(0, -scroll_info.nPos, NULL, NULL, NULL, NULL, 
             SW_ERASE | SW_INVALIDATE | SW_SCROLLCHILDREN);

当sipf_on为false时，表示“关闭输入法”，此时可以关闭滚动条，同时窗口恢复到弹出输入法之前的默认显示。

GetScrollInfo (SB_VERT, &scroll_info);
ScrollWindowEx(0, scroll_info.nPos, NULL, NULL, NULL, NULL, 
             SW_ERASE | SW_INVALIDATE | SW_SCROLLCHILDREN);

ShowScrollBar(SB_VERT, FALSE);
vert_scroll_pos_ = 0;

最后还需要注意的是，因为添加了垂直滚动条，所以需要响应WM_VSCROLL消息并进行处理。

void XXXDialog::OnVScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
{
    SCROLLINFO scroll_info = {sizeof(SCROLLINFO), 
                              SIF_PAGE | SIF_POS | SIF_RANGE | SIF_TRACKPOS, 
                              0, 
                              0, 
                              0, 
                              0, 
                              0};

    GetScrollInfo (SB_VERT, &scroll_info);

    int move_distance = 0;
    int new_position = 0;

    switch (nSBCode)
    {
    case SB_TOP:   
        scroll_info.nPos = scroll_info.nMin;   
        break;   
    case SB_BOTTOM:   
        scroll_info.nPos = scroll_info.nMax - scroll_info.nPage;   
        break;
    case SB_LINEDOWN:
        new_position = scroll_info.nPage + scroll_info.nPos;
        if(scroll_info.nMax > new_position)   
            move_distance = 5;   
        break;
    case SB_LINEUP:
        if(scroll_info.nPos <= scroll_info.nMin)   
            return;  
        move_distance = -5;   
        break;  
    case SB_PAGEUP:
        if(scroll_info.nPos <= scroll_info.nMin)   
            return;   
        new_position = (scroll_info.nPos - scroll_info.nPage);  
        move_distance = -(new_position <0 ? (int)scroll_info.nPage + new_position : (int)scroll_info.nPage);
        break;  
    case SB_PAGEDOWN:
        if(scroll_info.nMax <= scroll_info.nPos)   
            return;
        new_position = (scroll_info.nPos + scroll_info.nPage + scroll_info.nPage);
        move_distance = new_position >scroll_info.nMax ? scroll_info.nPage-(new_position - scroll_info.nMax) : scroll_info.nPage;
        break;
    case SB_THUMBTRACK:
    case SB_THUMBPOSITION:
        move_distance = (int)nPos - vert_scroll_pos_;
        break;
    }

    vert_scroll_pos_ += move_distance;
    if(0 != move_distance)
    {
        SetScrollPos(SB_VERT, GetScrollPos(SB_VERT) + move_distance);   
        ScrollWindowEx(0, -move_distance, NULL, NULL, NULL, NULL, SW_ERASE | SW_SCROLLCHILDREN);
    }

    CDialog::OnVScroll(nSBCode, nPos, pScrollBar);
}