Question

我想制作一个显示文本透明的静态控件的背景。经过2天的谷歌搜索后，我想出了这个：

class TLABEL : public TWINDOW {
private:
    HINSTANCE hInst;
public:

    static LRESULT CALLBACK SubclassCallback(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR userdata)
    {
        TLABEL* pThisWindow = (TLABEL*)userdata;

        //look for messages that we want to process ourselves
        switch (msg)
        {
            //make background transparent
            case WM_CTLCOLORSTATIC:
            {
                HDC hDC = (HDC)wParam;

                SetBkMode(hDC, TRANSPARENT);
                SetTextColor(hDC, RGB(0, 0, 0)); //text color black

                MessageBox(NULL, L"WM_CTLCOLORSTATIC", L"Error!",MB_ICONEXCLAMATION|MB_OK);

                return (LRESULT)GetStockObject(NULL_BRUSH);
            }

            case WM_ERASEBKGND:
            {
                return TRUE;;
            }

            //remove Subclass if window is destroyed
            case WM_NCDESTROY:
            {
                RemoveWindowSubclass(pThisWindow->handle, &TLABEL::SubclassCallback, uIdSubclass);
                return TRUE;
            }

        }

        //deliver all other messages to the original callback-function
        return DefSubclassProc(hWnd, msg, wParam, lParam);
    }

    //standard alignment left
    explicit TLABEL(int nx, int ny, int nwidth, int nheight, HWND hParent)
    {
        hInst = GetModuleHandle(NULL); //i know this is a bad practice
        handle = CreateWindowEx(WS_EX_TRANSPARENT,  //background transparent
                                L"STATIC", L"",  //class name + text
                                WS_CHILD | WS_VISIBLE | SS_LEFT,  //styles
                                nx, ny, nwidth, nheight,  //dimensions
                                hParent, NULL, hInst, NULL);

        //subclass window to catch messages we want to process ourselves
        SetWindowSubclass(this->handle, &TLABEL::SubclassCallback, 0, (DWORD_PTR)this);
    }

不知怎的，SubclassCallback（）函数从不接收WM_CTLCOLORSTATIC消息，但我知道该函数被调用，并且它接收WM_ERASEBKGND消息就好了。如果我在主窗口的消息处理程序中处理WM_CTLCOLORSTATIC消息它可以工作，不幸的是，这会消除为这样的静态控件创建单独的类所带来的所有好处

我没有找到任何提示，为什么WM_CTLCOLORSTATIC消息被发送到主窗口而不是我的静态控件，因为所有示例似乎都是这样做的。

我已经在WinXP-32机器上的VS2010 Express下编译了它

子类化静态控件以接收WM_CTLCOLORSTATIC

0 个答案: