我WM_EX_TRANSPARENT在某些窗口上使用窗口样式以尝试进行具有透明度的双缓冲。但是，我遇到了一个问题，因为当我InvalidateRect在父窗口上执行时，子窗口不会重绘。
迭代子窗口并让它们重新绘制自己是父窗口的责任，还是我做错了？如果它是父窗口的责任，我怎样才能得到父无效矩形内的所有子窗口？
这是一个完全可编译的示例，说明了我正在谈论的行为。当您将鼠标移到父窗口上时，您可以看到该按钮消失了。如果单击它，该按钮会自行重绘，但当您将鼠标移开并返回父窗口时，它会再次消失。
#include <Windows.h>
LRESULT CALLBACK WndProc(HWND window, UINT uMsg, WPARAM wParam, LPARAM lParam) {
switch (uMsg) {
case WM_CREATE:
return 0;
case WM_MOUSEMOVE:
InvalidateRect(window, NULL, true);
return 0;
case WM_NCDESTROY:
PostQuitMessage(0);
break;
}
return DefWindowProc(window, uMsg, wParam, lParam);
}
int PASCAL WinMain(HINSTANCE hinst, HINSTANCE, LPSTR, int nShowCmd) {
WNDCLASS wc;
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hinst;
wc.hIcon = NULL;
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wc.lpszMenuName = NULL;
wc.lpszClassName = "test_window";
RegisterClass(&wc);
HWND wnd = CreateWindowEx(WS_EX_TRANSPARENT, "test_window", "test", WS_CLIPCHILDREN | WS_OVERLAPPEDWINDOW, 50, 50, 400, 400, NULL, NULL, hinst, NULL);
ShowWindow(wnd, SW_SHOW);
HWND btn = CreateWindowEx(WS_EX_TRANSPARENT, "BUTTON", "button 1", WS_CHILD, 50, 50, 100, 50, wnd, NULL, hinst, NULL);
ShowWindow(btn, SW_SHOW);
MSG m;
while (GetMessage(&m, NULL, 0, 0)) {
TranslateMessage(&m);
DispatchMessage(&m);
}
return 0;
}
最终的解决方案
是按照下面建议的答案去做，然后在父窗口的WM_PAINT消息中向WM_PAINT每个孩子发送 a 并让孩子们在父母的双缓冲区中绘画（而不是在自己身上绘画任何东西），然后让父母BitBlt在它的缓冲区中（已被绘制到由它自己，然后由它的每个孩子从 Z 顺序的底部到顶部）进入它的HDC. 这允许在父项和子项中进行无闪烁绘图，并为子项提供透明度。这是我们得到的最终演示程序：
#include <Windows.h>
// the handle to the single child window
HWND child;
// parent's backbuffer so we can use it in the child
HDC bbuf = 0;
LRESULT CALLBACK WndProc(HWND window, UINT uMsg, WPARAM wParam, LPARAM lParam) {
switch (uMsg) {
case WM_CREATE:
return 0;
case WM_MOUSEMOVE:
InvalidateRect(window, NULL, true);
return 0;
case WM_PAINT: {
PAINTSTRUCT ps;
POINT mpos;
GetCursorPos(&mpos);
ScreenToClient(window, &mpos);
BeginPaint(window, &ps);
// create the backbuffer once
bbuf = bbuf ? bbuf : CreateCompatibleDC(ps.hdc);
// hardcoded size is the same in the CreateWindowEx call
static auto backbmp = CreateCompatibleBitmap(ps.hdc, 400, 400);
static auto unused = SelectObject(bbuf, backbmp);
POINT points[2] = {
{ 0, 0 },
{ mpos.x, mpos.y }
};
// painting into bbuf
// give ourselves a white background so we can see the wblack line
SelectObject(bbuf, (HBRUSH)GetStockObject(WHITE_BRUSH));
Rectangle(bbuf, 0, 0, 400, 400);
SelectObject(bbuf, (HBRUSH)GetStockObject(BLACK_BRUSH));
Polyline(bbuf, points, 2);
// get the child to paint itself into our bbuf
SendMessage(child, WM_PAINT, 0, 0);
// and after the child has drawn, bitblt everything onto the screen
BitBlt(ps.hdc, 0, 0, 400, 400, bbuf, 0, 0, SRCCOPY);
EndPaint(window, &ps);
return 0;
}
case WM_ERASEBKGND:
return 0;
case WM_NCDESTROY:
PostQuitMessage(0);
break;
}
return DefWindowProc(window, uMsg, wParam, lParam);
}
LRESULT CALLBACK ChildWndProc(HWND window, UINT uMsg, WPARAM wParam, LPARAM lParam) {
switch (uMsg) {
case WM_CREATE:
return 0;
case WM_PAINT: {
PAINTSTRUCT ps;
BeginPaint(window, &ps);
static auto backbuffer = CreateCompatibleDC(ps.hdc);
static auto backbmp = CreateCompatibleBitmap(ps.hdc, 100, 50);
static auto unused = SelectObject(backbuffer, backbmp);
// copy the parent's stuff into our backbuffer (the parent has already drawn)
BitBlt(backbuffer, 0, 0, 100, 50, bbuf, 50, 150, SRCCOPY);
RECT r = { 0, 0, 50, 100 };
// draw into our backbuffer
SetBkMode(backbuffer, TRANSPARENT);
SetTextColor(backbuffer, RGB(255, 0, 0));
DrawText(backbuffer, "hello", 5, &r, DT_NOCLIP | DT_TABSTOP | DT_EXPANDTABS | DT_NOPREFIX);
// bitblt our stuff into the parent's backbuffer
BitBlt(bbuf, 50, 150, 100, 50, backbuffer, 0, 0, SRCCOPY);
EndPaint(window, &ps);
return 0;
}
case WM_ERASEBKGND:
return 0;
}
return DefWindowProc(window, uMsg, wParam, lParam);
}
int PASCAL WinMain(HINSTANCE hinst, HINSTANCE, LPSTR, int nShowCmd) {
WNDCLASS wc;
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hinst;
wc.hIcon = NULL;
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wc.lpszMenuName = NULL;
wc.lpszClassName = "test_window";
RegisterClass(&wc);
wc.style = 0;
wc.lpfnWndProc = ChildWndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hinst;
wc.hIcon = NULL;
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wc.lpszMenuName = NULL;
wc.lpszClassName = "transparent_window";
RegisterClass(&wc);
HWND wnd = CreateWindowEx(NULL, "test_window", "test", WS_OVERLAPPEDWINDOW | WS_VISIBLE, 50, 50, 400, 400, NULL, NULL, hinst, NULL);
child = CreateWindowEx(NULL, "transparent_window", "", WS_VISIBLE | WS_CLIPSIBLINGS | WS_CLIPCHILDREN | WS_CHILD, 50, 150, 100, 50, wnd, NULL, hinst, NULL);
MSG m;
while (GetMessage(&m, NULL, 0, 0)) {
TranslateMessage(&m);
DispatchMessage(&m);
}
return 0;
}
再次感谢 johnathon 花了这么多时间帮助我解决这个问题。