如何将 OpenGL 渲染到半透明的 Win32 窗口？ [复制]

Question

我正在为 C 和 C++ 编写一个窗口库来处理 OpenGL 的无边界和非矩形窗口。我有一个问题：我希望库让用户绘制到 RGBA，我的意思是没有背景，那么窗口可以有任何形状。我做了很多研究，我认为我必须使用 DWM api 并模糊窗口（参见下面的代码）我使用 glClearColor(0.0f, 0.0f, 0.0f. 0.0f);它应该显示一个完全透明的窗口（所以什么都没有），但它仍然看到一个黑色的半透明矩形（就像 alpha chanel 是 ~0.1f），如果我改变颜色，窗口的颜色会改变，如果我设置一个更高阿尔法香奈儿，窗口更明显，所以它似乎工作但不正确。这是一个问题，我希望能够拥有完全透明的窗口。我正在使用 DWM，但如果有更好的解决方案，请告诉我。这个问题也可能来自OpenGL混合状态，我不知道。

代码：

#define UNICODE

#define GLEW_STATIC

#include <windows.h>
#include <dwmapi.h>
#include <stdlib.h>
#include <time.h>
#include <stdio.h>

#include <glew.h>

LRESULT CALLBACK wnd_proc(HWND hWnd, UINT uMsg, WPARAM wp, LPARAM lp);

int main(void){
    int initial_clock = clock();

    WNDCLASSEX wcx = {};
    wcx.cbSize = sizeof(WNDCLASSEX);
    wcx.lpszClassName = L"win32_class";
    wcx.lpfnWndProc = wnd_proc;
    RegisterClassEx(&wcx);

    HWND hWnd = CreateWindowEx(WS_EX_APPWINDOW, L"win32_class", L"Title",
        WS_POPUP, 100, 100, 800, 400, NULL, NULL, NULL, NULL);

    ShowWindow(hWnd, 1);

    HDC device_context = GetDC(hWnd);

    PIXELFORMATDESCRIPTOR pfd = {};
    pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 32;
    pfd.cDepthBits = 24;
    pfd.cStencilBits = 8;

    int pixel_format = ChoosePixelFormat(device_context, &pfd);
    SetPixelFormat(device_context, pixel_format, &pfd);
    HGLRC rendering_context = wglCreateContext(device_context);
    wglMakeCurrent(device_context, rendering_context);

    glewInit();

    DWM_BLURBEHIND blur = {};
    blur.dwFlags = DWM_BB_ENABLE;
    blur.fEnable = 1;
    blur.hRgnBlur = NULL;
    DwmEnableBlurBehindWindow(hWnd, &blur);

    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    MSG msg;
    while(GetMessage(&msg, NULL, 0, 0)){
        DispatchMessage(&msg);
        glClear(GL_COLOR_BUFFER_BIT);
        wglSwapLayerBuffers(device_context, WGL_SWAP_MAIN_PLANE);
    }
}

LRESULT CALLBACK wnd_proc(HWND hWnd, UINT uMsg, WPARAM wp, LPARAM lp){
    switch(uMsg){
        case WM_NCHITTEST: return HTCAPTION;
        default:           return DefWindowProc(hWnd, uMsg, wp, lp);
    }
}

Answer 1

你可以使用SetLayeredWindowAttributes函数。

设置分层窗口的不透明度和透明度颜色键。

添加：

LONG Style = GetWindowLong(hWnd, GWL_EXSTYLE); 
SetWindowLong(hWnd, GWL_EXSTYLE, Style | WS_EX_LAYERED);
SetLayeredWindowAttributes(hWnd, 0, 10, LWA_ALPHA);

当 bAlpha 为 0 时，窗口是完全透明的。当 bAlpha 为 255 时，窗口是不透明的。

调试（bAlpha = 10）：

完整代码：

#define UNICODE

#define GLEW_STATIC

#include <windows.h>
#include <dwmapi.h>
#include <stdlib.h>
#include <time.h>
#include <stdio.h>

#include <glew.h>

LRESULT CALLBACK wnd_proc(HWND hWnd, UINT uMsg, WPARAM wp, LPARAM lp);

int main(void){
    int initial_clock = clock();

    WNDCLASSEX wcx = {};
    wcx.cbSize = sizeof(WNDCLASSEX);
    wcx.lpszClassName = L"win32_class";
    wcx.lpfnWndProc = wnd_proc;
    RegisterClassEx(&wcx);

    HWND hWnd = CreateWindowEx(WS_EX_APPWINDOW, L"win32_class", L"Title",
        WS_POPUP, 100, 100, 800, 400, NULL, NULL, NULL, NULL);

    ShowWindow(hWnd, 1);

    HDC device_context = GetDC(hWnd);

    PIXELFORMATDESCRIPTOR pfd = {};
    pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 32;
    pfd.cDepthBits = 24;
    pfd.cStencilBits = 8;

    int pixel_format = ChoosePixelFormat(device_context, &pfd);
    SetPixelFormat(device_context, pixel_format, &pfd);
    HGLRC rendering_context = wglCreateContext(device_context);
    wglMakeCurrent(device_context, rendering_context);

    glewInit();

    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    MSG msg;
    while(GetMessage(&msg, NULL, 0, 0)){
        DispatchMessage(&msg);
        glClear(GL_COLOR_BUFFER_BIT);
        wglSwapLayerBuffers(device_context, WGL_SWAP_MAIN_PLANE);
    }
}

LRESULT CALLBACK wnd_proc(HWND hWnd, UINT uMsg, WPARAM wp, LPARAM lp){
    switch(uMsg){
        case WM_CREATE:
        {
            LONG Style = GetWindowLong(hWnd, GWL_EXSTYLE); 
            SetWindowLong(hWnd, GWL_EXSTYLE, Style | WS_EX_LAYERED);
            SetLayeredWindowAttributes(hWnd, 0, 10, LWA_ALPHA);
        }
        break;
        case WM_NCHITTEST: return HTCAPTION;
        default:           return DefWindowProc(hWnd, uMsg, wp, lp);
    }
}