create new WGL context when WGL_USE_BACKING_WINDOW is false

windows/wgl_context.cpp

@@ -11,6 +11,93 @@ namespace flutter_filament {
 WGLContext::WGLContext(flutter::PluginRegistrarWindows *pluginRegistrar,
                        flutter::TextureRegistrar *textureRegistrar)
     : FlutterRenderContext(pluginRegistrar, textureRegistrar) {
+
+  #if WGL_USE_BACKING_WINDOW
+  return;
+  #endif
+
+  auto hwnd = pluginRegistrar->GetView()->GetNativeWindow();
+
+  HDC whdc = GetDC(hwnd);
+  if (whdc == NULL) {
+    std::cout << "No device context for temporary window" << std::endl;
+    return;
+  }
+
+  std::cout << "No GL context exists, creating" << std::endl;
+
+  PIXELFORMATDESCRIPTOR pfd = {
+      sizeof(PIXELFORMATDESCRIPTOR),
+      1,
+      PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER, // Flags
+      PFD_TYPE_RGBA, // The kind of framebuffer. RGBA or palette.
+      24,            // Colordepth of the framebuffer.
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      0,
+      16, // Number of bits for the depthbuffer
+      0,  // Number of bits for the stencilbuffer
+      0,  // Number of Aux buffers in the framebuffer.
+      PFD_MAIN_PLANE,
+      0,
+      0,
+      0,
+      0};
+
+  int pixelFormat = ChoosePixelFormat(whdc, &pfd);
+  SetPixelFormat(whdc, pixelFormat, &pfd);
+
+  // We need a tmp context to retrieve and call wglCreateContextAttribsARB.
+  HGLRC tempContext = wglCreateContext(whdc);
+  if (!wglMakeCurrent(whdc, tempContext)) {
+    std::cout << "Failed to acquire temporary context" << std::endl;
+    return;
+  }
+
+  GLenum err = glGetError();
+
+  if (err != GL_NO_ERROR) {
+    std::cout << "GL Error @ 455 %d" << std::endl;
+    return;
+  }
+
+  PFNWGLCREATECONTEXTATTRIBSARBPROC wglCreateContextAttribs = nullptr;
+
+  wglCreateContextAttribs =
+      (PFNWGLCREATECONTEXTATTRIBSARBPROC)wglGetProcAddress(
+          "wglCreateContextAttribsARB");
+
+  if (!wglCreateContextAttribs) {
+    std::cout << "Failed to resolve wglCreateContextAttribsARB" << std::endl;
+    return;
+  }
+
+  for (int minor = 5; minor >= 1; minor--) {
+    std::vector<int> mAttribs = {WGL_CONTEXT_MAJOR_VERSION_ARB, 4,
+                                 WGL_CONTEXT_MINOR_VERSION_ARB, minor, 0};
+    _context = wglCreateContextAttribs(whdc, nullptr, mAttribs.data());
+    if (_context) {
+      break;
+    }
+  }
+
+  wglMakeCurrent(NULL, NULL);
+  wglDeleteContext(tempContext);
+
+  if (!_context || !wglMakeCurrent(whdc, _context)) {
+    std::cout << "Failed to create OpenGL context." << std::endl;
+    return;
+  }
 }
 
 void WGLContext::ResizeRenderingSurface(uint32_t width, uint32_t height, uint32_t left, uint32_t top) {