don't clear frame after swap

modules/v4d/src/v4d.cpp

@@ -509,18 +509,6 @@ bool V4D::display() {
 #else
             emscripten_webgl_commit_frame();
 #endif
-            {
-#ifndef __EMSCRIPTEN__
-                fbCtx().makeCurrent();
-                GL_CHECK(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0));
-//#else
-//                FrameBufferContext::GLScope glScope(fbCtx(), GL_FRAMEBUFFER);
-//#endif
-                GL_CHECK(glClearColor(0, 0, 0, 1));
-                GL_CHECK(glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT));
-#endif
-            }
-
             glfwPollEvents();
             result = !glfwWindowShouldClose(getGLFWWindow());
         });