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// Copyright 2020 The Druid Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! X11 implementation of `druid-shell`.
// TODO(x11/render_improvements): screen is currently flashing when resizing in perftest.
// Might be related to the "sleep scheduler" in XWindow::render()?
// TODO(x11/render_improvements): double-buffering / present strategies / etc?
// # Notes on error handling in X11
//
// In XCB, errors are reported asynchronously by default, by sending them to the event
// loop. You can also request a synchronous error for a given call; we use this in
// window initialization, but otherwise we take the async route.
//
// When checking for X11 errors synchronously, there are two places where the error could
// happen. An error on the request means the connection is broken. There's no need for
// extra error context here, because the fact that the connection broke has nothing to do
// with what we're trying to do. An error on the reply means there was something wrong with
// the request, and so we add context. This convention is used throughout the x11 backend.