// Copyright (c) 2017 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE-CHROMIUM file. #include "shell/browser/ui/views/electron_views_delegate.h" #include #include #include #include "base/functional/bind.h" #include "base/task/thread_pool.h" namespace { bool MonitorHasAutohideTaskbarForEdge(UINT edge, HMONITOR monitor) { APPBARDATA taskbar_data = {sizeof(APPBARDATA), nullptr, 0, edge}; taskbar_data.hWnd = ::GetForegroundWindow(); // MSDN documents an ABM_GETAUTOHIDEBAREX, which supposedly takes a monitor // rect and returns autohide bars on that monitor. This sounds like a good // idea for multi-monitor systems. Unfortunately, it appears to not work at // least some of the time (erroneously returning nullptr) and there's almost // no online documentation or other sample code using it that suggests ways to // address this problem. We do the following:- // 1. Use the ABM_GETAUTOHIDEBAR message. If it works, i.e. returns a valid // window we are done. // 2. If the ABM_GETAUTOHIDEBAR message does not work we query the auto hide // state of the taskbar and then retrieve its position. That call returns // the edge on which the taskbar is present. If it matches the edge we // are looking for, we are done. // NOTE: This call spins a nested run loop. HWND taskbar = reinterpret_cast( SHAppBarMessage(ABM_GETAUTOHIDEBAR, &taskbar_data)); if (!::IsWindow(taskbar)) { APPBARDATA new_taskbar_data = {sizeof(APPBARDATA), 0, 0, 0}; unsigned int taskbar_state = SHAppBarMessage(ABM_GETSTATE, &new_taskbar_data); if (!(taskbar_state & ABS_AUTOHIDE)) return false; new_taskbar_data.hWnd = ::FindWindow(L"Shell_TrayWnd", nullptr); if (!::IsWindow(new_taskbar_data.hWnd)) return false; SHAppBarMessage(ABM_GETTASKBARPOS, &new_taskbar_data); if (new_taskbar_data.uEdge == edge) taskbar = new_taskbar_data.hWnd; } // There is a potential race condition here: // 1. A maximized chrome window is fullscreened. // 2. It is switched back to maximized. // 3. In the process the window gets a WM_NCCALCSIZE message which calls us to // get the autohide state. // 4. The worker thread is invoked. It calls the API to get the autohide // state. On Windows versions earlier than Windows 7, taskbars could // easily be always on top or not. // This meant that we only want to look for taskbars which have the topmost // bit set. However this causes problems in cases where the window on the // main thread is still in the process of switching away from fullscreen. // In this case the taskbar might not yet have the topmost bit set. // 5. The main thread resumes and does not leave space for the taskbar and // hence it does not pop when hovered. // // To address point 4 above, it is best to not check for the WS_EX_TOPMOST // window style on the taskbar, as starting from Windows 7, the topmost // style is always set. We don't support XP and Vista anymore. if (::IsWindow(taskbar)) { if (MonitorFromWindow(taskbar, MONITOR_DEFAULTTONEAREST) == monitor) return true; // In some cases like when the autohide taskbar is on the left of the // secondary monitor, the MonitorFromWindow call above fails to return the // correct monitor the taskbar is on. We fallback to MonitorFromPoint for // the cursor position in that case, which seems to work well. POINT cursor_pos = {0}; GetCursorPos(&cursor_pos); if (MonitorFromPoint(cursor_pos, MONITOR_DEFAULTTONEAREST) == monitor) return true; } return false; } int GetAppbarAutohideEdgesOnWorkerThread(HMONITOR monitor) { DCHECK(monitor); int edges = 0; if (MonitorHasAutohideTaskbarForEdge(ABE_LEFT, monitor)) edges |= views::ViewsDelegate::EDGE_LEFT; if (MonitorHasAutohideTaskbarForEdge(ABE_TOP, monitor)) edges |= views::ViewsDelegate::EDGE_TOP; if (MonitorHasAutohideTaskbarForEdge(ABE_RIGHT, monitor)) edges |= views::ViewsDelegate::EDGE_RIGHT; if (MonitorHasAutohideTaskbarForEdge(ABE_BOTTOM, monitor)) edges |= views::ViewsDelegate::EDGE_BOTTOM; return edges; } } // namespace namespace electron { HICON ViewsDelegate::GetDefaultWindowIcon() const { // Use current exe's icon as default window icon. return LoadIcon(GetModuleHandle(nullptr), MAKEINTRESOURCE(1 /* IDR_MAINFRAME */)); } HICON ViewsDelegate::GetSmallWindowIcon() const { return GetDefaultWindowIcon(); } int ViewsDelegate::GetAppbarAutohideEdges(HMONITOR monitor, base::OnceClosure callback) { // Initialize the map with EDGE_BOTTOM. This is important, as if we return an // initial value of 0 (no auto-hide edges) then we'll go fullscreen and // windows will automatically remove WS_EX_TOPMOST from the appbar resulting // in us thinking there is no auto-hide edges. By returning at least one edge // we don't initially go fullscreen until we figure out the real auto-hide // edges. if (!appbar_autohide_edge_map_.contains(monitor)) appbar_autohide_edge_map_[monitor] = EDGE_BOTTOM; // We use the SHAppBarMessage API to get the taskbar autohide state. This API // spins a modal loop which could cause callers to be reentered. To avoid // that we retrieve the taskbar state in a worker thread. if (monitor && !in_autohide_edges_callback_) { // TODO(robliao): Annotate this task with .WithCOM() once supported. // https://crbug.com/662122 base::ThreadPool::PostTaskAndReplyWithResult( FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_BLOCKING}, base::BindOnce(&GetAppbarAutohideEdgesOnWorkerThread, monitor), base::BindOnce(&ViewsDelegate::OnGotAppbarAutohideEdges, weak_factory_.GetWeakPtr(), std::move(callback), monitor, appbar_autohide_edge_map_[monitor])); } return appbar_autohide_edge_map_[monitor]; } void ViewsDelegate::OnGotAppbarAutohideEdges(base::OnceClosure callback, HMONITOR monitor, int returned_edges, int edges) { appbar_autohide_edge_map_[monitor] = edges; if (returned_edges == edges) return; base::AutoReset in_callback_setter(&in_autohide_edges_callback_, true); std::move(callback).Run(); } } // namespace electron