in shell/browser/native_window_views_win.cc [200:381]
bool NativeWindowViews::PreHandleMSG(UINT message,
WPARAM w_param,
LPARAM l_param,
LRESULT* result) {
NotifyWindowMessage(message, w_param, l_param);
// Avoid side effects when calling SetWindowPlacement.
if (is_setting_window_placement_) {
// Let Chromium handle the WM_NCCALCSIZE message otherwise the window size
// would be wrong.
// See https://github.com/electron/electron/issues/22393 for more.
if (message == WM_NCCALCSIZE)
return false;
// Otherwise handle the message with default proc,
*result = DefWindowProc(GetAcceleratedWidget(), message, w_param, l_param);
// and tell Chromium to ignore this message.
return true;
}
switch (message) {
// Screen readers send WM_GETOBJECT in order to get the accessibility
// object, so take this opportunity to push Chromium into accessible
// mode if it isn't already, always say we didn't handle the message
// because we still want Chromium to handle returning the actual
// accessibility object.
case WM_GETOBJECT: {
if (checked_for_a11y_support_)
return false;
const DWORD obj_id = static_cast<DWORD>(l_param);
if (obj_id != static_cast<DWORD>(OBJID_CLIENT)) {
return false;
}
if (!IsScreenReaderActive()) {
return false;
}
checked_for_a11y_support_ = true;
auto* const axState = content::BrowserAccessibilityState::GetInstance();
if (axState && !axState->IsAccessibleBrowser()) {
axState->OnScreenReaderDetected();
Browser::Get()->OnAccessibilitySupportChanged();
}
return false;
}
case WM_GETMINMAXINFO: {
WINDOWPLACEMENT wp;
wp.length = sizeof(WINDOWPLACEMENT);
// We do this to work around a Windows bug, where the minimized Window
// would report that the closest display to it is not the one that it was
// previously on (but the leftmost one instead). We restore the position
// of the window during the restore operation, this way chromium can
// use the proper display to calculate the scale factor to use.
if (!last_normal_placement_bounds_.IsEmpty() &&
(IsVisible() || IsMinimized()) &&
GetWindowPlacement(GetAcceleratedWidget(), &wp)) {
wp.rcNormalPosition = last_normal_placement_bounds_.ToRECT();
// When calling SetWindowPlacement, Chromium would do window messages
// handling. But since we are already in PreHandleMSG this would cause
// crash in Chromium under some cases.
//
// We work around the crash by prevent Chromium from handling window
// messages until the SetWindowPlacement call is done.
//
// See https://github.com/electron/electron/issues/21614 for more.
is_setting_window_placement_ = true;
SetWindowPlacement(GetAcceleratedWidget(), &wp);
is_setting_window_placement_ = false;
last_normal_placement_bounds_ = gfx::Rect();
}
return false;
}
case WM_COMMAND:
// Handle thumbar button click message.
if (HIWORD(w_param) == THBN_CLICKED)
return taskbar_host_.HandleThumbarButtonEvent(LOWORD(w_param));
return false;
case WM_SIZING: {
is_resizing_ = true;
bool prevent_default = false;
gfx::Rect bounds = gfx::Rect(*reinterpret_cast<RECT*>(l_param));
HWND hwnd = GetAcceleratedWidget();
gfx::Rect dpi_bounds = ScreenToDIPRect(hwnd, bounds);
NotifyWindowWillResize(dpi_bounds, GetWindowResizeEdge(w_param),
&prevent_default);
if (prevent_default) {
::GetWindowRect(hwnd, reinterpret_cast<RECT*>(l_param));
return true; // Tells Windows that the Sizing is handled.
}
return false;
}
case WM_SIZE: {
// Handle window state change.
HandleSizeEvent(w_param, l_param);
return false;
}
case WM_EXITSIZEMOVE: {
if (is_resizing_) {
NotifyWindowResized();
is_resizing_ = false;
}
if (is_moving_) {
NotifyWindowMoved();
is_moving_ = false;
}
return false;
}
case WM_MOVING: {
is_moving_ = true;
bool prevent_default = false;
gfx::Rect bounds = gfx::Rect(*reinterpret_cast<RECT*>(l_param));
HWND hwnd = GetAcceleratedWidget();
gfx::Rect dpi_bounds = ScreenToDIPRect(hwnd, bounds);
NotifyWindowWillMove(dpi_bounds, &prevent_default);
if (!movable_ || prevent_default) {
::GetWindowRect(hwnd, reinterpret_cast<RECT*>(l_param));
return true; // Tells Windows that the Move is handled. If not true,
// frameless windows can be moved using
// -webkit-app-region: drag elements.
}
return false;
}
case WM_ENDSESSION: {
if (w_param) {
NotifyWindowEndSession();
}
return false;
}
case WM_PARENTNOTIFY: {
if (LOWORD(w_param) == WM_CREATE) {
// Because of reasons regarding legacy drivers and stuff, a window that
// matches the client area is created and used internally by Chromium.
// This is used when forwarding mouse messages. We only cache the first
// occurrence (the webview window) because dev tools also cause this
// message to be sent.
if (!legacy_window_) {
legacy_window_ = reinterpret_cast<HWND>(l_param);
}
}
return false;
}
case WM_CONTEXTMENU: {
bool prevent_default = false;
NotifyWindowSystemContextMenu(GET_X_LPARAM(l_param),
GET_Y_LPARAM(l_param), &prevent_default);
return prevent_default;
}
case WM_SYSCOMMAND: {
// Mask is needed to account for double clicking title bar to maximize
WPARAM max_mask = 0xFFF0;
if (transparent() && ((w_param & max_mask) == SC_MAXIMIZE)) {
return true;
}
return false;
}
case WM_INITMENU: {
// This is handling the scenario where the menu might get triggered by the
// user doing "alt + space" resulting in system maximization and restore
// being used on transparent windows when that does not work.
if (transparent()) {
HMENU menu = GetSystemMenu(GetAcceleratedWidget(), false);
EnableMenuItem(menu, SC_MAXIMIZE,
MF_BYCOMMAND | MF_DISABLED | MF_GRAYED);
EnableMenuItem(menu, SC_RESTORE,
MF_BYCOMMAND | MF_DISABLED | MF_GRAYED);
return true;
}
return false;
}
default: {
return false;
}
}
}