There was already a bug and it seemed easy to fix it, but, it took 2 years to fully fix the problem.
The root cause is as follows:
Chromium for Linux uses GtkFileChooserDialog to open a file-picker, but it is not modal to the X11 host window because GtkFileChooserDialog can be modal only to the parent GtkWindow. So I tried to allow the X11 host window to disable input event handling to make a file-picker modal: Here is the details:
Opening a file-picker
DisableEventListening() disables event listening for the host window using aura::ScopedWindowTargeter, which allows to temporarily replace the event-targeter with ui::NullEventTargeter. It returns a scope handle that is used to call |destroy_callback| when closing the file-picker.
class ScopedHandle {
public:
explicit ScopedHandle(const base::Closure& destroy_callback);
~ScopedHandle();
void CancelCallback();
private:
base::Closure destroy_callback_;
DISALLOW_COPY_AND_ASSIGN(ScopedHandle);
};
public:
explicit ScopedHandle(const base::Closure& destroy_callback);
~ScopedHandle();
void CancelCallback();
private:
base::Closure destroy_callback_;
DISALLOW_COPY_AND_ASSIGN(ScopedHandle);
};
In addition, we also set another destroy callback(OnFilePickerDestroy) to the GtkFileChooserDialog that can be called when the file-picker is closed.
Close the file-picker
As you can see, OnFilePickerDestroy deletes scoped_handle.
void OnFilePickerDestroy(views::DesktopWindowTreeHostX11::ScopedHandle*
scoped_handle) {
delete scoped_handle;
}
Then, |destroy_callback| of ScopedHandle below is automatically called.
void DesktopWindowTreeHostX11::EnableEventListening() {
DCHECK(modal_dialog_xid_);
modal_dialog_xid_ = 0;
targeter_for_modal_.reset();
}
You can find more details and discussion at here.
The first change list was reverted due to the UI freezing problem that happens when the users open a file-picker from a child window of the X11 host window. The second change list finally fixed this issue(BUG 408481, 579408). I also added a test case for the fix: BrowserSelectFileDialogTest.ModalTest.
