[Spice-devel] [PATCH 14/17] Create a class encapsulating the X11 display cursor capture

[Lukáš Hrázký]

On Fri, 2018-02-16 at 17:15 +0100, Christophe de Dinechin wrote:
> From: Christophe de Dinechin <dinechin at redhat.com>
> 
> This class will need to be moved to a separate file in a later patch.
> This is done in two steps to make the evolution of the code easier to track,
> as well as to facilitate later 'git bisect'
> 
> Signed-off-by: Christophe de Dinechin <dinechin at redhat.com>
> ---
>  src/spice-streaming-agent.cpp | 106 ++++++++++++++++++++++++++----------------
>  1 file changed, 66 insertions(+), 40 deletions(-)
> 
> diff --git a/src/spice-streaming-agent.cpp b/src/spice-streaming-agent.cpp
> index faf850c..f4df6be 100644
> --- a/src/spice-streaming-agent.cpp
> +++ b/src/spice-streaming-agent.cpp
> @@ -191,6 +191,70 @@ private:
>      std::unique_ptr<uint32_t[]> pixels;
>  };
>  
> +
> +class X11CursorThread
> +{
> +public:
> +    X11CursorThread(Stream &stream);
> +    ~X11CursorThread();
> +
> +    static void record_cursor_changes(X11CursorThread *self) { self->cursor_changes(); }
> +    void cursor_changes();
> +
> +private:
> +    Stream &stream;
> +    Display *display;
> +    std::thread thread;
> +};

I would still very much like this class to be a functor that is passed
to a thread. It IMHO makes for a better encapsulation. You can then
launch it any way you like, for example on the main thread in a test.

FWIW, I came up with the name CursorUpdater :) (since if it's not a
thread we can't call it so)

> +
> +
> +X11CursorThread::X11CursorThread(Stream &stream)
> +    : stream(stream),
> +      display(XOpenDisplay(NULL)),
> +      thread(record_cursor_changes, this)
> +{
> +    if (display == NULL) {
> +        throw std::runtime_error("failed to open display\n");
> +    }
> +    thread.detach();
> +}
> +
> +X11CursorThread::~X11CursorThread()
> +{
> +    XCloseDisplay(display);
> +}
> +
> +void X11CursorThread::cursor_changes()
> +{
> +    unsigned long last_serial = 0;
> +
> +    int event_base, error_base;
> +    if (!XFixesQueryExtension(display, &event_base, &error_base)) {
> +        syslog(LOG_WARNING, "XFixesQueryExtension failed, not sending cursor changes\n");
> +        return; // also terminates the thread
> +    }
> +    Window rootwindow = DefaultRootWindow(display);
> +    XFixesSelectCursorInput(display, rootwindow, XFixesDisplayCursorNotifyMask);
> +
> +    while (true) {
> +        XEvent event;
> +        XNextEvent(display, &event);
> +        if (event.type != event_base + 1)
> +            continue;
> +
> +        XFixesCursorImage *cursor = XFixesGetCursorImage(display);
> +        if (!cursor)
> +            continue;
> +
> +        if (cursor->cursor_serial == last_serial)
> +            continue;
> +
> +        last_serial = cursor->cursor_serial;
> +        if (!stream.send<X11CursorMessage>(cursor))
> +            syslog(LOG_WARNING, "FAILED to send cursor\n");
> +    }
> +}
> +
>  }} // namespace spice::streaming_agent
>  
>  
> @@ -338,29 +402,6 @@ static void usage(const char *progname)
>      exit(1);
>  }
>  
> -static void cursor_changes(Stream *stream, Display *display, int event_base)
> -{
> -    unsigned long last_serial = 0;
> -
> -    while (1) {
> -        XEvent event;
> -        XNextEvent(display, &event);
> -        if (event.type != event_base + 1)
> -            continue;
> -
> -        XFixesCursorImage *cursor = XFixesGetCursorImage(display);
> -        if (!cursor)
> -            continue;
> -
> -        if (cursor->cursor_serial == last_serial)
> -            continue;
> -
> -        last_serial = cursor->cursor_serial;
> -        if (!stream->send<X11CursorMessage>(cursor))
> -            syslog(LOG_WARNING, "FAILED to send cursor\n");
> -    }
> -}
> -
>  static void
>  do_capture(Stream &stream, const char *streamport, FILE *f_log)
>  {
> @@ -503,25 +544,10 @@ int main(int argc, char* argv[])
>          }
>      }
>  
> -    Display *display = XOpenDisplay(NULL);
> -    if (display == NULL) {
> -        syslog(LOG_ERR, "failed to open display\n");
> -        return EXIT_FAILURE;
> -    }
> -    int event_base, error_base;
> -    if (!XFixesQueryExtension(display, &event_base, &error_base)) {
> -        syslog(LOG_ERR, "XFixesQueryExtension failed\n");
> -        return EXIT_FAILURE;
> -    }
> -    Window rootwindow = DefaultRootWindow(display);
> -    XFixesSelectCursorInput(display, rootwindow, XFixesDisplayCursorNotifyMask);
> -
> -    Stream streamfd(streamport);
> -    std::thread cursor_th(cursor_changes, &streamfd, display, event_base);
> -    cursor_th.detach();
> -
>      int ret = EXIT_SUCCESS;
>      try {
> +        Stream streamfd(streamport);
> +        X11CursorThread cursor_thread(streamfd);
>          do_capture(streamfd, streamport, f_log);
>      }
>      catch (std::runtime_error &err) {