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

[Christophe de Dinechin]

> On 20 Feb 2018, at 16:42, Lukáš Hrázký <lhrazky at redhat.com> wrote:
> 
> 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.

Could be done that way too, but I might then have two classes, CursorUpdater and CursorThread. Will do that as a separate patch so that we can decide if it’s better.

(related bug not yet fixed in this series: agent does not die on Control-C)

> 
> 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) {
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