Hi R-Devel,
I've been working on an oscilloscope project using an Arduino
microcontroller board. I found that it's quite easy to get realtime
updates, e.g. 30+ frames per second, if I read data from the board in
a little Rcpp library. I have to use dev.hold() and dev.flush() to
keep the plot from flickering, which restricts me to the "cairo" X11
device.
I'd like to be able to add interactivity to the oscilloscope display,
for instance to bind a key to save the current plot to a file, or to
bind keys for adjusting the time scale etc.
However, I ran into two problems:
(1) setGraphicsEventHandlers only works on the "Xlib" X11 device,
which doesn't support buffering via dev.hold() - it flickers.
(2) getGraphicsEvent and friends lack some interface features which
are needed to use the functions in an asynchronous fashion. Typically,
event listener library functions have a "timeout" parameter, and the
ability to return already-queued events. But getGraphicsEvent() has
neither - it waits indefinitely (you can't set a timeout), and it
seems to ignore events which occurred before it was called (I can't
figure out why, from the code, I guess the normal R event processing
grabs events which occur between calls to getGraphicsEvent?).
It seems like it should be possible to set a handler for keyboard
events and have it execute in between plot updates when the user
presses a key - yet without blocking further updates if no key has
been pressed.
Is anyone interested in fixing (1) and (2)? Or is there some other
library or workaround to solve my problems?
Here is some code I used to play around with these functions:
X11(type="Xlib");
keydown = function(key) {
cat("Got key: ",key);
lastkey <<- key
}
setGraphicsEventHandlers(onKeybd = keydown);
plot(c(0,0));
getGraphicsEvent();
Well, I think it's great that getGraphicsEvent exists at all, and want
to salute Duncan Murdoch who is listed as the author. I hope I may
have helped by describing some new possible uses for these functions.
Thank you,
Frederick
... I just realized that setGraphicsEventHandlers or getGraphicsEvent could have an 'onIdle' callback, to be called somewhere in the polling loop of gevents.c:163 - I think this would solve my problem #2 in a minimally disruptive way. On Mon, Jun 06, 2016 at 06:38:45PM -0700, frederik at ofb.net wrote:> Hi R-Devel, > > I've been working on an oscilloscope project using an Arduino > microcontroller board. I found that it's quite easy to get realtime > updates, e.g. 30+ frames per second, if I read data from the board in > a little Rcpp library. I have to use dev.hold() and dev.flush() to > keep the plot from flickering, which restricts me to the "cairo" X11 > device. > > I'd like to be able to add interactivity to the oscilloscope display, > for instance to bind a key to save the current plot to a file, or to > bind keys for adjusting the time scale etc. > > However, I ran into two problems: > > (1) setGraphicsEventHandlers only works on the "Xlib" X11 device, > which doesn't support buffering via dev.hold() - it flickers. > > (2) getGraphicsEvent and friends lack some interface features which > are needed to use the functions in an asynchronous fashion. Typically, > event listener library functions have a "timeout" parameter, and the > ability to return already-queued events. But getGraphicsEvent() has > neither - it waits indefinitely (you can't set a timeout), and it > seems to ignore events which occurred before it was called (I can't > figure out why, from the code, I guess the normal R event processing > grabs events which occur between calls to getGraphicsEvent?). > > It seems like it should be possible to set a handler for keyboard > events and have it execute in between plot updates when the user > presses a key - yet without blocking further updates if no key has > been pressed. > > Is anyone interested in fixing (1) and (2)? Or is there some other > library or workaround to solve my problems? > > Here is some code I used to play around with these functions: > > X11(type="Xlib"); > > keydown = function(key) { > cat("Got key: ",key); > lastkey <<- key > } > > setGraphicsEventHandlers(onKeybd = keydown); > > plot(c(0,0)); > getGraphicsEvent(); > > Well, I think it's great that getGraphicsEvent exists at all, and want > to salute Duncan Murdoch who is listed as the author. I hope I may > have helped by describing some new possible uses for these functions. > > Thank you, > > Frederick > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel >
Hi Frederik,>>>>> <frederik at ofb.net> >>>>> on Tue, 7 Jun 2016 15:20:05 -0700 writes:> ... I just realized that setGraphicsEventHandlers or > getGraphicsEvent could have an 'onIdle' callback, to be > called somewhere in the polling loop of gevents.c:163 - I > think this would solve my problem #2 in a minimally > disruptive way. I hope you will get some feedback about this by one of the graphics/devices experts from within R core. I'm not among them at all, but they may be busy or travelling currently. Also, as you are studying the C code and the issues anyway, it may be worthwhile to consider (as small as possible!) patches to the source you could also post to the bugzilla site if you prefer; attaching as text/plain to R-devel does work fine, too. Best regards, Martin > On Mon, Jun 06, 2016 at 06:38:45PM -0700, frederik at ofb.net > wrote: >> Hi R-Devel, >> >> I've been working on an oscilloscope project using an >> Arduino microcontroller board. I found that it's quite >> easy to get realtime updates, e.g. 30+ frames per second, >> if I read data from the board in a little Rcpp library. I >> have to use dev.hold() and dev.flush() to keep the plot >> from flickering, which restricts me to the "cairo" X11 >> device. >> >> I'd like to be able to add interactivity to the >> oscilloscope display, for instance to bind a key to save >> the current plot to a file, or to bind keys for adjusting >> the time scale etc. >> >> However, I ran into two problems: >> >> (1) setGraphicsEventHandlers only works on the "Xlib" X11 >> device, which doesn't support buffering via dev.hold() - >> it flickers. >> >> (2) getGraphicsEvent and friends lack some interface >> features which are needed to use the functions in an >> asynchronous fashion. Typically, event listener library >> functions have a "timeout" parameter, and the ability to >> return already-queued events. But getGraphicsEvent() has >> neither - it waits indefinitely (you can't set a >> timeout), and it seems to ignore events which occurred >> before it was called (I can't figure out why, from the >> code, I guess the normal R event processing grabs events >> which occur between calls to getGraphicsEvent?). >> >> It seems like it should be possible to set a handler for >> keyboard events and have it execute in between plot >> updates when the user presses a key - yet without >> blocking further updates if no key has been pressed. >> >> Is anyone interested in fixing (1) and (2)? Or is there >> some other library or workaround to solve my problems? >> >> Here is some code I used to play around with these >> functions: >> >> X11(type="Xlib"); >> >> keydown = function(key) { cat("Got key: ",key); lastkey <<- key } >> >> setGraphicsEventHandlers(onKeybd = keydown); >> >> plot(c(0,0)); getGraphicsEvent(); >> >> Well, I think it's great that getGraphicsEvent exists at >> all, and want to salute Duncan Murdoch who is listed as >> the author. I hope I may have helped by describing some >> new possible uses for these functions. >> >> Thank you, >> >> Frederick >> >> ______________________________________________ >> R-devel at r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel