On Thursday, 11 June 2020 at 06:05:09 UTC, adnan338 wrote:
I would like to set a callback for the `download()` function
but I do not seem to find a way to add a callback to the
procedure.
Let's say, for example I have a GtkD Widget called "pb" (short
for progressBar).
I want to download a file from a url and when done, I want a
callback to access pb and increase by a certain number.
The GtkD progress bar API:
https://api.gtkd.org/gtk.ProgressBar.ProgressBar.setFraction.html
Normally, If it was dependent on a button, I would do something
like:
auto pb = new ProgressBar();
auto more = new Button("go-next", GtkIconSize.BUTTON);
more.addOnClicked(delegate void(Button _) {
if (activityMode.getActive()) // ignore this if
condition
pb.pulse;
else
pb.setFraction(pb.getFraction + pb.getPulseStep);
});
But how can I do this with `download()`?
From the docs on download() method it has an optional connection
reference
https://dlang.org/phobos/std_net_curl.html#.download
And connection has onProgress callback, you can add some global
variable and update it using this callback.
Now of course another problem left up to you, not thread safe
means you should expect the worst if you try to use the library
from multiple threads, this is especially true for UI libraries
as some OS implies some restrictions on UI interactions as well.
So you need to find relevant mechanism to do a event loop
scheduling and update progress bar using it by feeding the values
from somewhere else.
See https://dlang.org/phobos/std_net_curl.html#.HTTP under
"Tracking progress: " example.
It turns out you might not need to use download() at all.
Pseudocode:
// some global vars to track it
size_t bytesTotal;
size_t bytesReceived;
// in your downloader thread
auto http = HTTP();
http.method = HTTP.Method.get;
http.url = "http://upload.wikimedia.org/wikipedia/commons/"; ~
"5/53/Wikipedia-logo-en-big.png";
http.onReceive = (ubyte[] data) { bytesTotal = 0; bytesReceived
= 0; return data.length; };
http.onProgress = (size_t dltotal, size_t dlnow,
size_t ultotal, size_t ulnow)
{
bytesTotal = dltotal;
bytesReceived = dlnow;
return 0;
};
// somewhere in GTK do something like this, it is up to you to
find out how to do this
void check_dl_status()
{
// here we are using globals that updates on another thread
auto progressPct = bytesTotal / bytesReceived;
progresBar.setPercent (progressPct);
if (progressPct < 1)
event.publish (check_dl_status);
}
