java - Improve Performance On GUI log -

thanks yair altman's excellent post on undocumentedmatlab.com, i've tried implement gui logging program using rich editbox , underlying java components. here simplified version of code:

first code create panel

function jeditbox = logpanel()     hfig = figure('color', 'w');     hpanel = uipanel(hfig);      % prepare log editbox     hlogpanel = uicontrol('style', 'edit', 'max', 5, 'parent', hpanel, ...         'units', 'normalized', 'position', [0, 0.2, 1, 0.8], 'background', 'w');      % underlying java editbox, contained within scroll-panel     jscrollpanel = findjobj(hlogpanel);     try         jscrollpanel.setverticalscrollbarpolicy(jscrollpanel.java.vertical_scrollbar_as_needed);         jscrollpanel = jscrollpanel.getviewport();     catch %#ok<ctch>         % may possibly viewport, depending on release/platform etc.     end     jeditbox = handle(jscrollpanel.getview, 'callbackproperties');      % prevent user editing in log-panel     jeditbox.seteditable(false);      % set-up matlab callback function handle hyperlink clicks     set(jeditbox,'hyperlinkupdatecallback',@linkcallbackfcn);      % ensure have html-ready editbox     htmlclassname = 'javax.swing.text.html.htmleditorkit';     if ~isa(jeditbox.geteditorkit, htmlclassname)         jeditbox.setcontenttype('text/html');     end end 

then logging code:

function logmessage(jeditbox, text)     % newtext = [icontxt, msgtxt ' '];     text = [text '<br/>'];      % place html message segment @ bottom of editbox     currenthtml = char(jeditbox.gettext);     newhtml = strrep(currenthtml, '</body>', text);     jeditbox.settext(newhtml);     endposition = jeditbox.getdocument.getlength;     jeditbox.setcaretposition(endposition); end 

i have 2 problems:

1. there major performance issues in applications require large number of logged messages (i.e. > 500). using profiler , following code (note i've modified why return string rather printing command line), i've seen bottleneck settext(). can explain spikes in graph are?

   h = logpanel();  n = 1e3; time = nan(n, 1); profile on = 1:n     tic     logmessage(h, why)     time(i) = toc; end profile viewer avgtime = mean(time); figure('color', 'w') bar(time) hold on plot([0, n], avgtime*ones(1, 2), '-k', 'linewidth', 2) hold off title(sprintf('average time = %f [s]', avgtime)); 

   

   if add pause(0.1) after toc, graph looks like

   

   what's going on here?

2. this results in "flashy" log panel. each time write message, contents flicker scrolls top , bottom. once again, defect due settext(), forces caret beginning of document.

i'm looking solutions either of these problems, preferrably both.

of course, using gettext(), string manipulation , settext() bottleneck. force editor component convert it’s entire contents html representation , reparse entire html representation after change. editor not able detect added bit of text. more contents component has, higher performance loss.

if have swing text component , want append text @ end can use:

1. (the easy one) plain text:

   textcomp.setcaretposition(textcomp.getdocument().getlength()); textcomp.replaceselection("\nmore text"); 

2. (not harder) text in content type, e.g. html:

   document doc = textcomp.getdocument(); textcomp.geteditorkit().read(   new stringreader("more <i>styled</i> text"), doc, doc.getlength()); 

in second case, if want move caret end have add setcaretposition invocation in first case.