VizIR is super slow.

[mcourteaux]

Loading a page takes me about 12 seconds on a high-end desktop.
I recorded what's happening in Chromium with the performance profiler in the Developer Tools.

Trace-20230726T110312.json.zip

The first half of the time (below in green rectangle) is spent in init_tooltips, which calls out to some jQuery which takes all the time in querySelectorAll. The piece of offending code, according to the profile, is this one:

        function init_tooltips(btns, prefix) {
            var re = /(?:\-([^-]+))?$/;
            for (var i = 0; i < btns.size(); i++) {
                const button = btns[i];
                const tooltip = $(prefix + re.exec(button.id)[1])[0];
                button.is_clicked = false;
                button.addEventListener('mouseenter', ()=>{
                    if (!button.is_clicked)
                        showTooltip(button, tooltip);
                }
                );
                button.addEventListener('mouseleave', ()=>{
                    if (!button.is_clicked)
                        hideTooltip(tooltip);
                }
                );
                button.addEventListener('click', ()=>{
                    if (button.is_clicked) {
                        hideTooltip(tooltip);
                        button.is_clicked = false;
                    } else {
                        showTooltip(button, tooltip);
                        button.is_clicked = true;
                    }
                }
                );
            }
        }

The culprit is the $() call, I assume.

Second half of the time is spent in the same querySelectorAll but without a parent call.

[mcourteaux]

@maaz139 I think you made this tool?

[mcourteaux]

I'm working on this. Will open a Draft PR where I can document progress.

[mcourteaux]

#7713