move the details text follow with cursor

[tty5]

if not, it will can't be seen the details text when the column is
too long, beyond the display screen

[tty5]

@brendangregg

[yangoliver]

@brendangregg We encountered this issue too. While moving the cursor, the heatmap SVG data always showed at left bottom corner of the browser. When the map is bigger, we have to scroll the bar, that make the SVG data invisible because it always showed at fixed location.

[brendangregg]

Thanks, it mostly works, but there are cases where I'm examining the right side of a large heatmap and the text is no longer visible again (truncated to the right). It's also a bit visually distracting to have the text move around. Is there a way to fix the text to be the middle of the visible x-axis?