WPS power management

[seani]

Much along the lines of "is the light out when the fridge door is shut":

When the LCD/backlight is off, does RockBox continue to update the WPS?

I.e. is it still beavering away scrolling text, calculation percentages, animating various stuff, and then rendering it to some framebuffer, but you can't see the result, or is that sort of update suspended until the LCD wakes up?

If it *is* rendering invisibly, are there any potential savings on battery life, or is the additional CPU miniscule in comparison with everything else?

I ask because when fiddling with the scroll settings, when you see the screen activity on some tracks/WPS combinations, it looks expensive.

[NicolasP]

Yes, the WPS continues to be rendered when the backlight is off.
There is a simple reason why it does: on many targets, the screen is still readable even when the backlight is off.

[seani]

Ok, thanks. Any mileage in allowing this behaviour to be switchable, particularly in situations where the LCD controller itself is switched off?

Would a simplified WPS have any impact (i.e. no scrolling, minimum info etc.), or does the latency of generating the WPS /per-se/ outweigh any processing variations for a /particular/ WPS format?

[nls]

If you avoid peakmeters in your wps the required cpu to render it is probably immesurable...

[Vortex]

Yes, the WPS continues to be rendered when the backlight is off.

It depends on the target. On the Sansa, the LCD controller is shut off when the backlight is off. Therefore the image appears 'frozen' and does not get updated.

That's because you cannot read anything on the Sansa's display while the backlight is off. The Original Firmware actually does the same thing.

[seani]

If you avoid peakmeters in your wps the required cpu to render it is probably immesurable...

This was my question really. I've done a fair bit of work on embedded/limited resource targets in the past, but it was some time ago. I don't have any feel for how expensive rendering/scrolling text etc. would be on more modern targets.

The Gigabeat I'm using is probably several orders of magnitude more powerful than anything I've actually coded for.