Hello!
I have written my own watch face and I was trying to maximize battery life as much as possible. One consideration I had on mind was to only re-render the parts of the display I need to update, but I am struggling with that part.
Inspired by the onPartialUpdate() method, my idea was to re-render a small part of the display once a minute (the minutes value) and a full display update every hour (when minutes equals 0).
Something like this:
function onUpdate(dc) {
if (needAFullRedraw) {
...
View.onUpdate(dc);
} else {
dc.setClip(<dimensions>)
dc.setColor(Gfx.COLOR_WHITE, Gfx.COLOR_BLACK);
dc.clearClip();
dc.drawText(
x,
y,
Gfx.FONT_SYSTEM_NUMBER_THAI_HOT,
minutes.format("%02d"),
Gfx.TEXT_JUSTIFY_RIGHT
);
}
}
When a full redraw is not needed (needAFullRedraw = false) the minutes show up just fine and are updated accordingly. However, the rest of the display turns blank and I do not see any of the existing data that was previously set by View.onUpdate(). At least on a real device, on the emulator is all good regardless of the high-power mode or low-power mode setting.
On my watch, I measured the performance by logging the elapsed time within the onUpdate() method and it is definitely faster when only the minutes are re-rendered. However, I do not understand why everything else turns blank. Am I not supposed to mix View.onUpdate() and partial updates in the onUpdate() method? Thank you in advance!
PS: I understand that the main use case of onPartialUpdate() is to show up the seconds for a short amount of time, I just want to extend the idea of re-rendering a small part of the display in the onUpdate() method.
