Graph Gridlines / Target Range Offset

[channemann]

It appears as if there is an offset or scaling issue between the gridlines and the target range lines.

My graph boundaries are 40 - 240, and my target range is 80 - 180, with gridlines every 20. The lower and upper target range lines should therefor overlap normal gridlines. As you can see in the photo, it appears as if the upper target range line is offset from where it should be, sitting slightly lower (it's closer to 160 than 200).

[mddub]

Yeah, this is a result of the target range lines being an even number of pixels tall (4). I chose to make the extra pixel fall on the inside of the range (so the top looks a little low, and the bottom looks a little high). It just happens to be super noticeable on a shorter graph:

https://github.com/mddub/urchin-cgm/blob/ead0c4/src/graph_element.c#L63

They look less wrong if I reduce it from 4 to 3 pixels:

My on-wrist testing suggested 3 pixels was a little too thin, and 5 pixels... well, that just sounds crazy. Maybe you can try building with 3/5 and let me know how it feels. I'll have to think about this a little more.

[channemann]

3 feels pretty good, actually. Since they are pretty distinct from the
dashed lines, they don't need a lot of thickness to be glanceable. 5 is
definitely overkill. It's pretty minor, so I wouldn't sweat it.

On Thu, Jan 28, 2016 at 1:10 PM, Mark Wilson [email protected]
wrote:

Yeah, this is a result of the target range lines being an even number of
pixels tall (4). I chose to make the extra pixel fall on the inside of the
range (so the top looks a little low, and the bottom looks a little high).
It just happens to be super noticeable on a shorter graph:

https://github.com/mddub/urchin-cgm/blob/ead0c4/src/graph_element.c#L63

They look less wrong if I reduce it from 4 to 3 pixels:

https://camo.githubusercontent.com/5630c5c054b47b2248a38c39893a319860aa4a3a/687474703a2f2f692e696d6775722e636f6d2f6f7951554733432e706e67

https://camo.githubusercontent.com/cb394a2c1bd78539da0fbe2e823572d80eb74189/687474703a2f2f692e696d6775722e636f6d2f634f45416455732e706e67

My on-wrist testing suggested 3 pixels was a little too thin, and 5
pixels... well, that just sounds crazy. Maybe you can try building with 3/5
and let me know how it feels. I'll have to think about this a little more.

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Chris Hannemann
[email protected]