Chart can't display full range

[ellchr00]

LVGL version

v9.2.2

Platform

VSCODE in MinGW but irrelevant

What happened?

Using a chart (linechart) and setting the range to int32_t MIN and int32_t MAX and a series consistent of 0's does not draw the line in the middle. of the chart window.

I followed the issue into lv_chart.c and found the following problem: In the calculations there will be a wrap around depending on the chart drawing area and it is not possible to draw the full 4 byte range like this.

847: int32_t y_tmp = (int32_t)((int32_t)ser->y_points[p_prev] - chart->ymin[ser->y_axis_sec]) * h;
848: y_tmp = y_tmp / (chart->ymax[ser->y_axis_sec] - chart->ymin[ser->y_axis_sec]);

where h in my case are 133 (pixels) , with a y_point being 0 and chart->ymin being −2147483648.
y_tmp will be 1 instead of the expected 66 -> therefore the line will be at the bottom of the window instead of the middle

multiple instances of said calculations can be found within the code .....

I don't know what the best solution of this problem is .... either using int64_t (not available on all platforms) or via float (undesired performance issue ?)

What is your take on the problem ? Am I the only one experiencing it ? Looking forward to an answer ...

How to reproduce?

No response

[kisvegabor]

Hey,

Thank you for reporting and tracking this issue.

I don't know what the best solution of this problem is .... either using int64_t (not available on all platforms) or via float (undesired performance issue ?)

I agree with this. None of these solutions are ideal. 🙁

I wonder if we can eliminate the need for -2M..2M range, for example by scaling down the input data. E.g. can you just divide all values by 10k and use a +/- 200 range?