Fix int8_t overflow in RGB heatmap effect #18410
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The RGB heatmap effect currently has an issue where pressing the leftmost keys on the keyboard may light up the rightmost keys on the keyboard as well. This is because the distance calculation for the RGB heatmap effect uses int8_t to store the row distance and column distance. However, LED coordinates are stored as uint8_t, so it is possible to overflow the int8_t when calculating the row distance and column distance. Changing the row and column distance to int16_t fixes this overflow and resolves the original issue.
daskygit
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Sep 19, 2022
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Thanks, not sure how I missed this.
Ist this a problem that should be addressed? Or is it okay to rely on the keyboards to stay in the recommended range?
I think maybe a little bit of a rework is in order which is probably best submitted to develop. Reading through it again there's potential for a speed up and the user configurable defines should have some hard limits.
KarlK90
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Sep 19, 2022
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Thanks again. |
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Description
The RGB heatmap effect currently has an issue where pressing the leftmost keys on the keyboard may light up the rightmost keys on the keyboard as well.
This is because the distance calculation for the RGB heatmap effect uses
int8_tto store the row distance and column distance. However, LED coordinates are stored asuint8_t, so it is possible to overflow theint8_twhen calculating the row distance and column distance.Changing the row and column distance to
int16_tfixes this overflow and resolves the issue.QUESTION:
There might still be an issue if any keyboard does not follow the recommendation in https://github.com/qmk/qmk_firmware/blob/ecb4ba70b1d48835e75da6b0a8ad566c2f126b9f/docs/feature_rgb_matrix.md to define LED coordinates in the inclusive range
{ 0..224, 0..64 }. That document does suggest that the maximum value for both coordinates is255. If anyone does that, the intermediateint16_twill overflow again.Ist this a problem that should be addressed? Or is it okay to rely on the keyboards to stay in the recommended range?
I have reproduced the issue on a RP2040-based keyboard (my Lotus58; not in the main QMK repo) as well as an AVR-based keyboard (BM40HSRGB; in the main QMK repo). I have also verified the fix on both of them.
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Issues Fixed or Closed by This PR
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