Fix encoder breakage with 4 or more encoders #23595
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`(events->tail - 1) % MAX_QUEUED_ENCODER_EVENTS` did not calculate what the rest of code expected when `events->tail` was 0, except when `MAX_QUEUED_ENCODER_EVENTS` happened to be a power of 2, so the code seemed to work when the number of encoders was less than 4 (in that case `MAX_QUEUED_ENCODER_EVENTS` was set to 4), but broke when the number of encoders was 4 or more. Fix the queue full check to avoid negative numbers in calculations.
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Description
The encoder support was broken in various ways when having 4 or more encoders on any keyboard side (or, more precisely, when
MAX_QUEUED_ENCODER_EVENTSwas not a power of 2, which happened whenNUM_ENCODERS_MAX_PER_SIDEincreased above 3, unlessMAX_QUEUED_ENCODER_EVENTSwas set directly). In particular, with 4 encoders the encoder rotation did not have any effect.The problem was caused by
encoder_queue_full_advanced()always returningtrueeven when the queue was not actually full, which caused all encoder events to be dropped. The underlying reason was that(events->tail - 1) % MAX_QUEUED_ENCODER_EVENTSdid not calculate what the rest of code expected whenevents->tailwas 0, except whenMAX_QUEUED_ENCODER_EVENTShappened to be a power of 2, so the code seemed to work when the number of encoders was less than 4 (in that caseMAX_QUEUED_ENCODER_EVENTSwas set to 4), but broke when the number of encoders was 4 or more. With 4 encoders the code ended up calculating0xffff % 5U(or0xffffffff % 5Uon 32-bit platforms), which ended up being 0, so the initial state with an empty queue was mistakenly detected as full. But withMAX_QUEUED_ENCODER_EVENTS= 4 the result of0xffff % 4Uin the bad case happened to be what was expected, therefore the bug could not be noticed.Fix the queue full check to avoid negative numbers in calculations, so that the modulo operations would work as expected.
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