* Fix dirtying in oled_write_pixel()
Set the dirty bit for the block only if oled_write_pixel() actually
changed the buffer state. Without this check oled_write_pixel() could
not be used inside the oled_task_user() code using the “redraw always”
style, because the blocks touched by oled_write_pixel() would always
appear dirty, and oled_render() would not proceed beyond the first such
dirty block.
* Fix oled_write_pixel() with 90/270 degree rotation
Use oled_rotation_width instead of OLED_DISPLAY_WIDTH, so that a rotated
display would be handled correctly.
* Fix compilation with custom OLED_BLOCK_COUNT and OLED_BLOCK_SIZE
Some OLED sizes (e.g., 64×48) may require a nonstandard value of
OLED_BLOCK_COUNT. The documentation says that this value may be
redefined in config.h, but actually trying to redefine it caused a
compile error, because the macro was redefined in oled_driver.c.
Make the OLED_BLOCK_COUNT definition in oled_driver.c respect any
user override, and do the same for OLED_BLOCK_SIZE just in case.
* Fix handling of out-of-range bits in oled_dirty
If a custom OLED_BLOCK_COUNT value is specified, some bits in oled_dirty
may not correspond to existing blocks; however, if those bits are set
somewhere (e.g., by code with sets oled_dirty to ~0 or even -1),
oled_render() would try to handle them and could access memory beyond
oled_buffer and perform hardware operations with out of range values.
Prevent this by masking off unused bits in oled_render(), and also avoid
setting those bits in other functions.
* Fix potentially wrong dirtying in oled_write_char()
oled_write_char() tried to mark the position just beyond the written
character as dirty; use (OLED_FONT_WIDTH - 1) to dirty the last position
still belonging to the character instead.
* Fix `#define OLED_BLOCK_TYPE uint32_t` on AVR
Using uint32_t as OLED_BLOCK_TYPE did not work properly on AVR, because
some bit shifts were performed using 16-bit int. Add explicit casts to
OLED_BLOCK_TYPE to those shifts.
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