## Problem
`drawBmp()` allocates two row buffers via `malloc()` but doesn't check
if allocations succeed. On low memory, this causes a crash when the NULL
pointers are dereferenced.
## Fix
Add NULL check after both `malloc()` calls. If either fails, log error
and return early.
Changed `lib/GfxRenderer/GfxRenderer.cpp`.
## Test
- Defensive addition only - no logic changes
- Manual device testing appreciated
## Problem
`invertScreen()`, `storeBwBuffer()`, and `restoreBwBuffer()` dereference
`frameBuffer` without NULL validation. If the display isn't initialized,
these functions will crash.
## Fix
Add NULL checks before using `frameBuffer` in all three functions.
Follows the existing pattern from `drawPixel()` (line 11) which already
validates the pointer.
Changed `lib/GfxRenderer/GfxRenderer.cpp`.
## Test
- Follows existing validated pattern from `drawPixel()`
- No logic changes - only adds early return on NULL
- Manual device testing appreciated
## Summary
* Builds on top of
https://github.com/daveallie/crosspoint-reader/pull/16 - adresses
https://github.com/daveallie/crosspoint-reader/discussions/14
* This PR adds the ability for the user to supply a custom `sleep.bmp`
image at the root of the SD card that will be shown instead of the
default sleep screen if present.
* Supports:
* Different BPPs:
* 1bit
* 2bit
* 8bit
* 24bit
* 32bit (with alpha-channel ignored)
* Grayscale rendering
---------
Co-authored-by: Sam Davis <sam@sjd.co>
## Summary
- When allocating the `bwBuffer` required to restore the RED RAM in the
EPD, we were previously allocating the whole frame buffer in one
contiguous memory chunk (48kB)
- Depending on the state of memory fragmentation at the time of this
call, it may not be possible to allocate all that memory
- Instead, we now allocate 6 blocks of 8kB instead of the full 48kB,
this should mean the display updates are more resilient to different
memory conditions
## Additional Context
