• What is the goal of this PR? Implement a horizontal EPUB reading mode so books can be read in landscape orientation (both 90° and 270°), while keeping the rest of the UI in portrait. • What changes are included? ◦ Rendering / Display ▪ Added an orientation model to GfxRenderer (Portrait, LandscapeNormal, LandscapeFlipped) and made: ▪ drawPixel, drawImage, displayWindow map logical coordinates differently depending on orientation. ▪ getScreenWidth() / getScreenHeight() return orientation‑aware logical dimensions (480×800 in portrait, 800×480 in landscape). ◦ Settings / Configuration ▪ Extended CrossPointSettings with: ▪ landscapeReading (toggle for portrait vs. landscape EPUB reading). ▪ landscapeFlipped (toggle to flip landscape 180° so both horizontal holding directions are supported). ▪ Updated settings serialization/deserialization to persist these fields while remaining backward‑compatible with existing settings files. ▪ Updated SettingsActivity to expose two new toggles: ▪ “Landscape Reading” ▪ “Flip Landscape (swap top/bottom)” ◦ EPUB Reader ▪ In EpubReaderActivity: ▪ On onEnter, set GfxRenderer orientation based on the new settings (Portrait, LandscapeNormal, or LandscapeFlipped). ▪ On onExit, reset orientation back to Portrait so Home, WiFi, Settings, etc. continue to render as before. ▪ Adjusted renderStatusBar to position the status bar and battery indicator relative to GfxRenderer::getScreenHeight() instead of hard‑coded Y coordinates, so it stays correctly at the bottom in both portrait and landscape. ◦ EPUB Caching / Layout ▪ Extended Section cache metadata (section.bin) to include the logical screenWidth and screenHeight used when pages were generated; bumped SECTION_FILE_VERSION. ▪ Updated loadCacheMetadata to compare: ▪ font/margins/line compression/extraParagraphSpacing and screen dimensions; mismatches now invalidate and clear the cache. ▪ Updated persistPageDataToSD and all call sites in EpubReaderActivity to pass the current GfxRenderer::getScreenWidth() / getScreenHeight() so portrait and landscape caches are kept separate and correctly sized. Additional Context • Cache behavior / migration ◦ Existing section.bin files (old SECTION_FILE_VERSION) will be detected as incompatible and their caches cleared and rebuilt once per chapter when first opened after this change. ◦ Within a given orientation, caches will be reused as before. Switching orientation (portrait ↔ landscape) will cause a one‑time re‑index of each chapter in the new orientation. • Scope and risks ◦ Orientation changes are scoped to the EPUB reader; the Home screen, Settings, WiFi selection, sleep screens, and web server UI continue to assume portrait orientation. ◦ The renderer’s orientation is a static/global setting; if future code uses GfxRenderer outside the reader while a reader instance is active, it should be aware that orientation is no longer implicitly fixed. ◦ All drawing primitives now go through orientation‑aware coordinate transforms; any code that previously relied on edge‑case behavior or out‑of‑bounds writes might surface as logged “Outside range” warnings instead. • Testing suggestions / areas to focus on ◦ Verify in hardware: ▪ Portrait mode still renders correctly (boot, home, settings, WiFi, reader). ▪ Landscape reading in both directions: ▪ Landscape Reading = ON, Flip Landscape = OFF. ▪ Landscape Reading = ON, Flip Landscape = ON. ▪ Status bar (page X/Y, % progress, battery icon) is fully visible and aligned at the bottom in all three combinations. ◦ Open the same book: ▪ In portrait first, then switch to landscape and reopen it. ▪ Confirm that: ▪ Old portrait caches are rebuilt once for landscape (you should see the “Indexing…” page). ▪ Progress save/restore still works (resume opens to the correct page in the current orientation). ◦ Ensure grayscale rendering (the secondary pass in EpubReaderActivity::renderContents) still looks correct in both orientations. --------- Co-authored-by: Dave Allie <dave@daveallie.com> |
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CrossPoint Reader
Firmware for the Xteink X4 e-paper display reader (unaffiliated with Xteink). Built using PlatformIO and targeting the ESP32-C3 microcontroller.
CrossPoint Reader is a purpose-built firmware designed to be a drop-in, fully open-source replacement for the official Xteink firmware. It aims to match or improve upon the standard EPUB reading experience.
Motivation
E-paper devices are fantastic for reading, but most commercially available readers are closed systems with limited customisation. The Xteink X4 is an affordable, e-paper device, however the official firmware remains closed. CrossPoint exists partly as a fun side-project and partly to open up the ecosystem and truely unlock the device's potential.
CrossPoint Reader aims to:
- Provide a fully open-source alternative to the official firmware.
- Offer a document reader capable of handling EPUB content on constrained hardware.
- Support customisable font, layout, and display options.
- Run purely on the Xteink X4 hardware.
This project is not affiliated with Xteink; it's built as a community project.
Features & Usage
- EPUB parsing and rendering
- Image support within EPUB
- Saved reading position
- File explorer with file picker
- Basic EPUB picker from root directory
- Support nested folders
- EPUB picker with cover art
- Custom sleep screen
- Cover sleep screen
- Wifi book upload
- Wifi OTA updates
- Configurable font, layout, and display options
- Screen rotation
See the user guide for instructions on operating CrossPoint.
Installing
Web (latest firmware)
- Connect your Xteink X4 to your computer via USB-C
- Go to https://xteink.dve.al/ and click "Flash CrossPoint firmware"
To revert back to the official firmware, you can flash the latest official firmware from https://xteink.dve.al/, or swap back to the other partition using the "Swap boot partition" button here https://xteink.dve.al/debug.
Web (specific firmware version)
- Connect your Xteink X4 to your computer via USB-C
- Download the
firmware.binfile from the release of your choice via the releases page - Go to https://xteink.dve.al/ and flash the firmware file using the "OTA fast flash controls" section
To revert back to the official firmware, you can flash the latest official firmware from https://xteink.dve.al/, or swap back to the other partition using the "Swap boot partition" button here https://xteink.dve.al/debug.
Manual
See Development below.
Development
Prerequisites
- PlatformIO Core (
pio) or VS Code + PlatformIO IDE - Python 3.8+
- USB-C cable for flashing the ESP32-C3
- Xteink X4
Checking out the code
CrossPoint uses PlatformIO for building and flashing the firmware. To get started, clone the repository:
git clone --recursive https://github.com/daveallie/crosspoint-reader
# Or, if you've already cloned without --recursive:
git submodule update --init --recursive
Flashing your device
Connect your Xteink X4 to your computer via USB-C and run the following command.
pio run --target upload
Internals
CrossPoint Reader is pretty aggressive about caching data down to the SD card to minimise RAM usage. The ESP32-C3 only has ~380KB of usable RAM, so we have to be careful. A lot of the decisions made in the design of the firmware were based on this constraint.
EPUB caching
The first time chapters of an EPUB are loaded, they are cached to the SD card. Subsequent loads are served from the
cache. This cache directory exists at .crosspoint on the SD card. The structure is as follows:
.crosspoint/
├── epub_12471232/ # Each EPUB is cached to a subdirectory named `epub_<hash>`
│ ├── progress.bin # Stores reading progress (chapter, page, etc.)
│ ├── 0/ # Each chapter is stored in a subdirectory named by its index (based on the spine order)
│ │ ├── section.bin # Section metadata (page count)
│ │ ├── page_0.bin # Each page is stored in a separate file, it
│ │ ├── page_1.bin # contains the position (x, y) and text for each word
│ │ └── ...
│ ├── 1/
│ │ ├── section.bin
│ │ ├── page_0.bin
│ │ ├── page_1.bin
│ │ └── ...
│ └── ...
│
└── epub_189013891/
Deleting the .crosspoint directory will clear the cache.
Due the way it's currently implemented, the cache is not automatically cleared when the EPUB is deleted and moving an EPUB file will reset the reading progress.
Contributing
Contributions are very welcome!
If you're looking for a way to help out, take a look at the ideas discussion board. If there's something there you'd like to work on, leave a comment so that we can avoid duplicated effort.
To submit a contribution:
- Fork the repo
- Create a branch (
feature/dithering-improvement) - Make changes
- Submit a PR
CrossPoint Reader is not affiliated with Xteink or any manufacturer of the X4 hardware.
Huge shoutout to diy-esp32-epub-reader by atomic14, which was a project I took a lot of inspiration from as I was making CrossPoint.
