WIP: feat: Partial update

[kienvo]

Resolves #58

Summary by Sourcery

Implement partial update capability by adding protocol commands for setting a partial window and toggling partial mode, and integrate these into the display update sequence

New Features:

• Add methods to configure a partial display window and to enter/exit partial update mode for the e-paper display
• Integrate partial update setup into the image rendering and refresh workflow

Enhancements:

• Validate partial window parameters with bounds checks before sending commands

[sourcery-ai]

Reviewer's Guide

This PR adds support for partial updates on the E-Paper display by introducing new private methods to configure and control a partial window (_setPartialWindow, _partialIn, _partialOut) with input validation and bit-level command packing, and integrates these calls into the existing frame transmission and refresh sequence.

Sequence diagram for partial update integration in E-Paper refresh

sequenceDiagram
    participant App
    participant Protocol
    participant EPDController
    participant FlutterNfcKit

    App->>Protocol: refresh(id, image, epd)
    Protocol->>Protocol: _setPartialWindow(id, 0, epd.width/8-1, 0, epd.height-1, true)
    Protocol->>EPDController: epd.extractEpaperColorFrames(image)
    loop for each color frame
        Protocol->>EPDController: transmissionLines.current
        Protocol->>Protocol: writeFrame(id, color, transmissionLine)
    end
    Protocol->>Protocol: _setPartialWindow(id, 0, 15, 0, 200, true)
    Protocol->>Protocol: _partialIn(id)
    Protocol->>Protocol: _writeMsg([fw.epdCmd, epd.controller.refresh])
    Protocol->>FlutterNfcKit: finish()

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Class diagram for Protocol class with partial update methods

classDiagram
    class Protocol {
        +Future<Uint8List> enableEnergyHarvesting(Uint8List tagId)
        +Future<void> _sleep()
        +Future refresh(Uint8List id, Image image, EPD epd)
        -Future<Uint8List> _setPartialWindow(Uint8List tagId, int xsbank, int xebank, int ys, int ye, bool pt_scan)
        -void _partialIn(Uint8List tagId)
        -void _partialOut(Uint8List tagId)
    }

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File-Level Changes

Change	Details	Files
Implemented partial window configuration and control commands	Defined _setPartialWindow with parameter validation and bitwise assembly of window bytes Created _partialIn and _partialOut to send enter/exit partial mode commands Leveraged _writeMsg to dispatch EPD command and data sequences	lib/util/protocol.dart
Integrated partial update into the image transmission flow	Added initial _setPartialWindow call after power-on delay Inserted a second _setPartialWindow and _partialIn before issuing the refresh command Ensured the partial window parameters match display width/height and scanning flag	lib/util/protocol.dart

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#58	Implement partial updates to the e-paper display, allowing specific regions to be refreshed without affecting the entire screen.	✅

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[kienvo]

Partial refreshing won't fix the blurred pixels issue:

Hopefully #59 will fix this.