fix: resolved the issue of layer1 flickering when scrolling down

[guowei0105]

…irst time after booting up

Summary by CodeRabbit

• Bug Fixes

  • Corrected background layer reconfiguration during hide transitions to prevent stale state and display glitches.

• Refactor

  • Reworked background/layer management into an instance-based manager for clearer state handling and simpler call sites.

• Documentation

  • Added a brief docstring for the background JPEG loader for improved clarity.

[coderabbitai]

Walkthrough

Adds LTDC layer-1 reconfiguration when hiding Layer2 in the LCD driver and refactors homescreen Layer2 handling into a new Layer2Manager instance with related constants and instance-based APIs; also adds a docstring before a display function declaration.

Changes

Cohort / File(s)	Summary
LCD driver layer reconfiguration core/embed/extmod/modtrezorui/mipi_lcd.c	When target y <= -lcd_params.vres, builds and applies a LTDC_LAYERCONFIG for layer 1 (x0=0, x1=hres, y0=-vres, y1=vres, pixel_format, address=LAYER2_MEMORY_BASE) before disabling the layer and issuing a vertical-blank reload.
Homescreen Layer2 manager refactor core/src/trezor/lvglui/scrs/homescreen.py	Adds Layer2Manager class, constants (LAYER2_VISIBLE_Y, LAYER2_HIDDEN_Y, LAYER2_ANIM_TIME_MS, LAYER2_ANIM_DELAY_MS), converts classmethods/static access to instance methods (ensure_background, reset_background_cache, preload_background, set_visibility, cleanup_timers, schedule_once), and creates global l2_manager = Layer2Manager(display). Updates call sites to use l2_manager.
Header docstring addition core/embed/extmod/modtrezorui/modtrezorui-display.h	Adds a short Python-style docstring block immediately before cover_background_load_jpeg declaration; no signature or behavior changes.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

• Review migration of all call sites in core/src/trezor/lvglui/scrs/homescreen.py to ensure state is correctly handled by the new l2_manager instance.
• Verify LTDC layer reconfiguration in core/embed/extmod/modtrezorui/mipi_lcd.c for correct bounds/addresses and no visual artifacts.
• modtrezorui-display.h docstring is trivial.

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 11.54% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main fix: resolving layer1 flickering during scrolling by reconfiguring LTDC layer 1 before hiding it.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📥 Commits

Reviewing files that changed from the base of the PR and between ee0da40 and 7ecb484.

⛔ Files ignored due to path filters (1)

• core/mocks/generated/trezorui.pyi is excluded by !**/generated/**

📒 Files selected for processing (1)

• core/embed/extmod/modtrezorui/modtrezorui-display.h (1 hunks)

✅ Files skipped from review due to trivial changes (1)

• core/embed/extmod/modtrezorui/modtrezorui-display.h

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (3)

• GitHub Check: Gen check
• GitHub Check: Defs check
• GitHub Check: Style check

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[revan-zhang]

✅ Snyk checks have passed. No issues have been found so far.

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[coderabbitai]

Actionable comments posted: 4

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

core/src/trezor/lvglui/scrs/homescreen.py (1)

154-185: Catching bare Exception hides real errors.

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

Cache: Disabled due to data retention organization setting

Knowledge base: Disabled due to data retention organization setting

Disabled knowledge base sources:

• Jira integration is disabled by default for public repositories

You can enable these sources in your CodeRabbit configuration.

📥 Commits

Reviewing files that changed from the base of the PR and between 1cc58a3 and ee0da40.

⛔ Files ignored due to path filters (1)

• core/mocks/generated/trezorui.pyi is excluded by !**/generated/**

📒 Files selected for processing (2)

• core/embed/extmod/modtrezorui/mipi_lcd.c (1 hunks)
• core/src/trezor/lvglui/scrs/homescreen.py (13 hunks)

🧰 Additional context used

🪛 Ruff (0.14.4)

core/src/trezor/lvglui/scrs/homescreen.py

666-666: Do not catch blind exception: Exception

(BLE001)

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1277-1277: Do not catch blind exception: Exception

(BLE001)

🔇 Additional comments (1)

core/embed/extmod/modtrezorui/mipi_lcd.c (1)

1196-1197: Verify negative window coordinate validity.

Line 1196 sets config.y0 = -((int32_t)lcd_params.vres) (negative value). When this gets assigned to the STM32 HAL's WindowY0 (uint32_t), it converts to a very large positive number via two's complement. Confirm STM32H745 LTDC hardware accepts negative-derived coordinates or if this should use unsigned positive values instead.

[web]
Do STM32H745 LTDC layer window coordinates (WHPCR/WVPCR registers) support or require non-negative values?

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