A stable Wi-Fi address is a lifecycle policy, not merely a setting called “stable.” Decide which identity survives a reboot, profile replacement, firmware reinstall, factory reset and radio replacement. Then prove that the address observed by the network owner follows that policy. A reservation or admission entry can silently stop matching when an input to…
Keep the month being browsed, the date being edited and the committed device value in separate application fields. An LVGL calendar displays and reports dates; browsing a month or marking “today” must not itself change the device clock. Validate a complete year-month-day snapshot, then submit it only through an explicit Apply action. Applicability: LVGL v9.3.0…
Choose an observer registration API according to the target’s lifetime, then give every subscription exactly one cleanup path. Widget-associated observers can be removed automatically when that widget is deleted. A generic target pointer has no such lifecycle hook, even when the pointer happens to contain a widget address. Applicability: LVGL v9.3.0 with LV_USE_OBSERVER enabled, one…
A draw callback should describe pixels from already-prepared state. It must not change widget properties, create or delete widgets, or request another invalidation while rendering is in progress. Being on the correct UI thread does not make those operations legal during the drawing phase. Applicability: LVGL v9.3.0, a serialized UI owner, the ordinary software draw…
Expand dirty rectangles outward before rendering, using the controller’s window granularity and inclusive endpoints. Then prove that the expanded rectangle fits the logical display and that the draw buffer can hold at least one permitted transfer-height unit at the widest possible area. Changing coordinates only inside flush is too late to create missing pixels. Applicability:…
Place the persistent alarm view under the display’s top layer, then specify which rectangles may capture a pointer. Keep the full-screen top layer non-clickable unless the product deliberately requires a modal barrier. Visibility above a page and ownership of every touch are separate choices. Applicability: LVGL v9.3.0, one display, pointer input, rectangular untransformed objects and…
A custom decoder must clean up a failed open itself. Successful probing does not transfer every temporary resource to a future close callback. After a session opens successfully, give its caller one explicit close responsibility, including when incremental decoding stops early or fails. Applicability: this article pins LVGL v9.3.0 and a file-backed incremental decoder in…
Store a stable configuration value in the application model and derive the dropdown’s selected index from the current option table. Replacing or translating option text must not silently change that value. If the stored value disappears from the available choices, enter an explicit reconciliation state instead of accepting whichever option becomes index zero. Applicability: this…
Map each button-matrix index to a stable application action, and regenerate that mapping whenever the displayed button order changes. Do not dispatch by translated text, raw string-array position or remembered numeric index. Labels, row separators, control flags and action IDs must describe the same matrix generation. Applicability: this procedure pins LVGL v9.3.0 and a command…
Validate translation completeness independently of rendering, then give every existing text widget an explicit language-refresh strategy. A successful lookup does not prove a translation exists, because LVGL can return the key itself. A label that copied yesterday’s lookup does not automatically remember which key produced it. Applicability: this article pins LVGL v9.4.0 with LV_USE_TRANSLATION enabled….