The UI scale was folded into the pixel seam, with the root and `UIParent` at scale 1. Frames outside `UIParent` (dropdown menus, need/greed rolls, the world map) shrank with it, `UIParent:GetScale()` answered 1, and `GetCursorPosition()` was off by the scale.
In 1.12.1 the scale is `UIParent`'s own frame scale (`0x494550` → `0x76ac10`, floored at 0.64) over a 768-unit root. `GetScreenWidth`/`GetScreenHeight` divide by it (`0x494590`), and `GetCursorPosition` (`0x48b820`) does not.
Now the seam is `height/768`, and the scale is applied to `UIParent` at the load's end and on a resize. The nameplates' compensation is gone. Backdrops, hit insets and minimap pings now follow a frame's own scale (`0x76b580`, `0x77e8d0`); tooltips at the cursor and `OnCursorChanged` divide by it (`0x530b20`, `0x77db23`). Tests cover each, and a stock-UI comparison shows nothing inside `UIParent` moves.
Fixes#172🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>