feat(render): logical style metrics with a UI scale, so chrome has a consistent physical size

adapters/gtk4/gtk_plot_area.hpp

@@ -110,11 +110,14 @@ using FrameFn = std::function<void(Plot&, f64 dt)>;
 /// a delta is then a logical difference scaled by the factor in force now, never
 /// the difference of two device positions (see `DragAnchor`).
 ///
-/// Note that this also means the renderer's *style metrics* stay in device
-/// pixels: at scale 2 the label font is 24 device px = 12 logical px, so labels
-/// are smaller relative to the widget than at 1x. That is the same convention
-/// the GLFW and Qt adapters use, and a host that wants a constant logical text
-/// size scales `Renderer::style()` metrics by the factor itself.
+/// The same factor states the display to the *renderer*: it is written to
+/// `Renderer::style().ui_scale` every frame, which is what makes the chrome the
+/// same physical size at any scale. The style's metrics are logical (see the unit
+/// rule on `render::Style` -- spec §10 reverses the older convention that had them
+/// in device pixels and accepted smaller labels on a high-DPI host), so at scale 2
+/// the label font is 12 logical px drawn at 24 device px: the same size on screen as
+/// at 1x, not a smaller one. This is the same convention the GLFW, Qt and ImGui
+/// adapters use, and none of them has to scale a style metric by hand.
 ///
 /// ## Input
 ///