Breakpoints class abstract final

Window size classes for the adaptive design system.

The three thresholds match the Material 3 window size classes, which in practice also line up with the iPad form factors: below 600 is a phone, 600–840 a tablet in portrait or an unfolded foldable, 840–1200 a tablet in landscape, and beyond that a desktop-class window.

Breakpoints drive LAYOUT, never type size

This is the rule the whole file exists to enforce. A wider screen shows more content — more grid columns, a permanent sidebar, a detail pane next to the list — it does not show bigger text. Body text is 17pt on an iPhone SE and 17pt on a 13" iPad, exactly as it is in every first-party app on both platforms.

The only thing that legitimately changes text size is the user's own accessibility setting (Dynamic Type on iOS, font size on Android), which Flutter applies for you. For anything typographic go to AdaptiveTypography in templates/foundation/adaptive_typography.dart; never derive a fontSize from a value in this file.

Window width vs. available width

of reads the window through MediaQuery, which is the right measure for a full-screen page. A widget that occupies only part of the window — an iPad Slide Over pane, a detail pane, a dialog — must instead measure its own box with a LayoutBuilder and call fromWidth; otherwise a 300pt-wide pane on a 1200pt window believes it is a desktop.