Module window 

Windows: how one is asked for, what it can be told to do, and what it currently is.

Two display modes, and no third

DisplayMode has exactly two variants because the windowing rules in docs/notes/backends.md lock it at two. Exclusive/true fullscreen — the mode that changes the display’s video timing — is dropped by decision, not deferred:

• Wayland cannot modeset from a client, by design.
• macOS fights it.
• On Windows, borderless plus the DXGI flip model gets independent-flip and MPO latency close enough to exclusive that the remaining difference does not buy back the alt-tab disasters, the mode-restore-on-crash problem, or the multi-monitor breakage.

Resolution control lives one layer up instead: in Borderless the renderer draws to an offscreen target at whatever internal resolution it wants and upscales to the native surface, either with a blit or — where ShellCaps::HW_UPSCALE is set — by handing the compositor the smaller buffer. The shell only ever presents native-size surfaces. A DisplayMode that carried a resolution would be a promise this crate cannot keep.

If a “true fullscreen” request ever arrives, the answer is that it is this enum’s absence of a variant, not a ShellError::Unsupported.

Aspect ratio is a constraint, not a mode

The windowing rules describe windowed mode as “freeform or aspect-locked”, which reads like two modes. It is one mode with a constraint, and the constraint lives in SizeConstraints alongside min/max — where the windowing plan’s trait sketch, set_constraints(win, c) // min/max/aspect, already put it. Modelling it in both places would create a question with no good answer: if DisplayMode::Windowed { aspect: Some(16:9) } and SizeConstraints { aspect: Some(4:3) } disagree, which wins? Keeping one home also means an aspect lock survives a round trip through borderless and back, which is what a player toggling modes expects.

Structs

SizeConstraints

Limits the window system should enforce on an interactive resize.

WindowConfiguration

What the window system has actually told us about a window.

WindowDesc

Everything needed to create a window.

WindowState

A window’s current, observable state.

Enums

CloseReply

What to do about a close request.

DisplayMode

How a window is presented.

Window

Marker type for the Handle that names a window.

Type Aliases

WindowId

Identifier of a window created by a Shell.