screenpixels.h File Reference

Inverse-zoom helpers for screen-pixel-sized geometry. More...

Go to the source code of this file.

Namespaces
namespace	OpenSWMM
namespace	OpenSWMM::Render

Functions
constexpr double	OpenSWMM::Render::sceneSizeFromPixels (double pixelSize, double pixelsPerSceneUnit) noexcept
	Convert a screen-pixel size to a scene-space offset.
constexpr double	OpenSWMM::Render::pixelsFromSceneSize (double sceneSize, double pixelsPerSceneUnit) noexcept
	Inverse of sceneSizeFromPixels — convert a scene-space offset back to its on-screen pixel size at the current zoom.

Detailed Description

Inverse-zoom helpers for screen-pixel-sized geometry.

Author

Caleb Buahin caleb.nosp@m..bua.nosp@m.hin@g.nosp@m.mail.nosp@m..com

Date

2026

License\n GPL-3.0-or-later

    Plan reference: RENDERING_OUTPUT_SUBLAYERS_PLAN.md §2 Decision 2
    and §3 (SublayerContext carries pixelsPerSceneUnit so sublayer
    buildOrUpdateNode() implementations can emit screen-pixel-sized
    vertices regardless of zoom).

    Pixels-per-scene-unit is the absolute scale factor on the X-axis
    of the view matrix (`|m11|`). When the user zooms in by 2×,
    pixelsPerSceneUnit doubles; the same on-screen pixel size becomes
    a smaller scene-space offset.

    All functions are constexpr / noexcept / pure-numeric so they
    pull in no Qt headers. Keep this header dependency-free so it
    can be included from the tightest QSG inner loops.