ViewportState.h File Reference

ViewportState is the single source of truth for the editor render pane's screen↔document coordinate mapping. See docs/design_docs/0025-editor_ux.md for the full design rationale; this header is the public API. More...

#include "donner/base/Box.h"
#include "donner/base/Vector2.h"

Include dependency graph for ViewportState.h:

This graph shows which files directly or indirectly include this file:

Classes
struct	donner::editor::ViewportState
	All viewport state for a single frame of the render pane. Plain data, side-effect-free, copyable, ~80 bytes. More...

Namespaces
namespace	donner
	Top-level Donner namespace, which is split into different sub-namespaces such as donner::svg and donner::css.

Detailed Description

ViewportState is the single source of truth for the editor render pane's screen↔document coordinate mapping. See docs/design_docs/0025-editor_ux.md for the full design rationale; this header is the public API.

Conceptually a ViewportState is a value the main loop snapshots once at the top of each frame and then hands to every reader (async render dispatch, click math, overlay re-render, image draw, inspector text). Every reader consults the same value, so the four pieces never disagree about where the document is on screen.

Coordinate spaces:

• document / world: SVG viewBox coordinates.
• screen: ImGui screen-pixel coordinates in logical pixels, (0, 0) at the top-left of the OS window. On Retina, a mouse position of (100, 100) is the same logical pixel regardless of devicePixelRatio.
• device pixel: physical pixels in the rasterized bitmap. Equal to screen * devicePixelRatio. Only the SVG renderer's bitmap output and the GL texture upload care about this.

Zoom semantics: zoom == 1.0 means 100% — one SVG viewBox unit takes exactly one screen pixel. This is the initial state when the editor opens and the target of Cmd+0 / View → Reset Zoom. The user can pan freely if the document doesn't fit the window.