View and export

The editor’s right-hand column ends with a View and export panel that groups four pieces of view polish: switching the colour theme, saving and restoring camera positions, exporting the current view or selection to a file, and a print-style monochrome render mode. The logic that can be pure is pure and lives in reticle-app’s viewexport module, unit-tested without a window; the egui and GPU wiring is a thin layer in the app module.

Theme switching

Reticle opens in a dark theme. The Toggle theme button flips a stored Theme between dark and light, and the app applies it to the egui Visuals every frame at the top of its ui method, calling ctx.set_visuals with egui::Visuals::dark() or egui::Visuals::light(). Applying it each frame keeps the whole UI, panels and canvas chrome alike, consistent after a toggle.

The theme is part of the persisted view state: it is captured into the session snapshot alongside the camera, tool, and grid (see the session module) and serialized as a theme=dark or theme=light line, so the choice survives a restart. An unknown or missing value falls back to the dark default.

View bookmarks

A bookmark records where the camera was looking so you can return to it later. It stores only the world center and the zoom (pixels per DBU), not a snapshot of the document, so it stays a tiny value that reconstructs a live camera exactly.

• Type a name and press Save view to capture the current camera. A blank name is filled in with an auto-generated View N label so the entry is always clickable.
• Press a bookmark’s name button to jump back: the app rebuilds the camera with ViewCamera::new(center, pixels_per_dbu), which round-trips the saved position.
• Press the small x next to a bookmark to remove it.

Because a bookmark is just a (center, zoom) pair, saving and restoring is a pure round-trip through the camera constructor, which the tests pin down directly.

Exporting

Export has two independent choices: a scope and a format.

• Scope is either the whole View (every shape in the flattened scene) or just the current Selection. Exporting an empty selection is refused with a status message rather than writing a blank file.
• Format is SVG or PNG.

Files are written into the working directory as reticle-export.svg or reticle-export.png, and the status bar reports the path.

SVG

SVG is the primary export and is generated purely from the shape list by shapes_to_svg, a function of its inputs with no egui or GPU involvement. Each shape kind maps to one SVG element:

• a rectangle becomes a <rect>;
• a polygon becomes a <polygon> with its vertices;
• a path (wire) becomes a stroked <polyline> whose stroke width is the path width scaled into output pixels.

Shapes are placed by an affine fit of the export bounds onto the pixel canvas (the Projection type), preserving aspect ratio and flipping world +y up to image +y down so the picture matches the on-screen canvas. Fill colours come from the live layer table, the same colours the canvas draws with.

PNG

PNG export takes one of two paths:

• A full-colour export of the whole view reuses the native offscreen GPU renderer (render_document_offscreen) for a pixel-accurate frame that matches the canvas exactly. This is native-only and is skipped with a status note when no GPU is available.
• A selection export, or any monochrome export, uses the pure rasterizer in the viewexport module: a small scanline filler that paints each shape over a white page and feeds the crate’s dependency-free PNG encoder. It needs no GPU, so it is unit-tested, and it is what makes selection-only and print-mode PNG images possible.

On the web there is no filesystem and no blocking GPU context, so PNG export reports that it is native-only and SVG generation reports the byte count instead of writing a file.

Monochrome (print) mode

The Monochrome (print) mode checkbox switches both export paths to a print-style render: shapes are drawn as pure black on a white page regardless of their layer colour. In SVG, filled shapes become unfilled black outlines and wires stay black strokes; in the raster path every shape is filled black. This produces a clean, ink-friendly rendering suitable for printing or embedding in a document, independent of the on-screen theme.