pdfcraft/docs/development.md

Developing PdfCraft

Working instructions for agents and contributors are in AGENTS.md and CLAUDE.md. This page collects what the desktop app reads from its environment and where it writes its diagnostics.

Low-disk Cargo profile

When local build storage is constrained, select the opt-in low-disk profile explicitly:

cargo build --profile low-disk -p pdfcraft-cli
cargo test --profile low-disk -p pdfcraft-cos --lib

The profile inherits the normal development settings, including debug assertions and overflow checks. It uses line-table-only debug information for workspace code, which keeps file and line numbers in backtraces but omits local-variable and parameter details, and it disables incremental compilation for this profile only. Ordinary cargo build, cargo test, and release builds keep their existing profiles.

Cargo stores custom-profile artifacts separately under target/low-disk. Switching between the normal and low-disk profiles can therefore leave both sets of artifacts on disk. To remove only the low-disk artifacts, run cargo clean --profile low-disk.

Building PdfCraft requires Rust 1.95 or later: the UI crate and its egui and craft-ui dependencies need it, and the workspace rust-version states the same minimum.

Interface appearance

Display theme saves System, Light or Dark separately from the palette currently drawn. New installations still default to Light. System follows native appearance events on macOS and Windows. The native window keeps its inherited appearance in every mode; both egui style branches use the selected application palette, so desktop changes cannot override a manual choice.

On Linux the native app starts an XDG Settings portal subscription when System is first selected. It reads org.freedesktop.appearance / color-scheme, where numeric 1 requests Dark, 2 requests Light, and 0 means no preference. When that states no preference or is missing, it falls back to org.gnome.desktop.interface / color-scheme (prefer-dark, prefer-light, default), which XFCE's portal answers instead of the freedesktop namespace; KDE answers only the freedesktop one. The subscription is installed before the initial read. Initial results and later SettingChanged signals wake an idle window. There is no periodic desktop polling, and signals received in a manual mode update the cache without requesting frames.

System falls back to Light if no appearance is available, including an absent portal, an unsupported appearance backend, no preference, an unknown value or a failed connection. This does not rewrite the saved System choice. The watcher cancels when its window closes; it does not reconnect after a session-bus disconnection. Headless UI contexts use their supplied egui input and do not contact a desktop session bus. Page and document colours retain their existing behavior.

Logs

The desktop app writes its log records to standard error and to logs/pdfcraft.log in its settings folder, next to app.ron: Linux and FreeBSD ~/.local/share/pdfcraft/logs/ (or $XDG_DATA_HOME/pdfcraft/logs/), macOS ~/Library/Application Support/PdfCraft/logs/, Windows %APPDATA%\PdfCraft\data\logs\. In portable mode (a portable.txt file next to the executable, as the Windows portable zip ships) the settings folder is PdfCraftData\ beside the executable, and crash recovery and new digital IDs go there too. A start from a desktop menu, Finder or the Start menu has no terminal, so this file is what to attach to a bug report: a failed autosave, a page that would not render, a render worker that could not start and the report of an internal error all land there. Each launch moves the previous log to pdfcraft.1.log (and that one to pdfcraft.2.log), so the log of a run that crashed survives the next start. The file stops growing at 16 MiB. --version writes no file.

By default PdfCraft's own crates (pdfcraft*) log at info and everything else at warn. RUST_LOG replaces that with env_logger-style directives, for example RUST_LOG=debug, RUST_LOG=warn,pdfcraft_render=trace or RUST_LOG=info,wgpu_core=warn; a directive ending in * covers every target starting with it (pdfcraft*=debug). The logger is apps/pdfcraft/src/logging.rs. It never records the control-channel token or document passwords.

GPU surface limits

The desktop renderer enables the selected adapter's supported 2D texture extent, while keeping egui-wgpu's other device requirements. Restored windows on mixed-DPI monitors can exceed its default 8192-pixel extent even when the GPU supports a larger surface (#577). The enabled extent never exceeds the adapter's capability. A window larger than even that (restored at another monitor's scale, or stretched across monitors) gets a surface fitted within the limit and is drawn at a correspondingly lower scale instead of panicking in Surface::configure (vendored egui-wgpu, surface_fit; see vendor/README.md). On DX12, PdfCraft's Windows default, the surface is stretched over the window: softer, but complete and lined up with the pointer. wgpu's GL backend copies it unscaled into a corner of the window instead.

For blurry or incorrectly scaled UI reports, attach pdfcraft.log. Look for the successful startup renderer: line, which records the wgpu adapter, device type, backend and enabled texture limit, or the OpenGL renderer. Also look for the drawing it at … and scaling it up warning: it means PdfCraft hit the surface-size safety fallback and rendered below the physical window size, so softness is expected.

Renderer fallback

PdfCraft draws with wgpu, and starts again with eframe's own OpenGL renderer (glow) when wgpu fails before the app is created: no adapter, no device, or a window surface the device can't configure. The last of these was a panic, not an error, because wgpu's default error handler panics and eframe configures the surface before any app code runs; a 2015 Intel GPU whose driver timed out in Surface::configure on wgpu's GL backend closed PdfCraft at launch (#519). Vendored egui-wgpu configures a new window's surface inside winit::catch_errors and returns a validation, out-of-memory or internal error as WgpuError::ConfigureSurface (see vendor/README.md). Still a panic, as upstream: an error in a later reconfigure (resizing, a lost surface); a device lost during that first configure (wgpu reports it only to a callback, so the first frame panics, after the app has started); and a window shown at zero size, which is first configured on resize. If OpenGL can't start either, PdfCraft exits with both errors in the log. The fallback is logged at error, with the wgpu error. Renderer resource creation now uses the same scopes and returns WgpuError::CreateRenderer before the app is created, so a rejected egui_pipeline can also reach this retry instead of the uncaptured-error panic handler. This does not fix the failing driver's shader compilation, and explicit PDFCRAFT_RENDERER=wgpu still disables the retry. PDFCRAFT_RENDERER skips it or chooses OpenGL from the start.

Environment variables

Variable	Effect
RUST_LOG	Log levels for standard error and the log file (see Logs)
RUST_BACKTRACE	1 adds a backtrace to the report of an internal error
XDG_DATA_HOME	Linux/FreeBSD: base of the settings folder (pdfcraft/), the log folder and crash recovery
WGPU_POWER_PREF	GPU choice; by default PdfCraft draws on the GPU the Wayland compositor draws with (it says so through linux-dmabuf feedback), else the GPU that drives the primary display (Windows) or the built-in panel (Linux), else the low-power (integrated) GPU. The log says which one was chosen
WGPU_BACKEND	Graphics backend; by default Windows uses Direct3D 12, falling back to OpenGL
WGPU_VALIDATION_INDIRECT_CALL	1 turns wgpu's check of indirect draw arguments back on. PdfCraft draws nothing indirectly and turns it off, since the compute shader the check needs fails to compile on some drivers (Metal on an Intel Iris Pro), which lost the device at start-up
PDFCRAFT_RENDERER	gl starts with OpenGL (glow) and never loads wgpu; wgpu reports a wgpu failure instead of retrying with OpenGL; unset, wgpu is retried with OpenGL when it can't start (see Renderer fallback)
PDFCRAFT_TITLEBAR	Linux: app draws PdfCraft's own title bar (window buttons in the tab strip, in the order of GNOME's button-layout, and resize edges); system keeps the frame winit or the desktop draws; unset, PdfCraft draws its own when the Wayland compositor draws no frames (GNOME), and leaves it to the desktop otherwise (KDE, Sway, Hyprland, X11). Where PdfCraft draws it, Preferences ▸ Use system title bar switches back to winit's frame without a restart; system also hides that option
PDFCRAFT_BUILD_LABEL	Build time: a label for a local or patched build (letters, digits, inner dots), shown after the version in --version, About and the log (0.7.1 (titlebar)). packaging/linux/package.sh also puts it in the file names and the .rpm/.deb release (1.titlebar), which upgrades over the release of the same version
CRAFT_FONTS_DIR	Build time: a craft-fonts checkout to embed (Japanese fonts)
PDFCRAFT_SYSTEM_FONTS	0 stops the desktop app from using an installed font for characters its embedded fonts lack (cargo xtask screenshots sets it)