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.

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. 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 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
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)
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)