egui-cr

Immediate-mode GUI for Crystal — a 1:1 port of egui's architecture (Rust), rendered through sokol_gfx.

Layout

• docs/ANALYSIS.md — architecture analysis of upstream egui (crates, core types, widget model) that this port follows 1:1.
• egui-upstream/ — read-only reference clone of egui.
• vendor/sokol, vendor/fontstash — native C dependencies.
• src/egui/ — the port: platform-pure core (id, memory, input, context, response, sense, layout, ui, widgets/) plus the sokol backend (backend/sokol/).
• examples/hello.cr — button + label + label change (Hello World).

Build & run

crosspack deps        # verify/install build deps (crystal, GL, X11, xcursor)
crosspack build       # specs + native lib + examples -> builds/
./bin/hello

Or manually:

rake spec             # headless core specs
rake build:examples   # vendor C + crystal build
./bin/hello

Windows

The same rake targets work on Windows. Requirements:

• Crystal for Windows (x86_64-pc-windows-msvc)
• Visual Studio 2022 (or its Build Tools) with the Desktop development with C++ workload — the vendor C code is built with cl.exe, and Crystal's msvc target links against the MSVC/Windows-SDK runtimes
• Ruby + rake (gem install rake)

rake spec             &:: headless core specs
rake build:examples   &:: vendor C (cl.exe) + crystal build -> bin\
bin\hello

crosspack deps / crosspack build also work on Windows (host target windows-11.0; the matrix entry lands exes + DLLs into builds\windows\11.0\x86_64).

Differences from the Linux build:

• the native library is lib\egui_cr_sokol.lib (MSVC resolves @[Link("egui_cr_sokol")] to exactly that name; no lib prefix), and the examples pass the lib dir via /LIBPATH:, not -L
• FreeType binaries (x64 import lib + DLL, pinned by SHA256) are fetched by scripts\fetch_freetype.bat — wired into crosspack deps (freetype-dev) and rake build:native. bin\freetype.dll must ship next to the exes; its VC++ v14 runtime requirement is declared in the runtime deps: section (vc-redist → winget Microsoft.VCRedist.2015+.x64)
• the Windows system ports are native: file dialogs run the WinForms picker through PowerShell (-EncodedCommand), MessageBox calls MessageBoxW (user32), OpenUrl/reveal use ShellExecuteW (shell32), notifications are NotifyIcon balloons, and user dirs come from %APPDATA%/%LOCALAPPDATA% + SHGetKnownFolderPath; Linux keeps the zenity/kdialog/xdg-open subprocess ports

macOS

The same commands work on macOS (host target macos; artifacts land in builds/macos/aarch64 on Apple Silicon). Requirements:

• Crystal for macOS (brew install crystal)
• Xcode Command Line Tools (xcode-select --install)
• Homebrew FreeType + pkg-config (brew install freetype pkg-config) — X11/xcursor are not needed, sokol_app uses Cocoa there

Differences from the Linux build:

• the vendor C shim is compiled as Objective-C (cc -x objective-c) and linked against the Cocoa/OpenGL/QuartzCore frameworks
• system ports shell out to osascript/open (dialogs, message boxes, notifications, URL opening, user dirs) and manage the window through AppKit (NSWindow/NSScreen from the ObjC shim)

Status

Slice 1: the core frame loop (RawInput → begin_frame → app update → end_frame → paint), Id/Memory interaction tracking, Ui with vertical/horizontal layout, Label and Button widgets, sokol_app window + sokol_gfx rendering + fontstash text. See docs/ANALYSIS.md for the full upstream map and what is next.