cpposmui

A cross-platform C++26 GUI tool for reviewing and editing OpenStreetMap data, built on Dear ImGui. Inspired by JOSM, optimised for performance and changeset review workflows: load a base .osm dataset and an .osc changeset, and instantly see what changed — tag by tag, object by object — over a live satellite or OSM tile background.

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Features

• Visual diff panel — side-by-side before/after tag values, color-coded [+] added / [~] modified / [-] deleted per object
• Interactive slippy map — pan, scroll-to-zoom, click to select; ESRI World Imagery and OSM Standard tiles switchable at runtime
• Async tile cache — tiles fetched on a Boost.Asio thread pool; map stays responsive while loading
• Overpass API integration — built-in query editor, results auto-diffed against the loaded base dataset
• Tag editor — inline editable key/value table for any selected node, way, or relation
• OSM upload — OAuth2 login flow, changeset creation and upload to the live or dev API
• AI detection panel — optional ONNX Runtime backend for local feature-detection inference
• Spatial index — Boost.Geometry R-tree for viewport-culled rendering of large datasets

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Building

Prerequisites

Requirement	Version
CMake	3.25+
C++ compiler	GCC 14+, Clang 18+, or MSVC 2022 17.8+
libcurl	system install (see below)
OpenGL	system (included on all platforms)

All other dependencies (Dear ImGui, GLFW, glad, pugixml, Boost, nlohmann/json, Catch2, earcut) are fetched automatically by CMake via FetchContent at configure time — no manual installation needed.

Install libcurl:

# Debian/Ubuntu
sudo apt install libcurl4-openssl-dev

# macOS
brew install curl

# Windows (vcpkg)
vcpkg install curl:x64-windows

Linux / macOS

cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j$(nproc)

Windows (Visual Studio 2022)

cmake -B build -G "Visual Studio 17 2022" -A x64
cmake --build build --config Release

Running the tests

cmake --build build --target cpposmui_tests
ctest --test-dir build --output-on-failure

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Usage

cpposmui [base.osm] [changes.osc]

Both arguments are optional — files can also be loaded from the File menu at runtime.

Action	How
Load base dataset	File → Open .osm
Load changeset	File → Import .osc / diff
Query live OSM data	Overpass panel — edit QL, press Run
Browse changes	Diff panel — click any entry to highlight on map
Edit tags	Select an object on the map, edit in Tag editor
Upload to OSM	File → Upload — OAuth2 login required
Switch tile source	Combo box at bottom-left of the map

Config (API keys, OAuth tokens, last viewport) is saved automatically to %APPDATA%/cpposmui/config.json on Windows and ~/.config/cpposmui/config.json on Linux/macOS.

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Source layout

src/
  main.cpp              — GLFW + ImGui entry point, dockspace, menus, config I/O
  osm/
    types.hpp           — Node, Way, Relation, TagMap, ChangeSet, DiffState
    parser.cpp          — .osm / .osc XML parser (pugixml)
    diff.cpp            — tag diff, dataset diff, changeset enrichment & apply
    spatial_index.hpp   — Boost.Geometry R-tree for viewport culling
    tag_presets.hpp     — common OSM tag presets
    data_layer.hpp      — layered dataset abstraction
  map/
    tile_cache.cpp      — async tile fetcher + OpenGL texture upload
  net/
    http.cpp            — libcurl wrapper (Boost.Asio thread pool)
    overpass.cpp        — Overpass QL builder + async query runner
    oauth.cpp           — OAuth2 PKCE flow for OSM API
    osm_upload.cpp      — changeset create / upload
  ui/
    map_view.cpp        — slippy map rendering, OSM + diff overlay
    diff_panel.cpp      — collapsible diff tree with tag before/after tables
    tag_editor.cpp      — inline editable tag table
    overpass_panel.cpp  — Overpass query editor
    detection_panel.cpp — AI detection results viewer
  ai/
    detection.cpp       — ONNX Runtime inference wrapper
tests/
  test_parser.cpp       — OSM/OSC parse unit tests
  test_diff.cpp         — tag diff, changeset enrichment, apply
  test_spatial.cpp      — R-tree bbox query tests
  test_overpass.cpp     — Overpass QL builder tests
  data/
    simple.osm          — fixture: 4 nodes, 2 ways
    changes.osc         — fixture: create/modify/delete changeset

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Dependencies

Library	Version	Purpose
Dear ImGui	docking branch	All UI rendering
GLFW	3.4	Window + OpenGL context
glad2	GL 3.3 core	OpenGL loader
pugixml	1.15	OSM/OSC XML parsing
Boost.Asio + Geometry	1.86	Thread pool, R-tree spatial index
nlohmann/json	3.11.3	Overpass JSON, config I/O
earcut.hpp	2.2.4	Polygon triangulation
stb_image	—	PNG tile decoding
Catch2	3.x	Unit tests
ONNX Runtime	1.20.1	Optional local AI inference
libcurl	system	HTTP for tiles + Overpass + OSM API

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Tile sources

Source	URL template
ESRI World Imagery (default)	https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}
OSM Standard	https://tile.openstreetmap.org/{z}/{x}/{y}.png

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License

GNU General Public License v3.0