API coverage

“Does BUI support X?” usually comes down to a number. This page collects every coverage figure in the repository, with how it was counted, so you can decide quickly and know exactly what you’re getting.

At a glance

API	Coverage	Status
tkinter and ttk	7,846 of 7,846 public names	Complete
Qt syntax	About 220 of 920 public method names (~24%) on 25 core widget classes	Partial
Blender components (Python)	45 components	Complete
HTML elements (Rust, JavaScript)	113 of 113	Complete
CSS properties (Rust, JavaScript)	261 of 745 W3C properties render, 129 more parse	Partial
CSS 2.1 screen properties	90 of 90	Complete
Flexbox / Grid	12 of 12 / 23 of 23	Complete
Dear ImGui, C	399 of 399 functions	Complete
Dear ImGui, Python and safe Rust	366 of 399 functions	Partial
Image formats (every language)	PNG, JPEG, WebP (animated), GIF (animated), BMP, TGA, QOI, Radiance HDR, PNM, SVG; not yet AVIF, EXR, TIFF, JPEG XL, HEIC (Images)	Partial

tkinter

7,846 of 7,846. Every public member of every tkinter and ttk widget class exists, plus Tk, Toplevel, the variables, Event, PhotoImage and BitmapImage. The count is measured against the standard library.

Names existing isn’t the same as behaving the same, so there’s a second check: tests/test_tk_compat.py runs nine real tkinter programs on both the standard library and BUI and requires identical results. They are a calculator, a to-do list with a scrollbar, a validated form, a text editor with menus, a sortable table, a canvas, a scrollable frame, a notebook with a paned window and an option menu, and an events-and-variables program.

The modules covered: the tkinter package itself, ttk, messagebox, filedialog, simpledialog, colorchooser, commondialog, dialog, font, scrolledtext and constants.

What differs: some options only change Tk’s appearance (relief, borderwidth, activebackground, ttk.Style settings …). They’re accepted and returned by cget, but the look always comes from Blender’s theme. Tcl itself isn’t there: root.tk.call handles a few common commands. See tkinter compatibility for the details.

Qt syntax

About 220 of 920 public method names, across 25 core widget classes (~24%). There’s no Qt in the test environment, so the count comes from Qt’s own widget headers (reference/qtbase).

What’s there: widgets and layouts (box, grid, form, stacked), signals, QPainter, menus and actions, timers and property animations, and the common value types. setStyleSheet understands color, background on containers and font-weight: bold.

Missing:

• Model/view: QAbstractItemModel, QListView, QTreeView, QTableView, delegates.
• QSplitter, QDockWidget, QToolBar, QStackedWidget as a real class, QToolBox, QDateEdit and friends, QCalendarWidget.
• Most of QWidget’s wider surface: focus-policy details, setWindowFlags, geometry helpers, grab.
• Stylesheet selectors and pseudo-states, QPalette; QGraphicsScene; rich text.
• QSettings, QThread, QClipboard, drag and drop, QShortcut, OpenGL widgets.
• QMessageBox and QInputDialog as drawn dialogs.

Anything not implemented raises AttributeError: nothing fails silently.

HTML and CSS (Rust and JavaScript)

Counted by cargo test --test parity -- --nocapture in bindings/rust.

Area	Coverage
HTML elements (WHATWG index)	113 / 113 constructible, plus svg and math roots; 9 are Blender widgets
CSS properties	271 change layout or rendering; 137 more parse but have no effect
W3C property index (745 properties)	261 rendered (35%), 129 parsed without effect (17%), 355 not recognized (48%)
CSS 2.1, screen properties	90 / 90 rendered
Flexbox	12 / 12
Grid	23 / 23, including grid-template-areas and named lines

The two property counts use different lists: the first counts every property the engine handles, the second only the 745 in the W3C index.

Most of the unrecognized 355 aren’t everyday CSS:

Group	Properties
Draft border and corner shapes (corner-shape, border-*-clip …)	~78
SVG fill, stroke and markers	~40
Gap decorations (row-rule-* …)	38
Speech and aural	31
Animation triggers and scroll-driven animation	26
Paged media, regions, rhythm and others	~25
Everything else	~100

The biggest gaps among common properties: 3D transforms, OpenType font features and multi-column layout. Also, 2D transforms draw but don’t change hit testing.

Beyond properties: every CSS math function with mixed units, every length unit, var() and env(); CSS Color 4 and 5 (oklch, lab, color-mix(), relative colors, light-dark()); Selectors Level 4 (:has(), :is(), :where() …), nesting, ::before and ::after; @media ranges, @supports, @layer, @scope, @container, @font-face, @property; @keyframes animations and transitions.

Tailwind CSS

Tailwind v4, compiled on first use with the v4 default theme, like Tailwind’s JIT. Variants (state, structural, group-*, peer-*, has-*, data-*, aria-*, breakpoints, container queries, dark, motion-* …), arbitrary values and properties, /opacity and !important all work, and utilities sort the way Tailwind sorts them. In Rust, tw! and rsx! check classes at compile time and suggest fixes for typos.

There’s no single count for Tailwind: classes are generated from the theme and variants rather than listed.

Blender components

45 components in Python’s blenderui.components: layout, values, buttons, views, menus and pie menus, the color picker, the color ramp, curve and node editors, areas and templates. Ten of them are also available from Rust and JavaScript: Button, Checkbox, Radio, NumberField, NumberSlider, TextField, TextArea, ColorSwatch, Dropdown and ProgressBar.

Dear ImGui

BUI vendors Dear ImGui 1.93.1 WIP. It has 399 functions in namespace ImGui (overloads counted separately, obsolete ones excluded; 14 take a va_list) and 264 methods and constructors on its structs. The bindings add a default constructor to the 9 structs that declare none, for 273. Counted from bindings/imgui/gen/coverage.json, which the generator writes.

	namespace ImGui	Methods + constructors	Notes
C++	Everything	Everything	The real imgui.h
C	399 / 399	273 / 273	894 C functions with the Ex variants; all 41 structs
Python	366 / 399 (366 / 385 without va_list)	264 / 273	1,474 constants; fields of all structs
Rust FFI	385 / 399 (all but va_list)	272 / 273	879 of the 894 C functions
Rust safe layer	366 / 399	264 / 273	The rest is in sys

Skipped in Python and safe Rust (all reachable from C and the Rust FFI): the 14 va_list functions, functions taking an untyped void* value (like PushID(const void*) and the *Scalar widgets; use the typed ones), and functions taking C callbacks (the getter overloads of Combo, ListBox and the plot functions, allocator hooks, ImDrawList::AddCallback).

The Blender-widgets build keeps ImGui’s own drawing for window title bars, tooltips, plain popups, tables and the color picker.

Next steps