Changelog

Changes since the 1.4.0 release.

Last updated: October 2nd, 2026

📘 Upgrading from 2.0.0-beta.1?

See the 2.0.0-beta.2 changelog for changes since 2.0.0-beta.1

#Highlights

• Photon, a new analytic vector renderer: paths, strokes, SVG, and text render directly in pixel shaders at any zoom or transform. Enabled by default on GPU Views.
• A new type-safe JavaScript API (ultralight::js), native DOM API (ultralight::dom), and declarative data bindings API (ultralight::dom::data).
• HTML5 <video> and <audio> playback (WebM, VP9, Opus).
• GPU-accelerated HTML5 Canvas support, OffscreenCanvas, canvas filters, and all SVG filters on the GPU.
• Block-compressed .dds textures in <img> and CSS (Pro edition and above).
• Text editing, IME composition, multi-format clipboard, and native editing conventions per platform.
• AppCore: a flexible panel layout replaces Overlay; windows gain custom chrome, native backdrop materials, per-pixel transparency, popups, and light/dark OS theming.
• Profiler and render-trace diagnostics (Perfetto), a GCListener, memory profiles, and automatic idle reclamation.
• The SDK ships as a CMake package (find_package(Ultralight)), and the reference platform code (GPU drivers, font loaders, file systems, clipboards, audio outputs) is now Zlib-licensed source in the package's platform/ folder.

#Full Changelog (since v1.4)

#Major Improvements

Graphics & Compositor:

• Rewrite CPU renderer for better performance and accuracy
• Rewrite compositor to closely match upstream WebKit (now enabled by default)
• Apply the standard compositing policy on both renderers, so will-change, translateZ(0), and painted canvases promote layers as they do in Safari and Chrome
• Add a per-View render FPS cap (ViewConfig::max_render_fps / View::set_max_render_fps()) that throttles requestAnimationFrame, CSS animations, smooth scroll, and paint as one rate
• Add display-locked frame pacing: animation clocks sample the physical display's presentation time, and Renderer::RefreshDisplay() accepts a target timestamp, a declared refresh rate, and a custom clock
• Add View::set_visible() to suspend off-screen Views (pauses animations, fires visibilitychange, and optionally throttles JavaScript timers)
• Render composited text sharply under animated transforms instead of resampling a raster
• Improve support for CSS, SVG, clipping, backgrounds, and filters across the board
• Improve box-shadow performance (closed-form Gaussian on both renderers, significantly faster on GPU) and memory usage
• Route rounded borders, ellipses, and rounded rects through an analytic primitive so they render resolution-independently
• Unify shader pipeline (HLSL is now ground-truth across all GPU renderers; stock shaders for every program ship in platform/shaders)
• Add single-channel (A8) render targets and explicit blend state per draw to the GPU driver interface
• Add GPUDriver::GetDeviceCaps() so drivers can report MSAA support, texture limits, compressed formats, and partial redraw
• Drop MSAA from compositor intermediate render targets (a 1080p blur filter drops from about 152 MB to about 17 MB of VRAM) and from the analytic vector path

Photon (analytic vector graphics and text):

• Add Photon, an analytic vector rendering pipeline for the GPU renderer: path fills, strokes, dashes, clips, and text are evaluated directly in the pixel shader from cached curve data instead of being tessellated
• Enable Photon by default (Config::enable_photon, Config::enable_photon_text); text at or above Config::photon_text_min_px (16 px) renders analytically on both renderers
• Render text on the CPU renderer from the same unhinted outlines with fractional placement, so both renderers produce near-identical text
• Render text under rotation, skew, and non-uniform scale sharply at every size
• Add analytic Gaussian box shadows and blurred CSS text-shadow on both renderers
• Add conic gradients, gradient spread modes (pad, reflect, repeat), and gradient and pattern brushes on strokes, SVG paint servers, and text

Web Platform & CSS:

• Add support for CSS mask-image
• Add support for CSS mix-blend-mode
• Add GPU acceleration for SVG filters: all 17 primitives (feGaussianBlur, feDropShadow, feMerge, feComposite, feBlend, feColorMatrix, feComponentTransfer, feFlood, feOffset, feTile, feImage, feMorphology, feConvolveMatrix, feDisplacementMap, feTurbulence, feDiffuseLighting, feSpecularLighting) run on GPU Views, as do SVG-content filters and backdrop-filter: url() chains
• Add linearRGB color interpolation in SVG filters (color-interpolation-filters)
• Add support for SVG <mask> references and SVG2 context-fill / context-stroke
• Add CSS conic-gradient(), repeating-conic-gradient(), and canvas createConicGradient()
• Add support for background-clip: text
• Add support for background-repeat: space
• Add support for -webkit-text-stroke and CanvasRenderingContext2D.strokeText()
• Add support for image-rendering: pixelated / crisp-edges and canvas imageSmoothingEnabled / imageSmoothingQuality (nearest sampling matches Chromium byte-for-byte on both renderers)
• Unprefix backdrop-filter (-webkit-backdrop-filter remains an alias)
• Add the app-region CSS property, color-scheme support with a per-View pin, and prefers-color-scheme driven by Renderer::set_system_color_scheme()
• Turn on interactive form validation: an invalid control blocks submission, fires invalid, and takes focus; reportValidity() is available (add novalidate for 1.4 behavior)
• Fix the UA stylesheet so pre and code size at 13 px and the default font size setting takes effect to match mainstream browsers

Text & Fonts:

• Enable kerning and ligatures (text is now shaped through HarfBuzz)
• Add WOFF2 web font support
• Complete variable-font support: font-weight, font-stretch, font-style: oblique, font-optical-sizing, font-variation-settings, and @font-face descriptor ranges
• Add color emoji (CBDT bitmap strikes and COLRv0 layers, including COLRv1 fonts with a COLRv0 fallback) rendered in color on both renderers
• Add synthetic bold and synthetic oblique for families without those faces
• Add font profiles (Config::font_profile: Default, WindowsLike, MacOSLike, Light) with per-knob overrides (font_gamma, font_contrast, font_stem_darkening, font_embolden, font_blend_mode); AppCore picks the host platform's profile and generic font families automatically
• Replace the per-glyph grid-fitting cascade with one glyph positioning policy at every size, so small text no longer shakes during scroll or animation
• Add the cursive, fantasy, and pictograph generic families and default font sizes to ViewConfig
• Open the requested face of a .ttc font collection: font loaders pass the face index through FontFile::Create()

HTML5 Canvas:

• Enable GPU-accelerated HTML5 Canvas (HTMLCanvasElement)
• Enable OffscreenCanvas API
• Enable OffscreenCanvas painting on WebWorker threads
• Add support for HTML5 Canvas filters (CanvasRenderingContext2D.filter)
• Add support for willReadFrequently hint on CanvasRenderingContext2D (allows readback, forces CPU rendering)
• Enable createImageBitmap(canvas) in JavaScript
• Share decoded image pixels and GPU textures across drawImage() calls instead of copying per draw

Images & Compressed Textures (Pro edition and above):

• Add block-compressed textures: .dds files (BC1, BC2, BC3, BC7) load in <img>, CSS background-image, canvas drawImage(), and createImageBitmap(), uploaded to the GPU as raw blocks with no decode step
• Upload BCn natively in the Direct3D 11, Direct3D 12, Metal, and OpenGL reference drivers, with a software decompression fallback (parallel, 4K BC7 in about 12 ms) for the CPU renderer and drivers without the format
• Fix downscaled image drawing on both renderers

HTML5 Media (Pro edition and above):

• Add HTML5 <video> and <audio> playback (VP9 video, Opus audio, WebM container)
• Add support for transparent video (VP9 alpha channel) in GPU and CPU renderers
• Add HTTP byte-range streaming for media with progressive buffering and preload support
• Add stylized media controls for <video> / <audio> elements
• Add the AudioOutput platform interface with reference implementations for Windows (WASAPI), macOS (CoreAudio), and Linux (PulseAudio)
• Add Config::media_profile (Balanced, FavorMemory, FavorPerformance)
• Select video frames against the display's presentation time and use the audio device clock for A/V sync

JavaScript Bridge:

• Add ultralight::js, a typed header-only C++ API for JavaScript interop: navigation-surviving API registries (js::API), typed function/property/constant bindings with automatic marshaling (aggregate structs and enums included), Promise-returning async bindings (coroutine js::Task<T> or callback-style js::Resolver), native class binding, events, weak references, a worker pool, and zero-copy ArrayBuffer / typed-array interop
• Add the ULJS C API (<Ultralight/CAPI/CAPI_JS*.h>), the language-neutral core the C++ layer is built on (usable directly from C or via P/Invoke; future official language bindings build on the same core)
• Add self-describing schema: js::API::schema() / ulJSAPIGetSchema() emit versioned JSON, and tools/scripts/gen-typescript.py generates TypeScript declarations from it
• Add per-registry diagnostics (Off/Warn/Strict, defaulting to Config::diagnostics) with did-you-mean suggestions, lossy-conversion warnings, and a new NativeAPI console message source, plus the ul.diagnostics page-side registry
• Add per-(registry, View) origin policy: app-content-only injection by default, scheme://host[:port] allowlist rules, and a per-View filter callback
• Add bindings that survive back/forward cache restore
• Extend the JavaScriptCore C API: JSClassDefinition version 1000 with per-class private data and ...Ex callbacks, JSObjectMakeFunctionWithData(), UTF-8 batch property access, typed errors, promise inspection, JSArrayBufferDetach(), and external memory hints
• Remove AppCore's JSHelpers (<AppCore/JSHelpers.h>); the typed bridge replaces it (see the porting guide)

DOM API & Data Bindings (all editions):

• Add ultralight::dom (<Ultralight/DOM.h>) and the ULDOM C API, a native DOM API with the same names and syntax as the JavaScript DOM: documents, elements, text nodes, fragments, inline and computed styles, classList, dataset, forms and form-control selection, geometry and scrolling, events (capture, once, passive, delegation, synthetic dispatch), ranges, selections, and the window. Works with JavaScript disabled
• Add dom::Triggers, navigation-surviving DOM wiring: selector-addressed delegated listeners and DOM-ready hooks that apply to every page a View loads
• Add ultralight::dom::data (<Ultralight/dom/data/Context.h>) and the ULDOMData C API, declarative data binding from schema-described C++ models to ul-* markup and {{path}} templates, with two-way edits, actions, keyed lists, format pipes, and validators. A context belongs to your thread; Sync() publishes one atomic snapshot per tick
• Add ultralight::URL, ultralight::JSON, and ultralight::Color value types (with C mirrors), and ultralight::Vector<T>, an ABI-safe container for the library boundary
• Add View::GetDOMDocument(), View::AttachDOMTriggers(), View::AttachDOMDataContext(), and DOM-to-JavaScript interop (dom::ToJS / dom::FromJS)

Text Editing, IME & Clipboard:

• Add View::editor(), an Editor with a curated command set (Execute() / CanExecute()), text insertion, caret and selection geometry, and text-offset queries for native text-input integrations
• Add EditorListener with editable-state events (element kind, mutability, inputmode, enterkeyhint, bounds) for native IME and on-screen keyboard integration
• Add IME composition (SetComposition() with styled segments, Commit, Finish, Cancel), with reference IME handlers for Windows (IMM32) and macOS (NSTextInputClient) in AppCore
• Replace the plain-text Clipboard interface with multi-format ClipboardData payloads, so one copy carries text/plain and text/html together; AppCore's clipboards map CF_HTML and MIME-named formats on Windows and text/plain / text/html on macOS
• Add ViewConfig::clipboard_read_policy governing script-initiated paste
• Add match_native_editing_behavior (ViewConfig and AppCore Settings) so selection and caret behavior follow each host OS

Scrolling & Input:

• Rewrite smooth scroll animation using physics-based spring-mass system (matches macOS/iOS feel)
• Carry scroll positions at sub-pixel precision end to end, so composited scrolling is smooth at every device scale and position: fixed / position: sticky content no longer shakes at fractional scales
• Add back/forward mouse button support
• Add cursor coordinates to ScrollEvent for dispatching a scroll at a specific point
• Add View::is_settled() and LoadListener::OnPageSettled(), which fire once a page has stopped changing after load

Performance & Memory:

• Switch the WebCore and JavaScriptCore heap to bmalloc/libpas
• Add automatic idle memory reclamation (Config::idle_gc_enabled): a heavy page followed by navigation returns to the recycle floor on its own (800 MB to 225 MB within 30 s in the reference scenario)
• Add Config::memory_profile (Balanced, LowMemory, Performance) and Config::max_heap_size
• Add Renderer::Recycle(RecycleMode) (Lightweight is cheap enough to call every frame, Full suits idle periods) and make the automatic recycler run every Config::recycle_delay seconds
• Add the GCListener (Pro edition and above): OnRequestGC() lets you schedule the engine's collections onto a frame that hides the pause, with Renderer::CollectNow(), gc_status(), and CodeDropMode
• Reduce Windows private commit
• Park contended locks in the kernel instead of spinning
• Speed up style recalculation on custom-property-heavy pages 2-3x
• Reduce CSS and SVG filter chain memory usage
• Stop pinning AppCore's window thread to CPU 0 (whoops!)
• Increase performance in multiple profiled bottlenecks via improved parallelism

Diagnostics & Profiling:

• Add Config::diagnostics: a developer mode, the JavaScript and DOM diagnostics levels, and a minimum log level
• Add the Fatal and Debug log levels, and start every engine log message with a category tag ([render], [net], ...)
• Add a memory usage reporting API (Renderer::GetMemoryUsage() / LogMemoryUsage()) covering fonts, bitmaps, textures, caches, GPU resources by purpose, process working set and commit, and the allocator heaps
• Add Profiler platform API and Render Trace diagnostic system (runtime-toggleable tracing, jank detection) (Profiler: Pro edition and above; Render Trace: Enterprise edition and above)
• Add a built-in Perfetto backend (CreateProfilerPerfetto()) and Settings::enable_profiler for AppCore apps
• Add App::GetGPUMemoryStats() reporting driver-tracked GPU allocations and OS-reported process video memory
• Add compositor debug overlays (ViewConfig::enable_compositor_debug_info) and Config::paint_full_layers
• Trace every GPU driver call, GC cycle, and recycle pass as its own scope with resource attribution

Networking & Security:

• Upgrade LibreSSL from 3.0.2 to 3.9.2 (enables TLS 1.3 and patches many security vulnerabilities)
• Enable Public Suffix List for improved site compatibility and security
• Add Config::use_system_certificate_store (Windows) to verify TLS against the OS root store instead of the bundled cacert.pem
• Add Config::ignore_ssl_errors for development against self-signed certificates
• Increase CURL_MAX_WRITE_SIZE for better HTTP/2 throughput
• Report the real host platform in the default User-Agent string (1.4 reported Windows on every OS)

AppCore (Windows, Layout & Chrome):

• Replace Overlay with a flexible panel layout: Panel, Container (rows and columns with resizable dividers), and a Foreground layer of floating panels with anchors and auto-dismissal, buildable in one Window::BuildLayout() expression, with a full C API (<AppCore/CAPI/CAPI_Layout.h>)
• Add custom window chrome: WindowFlags::CustomChrome, hit-test regions, CSS app-region, window buttons, BeginDragMove() / BeginDragResize(), caption color, and corner styles
• Add native backdrop materials (Window::SetBackdrop(): Window, Popup, Overlay; Frosted or Matte; theme pin; Vivid rendition on Windows)
• Add per-pixel transparent windows (WindowFlags::Transparent) and Window::SetBackgroundColor()
• Add popup windows (Window::CreatePopup()) with engine-owned auto dismissal and WindowFlags::Popup
• Add window state control (Maximize, Minimize, Restore) and the OnWindowStateChanged, OnActivationChanged, OnBackdropChanged, OnDismiss, OnClear, and OnPaint listener callbacks
• Move window and monitor geometry to logical pixels (double), with device_width() / device_height() for device pixels and LogicalToDevice() / DeviceToLogical() conversions
• Add multi-monitor enumeration (App::monitor_count() / App::monitor()) and drive each View's refresh from its monitor's hardware display link, presenting capped frames on the display's frame lattice
• Add App::RunOnce(), PostTask(), PostDelayedTask(), and SetInterval() for running AppCore from an existing main loop
• Add idle detection: AppListener::OnIdle(), App::is_idle(), App::thread_utilization(), and the Settings idle thresholds
• Add Window::TakeScreenshot(), Window::SetIcon(), Settings::app_icon, Settings::device_scale_override, Settings::headless_paint_fps, and Settings::full_speed_loop
• Add the window-level editable-state stream (Window::OnEditableStateChange()) and forward the hovered panel's page cursor automatically
• Present and upload only the dirty region of CPU-rendered windows
• Add Window::ShowWhenReady() to show a new window once its pages have finished loading
• Update the Linux x64 port: OpenGL driver, GPU-less CPU windows, PulseAudio, X11 clipboard, and XIM input methods (X11; Wayland desktops through XWayland)
• Update the macOS port: Metal driver at parity with Direct3D 11 (two frames in flight, async presents), CADisplayLink / CVDisplayLink refresh, backdrop materials, popups, custom chrome, IME, CoreAudio, retina-correct text, and a GPU-less force_cpu_renderer path
• Publish the reference platform implementations (GPU drivers and contexts, font loaders, file systems, clipboards, audio outputs, shaders) as Zlib-licensed source in the SDK's platform/ folder and the ultralight-ux/Platform repository

SDK, Build & Packaging:

• Ship a CMake package: find_package(Ultralight), the Ultralight::AppCore / Ultralight / WebCore / UltralightCore targets, and ultralight_copy_runtime_files() to stage the runtime files
• Flatten the package layout (bin/, lib/, include/, resources/, inspector/, samples/, tools/, platform/, license/)
• Raise the toolchain floor to C++20 (Visual Studio 2022 or later on Windows, macOS 11.3 or later, GCC 11 or later or a C++20 clang on Linux)
• Build the Linux libraries against glibc 2.31 with a private copy of libc++, so apps can use either libstdc++ or libc++
• Add the generated <Ultralight/Config.h> with UL_HAS(x) and UL_EDITION_AT_LEAST(x) for compile-time edition and feature checks
• Enable Profile-Guided Optimization (PGO) and LTO in Release builds
• Switch to zlib-ng v2.3.2 for faster SIMD-accelerated decompression
• Patch ICU to avoid rare call_once deadlock during early init on Windows
• Adopt SemVer versioning scheme

#Major API Changes

Breaking Changes:

• The C++ headers now require C++20 (Visual Studio 2022 or later on Windows)
• Overlay and the ulOverlay* C API are removed; Panel replaces it (Window::AddPanel() / AdoptPanel(), ulWindowAddPanel()), and the layout tree arranges panels in rows, columns, and a floating foreground layer
• <AppCore/JSHelpers.h> is removed; use ultralight::js
• Window and Monitor geometry is logical pixels as double: Window::width() / height() and Monitor::width() / height() reported device pixels in 1.4. screen_width(), screen_height(), ScreenToPixels(), and PixelsToScreen() are removed
• WindowFlags is an enum class (WindowFlags::Titled | WindowFlags::Resizable)
• WindowListener::OnKeyEvent(), OnMouseEvent(), and OnScrollEvent() take a leading Window*; OnResize() receives logical double dimensions
• Clipboard::ReadPlainText() / WritePlainText() are replaced by Read() / Write() over ClipboardData; the C ULClipboard struct changed shape
• Surface::Scroll() is a new required method on custom surfaces (ULSurfaceDefinition gains a scroll callback, NULL is handled)
• GPUDriver::CreateTexture() takes a flags parameter and UpdateTexture() takes a dirty_rect; seven shader programs are required (FilterBasic, FilterBlur, FilterDropShadow, FillPhoton, FillPhotonGrid join Fill and FillPath); GPUState gains blend state, texture_4_id, and uniform_integer[8]; CommandType::Flush and VertexBufferFormat::_2f_2ui are new
• Every 1.4 C callback setter gained a trailing destroy_user_data parameter (the thirteen ulViewSet*Callback functions, ulAppSetUpdateCallback(), ulWindowSetCloseCallback(), ulWindowSetResizeCallback())
• LogLevel gains Fatal (now the first value) and Debug (the last), so Error, Warning, and Info changed value; the C ULLogLevel changed the same way
• RefPtr's boolean conversion is explicit
• KeyEvent is no longer trivially copyable
• Config::animation_timer_delay and Config::scroll_timer_delay are removed (use ViewConfig::max_render_fps)
• ulCreateScrollEvent() takes two extra cursor-coordinate parameters (pass -1, -1 for 1.4 behavior)

New Headers:

• <Ultralight/JS.h> and <Ultralight/js/*.h>: the JavaScript bridge
• <Ultralight/DOM.h> and <Ultralight/dom/*.h>: the DOM API
• <Ultralight/dom/data/Context.h>: data bindings
• <Ultralight/Editor.h>, <Ultralight/ClipboardData.h>, <Ultralight/Color.h>, <Ultralight/URL.h>, <Ultralight/JSON.h>, <Ultralight/Vector.h>, <Ultralight/GCListener.h>, <Ultralight/HolderTraits.h>, <Ultralight/OriginRules.h>, <Ultralight/DiagnosticsLevel.h>
• <Ultralight/platform/AudioOutput.h> (Pro edition and above), <Ultralight/platform/Profiler.h> (Pro edition and above)
• <Ultralight/Config.h> (generated edition and feature macros; distinct from <Ultralight/platform/Config.h>)
• <AppCore/Layout.h> and <AppCore/layout/*.h>: the layout tree
• <AppCore/GPUMemoryStats.h>
• C API: CAPI_JS*.h (5), CAPI_DOM*.h (9, not included by <Ultralight/CAPI.h>), CAPI_Editor.h, CAPI_Color.h, CAPI_URL.h, CAPI_AudioOutput.h, CAPI_Profiler.h, CAPI_ThreadFactory.h, <AppCore/CAPI/CAPI_Layout.h>

New Enums:

• BlendFactor (Zero, One, SrcColor, InvSrcColor, SrcAlpha, InvSrcAlpha, DestColor, InvDestColor, DestAlpha, InvDestAlpha, SrcAlphaSaturate)
• BlendEquation (Add, Subtract, RevSubtract, Min, Max)
• GPUTextureFlags (RenderTarget, Antialiased, Immutable) and GPUCompressedFormat
• RecycleMode (Lightweight, Full) and CodeDropMode (Nothing, Linked, All)
• MemoryProfile (Balanced, LowMemory, Performance)
• DiagnosticsLevel (Off, Warn, Strict, Auto)
• MediaProfile (Balanced, FavorMemory, FavorPerformance) (Pro edition and above)
• FontProfile (Default, MacOSLike, WindowsLike, Light) and FontBlendMode (Profile, GammaCorrected, SRGB)
• ColorScheme (Auto, Light, Dark) and ClipboardReadPolicy (Deny, AllowForAppContent, Allow)
• EditorCommand, EditableType, InputMode, EnterKeyHint
• AppCore: WindowFlags (now scoped, with Transparent, Popup, CustomChrome), WindowState, WindowButtons, BackdropMaterial, BackdropVariant, BackdropTheme, BackdropRendition, BackdropState, CornerStyle, HitRegionRole, ResizeEdge, Dismiss, FocusPolicy, AnchorCorner, AnchorAlign, AnchorFit

New Platform Interfaces:

• AudioOutput (set via Platform::set_audio_output()): embedder-implementable audio sink for HTML5 media (Pro edition and above)
• Profiler (set via Platform::set_profiler()): embedder-implementable performance profiler (Pro edition and above)
• ThreadFactory is now available from C (ulPlatformSetThreadFactory())

New API Functions:

• Renderer::RefreshDisplay(display_id, target_timestamp), Renderer::SetDisplayRefreshRate(), Renderer::SetDisplayUsesCustomClock()
• Renderer::PostTask() / PostDelayedTask() (from any thread), Renderer::Recycle(RecycleMode), Renderer::GetMemoryUsage()
• Renderer::set_system_color_scheme() / system_color_scheme()
• Renderer::set_gc_listener(), gc_status(), CollectNow(), Recycle(RecycleMode, CodeDropMode) (Pro edition and above)
• Renderer::BeginRenderTrace() / EndRenderTrace() / is_render_trace_active() (Enterprise edition and above)
• View::set_visible() / is_visible(), View::set_max_render_fps() / max_render_fps(), View::set_preferred_color_scheme(), View::is_settled(), View::Resize(width, height, device_scale)
• View::editor(), View::set_editor_listener(), View::GetJSContext(), View::AttachJSAPI() / DetachJSAPI(), View::GetDOMDocument(), View::AttachDOMTriggers(), View::AttachDOMDataContext()
• View::set_compositor_debug_info_enabled() / compositor_debug_info_enabled()
• LoadListener::OnPageSettled(), EditorListener (OnChangeEditableState(), OnUpdateComposition(), OnDiscardComposition())
• Surface::Scroll(), Surface::ShiftPixels(), Surface::LockPixelsSafe(), Surface::dirty_rect_count() / dirty_rect()
• GPUDriver::GetDeviceCaps()
• FontFile::Create(path_or_buffer, face_index) and FontFile::face_index()
• Bitmap::is_compressed(), Bitmap::MaxDimension, GetBitmapFormatInfo(), IsCompressedFormat()
• WeakPtr<T>, WeakRefCounted, MakeRefPtr<T>(), Rect::FromXYWH()
• ul_malloc() / ul_free() and the aligned and realloc variants (the library allocator, exported)
• CreateProfilerPerfetto() / DestroyProfilerPerfetto() (Pro edition and above)
• App::RunOnce(), App::PostTask() / PostDelayedTask() / SetInterval(), App::is_idle() / thread_utilization(), App::monitor_count() / monitor(), App::GetGPUMemoryStats(), App::is_profiler_active() / profiler_trace_path(), AppListener::OnIdle()
• Window::CreatePopup(), Window::ShowWhenReady(), Window::AddPanel() / AdoptPanel() / BuildLayout() / layout() / foreground() / FindPanel() / focused_panel() / ClearFocus(), Window::SetBackdrop(), Window::SetBackgroundColor(), Window::SetCaptionColor(), Window::SetCornerStyle(), Window::SetHitTestRegions(), Window::SetWindowButtons(), Window::BeginDragMove() / BeginDragResize(), Window::Maximize() / Minimize() / Restore(), Window::SetIcon(), Window::TakeScreenshot(), Window::Invalidate(), Window::device_width() / device_height(), Window::LogicalToDevice() / DeviceToLogical(), Window::OnFocusChange() / OnEditableStateChange()
• Monitor::device_width() / device_height()
• JavaScriptCore: JSObjectMakeFunctionWithData(), JSObjectGetPropertiesUTF8() / SetPropertiesUTF8() / MakeWithPropertiesUTF8() / GetOwnEntriesUTF8() / DefinePropertyUTF8() / DefineAccessorUTF8(), JSObjectFreeze(), JSObjectMakeTypedError(), JSValueGetErrorDetails(), JSValueIsFunctionObject(), JSPromiseGetStatus() / GetResult() / MarkAsHandled(), JSArrayBufferDetach() / IsDetached(), JSObjectSetExternalMemoryHint(), JSClassGetPrivate() / SetPrivate()

Changes to Existing API:

• View::LockJSContext(), View::JavaScriptVM(), and View::EvaluateScript() now accept an optional frame parameter to target a specific frame
• GPUState struct has new fields: blend_src_factor, blend_dst_factor, blend_equation, texture_4_id, uniform_integer[8]
• ShaderType has five new values, VertexBufferFormat has _2f_2ui (with Vertex_2f_2ui), and CommandType has Flush
• BitmapFormat enum has eight new values: RG8_UNORM, BC1_UNORM, BC2_UNORM, BC3_UNORM, BC7_UNORM, RGBA16F, RGBA16UI, RGBA32F
• MouseEvent::Button has kButton_Back and kButton_Forward; ScrollEvent has x and y (default -1)
• MessageSource has kMessageSource_NativeAPI
• Bitmap derives from WeakRefCounted
• ViewConfig struct has new fields: background_color, preferred_color_scheme, enable_compositor_debug_info, enable_canvas_filters (default true), match_native_editing_behavior, clipboard_read_policy, enable_hidden_timer_throttling, max_render_fps, allow_universal_access_from_file_urls (default true), javascript_can_open_windows_automatically, font_family_cursive, font_family_fantasy, font_family_pictograph, font_size_default, font_size_fixed
• ViewConfig::enable_compositor default changed from false to true (compositor enabled by default)
• ViewConfig::user_agent defaults to ULTRALIGHT_USER_AGENT, which reports the host platform
• Config struct has new fields: font_profile, font_blend_mode, font_contrast, font_stem_darkening, font_embolden, enable_photon, enable_photon_text, photon_text_min_px, page_settle_delay, page_settle_cycles, page_settle_tick, idle_gc_enabled, idle_gc_idle_time, memory_profile, max_heap_size, ignore_ssl_errors, use_system_certificate_store, paint_full_layers, resource_sample_interval, diagnostics, media_profile (Pro edition and above)
• Config::memory_cache_size default changed from 64 MiB to 256 MiB
• Config::recycle_delay default changed from 4.0 to 0.5 seconds and is now the automatic recycle interval; 0 disables the automatic recycler
• Config::font_gamma default changed from 1.8 to 0 (inherit from font_profile); Config::min_large_heap_size default changed from 32 MiB to 0 (derive from memory_profile)
• Settings struct has new fields: device_scale_override, auto_font_profile, auto_font_families, match_native_editing_behavior, idle_threshold, sustained_idle_time, idle_utilization_threshold, enable_profiler, headless_paint_fps, full_speed_loop, sync_animations_to_present, app_icon
• Engine log messages start with a category tag, and Debug messages are not sent to the Logger unless Config::diagnostics.min_log_level is lowered
• Surface::set_dirty_bounds() adds to the dirty area instead of replacing it
• FontFile gains a pure virtual face_index() (only code that subclasses FontFile is affected)
• JSValueGetType() returns the new kJSTypeBigInt for a BigInt (it returned kJSTypeObject)
• Window::MoveTo(), x(), and y() use global screen coordinates spanning all monitors (1.4 was relative to the window's monitor)
• <AppCore/AppCore.h> no longer includes <JavaScriptCore/JavaScript.h> transitively
• JSClassDefinition gained privateData and the ...Ex callback union (version-0 definitions work unchanged; recompile)
• UL_COMPILER_GCC_LIKE is a presence macro (#if defined(...))
• C API at full parity with the C++ API: every Config field has a ulConfigSet* setter, and about 590 new functions cover the DOM, JavaScript, Editor, Layout, URL, Color, and window surfaces

Deprecated:

• Renderer::RenderOnly() and ulRenderOnly() (use Render(), which skips hidden Views, and hide a View with View::set_visible(false))

Removed:

• Overlay (<AppCore/Overlay.h>) and the ULOverlay C API, replaced by Panel (<AppCore/layout/Panel.h>, ULPanel)
• <AppCore/JSHelpers.h> and everything it declared
• Settings::load_shaders_from_file_system and ulSettingsSetLoadShadersFromFileSystem (the setting had no effect; shaders are always loaded from memory)
• Config::animation_timer_delay, Config::scroll_timer_delay, ulConfigSetAnimationTimerDelay(), ulConfigSetScrollTimerDelay()
• Clipboard::ReadPlainText(), Clipboard::WritePlainText()
• Window::screen_width(), screen_height(), ScreenToPixels(), PixelsToScreen() and their C mirrors

#Major Bugfixes

GPU Renderer:

• Fix issue with premultiplied alpha being applied twice when drawing glyphs in GPU renderer
• Fix issue with transforms not being applied to glyphs when drawing with GPU renderer
• Fix issue where inverse clipping masks were ignored in GPU renderer
• Fix issue with clipping, box shadows, drop shadows, and blurs in GPU renderer
• Fix clipping issue in CanvasGPU (scissor rect wasn't being offset in created layers)
• Fix Image synchronization issue in GPU renderer
• Fix GPU stroke rendering for collinear path segments
• Fix nested clips on the GPU canvas blanking the clipped content
• Fix globalCompositeOperation being ignored inside ctx.clip(), and destination-out / source-atop / xor / source-out falling through as source-over on direct GPU canvas draws
• Fix clearRect() ignoring an active path clip on the GPU canvas
• Fix vector content inside opacity, mask, clip-path, and blend groups rendering without edge antialiasing
• Fix pooled render-target reuse corrupting transparency layers on some driver stacks (block dropouts on NVIDIA D3D11)
• Fix a draw sampling the texture that backs its own render target, which D3D11 and D3D12 silently voided
• Fix an access violation in the D3D12 driver on blend modes with a *_COLOR factor (such as Screen)
• Fix CSS repeating gradients clamping at 11 stops on the GPU
• Fix GPU radial gradients using an approximation instead of the exact two-point conical solve
• Fix dashed strokes at small user units (lost dots, dash-phase drift, fused subpaths) and seams at dash boundaries
• Fix an open path starting at the origin losing its first point, which cropped the leading half of rules and progress tracks
• Fix canvas-backed patterns rendering blank for dense fill regions
• Fix a hard crash when a box shadow spanning an extreme area exceeded Bitmap::MaxDimension
• Bound GPU path tessellation so pathological paths degrade instead of filling the geometry buffer
• Replace the modal message boxes the D3D11 and D3D12 drivers showed on GPU resource failures with logger warnings

CPU Renderer:

• Fix issue with DrawCanvas not applying alpha when drawing with CPU renderer
• Fix canvas globalAlpha and SVG stroke-opacity painting fully opaque on the CPU renderer
• Fix canvas full-canvas composite operations (source-in, source-out, destination-in, destination-atop) rendering blank on the CPU canvas
• Fix a crash and diagonal shear in CPU SVG reference filters when the filtered region width was not a multiple of 4 pixels
• Fix a transparent CPU View or popup hanging on first paint
• Fix issue with CPU renderer not using AVX2 during runtime when available

Canvas:

• Fix issue drawing CPU-backed ImageBuffers to GPU-backed GraphicsContext (texture corruption)
• Fix CanvasRenderingContext2D.filter on detached canvases
• Fix crash in CanvasGPU.cc when drawing GPU canvases to other GPU canvases
• Fix crash from unmatched save/restore in GPU canvas replay
• Fix canvas-source copies on the GPU backend (point-in-time snapshots, OffscreenCanvas placeholder commits, transferring contextless canvases)

Compositor & TextureMapper:

• Fix GPU BitmapTexturePool reusing textures while deferred commands still reference them
• Fix issue with texture mapper updating tile with fractional device scale
• Fix issue with TextureMapper layers being clipped to document bounds
• Fix stale tiles being retained across a tile-layout change, which composited content twice and double-blended transparent Views
• Fix clip-path rendering blank on composited layers and on SVG roots
• Fix potential overflow in TextureMapperTiledBackingStore::createOrDestroyTilesIfNeeded
• Fix issue where logical frame rect wasn't properly rounded up with fractional device scale
• Fix black flash in compositor (force clear to white when View is not transparent)
• Fix flicker during View::Resize
• Fix inline text not repainting when block dimensions are unchanged
• Fix re-entrant layer flush requests being dropped, which caused occasional partial repaints
• Fix antialiasing being silently stripped from content tiles when the texture pool returned a single-sample intermediate
• Fix the backdrop-filter snapshot including content painted above the element
• Fix overlay scrollbars painting over elements stacked above their scroller

CSS, Layout & Text:

• Fix drawing issue with background-clip: text
• Fix background-clip: text clipping under opacity
• Fix CSS transitions losing to !important declarations (transitions now take precedence per the CSS cascade spec)
• Fix dashed and dotted straight borders painting solid
• Fix thin rounded borders dropping a side, outlines on pill-shaped boxes painting square corners, and collapsed table borders disappearing at fractional device scales
• Fix SVG gradient rendering (apply gradient-space transform) and SVG spreadMethod being dropped
• Fix dashed SVG circles and ellipses (including pathLength progress rings) rendering solid
• Fix SVG markers placed at subdivision vertices instead of authored vertices, and markers dropped from gradient-stroked paths
• Fix SVG clipPath shapes in objectBoundingBox units clipping with visible facets
• Fix bounding-box reporting for individual SVG <tspan> elements
• Fix SVG text fill covering a neighboring glyph's stroke
• Fix gradient and pattern brushes on SVG text stroke and canvas strokeText() rendering black
• Fix undefined SVG filter inputs failing the whole filter, filter output sized to the content box instead of the filter region, and feConvolveMatrix bias being ignored on the GPU
• Fix CSS basic filters being applied in premultiplied space (color correctness)
• Fix CSS non-separable blend modes (HSL, soft-light) to match the W3C spec
• Fix stroke state (dash, cap, join, miter) leaking between elements
• Fix sizing of absolutely-positioned replaced elements from inset
• Fix variable-font advance widths
• Fix macOS system font families always opening face 0 (all weights rendered the first face with synthetic bold and oblique) and Apple Color Emoji sitting about 1/8 em too high
• Fix COLRv1 color fonts rendering as monochrome outlines
• Fix a family inside a .ttc font collection rendering the collection's first face
• Fix system-ui and BlinkMacSystemFont falling through to the fallback font on macOS
• Fix the engine font cache serving the wrong face on a hash collision
• Fix crash with color-mix() in color property
• Fix hang in CSS gamut mapping with NaN inputs
• Fix progressive WebP decode corruption (large WebP images intermittently rendering blank or with doubled semi-transparent regions)

Stability & Crashes:

• Fix crash in path triangulation
• Fix use-after-free in the texture atlas during recycling
• Fix crash during resource loads
• Fix JS engine crash after idle footprint shrink in pages using JS modules
• Fix font thread-race crashes under WebWorker / OffscreenCanvas
• Fix a stack-overflow crash when a thread's first park was contended (customer map-search crash)
• Fix an intermittent hang at process exit (roughly one in 15-30 launches) in the allocator's thread-local cache teardown
• Fix a hang under heavy JavaScript JIT tier-up where a worker thread exiting mid-registration orphaned a global lock
• Fix the renderer freezing when a page constructed Intl.DateTimeFormat for a locale absent from the trimmed ICU data
• Fix a crash in the matched-declarations cache sweep when a style resolver was destroyed mid-iteration (reproducible on Reddit)
• Fix ReportingObserver keeping whole documents alive after navigation (about 24 detached documents leaked per StackOverflow visit)
• Fix a crash after destroying and re-creating a Renderer (ICU data ownership)
• Fix a crash in View::LockJSContext() and View::JavaScriptVM() on Views with JavaScript disabled (both now return null)
• Fix a View's Surface being destroyed through its destructor instead of SurfaceFactory::DestroySurface()
• Fix a teardown race where a worker thread could still be releasing engine objects while the painter was destroyed
• Fix Config::min_large_heap_size and min_small_heap_size never reaching JavaScriptCore

Media:

• Fix seeks that never finalized when the target was past the last video frame
• Fix a seek that resumed into the paused state never showing the post-seek frame
• Fix audio remaining audible ahead of the picture after a scrub, and a false ended after a seek
• Fix canPlayType() advertising Vorbis, for which no decoder exists

Input & Scrolling:

• Fix numerical instability in smooth scroll at low framerates
• Fix scroll wheel events not working properly with Retina DPI scaling on macOS
• Fix composited scroll advancing in groups of device pixels at scales other than 1.0
• Fix position: fixed and position: sticky content drifting or shimmering during fractional-scale scroll
• Fix issue where hover state wouldn't be updated when mouse leaves a View
• Fix GetKeyFromVirtualKeyCode to map space, escape, numpad, and special keys per W3C spec
• Fix ClearFocus() leaving a pending focus grant armed
• Fix right-click not dispatching contextmenu on the page
• Fix Ctrl- and Shift-click when key events are built from Windows messages
• Fix the legacy wheelDelta reading about 11520 per notch instead of 120
• Fix gamepad.id being empty (the gamepad name was reported in gamepad.mapping)

View, Session & Downloads:

• Fix window.close() never reaching ViewListener::OnRequestClose(), View::CancelDownload() not stopping the transfer, and OnUpdateHistory() not firing
• Fix every navigation download reporting id 0
• Fix in-memory Sessions writing localStorage to disk and sharing it with any same-named Session

C API:

• Fix ulCreateRenderer() returning a non-NULL handle when the renderer failed to create
• Fix a second ULView handle for the same View turning off the callbacks set through the first
• Fix ulViewSetCreateInspectorViewCallback() never firing

Platform & Build:

• Fix issue on Windows where idle run loop wouldn't wake on external SendMessage() call
• Fix a timer destroying itself from its own callback having its user_data freed while the callback ran
• Fix App::Create() installing the built-in profiler over one the embedder had set
• Fix the reference FileLogger writing from several threads without a lock
• Fix POSIX absolute paths failing to load through file: URLs
• Fix Lock having a layout that varied with the consumer's NDEBUG setting
• Fix SDK build presets defaulting to Debug under the Visual Studio multi-config generator
• Fix StringSTL's Convert() failing to compile for string literals