Module types

Geometry and primitive value types used across the public API.

These are the cheap, copy-friendly types that flow through every widget builder, layout method and runtime hook:

• Color — RGBA in [0.0, 1.0] floats; Color::WHITE, Color::BLACK, Color::TRANSPARENT constants and a Color::hex(r, g, b) constructor for byte literals.
• Rect — axis-aligned (x, y, width, height); the universal layout / hit-test currency.
• Point — a 2D point used by hit testing and gesture progress.
• Size — a (width, height) pair without an origin.
• Corners — per-corner radius for the Container widget and any other rounded surface; coerces from f32 for the uniform case.
• WidgetId — a stable identifier, a &'static str name and a key, for focus management, paired with crate::App::take_focus_request.

Every type is Copy (or Clone) so passing them by value is the default. The crate root re-exports them all (ltk::Color, ltk::Rect, …) so application code rarely needs the ltk::types:: prefix.

Structs

• Color
  An RGBA color with floating-point channels in the range [0.0, 1.0].
• Corners
  Per-corner radii for a rounded rect, ordered top-left → top-right → bottom-right → bottom-left (clockwise from top-left, matching CSS border-radius’s long form). All four values are independent pixel radii — set any subset to 0.0 for a square corner, or use the top, bottom, left, right shortcuts for the common asymmetric cases.
• Length
  A size or distance value that may be expressed in absolute pixels or relative to the rendering surface. Every widget API that used to take f32 for a size, padding, spacing or font height now takes impl Into<Length>, so existing call sites keep compiling unchanged while new code can switch to viewport-relative units for layouts that must scale across screen sizes (portrait phone, landscape tablet, 4K desktop) without per-target tweaks.
• Point
  A 2-D point in screen coordinates (pixels, top-left origin).
• Rect
  An axis-aligned rectangle in screen coordinates.
• Size
  A width/height pair in pixels.
• WidgetId
  A stable widget identifier used for focus management.

Enums

• CompositeMode
  How a draw combines with what the canvas already holds: the Porter-Duff operators plus the separable modes with an exact premultiplied form. Set with Canvas::set_composite_mode.
• CursorShape
  Pointer cursor shape, sent to the compositor via wp_cursor_shape_v1 when the pointer enters a widget that declares one. Mirrors cursor_icon::CursorIcon 1:1 so the runtime can convert losslessly. Compositors that do not advertise wp_cursor_shape_v1 ignore these — the user sees their default system cursor.
• LengthBase
  One of the pure relative-or-absolute modes a Length can carry. Split out so Length itself can stay Copy while still supporting optional clamp bounds — the recursive Clamp variant of the original sketch would have forced a Box allocation, which on a widget tree that builds these values per frame is the wrong trade.
• Orientation
  Orientation of the main surface, derived from the dimensions recorded by set_viewport_size.
• PathCmd
  One command of a vector path, in canvas (surface) coordinates. Fed to Canvas::fill_path / stroke_path to render arbitrary shapes (e.g. an Android Path / a Lottie frame).
• WidgetScaling
  How a stock widget adapts its intrinsic geometry to the display when the app does not override it. The two modes ltk offers, chosen per process with set_widget_scaling:

Constants

• FLUID_MAX
  Upper auto-clamp factor of Length::fluid: a fluid value never resolves above px * FLUID_MAX, so it stays tasteful on a huge surface.
• FLUID_MIN
  Lower auto-clamp factor of Length::fluid: a fluid value never resolves below px * FLUID_MIN, so it stays usable on a tiny surface.

Functions

• WidgetId
  The id of a single widget, the same as WidgetId::keyed with key 0.
• density
  Current pixel density — the factor Length::dp multiplies its design pixels by. 1.0 until the runtime or set_density sets it.
• fluid_reference
  Current reference used by Length::fluid — the short-side px at which fluid( n ) resolves to n px before clamping.
• orientation
  Orientation of the main surface: Orientation::Landscape when wider than tall, Orientation::Portrait otherwise (square counts as portrait, matching Length::orient’s resolution rule). Usable straight from view() to pick a row or a column arrangement without tracking on_resize by hand — the runtime rebuilds the view on every resize, so a layout branched on this follows the window live.
• output_logical_size
  Logical size of the screen the main surface is on, or None before the compositor has described one. Unlike viewport_size it does not follow the window, so it can size things relative to the display.
• set_density
  Set the process-wide pixel density used by Length::dp (the WidgetScaling::Physical mode). The runtime sets it to the main surface’s buffer scale right before crate::App::on_scale_changed, so dp( n ) is n logical px by default; an app that wants a DPI-derived density overrides it from that callback. Default: 1.0.
• set_fluid_reference
  Set the reference surface (short-side px) that Length::fluid interprets its design pixels against. Call once at startup (e.g. before crate::run) to align the fluid scale to the surface mock-up the app was designed for. Default: 412 px.
• set_output_logical_size
  Record the logical size of the output the main surface is on. The runtime calls this when outputs appear, change or go away, and when the main surface enters one. ( 0, 0 ) clears it.
• set_text_scale
  Set the global text scale multiplier applied to every resolved font size (the accessibility “large text” factor). Clamped to [0.5, 3.0]. The run loop keeps it synced to the desktop’s org.gnome.desktop.interface text-scaling-factor GSettings key and repaints on change, so apps normally never call this themselves; embedders driving crate::core::UiSurface directly do.
• set_viewport_size
  Record the main surface’s physical dimensions. The runtime calls this on every configure, before App::on_resize; embedders driving core::UiSurface directly should call it themselves if they want viewport_size / orientation to reflect their surface.
• set_widget_scaling
  Set the process-wide WidgetScaling mode for stock-widget defaults. Call once at startup. Default: WidgetScaling::Fluid.
• text_scale
  Current text scale multiplier. Default 1.0.
• viewport_size
  Physical dimensions of the main surface as of the last configure. ( 0, 0 ) before the first one.
• widget_scaling
  Current WidgetScaling mode. WidgetScaling::Fluid until set_widget_scaling changes it.