Paint and render scene API

Declared by <huxerui/paint.h> and <huxerui/render_scene.h>.

Fills and image placement

• ImageFit: None, Contain, Cover, Fill, or ScaleDown.
• GradientStop, LinearGradient, and RadialGradient.
• ImageFillSource: ImageResource, ImageAsset, or VectorAsset.
• ImageFill: source, fit, alignment, sampling, tint, and opacity.
• VisualFill: value wrapper for Color, LinearGradient, RadialGradient, or ImageFill; construct from any alternative and inspect with Get().

Paint commands

PaintCommand is a variant of:

• DrawRectCommand, DrawLinearGradientCommand, DrawRadialGradientCommand.
• DrawTextCommand, TextRun, DrawTextRunsCommand.
• DrawImageCommand, DrawExternalTextureCommand.
• DrawCircleCommand, DrawArcCommand, DrawBorderCommand, DrawShadowCommand.
• FillPathCommand, StrokePathCommand, DrawPathShadowCommand.
• PushClipCommand, PopClipCommand, PushPathClipCommand.
• PushTransformCommand, PopTransformCommand.
• PlacePlatformViewCommand, whose queries expose identity, type, properties/revision, and bounds.

Each command is immutable platform-neutral data with equality. Command fields correspond to the matching PaintContext parameters.

PaintSequence and PaintContext

PaintSequence exposes Commands, conservative Bounds, Revision, and whether it contains external textures. PaintContext(sequence, bounds) records drawing through DrawRect, gradient, text/text-runs, image/image-rect, external texture, circle, arc, border, rect/path shadow, fill/stroke path, clip, and transform methods. Bounds() returns local recording bounds; Finish() validates balanced stacks and closes recording.

Render scene

• RenderClip: rectangular or path clip command.
• RenderNode: stable ID, parent-local offset, presentation transform, group opacity, descendant clips, child transform, content/foreground sequences, child pointers, visibility, and revision.
• RenderScene: non-owning root pointer.
• DamageRegion: full flag or dirty rectangles.
• RenderFrame: scene, damage, and revision.
• FrameCommit: render frame, immutable semantic frame, and optional absolute next-frame deadline.

The scene/frame types are the platform renderer boundary. Their non-owning pointers remain valid only until the next runtime frame construction or destruction.

Complete Canvas example

#include <huxerui/huxerui.h>

using namespace huxerui;

View StatusCanvas() {
  return Canvas([](PaintContext& paint, Size size) {
    const Point center {size.width / 2.0F, size.height / 2.0F};
    paint.DrawCircle(center, 36.0F, Color::Rgb(92, 61, 180));
    paint.DrawArc(center, 28.0F, -1.57F, 4.2F, Color::Rgb(255, 255, 255), 6.0F);
  }).With(Frame {.width = 160.0F, .height = 160.0F});
}

The painter receives local size and emits platform-neutral commands. It does not own a platform canvas or world-coordinate transform.