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Error Types

Renderer Errors​

pub enum ScreenshotError {
    SurfaceError(wgpu::SurfaceError),
    BufferMapError,
    ImageEncodingError,
}
pub enum NodeScreenshotError {
    NoLayout,
    NodeNotFound(Vec<usize>),
    EmptyRect,
    Render(ScreenshotError),
}

Frame Outcome​

pub enum FrameOutcome {
    Presented,       // Frame rendered successfully
    Reconfigure,     // Surface lost, must call resize() and retry
    Skipped,         // Nothing to draw (empty display list)
}

Pipeline Errors​

The pipeline functions use Option returns rather than Result for expected states:

  • compute_layout() returns None when the tree is empty
  • paint_tree_returning_layout() returns Option<LayoutBox> — None if no content
  • screenshot_node_to() returns NodeScreenshotError for missing or empty nodes

Parser Behavior​

The HTML parser is lenient. Invalid HTML is recovered gracefully:

  • Unknown tags drop their entire subtree silently
  • Mismatched tags follow auto-close rules
  • Invalid CSS properties are silently ignored (not parsed)
  • CSS parse errors don't prevent the rest of the stylesheet from working

Layout Behavior​

  • display: none children are excluded from layout (no error)
  • Unsupported CSS values fall back to defaults (e.g., unknown display value → block)
  • Missing fonts fall back to the first registered font
  • Images that fail to load are silently hidden
  • Gradients with invalid parameters degrade to a solid 1×1 transparent pixel

Error Handling Pattern​

For custom integrations, wrap the pipeline:

match lui::compute_layout(&tree, &mut text_ctx, &mut image_cache, vw, vh, scale) {
    Some(layout) => { /* render */ }
    None => { /* tree is empty, show placeholder */ }
}