### Diagram Initialization for Text Rendering Example

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/mod.rs.html

Sets up a simple two-node, one-edge diagram for testing text rendering functionality. This example demonstrates basic diagram construction.

```rust
use mmdflux::graph::geometry::{
    EngineHints, FRect, GraphGeometry, LayeredHints, LayoutEdge, PositionedNode,
};
use mmdflux::render::graph::{render_text_from_geometry, TextRenderOptions};
use mmdflux::{Diagram, Direction, Edge, Node, Shape};
use std::collections::{HashMap, HashSet};

let mut diagram = Diagram::new(Direction::LeftRight);
diagram.add_node(Node::new("A"));
diagram.add_node(Node::new("B"));
diagram.add_edge(Edge::new("A", "B"));

let geometry = GraphGeometry {
    nodes: HashMap::from([
        (
            "A".to_string(),
            PositionedNode {
                id: "A".to_string(),
                rect: FRect::new(0.0, 0.0, 9.0, 3.0),
                shape: Shape::Rectangle,
                label: "A".to_string(),
                parent: None,
            },
        ),
        (
            "B".to_string(),
            PositionedNode {
                id: "B".to_string(),
                rect: FRect::new(20.0, 0.0, 9.0, 3.0),
                shape: Shape::Rectangle,
                label: "B".to_string(),
                parent: None,
            },
        ),
    ]),
    // ... other fields omitted for brevity
};
```

--------------------------------

### Setup Graph and Run Layering

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/algorithms/layered/kernel/order.rs.html

Initializes a LayoutGraph from a Digraph, runs the acyclic and rank algorithms, normalizes the layout, and then applies the compound normalization and final ordering. This is a common setup for testing ordering algorithms.

```rust
let mut lg = LayoutGraph::from_digraph(&graph, |_, _| (10.0, 10.0));
crate::engines::graph::algorithms::layered::acyclic::run(&mut lg);
rank::run(&mut lg, &LayoutConfig::default());
rank::normalize(&mut lg);
crate::engines::graph::algorithms::layered::normalize::run(
    &mut lg,
    &std::collections::HashMap::new(),
    false,
);
```

--------------------------------

### Start Activation Bar in SVG

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/timeline/svg_layout.rs.html

Records the start of an activation bar for a participant, pushing its starting y-coordinate and depth onto a stack.

```rust
            SequenceEvent::ActivateStart { participant } => {
                let depth = activation_depth[*participant];
                activation_stacks[*participant].push((last_message_y, depth));
                activation_depth[*participant] += 1;
            }
```

--------------------------------

### Compute Layer Starts for Grid Projection

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/grid/derive/mod.rs.html

Calculates the starting positions for each layer based on the grid projection, node bounds, and layout orientation. This is used for transforming waypoints.

```rust
let layer_starts = grid_projection
        .map(|projection| compute_layer_starts(&projection.node_ranks, &node_bounds, is_vertical))
        .unwrap_or_default();
```

--------------------------------

### Autonumbering Start, Step, Off, and Resume

Source: https://docs.rs/mmdflux/latest/src/mmdflux/diagrams/sequence/compiler.rs.html

Tests the behavior of autonumbering with custom start and step values, disabling it, and then resuming it.

```rust
let model = compile_input("\nsequenceDiagram\n    autonumber 5 2
    participant A
    participant B
    A->>B: first
    B->>A: second
    autonumber off
    A->>B: third
    autonumber
    A->>B: fourth");

        let numbers: Vec<_> = model
            .events
            .iter()
            .filter_map(|event| match event {
                SequenceEvent::Message { number, .. } => Some(*number),
                _ => None,
            })
            .collect();
        assert_eq!(numbers, vec![Some(5), Some(7), None, Some(9)]);
        assert_eq!(model.autonumber, AutonumberState { enabled: true, next: 10,
```

--------------------------------

### Get Segment Start Cell

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/grid/label_placement.rs.html

Extracts the starting GridCell from a Segment, handling both Horizontal and Vertical segments.

```rust
fn segment_start_cell(seg: &Segment) -> GridCell {
    match *seg {
        Segment::Horizontal { y, x_start, .. } => (x_start, y),
        Segment::Vertical { x, y_start, .. } => (x, y_start),
    }
}
```

--------------------------------

### Helper: Simple A->B Tree Setup

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/algorithms/layered/kernel/network_simplex.rs.html

Sets up a basic directed graph with two nodes (A, B) and one edge (A->B), along with a SpanningTree structure, for testing simple tree scenarios.

```rust
    /// Helper: A->B, ranks 0,1. Tree: A(root)->B.
    fn make_simple_ab_tree() -> (LayoutGraph, SpanningTree) {
        let mut g: DiGraph<()> = DiGraph::new();
        g.add_node("A", ());
        g.add_node("B", ());

```

--------------------------------

### Insert Basis Start Cap If Needed

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/svg/edges/basis.rs.html

Inserts a control point at the start of a path if the first segment is shorter than the minimum stem length and collinear with subsequent segments. Ensures a minimum stem length from the start.

```rust
fn insert_basis_start_cap_if_needed(points: &mut Vec<Point>, min_stem: f64) {
    const EPS: f64 = 1e-6;
    if points.len() < 2 || min_stem <= 0.0 {
        return;
    }

    let base_vec = Point {
        x: points[1].x - points[0].x,
        y: points[1].y - points[0].y,
    };
    let first_segment_len = (base_vec.x * base_vec.x + base_vec.y * base_vec.y).sqrt();
    if first_segment_len <= EPS || first_segment_len + EPS >= min_stem {
        return;
    }

    let mut traversed = 0.0;
    for seg_idx in 0..(points.len() - 1) {
        let seg_vec = Point {
            x: points[seg_idx + 1].x - points[seg_idx].x,
            y: points[seg_idx + 1].y - points[seg_idx].y,
        };
        let seg_len = (seg_vec.x * seg_vec.x + seg_vec.y * seg_vec.y).sqrt();
        if seg_len <= EPS {
            continue;
        }
        if !vectors_share_ray(base_vec, seg_vec) {
            break;
        }
        if traversed + seg_len + EPS >= min_stem {
            let t = ((min_stem - traversed) / seg_len).clamp(0.0, 1.0);
            if t >= 1.0 - EPS {
                return;
            }
            let cap = Point {
                x: points[seg_idx].x + seg_vec.x * t,
                y: points[seg_idx].y + seg_vec.y * t,
            };
            if !points_approx_equal(cap, points[seg_idx])
                && !points_approx_equal(cap, points[seg_idx + 1])
            {
                points.insert(seg_idx + 1, cap);
            }
            return;
        }
        traversed += seg_len;
    }
}
```

--------------------------------

### Test Setup for Graph Layering Algorithms

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/algorithms/layered/kernel/order.rs.html

Sets up a directed graph with nodes and edges for testing layering algorithms. It initializes a DiGraph and adds nodes and edges.

```rust
fn setup_graph_and_run(
        nodes: &[&str],
        edges_list: &[(&str, &str)],
    ) -> (LayoutGraph, Vec<Vec<usize>>) {
        let mut graph: DiGraph<()> = DiGraph::new();
        for &n in nodes {
            graph.add_node(n, ());
        }
        for &(from, to) in edges_list {
            graph.add_edge(from, to);
        }


```

--------------------------------

### Start State Node Test

Source: https://docs.rs/mmdflux/latest/src/mmdflux/diagrams/state/compiler.rs.html

Checks that the start state ('[*]') is correctly compiled into a node with the 'SmallCircle' shape.

```rust
let graph = compile_state("stateDiagram-v2\n    [*] --> Idle");
let start_node = graph.nodes.values().find(|n| n.shape == Shape::SmallCircle);
assert!(start_node.is_some());
assert_eq!(graph.edges[0].to, "Idle");
```

--------------------------------

### Build LayoutGraph with Label Dummies

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/algorithms/layered/kernel/compartment_spacing.rs.html

Constructs a LayoutGraph from edges and attaches label dummy nodes. Used to set up graph structures for projection algorithms. Requires a `DiGraph` and a list of label parameters.

```rust
    fn build_with_label_dummies(
        edges: &[(&str, &str)],
        labels: &[(usize, i32, f64, f64, f64)],
    ) -> (LayoutGraph, std::collections::HashMap<usize, f64>) {
        let mut g: DiGraph<(f64, f64)> = DiGraph::new();
        let mut seen = std::collections::HashSet::new();
        for (src, tgt) in edges {
            if seen.insert(*src) {
                g.add_node(*src, (40.0, 20.0));
            }
            if seen.insert(*tgt) {
                g.add_node(*tgt, (40.0, 20.0));
            }
            g.add_edge(*src, *tgt);
        }
        let mut lg = LayoutGraph::from_digraph(&g, |_, dims| *dims);

        let mut cross = std::collections::HashMap::new();
        for (edge_index, rank, width, height, cross_center) in labels {
            let dummy_id = NodeId::from(format!(
```

```rust
_label{}\n                lg.node_ids.len())
            ;
            let dummy_idx = lg.node_ids.len();
            let dummy_node =
                DummyNode::edge_label(*edge_index, *rank, *width, *height, LabelPos::Center);

            lg.node_ids.push(dummy_id.clone());
            lg.node_index.insert(dummy_id.clone(), dummy_idx);
            lg.ranks.push(*rank);
            lg.order.push(dummy_idx);
            lg.positions.push(Point::default());
            lg.dimensions.push((*width, *height));
            lg.original_has_predecessor.push(false);
            lg.parents.push(None);
            lg.model_order.push(None);
            lg.dummy_nodes.insert(dummy_id, dummy_node);

            cross.insert(dummy_idx, *cross_center);
        }

        (lg, cross)
    }

```

--------------------------------

### Create New DiagramRegistry

Source: https://docs.rs/mmdflux/latest/mmdflux/registry/struct.DiagramRegistry.html

Instantiates a new, empty DiagramRegistry. Use this to start managing diagram types.

```rust
pub fn new() -> Self
```

--------------------------------

### OrthogonalRoutingOptions Preview Method

Source: https://docs.rs/mmdflux/latest/mmdflux/graph/routing/struct.OrthogonalRoutingOptions.html

Provides a conservative preview of orthogonal routing for forward edges only. Use this to initialize routing options with default behavior.

```rust
pub fn preview() -> Self
```

--------------------------------

### Get Cause for ParseError (Deprecated)

Source: https://docs.rs/mmdflux/latest/mmdflux/mmds/struct.ParseError.html

Deprecated method to get the underlying cause of the error. Replaced by Error::source.

```rust
fn cause(&self) -> Option<&dyn Error>
```

--------------------------------

### Get Description for ParseError (Deprecated)

Source: https://docs.rs/mmdflux/latest/mmdflux/mmds/struct.ParseError.html

Deprecated method to get a string description of the error. Use the Display implementation or to_string() instead.

```rust
fn description(&self) -> &str
```

--------------------------------

### Start SVG with Root Style

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/svg/mod.rs.html

Begins an SVG document, setting up the root <svg> tag with specified dimensions, font properties, and root styling. Includes optional CSS style block.

```rust
pub(crate) fn start_svg_with_root_style(
    &mut self,
    width: f64,
    height: f64,
    font_family: &str,
    font_size: f64,
    root_style: &SvgRootStyle,
) {
    let view_width = fmt_f64(width);
    let view_height = fmt_f64(height);
    let view_box = format!("0 0 {view_width} {view_height}");
    let mut style_parts = vec![
        format!("max-width: {view_width}px"),
        format!(
            "background-color: {}",
            root_style
                .background_color
                .as_deref()
                .unwrap_or("transparent")
        ),
    ];
    style_parts.extend(
        root_style
            .css_variables
            .iter()
            .map(|(name, value)| format!("{name}:{value}")),
    );
    let style = format!("{};", style_parts.join("; "));
    let line = format!(
        "<svg xmlns=\"http://www.w3.org/2000/svg\" width=\"100%\" viewBox=\"{view_box}\" style=\"{style}\" font-family=\"{font}\" font-size=\"{font_size}\">",
        view_box = view_box,
        style = style,
        font = escape_text(font_family),
        font_size = fmt_f64(font_size)
    );
    self.push_line(&line);
    self.indent += 1;

    if let Some(style_block) = &root_style.style_block {
        self.start_tag("<style>");
        for css_line in style_block.lines() {
            self.push_line(css_line);
        }
        self.end_tag("</style>");
    }
}
```

--------------------------------

### Clip Edge Points to Start of Rectangle

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/svg/edges/endpoints.rs.html

Clips a sequence of points representing an edge path so that the starting point lies within the specified rectangle. If the start point is outside, the original points are returned. If the path segment exiting the rectangle is found, an intersection point is calculated.

```rust
pub(super) fn clip_points_to_rect_start(points: &[Point], rect: &Rect) -> Vec<Point> {
    if points.len() < 2 {
        return points.to_vec();
    }
    if !point_inside_rect(rect, points[0]) {
        return points.to_vec();
    }

    let mut idx = 0usize;
    while idx + 1 < points.len() && point_inside_rect(rect, points[idx]) {
        idx += 1;
    }
    if idx == 0 || idx >= points.len() {
        return points.to_vec();
    }

    let inside = points[idx - 1];
    let outside = points[idx];
    let intersection = segment_rect_intersection(inside, outside, rect).unwrap_or(inside);

    let mut out = Vec::new();
    out.push(intersection);
    out.extend_from_slice(&points[idx..]);
    out
}
```

--------------------------------

### Initialize SvgBounds

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/svg/bounds.rs.html

Creates a new `SvgBounds` instance with infinite initial values, ready to track minimum and maximum coordinates.

```rust
fn new() -> Self {
        Self {
            min_x: f64::INFINITY,
            min_y: f64::INFINITY,
            max_x: f64::NEG_INFINITY,
            max_y: f64::NEG_INFINITY,
        }
    }
```

--------------------------------

### Build LayoutGraph and Run Pipeline

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/algorithms/layered/kernel/parent_dummy_chains.rs.html

Constructs a `LayoutGraph` from a `DiGraph`, applies various layout algorithms including `parent_dummy_chains`, and returns the processed graph.

```rust
fn build_external_node_subgraph_after_parent_dummy_chains() -> LayoutGraph {
        let mut g = DiGraph::new();

        // Add nodes
        g.add_node("us-east", (0, 0));
        g.add_node("us-west", (0, 0));

        // Titles
        g.set_has_title("Cloud");
        g.set_has_title("us-east");
        g.set_has_title("us-west");

        // Parent relationships for nodes
        g.set_parent("A", "us-east");
        g.set_parent("B", "us-east");
        g.set_parent("C", "us-west");
        g.set_parent("D", "us-west");

        // Parent relationships for nested subgraphs
        g.set_parent("us-east", "Cloud");
        g.set_parent("us-west", "Cloud");

        // Edges: A→B (0), C→D (1), E→A (2), E→C (3)
        g.add_edge("A", "B");
        g.add_edge("C", "D");
        g.add_edge("E", "A");
        g.add_edge("E", "C");

        let mut lg = LayoutGraph::from_digraph(&g, |_, dims| (dims.0 as f64, dims.1 as f64));

        // Run pipeline up through parent_dummy_chains (matching layout_with_labels)
        extract_self_edges(&mut lg);
        crate::engines::graph::algorithms::layered::acyclic::run(&mut lg);
        make_space_for_edge_labels(&mut lg);
        crate::engines::graph::algorithms::layered::nesting::run(&mut lg);
        rank::run(&mut lg, &LayoutConfig::default());
        rank::remove_empty_ranks(&mut lg);
        crate::engines::graph::algorithms::layered::nesting::cleanup(&mut lg);
        rank::normalize(&mut lg);
        crate::engines::graph::algorithms::layered::nesting::insert_title_nodes(&mut lg);
        rank::normalize(&mut lg);
        crate::engines::graph::algorithms::layered::nesting::assign_rank_minmax(&mut lg);
        normalize::run(&mut lg, &HashMap::new(), false);
        run(&mut lg);

        lg
    }

```

--------------------------------

### Parse Block Start

Source: https://docs.rs/mmdflux/latest/src/mmdflux/mermaid/sequence/mod.rs.html

Parses the start of control flow blocks like 'loop', 'alt', and 'opt'. Extracts the block kind and its optional label.

```rust
fn try_parse_block_start(line: &str) -> Option<SequenceStatement> {
    parse_keyword_line(line, "loop")
        .map(|label| SequenceStatement::BlockStart {
            kind: BlockKind::Loop,
            label,
        })
        .or_else(|| {
            parse_keyword_line(line, "alt").map(|label| SequenceStatement::BlockStart {
                kind: BlockKind::Alt,
                label,
            })
        })
        .or_else(|| {
            parse_keyword_line(line, "opt").map(|label| SequenceStatement::BlockStart {
                kind: BlockKind::Opt,
                label,
            })
        })
        .or_else(|| {
            // ... other block types like 'par' could be added here
        })
}
```

--------------------------------

### Test Compiler Lollipop Edge (Start)

Source: https://docs.rs/mmdflux/latest/src/mmdflux/diagrams/class/compiler.rs.html

Tests lollipop edges ('()--') where the circle marker is at the start, ensuring correct arrow and endpoint shape.

```rust
#[test]
fn compiler_lollipop_edge_uses_circle_marker_at_start() {
    let diagram = compile_class("classDiagram\nfoo ()-- Class01");
    assert_eq!(diagram.edges[0].arrow_start, Arrow::Circle);
    assert_eq!(diagram.edges[0].arrow_end, Arrow::None);
    assert!(!diagram.nodes.contains_key("foo"));
    let endpoint = &diagram.nodes[&diagram.edges[0].from];
    assert_eq!(endpoint.shape, Shape::TextBlock);
    assert_eq!(endpoint.label, "foo");
    assert_eq!(diagram.nodes["Class01"].shape, Shape::Rectangle);
}
```

--------------------------------

### FPoint::new

Source: https://docs.rs/mmdflux/latest/mmdflux/graph/space/struct.FPoint.html

Constructor for creating a new FPoint instance.

```APIDOC
### impl FPoint

#### pub fn new(x: f64, y: f64) -> Self

Creates a new FPoint with the given x and y coordinates.
```

--------------------------------

### Rebuild Points with Start Cap

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/svg/edges/basis.rs.html

Reconstructs a list of points by inserting a new start cap point into an existing sequence. Ensures the new sequence is deduplicated.

```rust
fn rebuild_with_start_cap(points: &[Point], seg_idx: usize, cap: Point) -> Vec<Point> {
    if points.len() < 2 || seg_idx >= points.len() - 1 {
        return points.to_vec();
    }

    let mut rebuilt = Vec::with_capacity(points.len() + 1);
    rebuilt.push(points[0]);
    rebuilt.push(cap);
    rebuilt.extend_from_slice(&points[(seg_idx + 1)..]);
    dedup_consecutive_svg_points(&rebuilt)
}
```

--------------------------------

### FRect constructor and methods

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/space.rs.html

Provides a constructor for FRect and methods to calculate the center x, center y, and center point of the rectangle.

```rust
impl FRect {
    pub fn new(x: f64, y: f64, width: f64, height: f64) -> Self {
        Self {
            x,
            y,
            width,
            height,
        }
    }

    pub fn center_x(&self) -> f64 {
        self.x + self.width / 2.0
    }

    pub fn center_y(&self) -> f64 {
        self.y + self.height / 2.0
    }

    pub fn center(&self) -> FPoint {
        FPoint {
            x: self.center_x(),
            y: self.center_y(),
        }
    }
}
```

--------------------------------

### Segment Start Point Retrieval

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/grid/routing/types.rs.html

Returns the starting `Point` of the segment. For vertical segments, `x` is fixed and `y` is `y_start`. For horizontal segments, `y` is fixed and `x` is `x_start`.

```rust
pub fn start_point(&self) -> Point {
    match self {
        Segment::Vertical { x, y_start, .. } => Point { x: *x, y: *y_start },
        Segment::Horizontal { y, x_start, .. } => Point { x: *x_start, y: *y },
    }
}
```

--------------------------------

### Build Compound Graph for Ordering

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/algorithms/layered/kernel/order.rs.html

Constructs a sample `LayoutGraph` with nested subgraphs and edges to test ordering algorithms. This setup is used to verify the placement of border nodes.

```rust
fn build_compound_for_ordering() -> LayoutGraph {
        let mut g: DiGraph<()> = DiGraph::new();
        g.add_node("X", ());
        g.add_node("A", ());
        g.add_node("B", ());
        g.add_node("sg1", ());
        g.add_edge("X", "A");
        g.add_edge("A", "B");
        g.set_parent("A", "sg1");
        g.set_parent("B", "sg1");

        let mut lg = LayoutGraph::from_digraph(&g, |_, _| (10.0, 10.0));
        nesting::run(&mut lg);
        rank::run(&mut lg, &LayoutConfig::default());
        rank::normalize(&mut lg);
        nesting::cleanup(&mut lg);
        nesting::assign_rank_minmax(&mut lg);
        border::add_segments(&mut lg);
        lg
    }
```

--------------------------------

### Parse Full Example State Diagram

Source: https://docs.rs/mmdflux/latest/src/mmdflux/mermaid/state/mod.rs.html

Parses a comprehensive state diagram with multiple states and transitions. Asserts the total number of statements.

```rust
let input = "stateDiagram-v2
    [*] --> Idle
    Idle --> Processing : submit
    Processing --> Done : complete
    Done --> [*]";
        let result = parse_state_diagram(input).unwrap();
        assert_eq!(result.model.statements.len(), 4);
```

--------------------------------

### Draw Source Launch Point for Edges

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/text/edge.rs.html

Draws the starting point of an edge if it has no start arrow, is not a self-loop, and has segments. It uses the `source_connection` function to determine the connection type.

```rust
fn draw_source_launch(
    canvas: &mut Canvas,
    routed: &RoutedEdge,
    charset: &CharSet,
    edge_color: Option<(u8, u8, u8)>,
) {
    if routed.edge.arrow_start != Arrow::None || routed.is_self_edge || routed.segments.is_empty() {
        return;
    }
    let Some(direction) = routed.source_connection else {
        return;
    };
    if canvas.set_with_connection(
        routed.start.x,
        routed.start.y,
        source_connection(direction),
        charset,
        routed.edge.stroke,
    ) {
        merge_edge_fg(canvas, routed.start.x, routed.start.y, edge_color);
    }
}
```

--------------------------------

### Run Layered Layout Computation

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/algorithms/layered/kernel/pipeline.rs.html

Main entry point for layout computation. Takes a directed graph, configuration, and a function to get node dimensions. Returns a LayoutResult.

```rust
pub fn run_layered_layout<N, F>(
    graph: &DiGraph<N>,
    config: &LayoutConfig,
    get_dimensions: F,
) -> LayoutResult
where
    F: Fn(&NodeId, &N) -> (f64, f64),
{
    layout(graph, config, get_dimensions)
}
```

--------------------------------

### Rect Transformation: Setting Start Position

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/routing/label_clamp.rs.html

Creates a new FRect with a specified start position along a given axis. This is used to adjust the position of a rectangle after clamping.

```rust
fn rect_with_axis_start(rect: FRect, axis: Axis, new_start: f64) -> FRect {
    match axis {
        Axis::Y => FRect::new(rect.x, new_start, rect.width, rect.height),
        Axis::X => FRect::new(new_start, rect.y, rect.width, rect.height),
    }
}
```

--------------------------------

### Build Path from Hints with Degenerate Layout Hint

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/routing/mod.rs.html

Builds a path from hints, falling back to nodes and waypoints when the layout hint is degenerate. The fallback uses provided waypoints.

```rust
geom.edges[0].layout_path_hint =
            Some(vec![FPoint::new(70.0, 35.0), FPoint::new(70.0, 35.0)]);
        geom.edges[0].waypoints = vec![FPoint::new(60.0, 55.0)];

        let path = orthogonal::hints::build_path_from_hints(&geom.edges[0], &geom);

        assert_eq!(
            path,
            vec![
                FPoint::new(70.0, 35.0),
                FPoint::new(60.0, 55.0),
                FPoint::new(70.0, 85.0),
            ]
        );
```

--------------------------------

### Handle Out-of-Bounds Coordinates

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/text/canvas.rs.html

Demonstrates attempting to set or get a cell outside the canvas dimensions. `set` returns false, and `get` returns None for out-of-bounds access.

```rust
let mut canvas = Canvas::new(5, 5);
assert!(!canvas.set(10, 10, 'X'));
assert!(canvas.get(10, 10).is_none());
```

--------------------------------

### Path from Prepared Points (Curved Mode)

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/svg/edges/path_emit.rs.html

Generates an SVG path using prepared points with the 'Basis' curve mode. Verifies the path starts correctly and includes a curve command ('C').

```rust
let path = path_from_prepared_points(
            &[
                Point { x: 0.0, y: 0.0 },
                Point { x: 10.0, y: 0.0 },
                Point { x: 10.0, y: 10.0 },
            ],
            &Edge::new("A", "B"),
            1.0,
            Curve::Basis,
            4.0,
            false,
            false,
        );

        assert!(path.starts_with("M0.00,0.00"));
        assert!(path.contains('C'));
```

--------------------------------

### MermaidLayeredEngine Initialization

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/mermaid.rs.html

Provides a constructor for creating a new instance of the MermaidLayeredEngine.

```rust
impl MermaidLayeredEngine {
    /// Create the Mermaid-compatible graph engine adapter.
    pub fn new() -> Self {
        Self
    }
}
```

--------------------------------

### Test Additional Block Starts Parsing

Source: https://docs.rs/mmdflux/latest/src/mmdflux/mermaid/sequence/mod.rs.html

Verifies the parsing of various block start statements like 'par', 'critical', and 'break', ensuring their kinds and labels are correctly identified.

```rust
    #[test]
    fn parse_additional_block_starts() {
        let stmts = parse_stmts(
            "sequenceDiagram\npar notifications\ncritical establish connection\nbreak success",
        );
        assert_eq!(
            stmts,
            vec![
                SequenceStatement::BlockStart {
                    kind: BlockKind::Par,
                    label: "notifications".to_string(),
                },
                SequenceStatement::BlockStart {
                    kind: BlockKind::Critical,
                    label: "establish connection".to_string(),
                },
                SequenceStatement::BlockStart {
                    kind: BlockKind::Break,
                    label: "success".to_string(),
                },
            ]
        );
    }
```

--------------------------------

### Path from Prepared Points (Rounded Mode)

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/svg/edges/path_emit.rs.html

Generates an SVG path using prepared points with a rounded corner style. Asserts the path starts correctly and uses quadratic Bezier curves ('Q').

```rust
let path = path_from_prepared_points(
            &[
                Point { x: 0.0, y: 0.0 },
                Point { x: 10.0, y: 0.0 },
                Point { x: 10.0, y: 10.0 },
            ],
            &Edge::new("A", "B"),
            1.0,
            Curve::Linear(CornerStyle::Rounded),
            4.0,
            false,
            false,
        );

        assert!(path.starts_with("M0.00,0.00"));
        assert!(path.contains('Q'));
```

--------------------------------

### High-Level API: Customizing Output with RenderConfig

Source: https://docs.rs/mmdflux/latest/index.html

Shows how to customize the rendering process using `RenderConfig`, including options for routing style, padding, and layout parameters.

```APIDOC
## Customizing output

Use `RenderConfig` to control layout direction, engine selection, edge routing, padding, color mode, and more:

```rust
use mmdflux::{OutputFormat, RenderConfig, render_diagram};
use mmdflux::LayoutConfig;
use mmdflux::format::RoutingStyle;

let config = RenderConfig {
    routing_style: Some(RoutingStyle::Direct),
    padding: Some(2),
    layout: LayoutConfig {
        rank_sep: 30.0,
        ..LayoutConfig::default()
    },
    ..RenderConfig::default()
};

let output = render_diagram("graph LR\n    A-->B-->C", OutputFormat::Text, &config).unwrap();
println!("{output}");
```
```

--------------------------------

### Concurrent Regions with Independent Star Scopes

Source: https://docs.rs/mmdflux/latest/src/mmdflux/diagrams/state/compiler.rs.html

Tests concurrent regions where each region has its own independent start and end pseudo-states. Verifies the correct number of start and end nodes are generated.

```rust
    #[test]
    fn compiler_concurrent_regions_independent_star_scopes() {
        let input = "\
stateDiagram-v2
    state Active {
        [*] --> A1
        A1 --> [*]
        --
        [*] --> B1
        B1 --> [*]
    }";
        let graph = compile_state(input);
        // Each region should have its own start and end pseudo-states.
        let start_nodes: Vec<_> = graph
            .nodes
            .values()
            .filter(|n| n.shape == Shape::SmallCircle)
            .collect();
        let end_nodes: Vec<_> = graph
            .nodes
            .values()
            .filter(|n| n.shape == Shape::FramedCircle)
            .collect();
        // Two start nodes (one per region) and two end nodes.
        assert_eq!(start_nodes.len(), 2);
        assert_eq!(end_nodes.len(), 2);
    }
```

--------------------------------

### Parse Start Arrow Head

Source: https://docs.rs/mmdflux/latest/src/mmdflux/mermaid/flowchart.rs.html

Parses the starting arrow head for a link, considering the first character of the input string. It maps characters like '<', 'x', and 'o' to specific ArrowHead variants.

```rust
fn parse_start_arrow_head(s: &str) -> ArrowHead {
    match s.chars().next() {
        Some('<') => ArrowHead::Normal,
        Some('x') => ArrowHead::Cross,
        Some('o') => ArrowHead::Circle,
        _ => ArrowHead::None,
    }
}
```

--------------------------------

### into_render_config Method

Source: https://docs.rs/mmdflux/latest/mmdflux/struct.RuntimeConfigInput.html

This method validates and converts a RuntimeConfigInput into a typed RenderConfig.

```APIDOC
### impl RuntimeConfigInput

#### pub fn into_render_config(self) -> Result<RenderConfig, RenderError>

Validate and convert into a typed `RenderConfig`.
```

--------------------------------

### Compute Tail Label Position for Vertical Path

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/routing/mod.rs.html

Computes the position for the tail label near the start of a vertical path. Ensures the label is close to the path's starting point.

```rust
let path = vec![FPoint::new(50.0, 0.0), FPoint::new(50.0, 100.0)];
        let (_head, tail) = compute_end_label_positions(&path);

        let tail = tail.unwrap();
        assert!(tail.y < 20.0, "tail near start, got y={}", tail.y);
```

--------------------------------

### Example Theme Definition: zinc-light

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/svg/theme.rs.html

Defines the 'zinc-light' theme using a `ThemeSeed`. This is a predefined theme with specific background and foreground colors.

```rust
named_theme(
    "zinc-light",
    ThemeSeed {
        bg: "#ffffff",
        fg: "#27272a",
        line: None,
        accent: None,
        muted: None,
        surface: None,
        border: None,
    },
),

```

--------------------------------

### Direct Route Graph Geometry

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/routing/mod.rs.html

Demonstrates setting up `GraphGeometry` with nodes and edges for direct routing. Asserts the expected path of the routed edge.

```rust
let mut diagram = Graph::new(crate::graph::Direction::TopDown);
        diagram.add_node(crate::graph::Node::new("A"));
        diagram.add_node(crate::graph::Node::new("B"));
        diagram.add_edge(crate::graph::Edge::new("A", "B"));

        let mut nodes = HashMap::new();
        nodes.insert(
            "A".into(),
            PositionedNode {
                id: "A".into(),
                rect: FRect::new(0.0, 0.0, 40.0, 20.0),
                shape: crate::graph::Shape::Rectangle,
                label: "A".into(),
                parent: None,
            },
        );
        nodes.insert(
            "B".into(),
            PositionedNode {
                id: "B".into(),
                rect: FRect::new(100.0, 0.0, 40.0, 20.0),
                shape: crate::graph::Shape::Rectangle,
                label: "B".into(),
                parent: None,
            },
        );

        let mut node_directions = HashMap::new();
        node_directions.insert("A".into(), crate::graph::Direction::LeftRight);
        node_directions.insert("B".into(), crate::graph::Direction::LeftRight);

        let geom = GraphGeometry {
            nodes,
            edges: vec![LayoutEdge {
                index: 0,
                from: "A".into(),
                to: "B".into(),
                waypoints: vec![],
                label_position: None,
                label_side: None,
                from_subgraph: None,
                to_subgraph: None,
                layout_path_hint: None,
                preserve_orthogonal_topology: false,
                label_geometry: None,
                effective_wrapped_lines: None,
            }],
            subgraphs: HashMap::new(),
            self_edges: vec![],
            direction: crate::graph::Direction::TopDown,
            node_directions,
            bounds: FRect::new(0.0, 0.0, 140.0, 20.0),
            reversed_edges: vec![],
            engine_hints: None,
            grid_projection: None,
            rerouted_edges: std::collections::HashSet::new(),
            enhanced_backward_routing: false,
        };

        let routed = route_graph_geometry(
            &diagram,
            &geom,
            EdgeRouting::DirectRoute,
            &default_proportional_text_metrics(),
        );
        assert_eq!(
            routed.edges[0].path,
            vec![FPoint::new(40.0, 10.0), FPoint::new(100.0, 10.0)]
        );
```

--------------------------------

### Draw Edge Path and Arrows

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/text/edge.rs.html

Renders the main path of an edge, including drawing each segment and placing arrows at the start and end points if configured. It also calls `draw_source_launch` for the starting point.

```rust
fn draw_edge_path_and_arrows(canvas: &mut Canvas, routed: &RoutedEdge, charset: &CharSet) {
    let edge_color = resolved_edge_stroke_color(routed);
    for segment in &routed.segments {
        draw_segment(canvas, segment, routed.edge.stroke, charset, edge_color);
    }
    draw_source_launch(canvas, routed, charset, edge_color);

    if routed.edge.arrow_end != Arrow::None {
        draw_arrow_with_entry(
            canvas,
            &routed.end,
            routed.entry_direction,
            charset,
            routed.edge.arrow_end,
            edge_color,
        );
    }

    if routed.edge.arrow_start != Arrow::None && !routed.is_self_edge {
        let exit_direction = exit_direction_from_segments(&routed.segments);
        draw_arrow_with_entry(
            canvas,
            &routed.start,
            exit_direction,
            charset,
            routed.edge.arrow_start,
            edge_color,
        );
    }
}
```

--------------------------------

### PathSimplification Simplify Method

Source: https://docs.rs/mmdflux/latest/src/mmdflux/simplification.rs.html

Simplifies a slice of points based on the `PathSimplification` level. For `Lossy`, it retains start, midpoint, and end. For `Minimal`, it retains only start and end. Other levels return a clone of the original points.

```rust
pub fn simplify<T: Clone>(&self, points: &[T]) -> Vec<T> {
    match self {
        PathSimplification::None => points.to_vec(),
        PathSimplification::Lossless => points.to_vec(),
        PathSimplification::Lossy if points.len() > 3 => {
            let mid = points.len() / 2;
            vec![
                points[0].clone(),
                points[mid].clone(),
                points[points.len() - 1].clone(),
            ]
        }
        PathSimplification::Minimal if points.len() > 2 => {
            vec![points[0].clone(), points[points.len() - 1].clone()]
        }
        _ => points.to_vec(),
    }
}
```

--------------------------------

### Test Dummy Node Initialization

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/algorithms/layered/kernel/graph.rs.html

Verifies the correct initialization and identification of dummy nodes within the layout graph structure.

```rust
        lg.original_has_predecessor.push(false);
        lg.dummy_nodes.insert(dummy_id, DummyNode::edge(0, 1));

        // Now index 2 is a dummy
        assert!(lg.is_dummy_index(2));
        assert!(!lg.is_dummy_index(0));
```

--------------------------------

### Set and Get Cell Content

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/text/canvas.rs.html

Modifies a character at a specific coordinate on the canvas or retrieves it. Returns true on successful set, false if out of bounds. `get` returns an Option containing the Cell if within bounds.

```rust
let mut canvas = Canvas::new(5, 5);
assert!(canvas.set(2, 3, 'X'));
assert_eq!(canvas.get(2, 3).unwrap().ch, 'X');
```

--------------------------------

### FRect::new

Source: https://docs.rs/mmdflux/latest/mmdflux/graph/space/struct.FRect.html

Creates a new FRect instance with the specified coordinates and dimensions.

```APIDOC
### pub fn new(x: f64, y: f64, width: f64, height: f64) -> Self

Creates a new FRect instance.
```

--------------------------------

### Path from Prepared Points (Straight Mode)

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/svg/edges/path_emit.rs.html

Generates an SVG path using prepared points with a sharp corner style, resulting in straight lines. Verifies the path starts correctly and does not contain curve commands ('Q', 'C'), ending with a line command ('L').

```rust
let path = path_from_prepared_points(
            &[
                Point { x: 0.0, y: 0.0 },
                Point { x: 10.0, y: 0.0 },
                Point { x: 10.0, y: 10.0 },
            ],
            &Edge::new("A", "B"),
            1.0,
            Curve::Linear(CornerStyle::Sharp),
            4.0,
            false,
            false,
        );

        assert!(path.starts_with("M0.00,0.00"));
        assert!(!path.contains('Q'));
        assert!(!path.contains('C'));
        assert!(path.ends_with("L10.00,10.00"));
```

--------------------------------

### Calculate Start Cap Point on Existing Run

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/svg/edges/basis.rs.html

Calculates the starting cap point for an existing run of points based on a minimum stem length. Returns the segment index and the cap point, or None if conditions are not met.

```rust
fn start_cap_point_on_existing_run(points: &[Point], min_stem: f64) -> Option<(usize, Point)> {
    const EPS: f64 = 1e-6;
    if points.len() < 2 || min_stem <= 0.0 {
        return None;
    }

    let base_vec = Point {
        x: points[1].x - points[0].x,
        y: points[1].y - points[0].y,
    };
    let first_segment_len = (base_vec.x * base_vec.x + base_vec.y * base_vec.y).sqrt();
    if first_segment_len <= EPS {
        return None;
    }

    let mut traversed = 0.0;
    let mut last_seg_idx_on_ray = 0usize;
    for seg_idx in 0..(points.len() - 1) {
        let seg_vec = Point {
            x: points[seg_idx + 1].x - points[seg_idx].x,
            y: points[seg_idx + 1].y - points[seg_idx].y,
        };
        let seg_len = (seg_vec.x * seg_vec.x + seg_vec.y * seg_vec.y).sqrt();
        if seg_len <= EPS {
            continue;
        }
        if !vectors_share_ray(base_vec, seg_vec) {
            break;
        }
        last_seg_idx_on_ray = seg_idx;
        if traversed + seg_len + EPS >= min_stem {
            let t = ((min_stem - traversed) / seg_len).clamp(0.0, 1.0);
            let cap = Point {
                x: points[seg_idx].x + seg_vec.x * t,
                y: points[seg_idx].y + seg_vec.y * t,
            };
            return Some((seg_idx, cap));
        }
        traversed += seg_len;
    }

    Some((last_seg_idx_on_ray, points[last_seg_idx_on_ray + 1]))
}
```

--------------------------------

### Helper: Dummy LayoutGraph for Sorting Tests

Source: https://docs.rs/mmdflux/latest/src/mmdflux/engines/graph/algorithms/layered/kernel/order.rs.html

Creates a dummy `LayoutGraph` with a specified number of nodes, each having a sequential `model_order` for use in sorting tests.

```rust
    /// Create a dummy LayoutGraph with enough nodes for sort_entries tests.
    /// Node indices 0..=max_node are created with sequential model_order.
    fn dummy_graph_for_sort(max_node: usize) -> LayoutGraph {
        let mut graph: DiGraph<()> = DiGraph::new();
        let names: Vec<String> = (0..=max_node).map(|i| format!("n{i}")).collect();
        for name in &names {
            graph.add_node(name.as_str(), ());
        }
        LayoutGraph::from_digraph(&graph, |_, _| (10.0, 10.0))
    }
```

--------------------------------

### PathSimplification Enum Definition

Source: https://docs.rs/mmdflux/latest/src/mmdflux/simplification.rs.html

Defines the levels of path simplification available for MMDS and SVG output. Use `Lossless` by default for no visible change, `Lossy` to reduce points to start, midpoint, and end, or `Minimal` for just start and end points.

```rust
pub enum PathSimplification {
    /// No simplification. All routed waypoints are retained.
    None,
    /// Lossless: remove redundant collinear and duplicate interior points.
    #[default]
    Lossless,
    /// Lossy: reduce to start, midpoint, and end (3 points max).
    Lossy,
    /// Minimal: start and end only (2 points max).
    Minimal,
}
```

--------------------------------

### LayoutEdge with Optional Path Hint

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/geometry.rs.html

Illustrates the construction of a LayoutEdge, highlighting that the layout_path_hint field is optional and defaults to None.

```rust
let edge = LayoutEdge {
            index: 0,
            from: "A".into(),
            to: "B".into(),
            waypoints: vec![FPoint::new(1.0, 2.0)],
            label_position: None,
            label_side: None,
            from_subgraph: None,
            to_subgraph: None,
            layout_path_hint: None,
            preserve_orthogonal_topology: false,
            label_geometry: None,
            effective_wrapped_lines: None,
        };
        assert!(edge.layout_path_hint.is_none());
        assert_eq!(edge.waypoints.len(), 1);
```

--------------------------------

### Find a point adjacent to another point at a given distance

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/svg/edges/endpoints.rs.html

Calculates a new point that is a specified distance away from a starting point, along the line defined by the starting point and a second reference point. Handles cases where the points are coincident.

```rust
fn find_adjacent_point(point_a: Point, point_b: Point, distance: f64) -> Point {
    let x_diff = point_b.x - point_a.x;
    let y_diff = point_b.y - point_a.y;
    let length = (x_diff * x_diff + y_diff * y_diff).sqrt();
    if length <= f64::EPSILON {
        return point_b;
    }
    let ratio = distance / length;
    Point {
        x: point_b.x - ratio * x_diff,
        y: point_b.y - ratio * y_diff,
    }
}
```

--------------------------------

### ForkJoin Shape Example

Source: https://docs.rs/mmdflux/latest/mmdflux/graph/enum.Shape.html

Represents a fork or join bar.

```rust
@{shape: fork}
```

--------------------------------

### Self Edges Routing Test Setup

Source: https://docs.rs/mmdflux/latest/src/mmdflux/graph/routing/mod.rs.html

Initializes a graph and geometry for testing self-edge routing. Includes adding a self-edge with specified points.

```rust
let (diagram, mut geom) = simple_geometry();
        geom.self_edges.push(SelfEdgeGeometry {
            node_id: "A".into(),
            edge_index: 1,
            points: vec![
```

--------------------------------

### Compile Open Solid Edge with Default Minlen

Source: https://docs.rs/mmdflux/latest/src/mmdflux/diagrams/flowchart/compiler.rs.html

Tests the compilation of an open solid edge (represented by '---'), verifying its default minimum length behavior.

```rust
fn test_build_diagram_open_solid_edge_default_minlen() {
        let flowchart = parse_flowchart("graph TD
A --- B
").unwrap();

```

--------------------------------

### TextBlock Shape Example

Source: https://docs.rs/mmdflux/latest/mmdflux/graph/enum.Shape.html

Represents a text block with no border.

```rust
@{shape: text}
```

--------------------------------

### Compact Bottom Launch Rendering

Source: https://docs.rs/mmdflux/latest/src/mmdflux/render/graph/text/edge.rs.html

Tests the rendering of a compact bottom launch edge, verifying the corner is positioned at the start cell.

```rust
let charset = CharSet::unicode();
        let mut canvas = Canvas::new(12, 8);
        let routed = RoutedEdge {
            edge: Edge::new("A", "B"),
            start: Point::new(2, 3),
            end: Point::new(8, 6),
            segments: vec![
                Segment::Horizontal {
                    y: 3,
                    x_start: 2,
                    x_end: 8,
                },
                Segment::Vertical {
                    x: 8,
                    y_start: 3,
                    y_end: 6,
                },
            ],
            source_connection: Some(AttachDirection::Top),
            entry_direction: AttachDirection::Top,
            is_backward: false,
            is_self_edge: false,
```

--------------------------------

### Diamond Shape Example

Source: https://docs.rs/mmdflux/latest/mmdflux/graph/enum.Shape.html

Represents a diamond or decision shape.

```rust
{text}
```