Hang caused by stroke-dash array:none

[jake-b]

I am trying SVGView in a project, and found that the following SVG causes a crash/infinite loop/pinwheel hang.

My AI helper churned for a while and identified stroke​-dasharray​:none as the culprit. The SVG style is parsed by SVGView as [0​.0] (a zero-length dash pattern). When CoreGraphics tries to render this, it infinite-loops trying to tile zero-length dashes across the path. The AI tell me that SVG spec says stroke​-dasharray​:none means "solid line" (empty array), not [0].

I added some code to sanitize the SVG before being passed to SVGView in my app, but I offer this in case it helps someone else.

[jake-b]

As authored by Claude:

Description:

When an SVG element has stroke​-dasharray set to none (either as an XML attribute or in an inline style), SVGView parses it as a dash array of [0​.0] instead of an empty array []. This produces Stroke​Style(dash: [0​.0]), which causes CoreGraphics to enter an infinite loop when rendering the stroked path — the renderer attempts to tile zero-length dashes (0 on, 0 off) across the path's arc length, never making progress.

Per the SVG spec, stroke​-dasharray: none means "no dash pattern" (i.e., a solid line). It should be treated as an empty dash array.

##Root cause:

In SVGParser​Primitives​.swift, get​Stroke​Dashes splits the raw string by , and converts each component via double​From​String. When the value is "none", splitting produces ["none"], and double​From​String("none") returns 0 (line 32 of SVGParser​Basics​.swift), resulting in dashes = [0​.0].

// SVGParserPrimitives.swift, getStrokeDashes
let separatedValues = strokeDashes.components(separatedBy: CharacterSet(charactersIn: " ,"))
separatedValues.forEach { value in
    if let doubleValue = doubleFromString(value) {
        dashes.append(CGFloat(doubleValue))
    }
}

Suggested Fix:

Return an empty array early when the raw value is "none":

static func getStrokeDashes(_ style: [String: String]) -> [CGFloat] {
    var dashes = [CGFloat]()
    if let strokeDashes = style["stroke-dasharray"] {
        if strokeDashes.trimmingCharacters(in: .whitespaces).lowercased() == "none" {
            return dashes
        }
        let separatedValues = strokeDashes.components(separatedBy: CharacterSet(charactersIn: " ,"))
        separatedValues.forEach { value in
            if let doubleValue = doubleFromString(value) {
                dashes.append(CGFloat(doubleValue))
            }
        }
    }
    return dashes
}

Reproduction:

Any SVG with stroke​-dasharray​:none in its style will trigger this. Inkscape-generated SVGs commonly include this. Example minimal SVG:

Note from Jake the Human: I included the SVG that was giving me this issue above

Additional Detail

There's also a secondary (non-hanging) bug worth mentioning separately or in the same issue: parse​Dimension in SVGStructure​Parsers​.swift fails on width/height values with CSS unit suffixes (e.g., "70mm", "18​.52cm") because it uses bare Double() conversion which rejects non-numeric characters. It falls back to SVGLength​.percent(100), which computes to zero size from bounds(). This makes the SVG invisible rather than causing a hang, so it's a different severity — up to you whether to file it separately.