SWT SVG Renderer

A lightweight SVG renderer for SWT that parses SVG icons into an immutable in-memory tree and renders them directly onto SWT GC. No AWT bridge, no external dependencies beyond org.w3c.dom (included in JDK).

Designed for icon rendering with a constrained SVG subset. Unsupported elements are silently skipped, so SVGs exported from common editors (Inkscape, Illustrator) work as long as the visible content uses supported features.

Features

• Parse once, render at any size — resolution-independent icons
• currentColor support for icon theming (light/dark mode, disabled state)
• Uniform and stretch scaling modes
• Immutable after parse — thread-safe, no SWT resource ownership
• All SWT resources (Color, Path, Transform) created and disposed per render call
• Java 11+, zero dependencies beyond SWT and JDK

Supported SVG Subset

Elements: <svg>, <g>, <path>, <rect> (with rx/ry), <circle>, <ellipse>, <line>, <polyline>, <polygon>

Path commands: M, L, H, V, C, S, Q, T, A, Z (absolute and relative)

Presentation attributes: fill, fill-opacity, fill-rule, stroke, stroke-width, stroke-opacity, stroke-linecap, stroke-linejoin, opacity, transform, display, inline style

Colors: #RGB, #RRGGBB, rgb(r,g,b), 147 named CSS colors, currentColor, none, inherit

Transforms: translate, scale, rotate, matrix, skewX, skewY

API

The public API consists of three classes in org.netxms.ui.svg:

SVGImage

// Parse
SVGImage icon = SVGImage.createFromFile(new File("icon.svg"));
SVGImage icon = SVGImage.createFromStream(inputStream);
SVGImage icon = SVGImage.createFromString(svgContent);

// Render (black, uniform scale)
icon.render(gc, x, y, width, height);

// Render with theme color
icon.render(gc, x, y, width, height, currentColor);

// Render with theme color and scale mode
icon.render(gc, x, y, width, height, currentColor, ScaleMode.STRETCH);

// Query intrinsic dimensions
float w = icon.getWidth();      // -1 if unknown
float h = icon.getHeight();     // -1 if unknown
float ar = icon.getAspectRatio(); // -1 if unknown

ScaleMode

Value	Behavior
UNIFORM	Fit inside the target box preserving aspect ratio, centered (default)
STRETCH	Stretch to fill the entire box

SVGParseException

Checked exception thrown by the createFrom* factory methods when the SVG XML is malformed or the root element is not <svg>.

Usage Example

// Load icon once at startup
SVGImage icon = SVGImage.createFromStream(
      getClass().getResourceAsStream("/icons/settings.svg"));

// Render in a paint listener — adapts to any size
canvas.addPaintListener(e -> {
    icon.render(e.gc, 0, 0, canvas.getSize().x, canvas.getSize().y,
                e.gc.getForeground());
});

Building

mvn install

This builds both modules:

• swt-svg-renderer — the library (with javadoc and source jars)
• demo — a sample SWT application

Running the Demo

cd demo
mvn exec:java

Project Structure

pom.xml                             — aggregator POM
swt-svg-renderer/
  pom.xml                           — library (standalone, no parent)
  src/main/java/org/netxms/ui/svg/
    SVGImage.java                   — public API: parse + render
    SVGParseException.java          — checked parse exception
    ScaleMode.java                  — UNIFORM / STRETCH enum
  src/main/java/org/netxms/ui/svg/internal/
    ...                             — parser, renderer, node tree
  src/test/                         — JUnit 5 tests + SVG fixtures
demo/
  pom.xml                           — demo app
  src/main/java/.../SVGDemo.java    — SWT shell with sample icons
  src/main/resources/icons/         — sample SVG icons

Requirements

• Java 11+
• SWT (provided scope — supplied by the host application)