SVG Native Viewer

SVG Native viewer is a library that parses and renders SVG Native documents.

SVG Native

SVG Native is an upcoming specification of the SVG WG based on SVG OpenType . SVG Native will be a strict subset of SVG 1.1 and SVG 2.0.

Supported features in SVG Native (in comparison to SVG1.1/SVG2)

• No stylesheet support (CSS/XSL) with the exception of the basic inheritance model and the following presentation attributes:
  • clip-path
  • clip-rule
  • color
  • display
  • fill
  • fill-opacity
  • fill-rule
  • opacity
  • stroke
  • stroke-dasharray
  • stroke-dashoffset
  • stroke-linecap
  • stroke-linejoin
  • stroke-miterlimit
  • stroke-opacity
  • stroke-width
  • stop-color
  • stop-opacity
  • visibility
• CSS properties do not support any default property values like inherit, initial, unset, or revert.
• No support for scripting, interactions, events, animations, filters, masks, patterns, texts.
• No support for inner <svg> or <symbol> elements.
• No support for XML namespaces with the exception of the SVG namespace and the Xlink namespace.
• No support of objectBoundingBox on gradientUnits or clipPathUnits.
• The var() CSS value function is limited to the CSS properties fill, stroke, stop-color and color. Only color values are allowed. currentColor is supported.

A valid SVG Native document is always a valid SVG1.1/2.0 document.

SVG Native Viewer Library

SVG Native Viewer is a C++11 based project and can either be included in the source code of a client directly or linked statically or dynamically.

For rendering, SVG Native Viewer requires a rendering port. Already existing ports include:

• StringSVGRenderer for testing purposes,
• CGSVGRenderer a rendering port using CoreGraphics (Quartz 2D).
• SkiaSVGRenderer a rendering port using Skia. (Skia requires a C++14 compatible compiler!)
• CairoSVGRenderer a rendering port using Cairo Graphics.
• GDIPlusSVGRenderer a rendering port using GDI+.
• D2DSVGRenderer a rendering port using Direct2D.

New ports need to inherit from SVGRenderer and implement the virtual functions.

Here an example how to use SVG Native Viewer with Skia SkiaSVGRenderer:

// Create the renderer object
auto renderer = std::make_shared<SVGNative::SkiaSVGRenderer>();

// Create SVGDocument object and parse the passed SVG string.
auto doc = std::unique_ptr<SVGNative::SVGDocument>
(SVGNative::SVGDocument::CreateSVGDocument(svgInput.c_str(), renderer));

// Setup SkSurface for drawing
auto skRasterSurface = SkSurface::MakeRasterN32Premul(doc->Width(),
                                                      doc->Height());
auto skRasterCanvas = skRasterSurface->getCanvas();

// Pass SkCanvas to renderer object
renderer->SetSkCanvas(skRasterCanvas);

// Pass drawing commands for SVG document to renderer.
doc->Render();

// Pass drawing commands for SVG document to renderer the element (and
// its descendants)
// with the XML ID "ref1".
std::string id1{"ref1"}
doc->Render(id1);

// The Render() function may get called multiple times. This can be
// used to render a combination of glyphs specified in the same SVG
// document.
std::string id2{"ref2"}
doc->Render(id2);

Refer to the examples in the example/ directory for other port examples.

Requirements

Submodules

This repository uses submodules. To initiate and keep submodules up-to-date run the following command:

git submodule update --init

Submodules are located in the third_party/ directory. Used submodules:

• stylesheet (optional) Needed if compiled with limited CSS style support (deprecated).
• cpp-base64 (optional) Needed by some ports for decoding base64 encoded raster image support.
• boost_variant_property_tree (optional) Minimal version of Boost stripped down to the requirements of variant and property_tree. Used if Boost was not installed on the system.

Windows

Install:

• CMake Download and run the installer
• Boost Download the ZIP-package and extract the package into C:>\Program Files\boost_x.y.z\ (See below how to specify a different Boost installation directory by a CMake option.)
• MS Visual Studio 2017 or up Download and install with the installer. Make sure Visual C++ gets installed. (You maybe be able to use the "Community" version for free for non-commercial/enterprise use. See the website from MS for license details.)

OSX

With Homebrew:

brew install cmake
brew install llvm
brew install boost

LINUX

• Apt

sudo apt-get install build-essential libboost-system-dev cmake

Building

Create project files

For Windows 64 bit:

cmake -Bbuild/win64 -H. -G "Visual Studio 15 2017 Win64"

For Windows 32 bit:

cmake -Bbuild/win32 -H. -G "Visual Studio 15 2017"

Omit -H when running in PowerShell.

For macOS

cmake -Bbuild/mac -H. -G "Xcode"

For Linux

cmake -Bbuild/linux -H.

On Linux you may choose to use GCC or Clang/LLVM. Add the following to the command above to choose between one and the other:

• -DCMAKE_CXX_COMPILER=g++ for GCC
• -DCMAKE_CXX_COMPILER=clang for Clang/LLVM

On Windows you may choose to use Clang/LLVM as compiler. For help, follow the instructions of the linked MS Visual Studio LLVM Extension. Add -T "LLVM" to the project generation command above.

To specify a different Boost installation directory on Windows use the following command:

• -DBOOST_ROOT=X:\path\to\boost

The following arguments can be passed with the -D flag and the options ON or OFF:

• LIB_ONLY Only compile the library without examples. Default OFF.
• SHARED If ON, builds a dynamic library. Static otherwise. Default OFF.
• PLATFORM_XML If ON, uses libxml2 or Epat if provided by the system. Otherwise RapidXML via boost. Default OFF.
• TEXT adds the Text port to the library. Default ON.
• CG adds the CoreGraphics/Quartz2D port to the library. Default OFF.
• SKIA adds the Skia port to the library. Default OFF.
• GDIPLUS adds the GDI+ port to the library. Default OFF.
• D2D adds the Direct2D port to the library. Default OFF.
• CAIRO adds the Cairo Graphics port to the library. Default OFF.
• TESTING enables automated testing using Google Tests. Default ON.

To enable the deprecated CSS styling support:

• STYLE adds limited, deprecated support for <style> element and style attribute. Default OFF. (This option will get removed eventually.)

The following example creates project files for the library with the Text, CoreGraphics/Quartz2D and Skia port and the example applications. Example:

cmake -Bbuild/mac -H. -G "Xcode" -DCG=ON -DSKIA=ON

Note: For testing, build with the TEXT option set to ON and LIB_ONLY option set to OFF. (The default for both.)

Build

Replace win64 with your platform (mac for Xcode on macOS)

cmake --build build/win64 --config Release

Boost requirements

Only the header version of Boost is required. The following Boost features are used:

• Boost RapidXML (Can be replaced by libxml2.)
• boost::variant to handle different SVG paint types of fill and stroke as well as different color value types.
• Boost string functions like boost::tokenizer, boost::trim. (Only used by deprecated CSS <style> element parsing.)

Tests

SVG Native Viewer has two testing mechanisms. A python script that performs the renderings on the Text port and compares the renderings with the existing ones and automated software testing using Google Tests framework.

Text port testing

To use the python script:

1. Make sure your system has Python installed.
2. By default, CMake creates the project files for SVGNativeViewerLib and testSVGNative. Follow the steps above to build the test app.
3. Run

python script/runTest.py --tests=test/

Here the argument list of runTest.py:

• --test the folder with the test files.
• --program the path to testSVGNative. If not provided uses the default, relative build path.
• --debug Debug build or Release build of testSVGNative. Only relevant if --program was not set and defaults to --debug.

Google Test based testing

In order to build and run the tests, pass the argument -DTESTING=ON when running Cmake. Cmake will automatically download and build Google Tests and compile the tests. In order to run the tests you can run make test or just use ctest in the build folder.

Ultimately, we aim to improve software unit testing as well as add rendering tests to ensure that SVG Native Viewer's renderings are accurate.

Known limitations in SVG Native Viewer

• preserveAspectRatio is not supported on the <svg> element yet.
• Furthermore, there might be limitations on certain platforms. (E.g. missing gradient spread-method support on CoreGraphics.)

Contributing

Contributions are welcomed! Read the Contributing Guide for more information.

Licensing

This project is licensed under the Apache V2 License. See LICENSE for more information.