pa-0 / vb6-svg

SVG and SVGZ support for VB6 projects (c/o resvg)

VB6-SVG provides full SVG (and SVGZ) support for VB6 projects

This is possible thanks to resvg, a comprehensive portable SVG library by Yevhenii Reizner:

https://github.com/RazrFalcon/resvg

resvg is available under an MPL-2 license. Please see resvg-LICENSE.md for full details.

System requirements

This project is 100% portable. You simply need to ship resvg.dll alongside your application (perhaps in an app subfolder).

This project has been tested on Win 7, 10, and 11. It theoretically supports Windows Vista, but testing this is TBD.

This project will not work on Windows XP.

How to use VB6-SVG

An interactive demonstration of VB6-SVG is included in this repository. It is extensively commented, but if you would like a brief overview of how to use this code in your own VB6 project, keep reading.

VB6-SVG has three mandatory components. All three must be added to your VB6 project:

1. resvg.dll
2. svgSupport.bas
3. svgImage.cls

svgSupport handles resvg initialization, shutdown, and a bunch of associated resource management and GDI interop.

svgImage is a lightweight convenience class for managing individual SVG image instances. Create instances of this class by calling svgSupport.LoadSVG_FromFile().

Adding SVG support to your own VB6 projects is simple:

1. Ensure you have read and understood both LICENSE.md (for the VB6 code) and resvg-LICENSE.md (for resvg).
2. Ship resvg.dll with your app. This is a traditional DLL, not an ActiveX dll, so you do not need to register it. Just make sure it is available in a predictable location.
3. Somewhere in your VB6 project initialization, add one line of code:

svgSupport.StartSVGSupport "C:\[path-to-resvg-folder]\resvg.dll"

That line of code will initialize resvg and prepare a bunch of SVG-related resources.

4. Create (unlimited) svgImage instances by calling:

svgSupport.LoadSVG_FromFile()

Each svgImage instance manages a single SVG image. svgImage stores a parsed SVG "tree", allowing you to render the SVG over-and-over at whatever position(s), size(s), and opacities you desire. You can query individual instances for their default width/height, or draw them at whatever width/height you want using the DrawSVGtoDC() function. As you'd expect for vector images, resizing and painting is always non-destructive.

5. svgImage instances manage their own resources. You do not need to manage them manually, with one exception (see (6), below).

6. Before your program exits, ensure all svgImage instances have gone out of scope (or been manually freed), then add one line of code to your program shutdown process:

svgSupport.StopSVGSupport

This will free all shared GDI and SVG resources used by the project, then manually unload resvg itself.

As you can imagine, if you are using module- or global- (ugh) svgImage class instances, they need to be freed before calling StopSVGSupport, because once resvg is released, SVG management is over.

7. (Optional) some manual processing is required to allow painting SVGs to arbitrary Windows DCs. Performance is significantly improved when compiled to native code with the Remove Array Bounds Checks optimization enabled. Please do this.

8. That's it! If you encounter any bugs or unexpected behavior, please file an issue at GitHub.

Licensing

The VB6 portion of this project is available under a Simplified BSD license. Full details are provided in LICENSE.md.

resvg is available under an MPL-2 license. Full details are provided in resvg-LICENSE.md.

Many thanks to Yevhenii Reizner for his work on resvg.