Provide separate factory methods for SystemFontMetrics and IndexedFontMetrics

[obecker]

Hi, it would be great if the SimpleFontMetrics API could be extended to select specifically either the SystemFontMetrics or the IndexedFontMetrics implementation (actually - for my use case it would be enough to have access to the IndexedFontMetrics).

Background: I'm using this library for creating SVG images and have some tests that contain assertions for the entire generated markup. To my surprise these tests failed when executed automatically within GitHub Actions (I guess this might be a problem in general on CI environments). The cause were slightly different values returned from the fontmetrics library. Apparently the SystemFontMetrics on the CI environment and on my local machine behave differently.

Now I was able to implement a workaround that uses only the IndexedFontMetrics (luckily these inner classes are public and static), and this fixed the tests. However, it would be great if I could get rid of this extra code and use an appropriate factory method in SimpleFontMetrics instead.

Thanks for this library! 🙂

[ggrandes]

I will appreciate the feedback!

[obecker]

Thank you! This simplifies my code significantly. 😄