Consume SVG rasterizer via capability in SWT tests bundle

[HeikoKlare]

Currently, requiring an SVG rasterizer needs manual placement of an according fragment on the classpath. With this change, requiring SVG support can be defined explicitly via a required capability that is provided by the according SWT fragment.

Contributes to #1944

[HeikoKlare]

@laeubi I am not sure whether this is the correct way of doing it, but at least it seems to work when locally executing the build.

I also tried with a "custom" capability (not using osgi.extender) but that did not work.

[laeubi]

Im not sure if this is really an extender

An Extender is a bundle that uses the life cycle events from another bundle, the extendee, to extend that bundle's functionality when that bundle is active. It can use metadata (headers, or files inside the extendee) to control its functionality.

I have added a suggestion how I would assume it should work to use a custom namespace, or maybe osgi.implementation would be more suitable

The Implementation Namespace is intended to be used for:
Preventing a bundle from resolving if there is not at least one bundle that provides an implementation of the specified specification or contract.

then it might look similar to

Provide-Capability: osgi.implementation;
    osgi.implementation="swt.svg";
    version:Version="1.0";
    uses:="<packages that are used e.g. jsvg>"

[laeubi]

Suggested change

	Provide-Capability: osgi.extender;osgi.extender="org.eclipse.swt.svgrasterizer"
	Provide-Capability: swt.renderer;swt.renderer="svg"

[laeubi]

Suggested change

	Require-Capability: osgi.extender;filter:="(osgi.extender=org.eclipse.swt.svgrasterizer)"
	Require-Capability: swt.renderer;filter:="(swt.renderer=svg)"

[github-actions]

Test Results

   545 files  ±0     545 suites  ±0   31m 40s ⏱️ + 5m 13s
 4 367 tests ±0   4 351 ✅ ±0   16 💤 ±0  0 ❌ ±0 
16 616 runs  ±0  16 502 ✅ ±0  114 💤 ±0  0 ❌ ±0 

Results for commit 69fe298. ± Comparison against base commit d8b1f98.

♻️ This comment has been updated with latest results.

[HeikoKlare]

Thank you for the pointer! The osgi.implementation namespace sounds like the exact right thing for this. I have adapted the PR accordingly.

[HeikoKlare]

@laeubi are you fine with these changes now and would you expect them to fix #1944?

In that case, I would propose to merge and maybe trigger a new I-Build to see if tests are running fine again.

[laeubi]

Looks good to me

[HannesWell]

With the given reference I have the impression that the osgi.implementation namespace is inteded for implementations of OSGi specifications not arbitrary specs.
While it would probably not be harmful to use the osgi-namespace, I think a custom one would be more suitable, for example:

Suggested change

	Provide-Capability: osgi.implementation;
	osgi.implementation="swt.svgrasterizer";
	version:Version="1.0"
	Provide-Capability: eclipse.swt.implementation;image.format="svg";version:Version="1.0"

Later we could then also use this namespace to introduce a requirement of o.e.swt to it's name fragments that could then provide Provide-Capability: eclipse.swt.implementation;implementation="native" or similar.

[HannesWell]

Thanks for the update, this is more compact and a bit more generic.

[HeikoKlare]

Thank you all for your input! Hopefully this even fixes #1944.