perf: only do expensive reload when texture changes

[jellyedwards]

This change is aimed to solve #10664 - only upload the texture to the GC if the texture has changed as it's an expensive operation and leads to reduced performance.

[jellyedwards]

Sorry, just noticed a test failed:

Chrome 80.0.3987 (Windows 10.0.0) HTML Image loading handles error event FAILED
Error: Uncaught Error: expected false to equal true
Chrome 80.0.3987 (Windows 10.0.0) HTML Image loading handles error event FAILED
Error: Uncaught Error: expected false to equal true

I'll look into it...

[fredj]

@jellyedwards is it this test that is failing ?
https://github.com/openlayers/openlayers/blob/master/test/spec/ol/image.test.js#L35-L44

[jellyedwards]

@fredj yes that looks like it, I'll just try it on the original to double-check it wasn't there before my fix for the issue...

[jellyedwards]

@fredj yeah that test failed before my changes too. This is my first time contributing, but I could look into why that test is failing. Just to speed things up how do you run a single test?

[fredj]

This test is only failing on Windows and it's related to the timeout value; I've changed the value from 200 to 500ms and it is passing:

diff --git a/test/spec/ol/image.test.js b/test/spec/ol/image.test.js
index bf6e19ef0..b6f75abf4 100644
--- a/test/spec/ol/image.test.js
+++ b/test/spec/ol/image.test.js
@@ -40,7 +40,7 @@ describe('HTML Image loading', function() {
       expect(handleLoad.called).to.be(false);
       expect(handleError.called).to.be(true);
       done();
-    }, 200);
+    }, 500);
   });

   it('handles cancelation', function(done) {

[jahow]

Thanks @jellyedwards!

Please let me know if you want to include a fix for the failing test on Windows before merging.

[fredj]

@jahow I'm creating a PR for the failing test. This one can be merged.