Fix #8273: Layer#setPaintProperty returns true for CrossFadedDataDriv…

[ahk]

This patch fixes a bug reported in issue #8273. Users were unable to update line-pattern property images via Map#setPaintProperty. There is only one change and it removes an unnecessary check that the previous value for this property didn't exist. As long as the value has changed (which is checked in Style#setPaintProperty before deferral to the layer) then the layer needs to be updated, or for example the image used for the property value isn't added to the texture atlas.

It's possible this affects performance, but benchmarks didn't seem to indicate that. I can imagine that some updates from a non-image value would only need re-layout on changing to or from a null value. Any opinions on that question are greatly appreciated.

Launch Checklist

• briefly describe the changes in this PR
• write tests for all new functionality
• post benchmark scores
• manually test the debug page

[peterqliu]

👍 want to add a new test ensuring this keeps working moving forward?

[ahk]

👍 want to add a new test ensuring this keeps working moving forward?

Is it correct to try to land a test in test/unit/style/style_layer.test.js ?

[peterqliu]

@ahk yep, set it up to reproduce the erstwhile error state and make sure getPaintProperty returns what you expect

can also do a render test to make sure the proper pattern applies, but seems like a unit test should suffice

[asheemmamoowala]

I think adding a render test would be more useful than a unit test for this case.

[ahk]

@asheemmamoowala I read through a ton of the render tests, wanted to make sure my thinking was correct before I created one. I think I should land a test into the regressions directory. I feel this test is the best example of what I'm trying to do (exercise StyleLayer#setPaintProperty), I just want to switch out fill-pattern for line-pattern as the property I'm updating.

[mourner]

@ahk correct! One small note is that we're trying to add small-sized tests if possible (so not 512x512 like the one above, but e.g. 64x64 if it still can exercise the bug).

[mourner]

🚢

[ahk]