TilemapGPULayer render issue causing lines between tiles

Version

• Phaser Version: 4.1
• Operating system: W11

Description

I have a hard time rendering a tilemap correctly utilizing a TilemapGPULayer. No matter if I try to use an adjusted tileset that makes use of extruded tile borders or not, there are issues rendering the layer. using a normal layer works normally.

My findings:

• having mipmapFilter: "LINEAR_MIPMAP_LINEAR" in the game config breaks stuff (hello old friend, i missed having issues caused by you)
• having a tilemap gpu layer instead of a normal layer breaks stuff in bubbits for me in any case, even without that mipmapFilter
• going for 4096x4096 texture size for the tileset (as advised) makes it very difficult to have margin and spacing that perfectly fits tile count and those target dimensions. (maybe you can math how to do it correctly) but did not lead to less lines showing for me ingame when i just forced correct dimensions via image canvas size (did lead to phaser warning of not fitting number of tiles)

Example Test Code

Maybe this codepen is a good starting point to get down to these render issues, it shows different kinds of tilemaps, both normal and gpu using both, sets with and without margin and spacing.

https://codepen.io/SaintFlow/pen/vEgyVZa

Start with the linked CodePen and reproduce the artifact in TilemapGPULayer using the provided tilesets, comparing it with a normal layer. Check the effect of mipmapFilter: "LINEAR_MIPMAP_LINEAR" and the margin, spacing, and texture-size variants. Done means the GPU layer renders without lines between tiles across the reported configurations, or the failing configuration and cause are documented.