If a tileset is marked as "tiled", it will not show tiles under some circumstances

[CosmoMyzrailGorynych]

Reported by Kosmo#7595 at Discord.
There are also gaps between tiles while in-editor, if you compare two screenshots. This will be solved by a new room editor, though, as it will simplify tile placement.

Describe the bug

I checked "Is it tiled?" checkbox in those tilesets. When I remove it everything looks great.

To Reproduce

16x16Test.zip

(still needs the steps to reproduce)

Expected behavior
Tiles should display like in the editor.

Screenshots (recommended)

Example project (strongly recommended)

16x16Test.zip

Versions:

• OS: Windows
• ct.js version: next-3

[CosmoMyzrailGorynych]

So the issue affects only those textures that are marked as "tiled". As ct.js now extrudes the sides of textures in all directions (added in ba52f95), there are no issues with tiling regular sprites/tiles without this option.

In 04ddc3d, the checkbox "Is tiled" got renamed into "Use as background", and it prohibits slicing an image when active. This checkbox is now needed for backgrounds only, as they require to be packed as separate files or will have issues with UVs and mipmapping when the stage is scaled (e.g. with default ct.fittoscreen behavior).