Tiled: selecting terrain brush on wrong layer can have massive consequences

[Bobjt]

Tiled doesn't freeze but hangs the main thread for quite some time if I select the wrong layer in conjunction with the terrains brush. Stack trace attached (though it may not be needed).
Uploading Spindump-062817-terrain-brush.txt…

Steps to reproduce:

• create a 300 x 300 map (or, create a new layer in an existing map)
• select the terrain brush + a terrain and move mouse over the empty layer
• witness hang for about a minute

The hang is avoided if I first fill the new layer with a tile that exists in the selected terrain. I didn't search for existing issues, so apologies if this is a duplicate report.

[Bobjt]

Re-uploading and including a spindump from a permanent lock.

Spindump-062817-terrain-lock-this-one-is-a-permanent-hang.txt

Spindump-062817-terrain-brush.txt

I'll try to get a repro' case posted here.

[Bobjt]

It looks like the terrain logic is doing some weird stuff.

Here's a capture of the eventual preview from a long hang:

And the map without the terrain tool preview looks like this:

It was still hung however after this preview was rendered (maybe interactively hanging for long periods, if that makes any sense)

[Bobjt]

Steps to reproduce:

1) open the attached overworld-draft-200.tmx

• the external tileset it depends on is in the "_tilesets.zip" bundle - it's the addlsheet1.tsx
• the graphics that addlsheet1.tsx depends on is attached. Unzip: addlsheet1.png.zip

2) in Tiled, select the layer "Layer 0 a" (this is the layer on which all tiles are currently defined. All tiles on this layer are member of the various terrain definitions (even the clear portions). You'll see those after opening the terrains window on this map.

3) select the terrain definition "oworld1 mountains" and bring the cursor over to the center of the map.

4) experience the hang. That's all.

addlsheet1.png.zip
overworld-draft-200.tmx.zip
_tilesets.zip

[bjorn]

So, this is due to a combination of factors:

• Your "oworld1 mountains" terrain only has transitions to "nothing". In your tileset there does not exist any way to connect "oworld1 mountains" to the terrains used by the existing tiles on the "Layer 0 a". This causes it to change the whole map as it futilely tries to fix up the border, which keeps expanding to fill the whole map (which is relatively large). Using "oworld1 mountains" on an empty layer works fine, because the border is immediately fine.

• Your tileset contains a _huge_ amount of tiles (65536). This is part of the problem because at the moment the terrain tool uses a linear search through the tiles in the tileset to find one that matches a certain terrain criteria. A workaround is to separate your terrain tiles into a smaller tileset (though that can only make it about 100x faster).

The solution would be:

• Improve the lookup of tiles to not be a linear search through the whole tileset.

• Improve the algorithm filling the map, such that it searches for the smallest modification and will give up after some time.

[bjorn]

This issue is something to keep an eye on in relation to Wang Tiles (#1455), which @Bdtrotte is working on. Wang Tiles may replace the terrain tool as a more flexible solution and we could make sure that the approach does not suffer from the above issues.

[Bdtrotte]

Yeah, I think so too. I haven't thought this far ahead yet... but hopefully finding the transitions will be much faster with the hash maps already in place. I imagine the eventual "wang brush" will be able to match the functionality of the terrain brush

[bjorn]

While making the Terrain Brush work for infinite maps, I had to apply some kind of limit to the area affected by the brush. This also helped a great deal in resolving this issue, though the wait is still considerable. It is only processing for about 5 seconds on my machine after the above change, which is definitely less fatal.

[bjorn]

With the Wang Brush now improved such that it could entirely replace the Terrain Brush (see #2888) I think we have also resolved this issue. This is because in addition to limiting the area it is changing, it only searches those tiles which have Wang colors assigned, rather than iterating the whole tileset.

I've opened the example attached in https://github.com/bjorn/tiled/issues/1632#issuecomment-312073879 and while it still can't do anything useful with "oworld1 mountains", it's now very responsive. It's also fast while editing with any of the more properly set up terrains.

I hope it still helps you, @Bobjt, but in any case thank you again for your amazing support of Tiled!