From 2df1a7a298c0ede12ccff74eed39747bf75e0445 Mon Sep 17 00:00:00 2001
From: Cooper Harasyn <charasyn@outlook.com>
Date: Sat, 29 Mar 2025 12:38:46 -0700
Subject: [PATCH] Make invalid subpalettes visible to the user

This will prevent issues such as those seen in the EBBR project, where it's unclear that certain tiles will not show as expected in-game.
---
 src/coilsnake/fts_interpreter.py     | 24 +++++++++++++++++++-----
 src/tileeditor/arrangement_editor.py |  3 +++
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/src/coilsnake/fts_interpreter.py b/src/coilsnake/fts_interpreter.py
index 41f67fc..1e40596 100644
--- a/src/coilsnake/fts_interpreter.py
+++ b/src/coilsnake/fts_interpreter.py
@@ -208,6 +208,21 @@ def __init__(self, tile):
             self.metadata.append(int(self.tile[i] + self.tile[i+1] + self.tile[i+2] + self.tile[i+3], 16))
             self.collision.append(int(self.tile[i+4] + self.tile[i+5], 16))
     
+    @staticmethod
+    def _createErrorMinitile():
+        img = Image.new("RGBA", (8, 8))
+        # Make a red + light-green checkerboard to indicate an error.
+        c1 = (255, 0, 0, 255)
+        c2 = (0, 255, 160, 255)
+        for y in range(8):
+            for x in range(8):
+                c = c2 if (x ^ y) & 0b100 else c1
+                img.putpixel((x, y), c)
+        return img
+
+    # Make one instance of this minitile once, and reuse it in each 
+    _ERROR_MINITILE = _createErrorMinitile()
+
     def getMetadata(self, id):
         """Return the SNES metadata of a given minitile placement in a tile"""
         return self.metadata[id]
@@ -221,11 +236,7 @@ def getMinitileID(self, id):
     def getMinitileSubpalette(self, id):
         """Get subpalette from placement metadata"""
         metadata = self.getMetadata(id)
-        # TODO Verify that this fix for metadata avoidance causing backwards indexing in non-vanilla projects is correct
-        # See DM with Gabbi about the issue (causing bright green tiles in EBBR)
         subPal = (((metadata & 0x1C00) >> 10)-2)
-        if subPal < 0:
-            return 0
         return subPal # minitile subpalette is bits 10-12 (bit 13 - priority flag - is irrelevant and never set in fts files). Subtract 2 because the first two are reserved for other things in the game, and we are indexing from 0
 
     def getMinitileHorizontalFlip(self, id):
@@ -271,7 +282,10 @@ def toImage(self, palette: Palette, fts: FullTileset, fgOnly=False, bgOnly=False
         x = 0
         y = 0
         for id, subpalette, hflip, vflip, collision in self.getMinitileDataList():
-            if fgOnly:
+            if subpalette < 0:
+                # This tile has an invalid subpalette. Display an error checkerboard pattern to indicate to the user that they should replace it.
+                minitile = self._ERROR_MINITILE
+            elif fgOnly:
                 minitile = fts.minitiles[id].ForegroundToImage(palette.subpalettes[subpalette])
             elif bgOnly:
                 minitile = fts.minitiles[id].BackgroundToImage(palette.subpalettes[subpalette])
diff --git a/src/tileeditor/arrangement_editor.py b/src/tileeditor/arrangement_editor.py
index d539938..d8d54f8 100644
--- a/src/tileeditor/arrangement_editor.py
+++ b/src/tileeditor/arrangement_editor.py
@@ -85,5 +85,8 @@ def pickMinitile(self, pos: QPoint, nosubpal: bool=False):
         
         if not nosubpal:
             subpalette = self.currentTile.getMinitileSubpalette(index)
+            if subpalette < 0:
+                # The tile has an invalid subpalette. For "pick" purposes, fall back to subpalette 0.
+                subpalette = 0
             self.state.tileEditor.paletteView.setSubpaletteIndex(subpalette)
             self.state.tileEditor.onSubpaletteSelect()
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