From e64a1ae7a1eb6d0b77d88246976641fd61df0f61 Mon Sep 17 00:00:00 2001
From: Adrian Cochrane <adrian@openwork.nz>
Date: Sat, 3 Jun 2023 13:35:31 +1200
Subject: [PATCH] Correct coordinate-space involved in rect unionizing.

---
 Graphics/Layout/Inline.hs | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/Graphics/Layout/Inline.hs b/Graphics/Layout/Inline.hs
index f5a53a7..283fbfb 100644
--- a/Graphics/Layout/Inline.hs
+++ b/Graphics/Layout/Inline.hs
@@ -12,6 +12,7 @@ import Data.Text.ParagraphLayout.Rich (Paragraph(..), ParagraphOptions(..),
 import Data.Text.ParagraphLayout.Rect (Rect(..),
                                 width, height, x_max, x_min, y_min, y_max)
 import Data.Int (Int32)
+import Debug.Trace (trace) -- To warn about unexpected branches!
 
 import Graphics.Layout.Box hiding (min, max, width, height)
 import qualified Graphics.Layout.Box as Box
@@ -113,13 +114,8 @@ fragmentSize self = Size (c $ width r) (c $ height r)
 treeRect :: (CastDouble m, CastDouble n) =>
         FragmentTree (a, PaddedBox m n, c) -> Rect Int32
 treeRect (Branch AncestorBox { boxUserData = (_, box', _)} childs) =
-        foldr unionRect (Rect 0 0 0 0) $ map treeRect childs
+        unions $ map treeRect childs
     where
-        unionRect a b = Rect
-            (x_min a `min` x_min b - leftSpace box)
-            (y_min a `min` y_min b - topSpace box)
-            (x_max a `max` x_max b - x_min a `min` x_min b + hSpace box)
-            (y_max a `max` y_max b - y_min a `min` x_min b + vSpace box)
         box :: PaddedBox Int32 Int32
         box = mapX' unscale $ mapY' unscale box'
 treeRect (Leaf self) = fragmentRect self
@@ -191,3 +187,26 @@ positionTree (x, y) self@(Leaf (Fragment (a, b, c) d _ f g h)) =
 treeInner :: FragmentTree (a, b, c) -> c
 treeInner (Branch AncestorBox { boxUserData = (_, _, ret) } _) = ret
 treeInner (Leaf Fragment { fragmentUserData = (_, _, ret) }) = ret
+
+------
+--- Taken from Balkón
+------
+-- | Calculate the smallest rectangle that completely contains all the given
+-- rectangles.
+unions [] = trace "No rects to union!" $ Rect 0 0 0 0
+unions rects = foldr1 union rects
+
+-- | Calculate the smallest rectangle that completely contains the given two
+-- rectangles.
+--
+-- The origin of the resulting rectangle will be the corner with the lowest
+-- X coordinate and the highest Y coordinate, regardless of the origin of the
+-- input rectangles.
+union :: (Num a, Ord a) => Rect a -> Rect a -> Rect a
+union a b = Rect x_low y_high dx (-dy) where
+    x_low = x_min a `min` x_min b
+    y_low = y_min a `min` y_min b
+    x_high = x_max a `max` x_max b
+    y_high = y_max a `max` y_max b
+    dx = x_high - x_low
+    dy = y_high - y_low
-- 
2.30.2