From 7d7cb04a82eb7945e379fcbfa3eb476020f238fe Mon Sep 17 00:00:00 2001
From: Adrian Cochrane <adrian@openwork.nz>
Date: Wed, 15 Mar 2023 16:05:31 +1300
Subject: [PATCH] Expose utility to inform atlas construction.

---
 Graphics/Layout.hs | 16 ++++++++++++++--
 cattrap.cabal      |  4 +++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/Graphics/Layout.hs b/Graphics/Layout.hs
index 1f1dc15..0335beb 100644
--- a/Graphics/Layout.hs
+++ b/Graphics/Layout.hs
@@ -1,16 +1,22 @@
 {-# LANGUAGE OverloadedStrings, RecordWildCards #-}
 module Graphics.Layout where
 
-import Data.Text.ParagraphLayout (Paragraph(..), ParagraphOptions(..), Fragment)
+import Data.Text.ParagraphLayout (Paragraph(..), ParagraphOptions(..), Fragment(..))
 
 import Graphics.Layout.Box as B
 import Graphics.Layout.Grid as G
 import Graphics.Layout.Flow as F
 import Graphics.Layout.Inline as I
-import Graphics.Layout.CSS.Internal (Font')
+import Graphics.Layout.CSS.Internal (Font'(..))
 
 import Data.Maybe (fromMaybe)
 
+-- To gather glyphs for atlases.
+import qualified Data.IntSet as IS
+import qualified Data.Map.Strict as M
+import qualified Data.Text.Glyphize as Hb
+import Graphics.Text.Font.Choose (Pattern)
+
 data LayoutItem m n x =
     LayoutFlow x (PaddedBox m n) [LayoutItem m n x]
     | LayoutGrid x (Grid m n) [(GridItem m n, LayoutItem m n x)]
@@ -315,3 +321,9 @@ boxLayout parent self paginate = self8
     (_, self6) = boxMaxHeight parent self5
     (_, self7) = boxHeight parent self6
     self8 = boxPosition (0, 0) self7
+
+-- Useful for assembling glyph atlases.
+glyphsPerFont :: LayoutItem x y z -> M.Map Pattern IS.IntSet
+glyphsPerFont (LayoutSpan _ font self) = pattern font `M.singleton` IS.fromList glyphs
+  where glyphs = map fromEnum $ map Hb.codepoint $ map fst $ fragmentGlyphs self
+glyphsPerFont node = M.unionsWith IS.union $ map glyphsPerFont $ layoutGetChilds node
diff --git a/cattrap.cabal b/cattrap.cabal
index 9802aa2..d996870 100644
--- a/cattrap.cabal
+++ b/cattrap.cabal
@@ -23,7 +23,9 @@ library
                         Graphics.Layout.Inline, Graphics.Layout.Inline.CSS
   -- other-modules:
   -- other-extensions:
-  build-depends:       base >=4.12 && <4.16, css-syntax, scientific, text, stylist-traits, fontconfig-pure, harfbuzz-pure, bytestring, balkon
+  build-depends:       base >=4.12 && <4.16, containers,
+                        css-syntax, scientific, text, stylist-traits,
+                        fontconfig-pure, harfbuzz-pure, bytestring, balkon
   -- hs-source-dirs:
   default-language:    Haskell2010
   ghc-options:         -Wincomplete-patterns
-- 
2.30.2