From 63a571647035682e5d177186b58d59a58ce37a8c Mon Sep 17 00:00:00 2001
From: Jaro <jaro@argonaut-constellation.org>
Date: Wed, 26 Apr 2023 19:26:55 +0200
Subject: [PATCH] Define BoxOptions and TextOptions for formatting.

Differentiating the two record types reflects the fact that the root
inline box cannot be styled but its text contents can.
---
 balkon.cabal                                  |  2 +
 .../ParagraphLayout/Internal/BoxOptions.hs    | 52 +++++++++++++++++++
 .../ParagraphLayout/Internal/TextOptions.hs   | 50 ++++++++++++++++++
 3 files changed, 104 insertions(+)
 create mode 100644 src/Data/Text/ParagraphLayout/Internal/BoxOptions.hs
 create mode 100644 src/Data/Text/ParagraphLayout/Internal/TextOptions.hs

diff --git a/balkon.cabal b/balkon.cabal
index 41f9d4d..31af3d7 100644
--- a/balkon.cabal
+++ b/balkon.cabal
@@ -102,6 +102,7 @@ library balkon-internal
     -- Modules exported to tests and to the public part of the library.
     exposed-modules:
         Data.Text.ParagraphLayout.Internal.BiDiReorder,
+        Data.Text.ParagraphLayout.Internal.BoxOptions,
         Data.Text.ParagraphLayout.Internal.Break,
         Data.Text.ParagraphLayout.Internal.Fragment,
         Data.Text.ParagraphLayout.Internal.LineHeight,
@@ -117,6 +118,7 @@ library balkon-internal
         Data.Text.ParagraphLayout.Internal.Run,
         Data.Text.ParagraphLayout.Internal.Span,
         Data.Text.ParagraphLayout.Internal.TextContainer,
+        Data.Text.ParagraphLayout.Internal.TextOptions,
         Data.Text.ParagraphLayout.Internal.Zipper
 
     -- Modules used purely internally and not in any tests.
diff --git a/src/Data/Text/ParagraphLayout/Internal/BoxOptions.hs b/src/Data/Text/ParagraphLayout/Internal/BoxOptions.hs
new file mode 100644
index 0000000..1a96ed7
--- /dev/null
+++ b/src/Data/Text/ParagraphLayout/Internal/BoxOptions.hs
@@ -0,0 +1,52 @@
+module Data.Text.ParagraphLayout.Internal.BoxOptions
+    ( BoxOptions (..)
+    , BoxSpacing (..)
+    , defaultBoxOptions
+    )
+where
+
+import Data.Int (Int32)
+
+-- | Style options to be applied to an inline box.
+--
+-- This record type is likely to be extended in the future.
+-- Use `defaultBoxOptions` and update it with specific record selectors
+-- instead of constructing `BoxOptions` directly.
+data BoxOptions = BoxOptions
+
+    { boxSpacing :: BoxSpacing
+    -- Determines amount of empty space to add before the first fragment
+    -- and/or after the last fragment of this box.
+    --
+    -- This can be used to reserve space for a left margin, border,
+    -- and/or padding.
+
+    }
+    deriving (Eq)
+
+-- | Determines the amount of empty space to add around a box.
+data BoxSpacing
+
+    -- | Specification using absolute directions, unaffected by text direction.
+    --
+    -- (However, text direction is still used in case of fragmentation,
+    -- to determine how to map the first (last) fragment to left (right).)
+    = BoxSpacingLeftRight
+
+        Int32
+        -- ^ Amount of empty space to add to the left side of the
+        -- first fragment (for LTR text) or last fragment (for RTL text)
+        -- created from this box.
+
+        Int32
+        -- ^ Amount of empty space to add to the right side of the
+        -- first fragment (for RTL text) or last fragment (for LTR text)
+        -- created from this box.
+
+    deriving (Eq, Show, Read)
+
+-- | `BoxOptions` with default values.
+defaultBoxOptions :: BoxOptions
+defaultBoxOptions = BoxOptions
+    { boxSpacing = BoxSpacingLeftRight 0 0
+    }
diff --git a/src/Data/Text/ParagraphLayout/Internal/TextOptions.hs b/src/Data/Text/ParagraphLayout/Internal/TextOptions.hs
new file mode 100644
index 0000000..f55f35a
--- /dev/null
+++ b/src/Data/Text/ParagraphLayout/Internal/TextOptions.hs
@@ -0,0 +1,50 @@
+module Data.Text.ParagraphLayout.Internal.TextOptions
+    ( TextOptions (..)
+    , defaultTextOptions
+    )
+where
+
+import Data.Text.Glyphize (Font, emptyFont)
+
+import Data.Text.ParagraphLayout.Internal.LineHeight
+
+-- | Style options to be applied to a text sequence.
+--
+-- This record type is likely to be extended in the future.
+-- Use `defaultTextOptions` and update it with specific record selectors
+-- instead of constructing `TextOptions` directly.
+data TextOptions = TextOptions
+
+    { textFont :: Font
+    -- ^ Font to be used for shaping and measurement.
+    -- Make sure to set its scale (see `Data.Text.Glyphize.optionScale`) using
+    -- the same units that you want in the output.
+
+    , textLineHeight :: LineHeight
+    -- ^ Preferred line height of the resulting fragments.
+
+    , textLanguage :: String
+    -- ^ IETF BCP 47 language tag, such as the value expected to be found in
+    -- the HTML @lang@ attribute, specifying the primary language for the
+    -- span's text content. An empty string explicitly means "language unknown".
+    --
+    -- Used for selecting the appropriate glyphs and line breaking rules,
+    -- primarily in East Asian languages.
+
+    -- TODO: textVerticalAlign
+    -- TODO: textLetterSpacing
+    -- TODO: textWordSpacing
+    -- TODO: textDirection
+    -- TODO: textFontFeatures
+    -- TODO: textSoftBreaks
+
+    }
+    deriving (Eq)
+
+-- | `TextOptions` with default values.
+defaultTextOptions :: TextOptions
+defaultTextOptions = TextOptions
+    { textFont = emptyFont
+    , textLineHeight = Normal
+    , textLanguage = ""
+    }
-- 
2.30.2