From b89500d0ec4226e51326a27f37ac0aa903362ec7 Mon Sep 17 00:00:00 2001
From: Jaro <jaro@argonaut-constellation.org>
Date: Fri, 24 Feb 2023 22:00:41 +0100
Subject: [PATCH] Calculate fragment position continuously.

This merges the various "arrange" functions into the layout functions,
which will be used to detect overflows for line breaking.
---
 src/Data/Text/ParagraphLayout/Plain.hs | 60 +++++++++++++-------------
 1 file changed, 29 insertions(+), 31 deletions(-)

diff --git a/src/Data/Text/ParagraphLayout/Plain.hs b/src/Data/Text/ParagraphLayout/Plain.hs
index a50a6fe..72d422b 100644
--- a/src/Data/Text/ParagraphLayout/Plain.hs
+++ b/src/Data/Text/ParagraphLayout/Plain.hs
@@ -110,19 +110,42 @@ containGlyphsH lineHeight ps = Rect
 -- will be shaped using a single font, aligned to the left for LTR text or to
 -- the right for RTL text.
 layoutPlain :: Paragraph -> ParagraphLayout
-layoutPlain paragraph = ParagraphLayout pRect arrangedLayouts
+layoutPlain paragraph = ParagraphLayout pRect layouts
     where
         pRect = containRects allRects
-        allRects = concat $ map spanRects arrangedLayouts
-        arrangedLayouts = snd $ arrangeSpansH 0 $ layouts
-        layouts = map layoutSpan spans
+        allRects = concat $ map spanRects layouts
+        layouts = snd $ addSpansH 0 spans
         spans = resolveSpans paragraph
 
+-- | Calculate layout for all given spans,
+-- arrange them in one horizontal direction starting from the given x_offset,
+-- and return the final x_offset for continuation.
+addSpansH :: Int32 -> [RS.ResolvedSpan] -> (Int32, [SpanLayout])
+addSpansH currentX rss = mapAccumL addSpanH currentX rss
+
 -- TODO: Break lines.
 -- TODO: Allow a run across multiple spans (e.g. if they only differ by colour).
-layoutSpan :: RS.ResolvedSpan -> SpanLayout
-layoutSpan rs = SpanLayout (map layoutRun $ spanToRuns rs)
 
+-- | Calculate layout for the given span, arrange each of its fragments
+-- in one horizontal direction starting from the given x_offset,
+-- and return the final x_offset for continuation.
+addSpanH :: Int32 -> RS.ResolvedSpan -> (Int32, SpanLayout)
+addSpanH currentX rs = (nextX, SpanLayout frags)
+    where (nextX, frags) = mapAccumL addRunH currentX $ spanToRuns rs
+
+-- | Calculate layout for the given run,
+-- place the generated fragment horizontally at the given x_offset,
+-- and return the final x_offset for continuation.
+addRunH :: Int32 -> Run -> (Int32, Fragment)
+addRunH currentX run = (nextX, nextFrag)
+    where
+        frag = layoutRun run
+        rect = fragmentRect frag
+        nextX = currentX + x_size rect
+        nextFrag = frag { fragmentRect = nextRect }
+        nextRect = rect { x_origin = currentX }
+
+-- | Calculate layout for the given run independently of its position.
 layoutRun :: Run -> Fragment
 layoutRun run = Fragment rect (penX, penY) glyphs
     where
@@ -183,28 +206,3 @@ cut arr off s = (end, t)
         len = spanLength s
         end = off + len
         t = Text arr (fromIntegral off) (fromIntegral len)
-
--- | Arrange all fragments in multiple spans in one horizontal direction
--- and return the final x_offset for continuation.
-arrangeSpansH :: Int32 -> [SpanLayout] -> (Int32, [SpanLayout])
-arrangeSpansH currentX sls = mapAccumL arrangeSpanH currentX sls
-
--- | Arrange all fragments in one span in one horizontal direction
--- and return the final x_offset for continuation.
-arrangeSpanH :: Int32 -> SpanLayout -> (Int32, SpanLayout)
-arrangeSpanH currentX (SpanLayout frags) = (nextX, SpanLayout newFragments)
-    where (nextX, newFragments) = arrangeFragmentsH currentX frags
-
--- | Arrange fragments in one horizontal direction
--- and return the final x_offset for continuation.
-arrangeFragmentsH :: Int32 -> [Fragment] -> (Int32, [Fragment])
-arrangeFragmentsH currentX frags = mapAccumL arrangeFragmentH currentX frags
-
--- | Set the horizontal offset of the given box
--- and return the x coordinate of its other side for continuation.
-arrangeFragmentH :: Int32 -> Fragment -> (Int32, Fragment)
-arrangeFragmentH currentX frag = (nextX, frag { fragmentRect = newRect })
-    where
-        rect = fragmentRect frag
-        nextX = currentX + x_size rect
-        newRect = rect { x_origin = currentX }
-- 
2.30.2