Improve shape of "s" under extra wides (be5invis#2460) (be5invis#2461)

Author: be5invis

packages/font-glyphs/src/letter/latin/s.ptl

@@ -39,6 +39,13 @@ glyph-block Letter-Latin-S : begin
 			yLoopTop -- 0.333 * XH + 0.125 * fine
 			swBefore -- sw
 
+	define [SNeck df height stroke ess] : begin
+		local adjustFactor : 0.1 * (df.rightSB - df.leftSB) / height
+		return : list
+			~~~ [alsoThru 0.5 (0.7 + adjustFactor)]
+			g4 [pre@mix@post 0.5] [pre@mix@post 0.5] [widths.center ess]
+			~~~ [alsoThru 0.5 (0.3 - adjustFactor)]
+
 	define [SStrokeImpl df top bot st sb stroke refSwEss] : begin
 		local ess : refSwEss * stroke / Stroke
 		define archDepth : AdviceSArchDepth (top - bot) (-1) stroke
@@ -52,7 +59,7 @@ glyph-block Letter-Latin-S : begin
 					hookstart top (sw -- stroke)
 
 			g4   df.leftSB (top - archDepth)
-			alsoThru.g2 0.5 0.5 [widths.center ess]
+			~~~ [SNeck df (top - bot) stroke ess]
 			g4   (df.rightSB - SOBot) (bot + archDepth) [widths.rhs stroke]
 
 			match sb
@@ -72,7 +79,7 @@ glyph-block Letter-Latin-S : begin
 					g4   df.leftSB (CAP - Hook) [widths.rhs stroke]
 					hookstart CAP (sw -- stroke)
 			g4   df.rightSB (CAP - archDepth)
-			alsoThru.g2 0.5 0.5 [widths.center ess]
+			~~~ [SNeck df CAP stroke ess]
 			g4   (df.leftSB + SOBot) archDepth [widths.lhs stroke]
 			match sb
 				[Just SLAB-CLASSICAL] : SerifedArcEnd.LtrLhs df.rightSB 0 stroke Hook
@@ -94,7 +101,7 @@ glyph-block Letter-Latin-S : begin
 						hookstart XH (sw -- stroke)
 
 			g4   (df.leftSB - OX) (XH - archDepth)
-			alsoThru.g2 0.5 0.5 [widths.center ess]
+			~~~ [SNeck df XH stroke ess]
 			g4   (df.rightSB + OX - SOBot) (archDepth) [widths.rhs stroke]
 
 			match sb
@@ -116,10 +123,9 @@ glyph-block Letter-Latin-S : begin
 			g4   (df.rightSB + OX / 4 - [HSwToV soStart]) (top - hook)
 			hookstart (top - soStart) (sw -- fine)
 			g4   (df.leftSB + oXLeftTop + offsetLT.x) (top - archDepth + offsetLT.y)
-			g2
-				offsetC.x + [mix (df.leftSB + oXLeftTop + offsetLT.x) (df.rightSB - SOBot - offsetRB.x) 0.5]
-				offsetC.y + [mix (top - archDepth)                (archDepth)                       0.5]
-				widths.center stroke
+			~~~ [virt pre@ (top - archDepth)]
+			~~~ [g4 [pre@mix@post 0.5 offsetC.x] [pre@mix@post 0.5 offsetC.y] [widths.center stroke]]
+			~~~ [virt post@ (archDepth)]
 			g4   (df.rightSB - SOBot - offsetRB.x) (archDepth + offsetRB.y) [widths.rhs fine]
 			hookend soEnd (sw -- fine)
 			g4   (df.leftSB + SOBot + [HSwToV soEnd]) (hook) [widths.rhs fine]
@@ -136,7 +142,7 @@ glyph-block Letter-Latin-S : begin
 					g4 df.rightSB (top - Hook) [widths.lhs stroke]
 					hookstart top (sw -- stroke)
 			g4   df.leftSB (top - archDepth)
-			alsoThru.g2 0.5 0.5 [widths.center ess]
+			~~~ [SNeck df top stroke ess]
 			g4   (df.rightSB - SOBot) (archDepth) [widths.rhs stroke]
 			arcvh
 			flat [arch.adjust-x.top df.middle] 0 [widths.rhs Stroke]
@@ -152,7 +158,7 @@ glyph-block Letter-Latin-S : begin
 					g4   (df.leftSB - OX) (XH - SHook) [widths.rhs stroke]
 					hookstart XH (sw -- stroke)
 			g4   (df.rightSB + OX) (XH - archDepth)
-			alsoThru.g2 0.5 0.5 [widths.center ess]
+			~~~ [SNeck df XH stroke ess]
 			g4   (df.leftSB - OX + SOBot) (archDepth) [widths.lhs stroke]
 			match sb
 				[Just SLAB-CLASSICAL] : SerifedArcEnd.LtrLhs df.rightSB 0 stroke SHook

params/shape-width.toml

@@ -14,6 +14,7 @@ tbalance        = 1
 tbalance2       = 1
 archDepth       = 1
 smallArchDepth  = 1
+essRatio        = 1
 
 # "Grade 9"
 [shapeWidth.blend.720]
@@ -32,6 +33,7 @@ tbalance        = 1.210
 tbalance2       = 1.210
 archDepth       = 1.103
 smallArchDepth  = 1.103
+essRatio        = 0.953
 
 # "Grade 8"
 [shapeWidth.blend.657]
@@ -66,6 +68,7 @@ tbalance        = 1.100
 tbalance2       = 1.100
 archDepth       = 1.050
 smallArchDepth  = 1.050
+essRatio        = 1
 
 # "Grade 6"
 [shapeWidth.blend.547]
@@ -119,6 +122,7 @@ tbalance        = 0.909
 tbalance2       = 0.909
 archDepth       = 0.952
 smallArchDepth  = 0.952
+essRatio        = 1
 
 # Slab correlation
 [shapeWidth-serifs-slab.multiplies.blend.500]