Add support for italicized output when terminfo supports it

src/Graphics/Vty/Attributes.hs

@@ -38,6 +38,7 @@ module Graphics.Vty.Attributes
   , Style
   , withStyle
   , standout
+  , italic
   , underline
   , reverseVideo
   , blink
@@ -103,14 +104,15 @@ data Attr = Attr
 --      __ - unused
 --
 --  Next is the style flags
---      SURBDO__
+--      SURBDOI_
 --      S - standout
 --      U - underline
 --      R - reverse video
 --      B - blink
 --      D - dim
 --      O - bold
---      __ - unused
+--      I - italic
+--      _ - unused
 --
 --  Then the foreground color encoded into 8 bits.
 --  Then the background color encoded into 8 bits.
@@ -187,15 +189,18 @@ type Style = Word8
 --
 --      * bold/bright
 --
+--      * italic
+--
 --  (The invisible, protect, and altcharset display attributes some
 --  terminals support are not supported via VTY.)
-standout, underline, reverseVideo, blink, dim, bold :: Style
+standout, underline, reverseVideo, blink, dim, bold, italic :: Style
 standout        = 0x01
 underline       = 0x02
 reverseVideo   = 0x04
 blink           = 0x08
 dim             = 0x10
 bold            = 0x20
+italic          = 0x40
 
 defaultStyleMask :: Style
 defaultStyleMask = 0x00

src/Graphics/Vty/DisplayAttributes.hs

@@ -94,6 +94,8 @@ data DisplayColorDiff
 data StyleStateChange
     = ApplyStandout
     | RemoveStandout
+    | ApplyItalic
+    | RemoveItalic
     | ApplyUnderline
     | RemoveUnderline
     | ApplyReverseVideo
@@ -141,6 +143,7 @@ diffStyles prev cur
     = mconcat
     [ styleDiff standout      ApplyStandout     RemoveStandout
     , styleDiff underline     ApplyUnderline    RemoveUnderline
+    , styleDiff italic        ApplyItalic       RemoveItalic
     , styleDiff reverseVideo  ApplyReverseVideo RemoveReverseVideo
     , styleDiff blink         ApplyBlink        RemoveBlink
     , styleDiff dim           ApplyDim          RemoveDim

src/Graphics/Vty/Output/TerminfoBased.hs

@@ -62,6 +62,8 @@ data DisplayAttrCaps = DisplayAttrCaps
     { setAttrStates :: Maybe CapExpression
     , enterStandout :: Maybe CapExpression
     , exitStandout :: Maybe CapExpression
+    , enterItalic :: Maybe CapExpression
+    , exitItalic :: Maybe CapExpression
     , enterUnderline :: Maybe CapExpression
     , exitUnderline :: Maybe CapExpression
     , enterReverseVideo :: Maybe CapExpression
@@ -227,6 +229,8 @@ currentDisplayAttrCaps ti
     <*> probeCap ti "sgr"
     <*> probeCap ti "smso"
     <*> probeCap ti "rmso"
+    <*> probeCap ti "sitm"
+    <*> probeCap ti "ritm"
     <*> probeCap ti "smul"
     <*> probeCap ti "rmul"
     <*> probeCap ti "rev"
@@ -434,6 +438,7 @@ data DisplayAttrSeq
 data DisplayAttrState = DisplayAttrState
     { applyStandout :: Bool
     , applyUnderline :: Bool
+    , applyItalic :: Bool
     , applyReverseVideo :: Bool
     , applyBlink :: Bool
     , applyDim :: Bool
@@ -444,6 +449,7 @@ sgrArgsForState :: DisplayAttrState -> [CapParam]
 sgrArgsForState attrState = map (\b -> if b then 1 else 0)
     [ applyStandout attrState
     , applyUnderline attrState
+    , applyItalic attrState
     , applyReverseVideo attrState
     , applyBlink attrState
     , applyDim attrState
@@ -470,6 +476,8 @@ reqDisplayCapSeqFor caps s diffs
         -- set state cap then just use the set state cap.
         ( True, True  ) -> SetState $ stateForStyle s
     where
+        noEnterExitCap ApplyItalic = isNothing $ enterItalic caps
+        noEnterExitCap RemoveItalic = isNothing $ exitItalic caps
         noEnterExitCap ApplyStandout = isNothing $ enterStandout caps
         noEnterExitCap RemoveStandout = isNothing $ exitStandout caps
         noEnterExitCap ApplyUnderline = isNothing $ enterUnderline caps
@@ -482,6 +490,8 @@ reqDisplayCapSeqFor caps s diffs
         noEnterExitCap RemoveDim = True
         noEnterExitCap ApplyBold = isNothing $ enterBoldMode caps
         noEnterExitCap RemoveBold = True
+        enterExitCap ApplyItalic = fromJust $ enterItalic caps
+        enterExitCap RemoveItalic = fromJust $ exitItalic caps
         enterExitCap ApplyStandout = fromJust $ enterStandout caps
         enterExitCap RemoveStandout = fromJust $ exitStandout caps
         enterExitCap ApplyUnderline = fromJust $ enterUnderline caps
@@ -495,6 +505,7 @@ stateForStyle :: Style -> DisplayAttrState
 stateForStyle s = DisplayAttrState
     { applyStandout = isStyleSet standout
     , applyUnderline = isStyleSet underline
+    , applyItalic = isStyleSet italic
     , applyReverseVideo = isStyleSet reverseVideo
     , applyBlink = isStyleSet blink
     , applyDim = isStyleSet dim
@@ -506,6 +517,7 @@ styleToApplySeq :: Style -> [StyleStateChange]
 styleToApplySeq s = concat
     [ applyIfRequired ApplyStandout standout
     , applyIfRequired ApplyUnderline underline
+    , applyIfRequired ApplyItalic italic
     , applyIfRequired ApplyReverseVideo reverseVideo
     , applyIfRequired ApplyBlink blink
     , applyIfRequired ApplyDim dim