Use XFT fonts if available

The silent error `user error (createFontSet)` would break certain
modules (like the prompt) by simply not showing anything.

Pango 1.44 dropped support for FreeType in favor of HarfBuzz, losing
support for traditional BDF/PCF bitmap fonts.  Hence, some distributions
don't ship `xorg-fonts-misc` anymore.

Fixes xmonad#348

CHANGES.md

@@ -4,6 +4,16 @@
 
 ### Breaking Changes
 
+  * All modules that export bitmap fonts as their default
+
+    - If xmonad is compiled with XFT support (the default), use an XFT
+      font instead.  The previous default expected an X11 misc font
+      (PCF), which is not supported in pango 1.44 anymore and thus some
+      distributions have stopped shipping these.
+
+      This fixes the silent `user error (createFontSet)`; this would
+      break the respective modules.
+
   * `XMonad.Prompt`
 
     - Now `mkComplFunFromList` and `mkComplFunFromList'` take an

XMonad/Actions/ShowText.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE CPP                #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  XMonad.Actions.ShowText
@@ -74,7 +75,11 @@ data ShowTextConfig =
 
 instance Default ShowTextConfig where
   def =
+#ifdef XFT
+    STC { st_font = "xft:monospace-20"
+#else
     STC { st_font = "-misc-fixed-*-*-*-*-20-*-*-*-*-*-*-*"
+#endif
         , st_bg   = "black"
         , st_fg   = "white"
     }

XMonad/Layout/Decoration.hs

@@ -1,4 +1,10 @@
-{-# LANGUAGE DeriveDataTypeable, FlexibleContexts, FlexibleInstances, MultiParamTypeClasses, PatternGuards, TypeSynonymInstances #-}
+{-# LANGUAGE DeriveDataTypeable    #-}
+{-# LANGUAGE FlexibleContexts      #-}
+{-# LANGUAGE FlexibleInstances     #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE PatternGuards         #-}
+{-# LANGUAGE TypeSynonymInstances  #-}
+{-# LANGUAGE CPP                   #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  XMonad.Layout.Decoration
@@ -104,7 +110,11 @@ instance Default Theme where
           , activeTextColor     = "#FFFFFF"
           , inactiveTextColor   = "#BFBFBF"
           , urgentTextColor     = "#FF0000"
+#ifdef XFT
+          , fontName            = "xft:monospace"
+#else
           , fontName            = "-misc-fixed-*-*-*-*-10-*-*-*-*-*-*-*"
+#endif
           , decoWidth           = 200
           , decoHeight          = 20
           , windowTitleAddons   = []

XMonad/Layout/ShowWName.hs

@@ -1,4 +1,7 @@
-{-# LANGUAGE PatternGuards, FlexibleInstances, MultiParamTypeClasses #-}
+{-# LANGUAGE FlexibleInstances     #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE PatternGuards         #-}
+{-# LANGUAGE CPP                   #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  XMonad.Layout.ShowWName
@@ -62,7 +65,11 @@ data SWNConfig =
 
 instance Default SWNConfig where
   def =
+#ifdef XFT
+    SWNC { swn_font    = "xft:monospace-20"
+#else
     SWNC { swn_font    = "-misc-fixed-*-*-*-*-20-*-*-*-*-*-*-*"
+#endif
          , swn_bgcolor = "black"
          , swn_color   = "white"
          , swn_fade    = 1

XMonad/Prompt.hs

@@ -3,6 +3,7 @@
 {-# LANGUAGE MultiWayIf #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE ExistentialQuantification #-}
+{-# LANGUAGE CPP #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  XMonad.Prompt
@@ -310,7 +311,11 @@ instance Default XPColor where
 
 instance Default XPConfig where
   def =
+#ifdef XFT
+    XPC { font                  = "xft:monospace-12"
+#else
     XPC { font                  = "-misc-fixed-*-*-*-*-12-*-*-*-*-*-*-*"
+#endif
         , bgColor               = bgNormal def
         , fgColor               = fgNormal def
         , bgHLight              = bgHighlight def