cairo: alpha (still pseudo, via xrender)

1 files changed, 138 insertions, 0 deletions

diff --git a/src/Xmobar/X11/XRender.hsc b/src/Xmobar/X11/XRender.hsc
new file mode 100644
index 0000000..5ad0391
--- /dev/null
+++ b/src/Xmobar/X11/XRender.hsc
@@ -0,0 +1,138 @@
+------------------------------------------------------------------------------
+-- |
+-- Module: Xmobar.X11.XRender
+-- Copyright: (c) 2012, 2014, 2015, 2017, 2022 Jose Antonio Ortega Ruiz
+--            (c) Clemens Fruhwirth <clemens@endorphin.org> 2007
+-- License: BSD3-style (see LICENSE)
+--
+-- Maintainer: jao@gnu.org
+-- Stability: unstable
+-- Portability: unportable
+-- Created: Sun Sep 11, 2022 01:27
+--
+--
+-- A couple of utilities imported from libxrender to allow alpha blending of
+-- an image backgrond.
+--
+------------------------------------------------------------------------------
+
+{-# LANGUAGE ForeignFunctionInterface, EmptyDataDecls #-}
+
+module Xmobar.X11.XRender (drawBackground) where
+
+import Graphics.X11
+import Graphics.X11.Xrender
+import Graphics.X11.Xlib.Extras (xGetWindowProperty, xFree)
+import Control.Monad (when)
+
+import Foreign
+import Foreign.C.Types
+
+#include <X11/extensions/Xrender.h>
+
+type Picture = XID
+type PictOp = CInt
+
+data XRenderPictFormat
+data XRenderPictureAttributes = XRenderPictureAttributes
+
+-- foreign import ccall unsafe "X11/extensions/Xrender.h XRenderFillRectangle"
+-- xRenderFillRectangle :: Display -> PictOp -> Picture -> Ptr XRenderColor -> CInt -> CInt -> CUInt -> CUInt -> IO ()
+foreign import ccall unsafe "X11/extensions/Xrender.h XRenderComposite"
+  xRenderComposite :: Display -> PictOp -> Picture -> Picture -> Picture -> CInt -> CInt -> CInt -> CInt -> CInt -> CInt -> CUInt -> CUInt -> IO ()
+foreign import ccall unsafe "X11/extensions/Xrender.h XRenderCreateSolidFill"
+  xRenderCreateSolidFill :: Display -> Ptr XRenderColor -> IO Picture
+foreign import ccall unsafe "X11/extensions/Xrender.h XRenderFreePicture"
+  xRenderFreePicture :: Display -> Picture -> IO ()
+foreign import ccall unsafe "string.h" memset :: Ptr a -> CInt -> CSize -> IO ()
+foreign import ccall unsafe "X11/extensions/Xrender.h XRenderFindStandardFormat"
+  xRenderFindStandardFormat :: Display -> CInt -> IO (Ptr XRenderPictFormat)
+foreign import ccall unsafe "X11/extensions/Xrender.h XRenderCreatePicture"
+  xRenderCreatePicture :: Display -> Drawable -> Ptr XRenderPictFormat -> CULong -> Ptr XRenderPictureAttributes -> IO Picture
+
+-- Attributes not supported
+instance Storable XRenderPictureAttributes where
+    sizeOf _ = #{size XRenderPictureAttributes}
+    alignment _ = alignment (undefined :: CInt)
+    peek _ = return XRenderPictureAttributes
+    poke p XRenderPictureAttributes =
+        memset p 0 #{size XRenderPictureAttributes}
+
+-- | Convenience function, gives us an XRender handle to a traditional
+-- Pixmap.  Don't let it escape.
+withRenderPicture :: Display -> Drawable -> (Picture -> IO a) -> IO ()
+withRenderPicture d p f = do
+    format <- xRenderFindStandardFormat d 1 -- PictStandardRGB24
+    alloca $ \attr -> do
+        pic <- xRenderCreatePicture d p format 0 attr
+        f pic
+        xRenderFreePicture d pic
+
+-- | Convenience function, gives us an XRender picture that is a solid
+-- fill of color 'c'.  Don't let it escape.
+withRenderFill :: Display -> XRenderColor -> (Picture -> IO a) -> IO ()
+withRenderFill d c f = do
+    pic <- with c (xRenderCreateSolidFill d)
+    f pic
+    xRenderFreePicture d pic
+
+-- | Drawing the background to a pixmap and taking into account
+-- transparency
+drawBackground ::  Display -> Drawable -> String -> Int -> Rectangle -> IO ()
+drawBackground d p bgc alpha (Rectangle x y wid ht) = do
+  let render opt bg pic m =
+        xRenderComposite d opt bg m pic
+                        (fromIntegral x) (fromIntegral y) 0 0
+                        0 0 (fromIntegral wid) (fromIntegral ht)
+  withRenderPicture d p $ \pic -> do
+    -- Handle background color
+    bgcolor <- parseRenderColor d bgc
+    withRenderFill d bgcolor $ \bgfill ->
+      withRenderFill d
+                     (XRenderColor 0 0 0 (257 * alpha))
+                     (render pictOpSrc bgfill pic)
+    -- Handle transparency
+    internAtom d "_XROOTPMAP_ID" False >>= \xid ->
+      let xroot = defaultRootWindow d in
+      alloca $ \x1 ->
+      alloca $ \x2 ->
+      alloca $ \x3 ->
+      alloca $ \x4 ->
+      alloca $ \pprop -> do
+        xGetWindowProperty d xroot xid 0 1 False 20 x1 x2 x3 x4 pprop
+        prop <- peek pprop
+        when (prop /= nullPtr) $ do
+          rootbg <- peek (castPtr prop) :: IO Pixmap
+          xFree prop
+          withRenderPicture d rootbg $ \bgpic ->
+            withRenderFill d (XRenderColor 0 0 0 (0xFFFF - 257 * alpha))
+                           (render pictOpAdd bgpic pic)
+
+-- | Parses color into XRender color (allocation not necessary!)
+parseRenderColor :: Display -> String -> IO XRenderColor
+parseRenderColor d c = do
+    let colormap = defaultColormap d (defaultScreen d)
+    Color _ red green blue _ <- parseColor d colormap c
+    return $ XRenderColor (fromIntegral red)
+                          (fromIntegral green)
+                          (fromIntegral blue)
+                          0xFFFF
+
+pictOpSrc, pictOpAdd :: PictOp
+pictOpSrc = 1
+pictOpAdd = 12
+
+-- pictOpMinimum = 0
+-- pictOpClear = 0
+-- pictOpDst = 2
+-- pictOpOver = 3
+-- pictOpOverReverse = 4
+-- pictOpIn = 5
+-- pictOpInReverse = 6
+-- pictOpOut = 7
+-- pictOpOutReverse = 8
+-- pictOpAtop = 9
+-- pictOpAtopReverse = 10
+-- pictOpXor = 11
+-- pictOpSaturate = 13
+-- pictOpMaximum = 13