cdp-hs
A Haskell library for the Chrome Devtools Protocol (CDP), generated from the protocol's definition files.
Quick start
cdp contains the generated library.
To get started:
- Clone the repo with submodules
git clone --recurse-submodules https://github.com/arsalan0c/cdp-hs.git - Switch directories to the CDP library:
cd cdp - Drop into nix environment:
nix-shell --pure - Generate cabal file:
hpack - Run Chromium with debugging port enabled:
chromium --headless --remote-debugging-port=9222 http://wikipedia.com - Run the example program to print the browser's version info :
cabal run cdp-exe
Example usage
Print a page to PDF, with Base64 encoded data being read in chunks:
module Main where
import Data.Default
import Data.Maybe
import System.Process
import qualified CDP as CDP
main :: IO ()
main = do
putStrLn "Starting CDP example"
-- run the 'printPDF' program with default configuration
CDP.runClient def printPDF
printPDF :: CDP.Handle CDP.Event -> IO ()
printPDF handle = do
-- send the Page.printToPDF command
r <- CDP.pagePrintToPdf handle $
CDP.PPagePrintToPdf Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing $
CDP.PPagePrintToPdfTransferModeReturnAsStream
-- obtain stream handle from which to read pdf data
let streamHandle = fromJust . CDP.pagePrintToPdfStream $ r
-- read pdf data 24000 bytes at a time
let params = CDP.PIoRead streamHandle Nothing $ Just 24000
reads <- whileTrue (not . CDP.ioReadEof) $ CDP.ioRead handle params
let dat = concatMap CDP.ioReadData $ reads
-- decode pdf to a file
let path = "mypdfs.pdf"
readProcess "base64" ["--decode", "-o", path] dat
callCommand $ unwords ["open", path]
whileTrue :: Monad m => (a -> Bool) -> m a -> m [a]
whileTrue f act = do
a <- act
if f a
then pure . (a :) =<< whileTrue f act
else pure [a]Generating the CDP library
- Build the generator library:
nix-build --attr exe - Run the generator:
result/bin/gen-exe
cdp, the library folder, will contain the newly generated code.
Current state
Commands and events for all non-deprecated domains are supported.
Upcoming features:
- sessions
Acknowledgements
This began as a Summer of Haskell / GSoC project. Albert Krewinkel (@tarleb), Jasper Van der Jeugt (@jaspervdj) and Romain Lesur (@RLesur) provided valuable feedback and support which along with raising the library's quality, has made this all the more enjoyable to work on.