Wrap the OpenGL 3 backend (#20)

src/DearImGui/OpenGL2.hs

@@ -0,0 +1,65 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE TemplateHaskell #-}
+
+{-|
+Module: DearImGui.OpenGL
+
+OpenGL 2 backend for Dear ImGui.
+-}
+
+module DearImGui.OpenGL2
+  ( openGL2Init
+  , openGL2Shutdown
+  , openGL2NewFrame
+  , openGL2RenderDrawData
+  )
+  where
+
+-- inline-c
+import qualified Language.C.Inline as C
+
+-- inline-c-cpp
+import qualified Language.C.Inline.Cpp as Cpp
+
+-- transformers
+import Control.Monad.IO.Class
+  ( MonadIO, liftIO )
+
+-- DearImGui
+import DearImGui
+  ( DrawData(..) )
+
+
+C.context (Cpp.cppCtx <> C.bsCtx)
+C.include "imgui.h"
+C.include "backends/imgui_impl_opengl2.h"
+Cpp.using "namespace ImGui"
+
+
+-- | Wraps @ImGui_ImplOpenGL2_Init@.
+openGL2Init :: MonadIO m => m Bool
+openGL2Init = liftIO do
+  ( 0 /= ) <$> [C.exp| bool { ImGui_ImplOpenGL2_Init() } |]
+
+
+-- | Wraps @ImGui_ImplOpenGL2_Shutdown@.
+openGL2Shutdown :: MonadIO m => m ()
+openGL2Shutdown = liftIO do
+  [C.exp| void { ImGui_ImplOpenGL2_Shutdown(); } |]
+
+
+-- | Wraps @ImGui_ImplOpenGL2_NewFrame@.
+openGL2NewFrame :: MonadIO m => m ()
+openGL2NewFrame = liftIO do
+  [C.exp| void { ImGui_ImplOpenGL2_NewFrame(); } |]
+
+
+-- | Wraps @ImGui_ImplOpenGL2_RenderDrawData@.
+openGL2RenderDrawData :: MonadIO m => DrawData -> m ()
+openGL2RenderDrawData (DrawData ptr) = liftIO do
+  [C.exp| void { ImGui_ImplOpenGL2_RenderDrawData((ImDrawData*) $( void* ptr )) } |]