add cabal flags for backend selection

Main.hs

@@ -7,6 +7,9 @@ module Main (main) where
 
 import Data.IORef
 import DearImGui
+import DearImGui.OpenGL
+import DearImGui.SDL
+import DearImGui.SDL.OpenGL
 import Control.Exception
 import Graphics.GL
 import SDL

hs-dear-imgui.cabal

@@ -3,25 +3,79 @@ name: dear-imgui
 version: 1.0.0
 build-type: Simple
 
+flag opengl
+  description:
+    Enable OpenGL backend.
+  default:
+    True
+  manual:
+    False
+
+flag sdl
+  description:
+    Enable SDL backend.
+  default:
+    True
+  manual:
+    False
+
 library
-  exposed-modules: DearImGui
-  hs-source-dirs: src
-  default-language: Haskell2010
-  ghc-options: -Wall
+  exposed-modules:
+    DearImGui
+  hs-source-dirs:
+    src
+  default-language:
+    Haskell2010
+  ghc-options:
+    -Wall
   cxx-sources:
     imgui/imgui.cpp
-    imgui/backends/imgui_impl_opengl2.cpp
-    imgui/backends/imgui_impl_sdl.cpp
+    imgui/imgui_demo.cpp
+    imgui/imgui_draw.cpp
     imgui/imgui_tables.cpp
     imgui/imgui_widgets.cpp
-    imgui/imgui_draw.cpp
-    imgui/imgui_demo.cpp
-  cxx-options: -std=c++11
-  extra-libraries: stdc++
-  pkgconfig-depends: sdl2
-  include-dirs: imgui
-  build-depends: base, inline-c, inline-c-cpp, sdl2, StateVar
-  extra-libraries: GL
+  cxx-options:
+    -std=c++11
+  extra-libraries:
+    stdc++
+  include-dirs:
+    imgui
+  build-depends:
+      base
+    , inline-c
+    , inline-c-cpp
+    , StateVar
+
+  if flag(opengl)
+    exposed-modules:
+      DearImGui.OpenGL
+    cxx-sources:
+      imgui/backends/imgui_impl_opengl2.cpp
+    if os(windows)
+      extra-libraries:
+        opengl32
+    else
+      extra-libraries:
+        GL
+
+  if flag(sdl)
+    exposed-modules:
+      DearImGui.SDL
+    build-depends:
+      sdl2
+    cxx-sources:
+      imgui/backends/imgui_impl_sdl.cpp
+
+    if os(windows) || os(darwin)
+      extra-libraries:
+        sdl2
+    else
+      pkgconfig-depends:
+        sdl2
+
+    if flag(opengl)
+      exposed-modules:
+        DearImGui.SDL.OpenGL
 
 
 executable test

src/DearImGui.hs

@@ -6,6 +6,12 @@
 {-# LANGUAGE QuasiQuotes #-}
 {-# LANGUAGE TemplateHaskell #-}
 
+{-|
+Module: DearImGui
+
+Main ImGui module, exporting the functions to create a GUI.
+-}
+
 module DearImGui
   ( -- * Context Creation and Access
     Context(..)
@@ -20,18 +26,6 @@ module DearImGui
   , getDrawData
   , checkVersion
 
-    -- ** SDL2
-  , sdl2InitForOpenGL
-  , sdl2NewFrame
-  , sdl2Shutdown
-  , pollEventWithImGui
-
-    -- ** OpenGL 2
-  , openGL2Init
-  , openGL2Shutdown
-  , openGL2NewFrame
-  , openGL2RenderDrawData
-
     -- * Demo, Debug, Information
   , showDemoWindow
   , showMetricsWindow
@@ -103,26 +97,28 @@ module DearImGui
   )
   where
 
-import Control.Monad ( when )
-import Control.Monad.IO.Class ( MonadIO, liftIO )
+-- base
 import Data.Bool
-import Data.StateVar
 import Foreign
 import Foreign.C
+
+-- inline-c
 import qualified Language.C.Inline as C
+
+-- inline-c-cpp
 import qualified Language.C.Inline.Cpp as Cpp
-import SDL
-import SDL.Internal.Types
-import SDL.Raw.Enum as Raw
-import qualified SDL.Raw.Event as Raw
-import Unsafe.Coerce ( unsafeCoerce )
+
+-- StateVar
+import Data.StateVar
+  ( HasGetter(get), HasSetter, ($=!) )
+
+-- transformers
+import Control.Monad.IO.Class
+  ( MonadIO, liftIO )
+
 
 C.context (Cpp.cppCtx <> C.bsCtx)
 C.include "imgui.h"
-C.include "backends/imgui_impl_opengl2.h"
-C.include "backends/imgui_impl_sdl.h"
-C.include "SDL.h"
-C.include "SDL_opengl.h"
 Cpp.using "namespace ImGui"
 
 
@@ -184,68 +180,6 @@ checkVersion = liftIO do
   [C.exp| void { IMGUI_CHECKVERSION(); } |]
 
 
--- | Wraps @ImGui_ImplSDL2_InitForOpenGL@.
-sdl2InitForOpenGL :: MonadIO m => Window -> GLContext -> m ()
-sdl2InitForOpenGL (Window windowPtr) glContext = liftIO do
-  [C.exp| void { ImGui_ImplSDL2_InitForOpenGL((SDL_Window*)$(void* windowPtr), $(void* glContextPtr)); } |]
-  where
-    glContextPtr :: Ptr ()
-    glContextPtr = unsafeCoerce glContext
-
-
--- | Wraps @ImGui_ImplSDL2_NewFrame@.
-sdl2NewFrame :: MonadIO m => Window -> m ()
-sdl2NewFrame (Window windowPtr) = liftIO do
-  [C.exp| void { ImGui_ImplSDL2_NewFrame((SDL_Window*)($(void* windowPtr))); } |]
-
-
--- | Wraps @ImGui_ImplSDL2_Shutdown@.
-sdl2Shutdown :: MonadIO m => m ()
-sdl2Shutdown = liftIO do
-  [C.exp| void { ImGui_ImplSDL2_Shutdown(); } |]
-
-
--- | Call the SDL2 'pollEvent' function, while also dispatching the event to
--- Dear ImGui. You should use this in your application instead of 'pollEvent'.
-pollEventWithImGui :: MonadIO m => m (Maybe Event)
-pollEventWithImGui = liftIO do
-  alloca \evPtr -> do
-    pumpEvents
-
-    -- We use NULL first to check if there's an event.
-    nEvents <- Raw.peepEvents evPtr 1 Raw.SDL_PEEKEVENT Raw.SDL_FIRSTEVENT Raw.SDL_LASTEVENT
-
-    when (nEvents > 0) do
-      let evPtr' = castPtr evPtr :: Ptr ()
-      [C.exp| void { ImGui_ImplSDL2_ProcessEvent((SDL_Event*) $(void* evPtr')) } |]
-
-    pollEvent
-
-
--- | Wraps @ImGui_ImplOpenGL2_Init@.
-openGL2Init :: MonadIO m => m ()
-openGL2Init = liftIO do
-  [C.exp| void { 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 )) } |]
-
-
 -- | Create demo window. Demonstrate most ImGui features. Call this to learn
 -- about the library! Try to make it always available in your application!
 showDemoWindow :: MonadIO m => m ()

src/DearImGui/OpenGL.hs

@@ -0,0 +1,65 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE TemplateHaskell #-}
+
+{-|
+Module: DearImGui.OpenGL
+
+OpenGL backend for Dear ImGui.
+-}
+
+module DearImGui.OpenGL
+  ( 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 ()
+openGL2Init = liftIO do
+  [C.exp| void { 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 )) } |]

src/DearImGui/SDL.hs

@@ -0,0 +1,83 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE TemplateHaskell #-}
+
+{-|
+Module: DearImGui.SDL
+
+SDL2 specific functions backend for Dear ImGui.
+
+Modules for initialising a backend with SDL2 can be found under the corresponding backend,
+e.g. "DearImGui.SDL.OpenGL".
+-}
+
+module DearImGui.SDL (
+    -- ** SDL2
+    sdl2NewFrame
+  , sdl2Shutdown
+  , pollEventWithImGui
+  )
+  where
+
+-- base
+import Control.Monad
+  ( when )
+import Foreign.Marshal.Alloc
+  ( alloca )
+import Foreign.Ptr
+  ( Ptr, castPtr )
+
+-- inline-c
+import qualified Language.C.Inline as C
+
+-- inline-c-cpp
+import qualified Language.C.Inline.Cpp as Cpp
+
+-- sdl2
+import SDL
+import SDL.Internal.Types
+import SDL.Raw.Enum as Raw
+import qualified SDL.Raw.Event as Raw
+
+-- transformers
+import Control.Monad.IO.Class
+  ( MonadIO, liftIO )
+
+
+C.context (Cpp.cppCtx <> C.bsCtx)
+C.include "imgui.h"
+C.include "backends/imgui_impl_sdl.h"
+C.include "SDL.h"
+Cpp.using "namespace ImGui"
+
+
+-- | Wraps @ImGui_ImplSDL2_NewFrame@.
+sdl2NewFrame :: MonadIO m => Window -> m ()
+sdl2NewFrame (Window windowPtr) = liftIO do
+  [C.exp| void { ImGui_ImplSDL2_NewFrame((SDL_Window*)($(void* windowPtr))); } |]
+
+
+-- | Wraps @ImGui_ImplSDL2_Shutdown@.
+sdl2Shutdown :: MonadIO m => m ()
+sdl2Shutdown = liftIO do
+  [C.exp| void { ImGui_ImplSDL2_Shutdown(); } |]
+
+-- | Call the SDL2 'pollEvent' function, while also dispatching the event to
+-- Dear ImGui. You should use this in your application instead of 'pollEvent'.
+pollEventWithImGui :: MonadIO m => m (Maybe Event)
+pollEventWithImGui = liftIO do
+  alloca \evPtr -> do
+    pumpEvents
+
+    -- We use NULL first to check if there's an event.
+    nEvents <- Raw.peepEvents evPtr 1 Raw.SDL_PEEKEVENT Raw.SDL_FIRSTEVENT Raw.SDL_LASTEVENT
+
+    when (nEvents > 0) do
+      let evPtr' = castPtr evPtr :: Ptr ()
+      [C.exp| void { ImGui_ImplSDL2_ProcessEvent((SDL_Event*) $(void* evPtr')) } |]
+
+    pollEvent

src/DearImGui/SDL/OpenGL.hs

@@ -0,0 +1,57 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE TemplateHaskell #-}
+
+{-|
+Module: DearImGUI.SDL.OpenGL
+
+Initialising the OpenGL backend for Dear ImGui using SDL2.
+-}
+
+module DearImGui.SDL.OpenGL
+  ( sdl2InitForOpenGL )
+  where
+
+-- base
+import Foreign.Ptr
+  ( Ptr )
+import Unsafe.Coerce
+  ( unsafeCoerce )
+
+-- inline-c
+import qualified Language.C.Inline as C
+
+-- inline-c-cpp
+import qualified Language.C.Inline.Cpp as Cpp
+
+-- sdl2
+import SDL
+  ( GLContext )
+import SDL.Internal.Types
+  ( Window(..) )
+
+-- transformers
+import Control.Monad.IO.Class
+  ( MonadIO, liftIO )
+
+
+C.context (Cpp.cppCtx <> C.bsCtx)
+C.include "imgui.h"
+C.include "backends/imgui_impl_opengl2.h"
+C.include "backends/imgui_impl_sdl.h"
+C.include "SDL.h"
+C.include "SDL_opengl.h"
+Cpp.using "namespace ImGui"
+
+
+-- | Wraps @ImGui_ImplSDL2_InitForOpenGL@.
+sdl2InitForOpenGL :: MonadIO m => Window -> GLContext -> m ()
+sdl2InitForOpenGL (Window windowPtr) glContext = liftIO do
+  [C.exp| void { ImGui_ImplSDL2_InitForOpenGL((SDL_Window*)$(void* windowPtr), $(void* glContextPtr)); } |]
+  where
+    glContextPtr :: Ptr ()
+    glContextPtr = unsafeCoerce glContext