Add support for SDL2 Renderer backend (#193)

* Add DearImGui.Raw.framerate
* Add DearImGui.withCloseableWindow
* Closes #191: Add support for SDL2 Renderer backend
* Add sdl-renderer flag to protect against older SDL versions that do not have SDL_RenderGeometry

src/DearImGui.hs

@@ -45,6 +45,7 @@ module DearImGui
     -- * Windows
   , withWindow
   , withWindowOpen
+  , withCloseableWindow
   , withFullscreen
   , fullscreenFlags
 
@@ -335,6 +336,7 @@ module DearImGui
   , Raw.getBackgroundDrawList
   , Raw.getForegroundDrawList
   , Raw.imCol32
+  , Raw.framerate
 
     -- * Types
   , module DearImGui.Enums
@@ -415,6 +417,26 @@ withWindowOpen :: MonadUnliftIO m => Text -> m () -> m ()
 withWindowOpen name action =
   withWindow name (`when` action)
 
+-- | Append items to a closeable window unless it is collapsed or fully clipped.
+--
+-- You may append multiple times to the same window during the same frame
+-- by calling 'withWindowOpen' in multiple places.
+--
+-- The 'Bool' state variable will be set to 'False' when the window's close
+-- button is pressed.
+withCloseableWindow :: (HasSetter ref Bool, MonadUnliftIO m) => Text -> ref -> m () -> m ()
+withCloseableWindow name ref action = bracket open close (`when` action)
+  where
+    open = liftIO do
+      with 1 \boolPtr -> do
+        Text.withCString name \namePtr -> do
+          isVisible <- Raw.begin namePtr (Just boolPtr) Nothing
+          isOpen <- peek boolPtr
+          when (isOpen == 0) $ ref $=! False
+          pure isVisible
+
+    close = liftIO . const Raw.end
+
 -- | Append items to a fullscreen window.
 --
 -- The action runs inside a window that is set to behave as a backdrop.

src/DearImGui/Raw.hs

@@ -249,6 +249,7 @@ module DearImGui.Raw
   , getBackgroundDrawList
   , getForegroundDrawList
   , imCol32
+  , framerate
 
     -- * Types
   , module DearImGui.Enums
@@ -1779,6 +1780,12 @@ wantCaptureKeyboard :: MonadIO m => m Bool
 wantCaptureKeyboard = liftIO do
   (0 /=) <$> [C.exp| bool { GetIO().WantCaptureKeyboard } |]
 
+-- | Estimate of application framerate (rolling average over 60 frames), in
+-- frame per second. Solely for convenience.
+framerate :: MonadIO m => m Float
+framerate = liftIO do
+  realToFrac <$> [C.exp| float { GetIO().Framerate } |]
+
 -- | This draw list will be the first rendering one.
 --
 -- Useful to quickly draw shapes/text behind dear imgui contents.

src/DearImGui/Raw/IO.hs

@@ -120,14 +120,11 @@ setUserData ptr = liftIO do
 
 {- TODO:
 
-bool   WantCaptureMouse;         // Set when Dear ImGui will use mouse inputs, in this case do not dispatch them to your main game/application (either way, always pass on mouse inputs to imgui). (e.g. unclicked mouse is hovering over an imgui window, widget is active, mouse was clicked over an imgui window, etc.).
-bool   WantCaptureKeyboard;      // Set when Dear ImGui will use keyboard inputs, in this case do not dispatch them to your main game/application (either way, always pass keyboard inputs to imgui). (e.g. InputText active, or an imgui window is focused and navigation is enabled, etc.).
 bool   WantTextInput;            // Mobile/console: when set, you may display an on-screen keyboard. This is set by Dear ImGui when it wants textual keyboard input to happen (e.g. when a InputText widget is active).
 bool   WantSetMousePos;          // MousePos has been altered, backend should reposition mouse on next frame. Rarely used! Set only when ImGuiConfigFlags_NavEnableSetMousePos flag is enabled.
 bool   WantSaveIniSettings;      // When manual .ini load/save is active (io.IniFilename == NULL), this will be set to notify your application that you can call SaveIniSettingsToMemory() and save yourself. Important: clear io.WantSaveIniSettings yourself after saving!
 bool   NavActive;                // Keyboard/Gamepad navigation is currently allowed (will handle ImGuiKey_NavXXX events) = a window is focused and it doesn't use the ImGuiWindowFlags_NoNavInputs flag.
 bool   NavVisible;               // Keyboard/Gamepad navigation is visible and allowed (will handle ImGuiKey_NavXXX events).
-float  Framerate;                // Rough estimate of application framerate, in frame per second. Solely for convenience. Rolling average estimation based on io.DeltaTime over 120 frames.
 int    MetricsRenderVertices;    // Vertices output during last call to Render()
 int    MetricsRenderIndices;     // Indices output during last call to Render() = number of triangles * 3
 int    MetricsRenderWindows;     // Number of visible windows

src/DearImGui/SDL/Renderer.hs

@@ -0,0 +1,74 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE TemplateHaskell #-}
+
+{-|
+Module: DearImGUI.SDL.Renderer
+
+Initialising the SDL2 renderer backend for Dear ImGui.
+-}
+
+module DearImGui.SDL.Renderer
+  ( sdl2InitForSDLRenderer
+  , sdlRendererInit
+  , sdlRendererShutdown
+  , sdlRendererNewFrame
+  , sdlRendererRenderDrawData
+  )
+  where
+
+-- inline-c
+import qualified Language.C.Inline as C
+
+-- inline-c-cpp
+import qualified Language.C.Inline.Cpp as Cpp
+
+-- sdl2
+import SDL.Internal.Types
+  ( Renderer(..), Window(..) )
+
+-- 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_sdlrenderer2.h"
+C.include "backends/imgui_impl_sdl2.h"
+C.include "SDL.h"
+Cpp.using "namespace ImGui"
+
+
+-- | Wraps @ImGui_ImplSDL2_InitForSDLRenderer@.
+sdl2InitForSDLRenderer :: MonadIO m => Window -> Renderer -> m Bool
+sdl2InitForSDLRenderer (Window windowPtr) (Renderer renderPtr) = liftIO do
+  (0 /=) <$> [C.exp| bool { ImGui_ImplSDL2_InitForSDLRenderer((SDL_Window*)$(void* windowPtr), (SDL_Renderer*)$(void* renderPtr)) } |]
+
+-- | Wraps @ImGui_ImplSDLRenderer2_Init@.
+sdlRendererInit :: MonadIO m => Renderer -> m Bool
+sdlRendererInit (Renderer renderPtr) = liftIO do
+  (0 /=) <$> [C.exp| bool { ImGui_ImplSDLRenderer2_Init((SDL_Renderer*)$(void* renderPtr)) } |]
+
+-- | Wraps @ImGui_ImplSDLRenderer2_Shutdown@.
+sdlRendererShutdown :: MonadIO m => m ()
+sdlRendererShutdown = liftIO do
+  [C.exp| void { ImGui_ImplSDLRenderer2_Shutdown(); } |]
+
+-- | Wraps @ImGui_ImplSDLRenderer2_NewFrame@.
+sdlRendererNewFrame :: MonadIO m => m ()
+sdlRendererNewFrame = liftIO do
+  [C.exp| void { ImGui_ImplSDLRenderer2_NewFrame(); } |]
+
+-- | Wraps @ImGui_ImplSDLRenderer2_RenderDrawData@.
+sdlRendererRenderDrawData :: MonadIO m => DrawData -> m ()
+sdlRendererRenderDrawData (DrawData ptr) = liftIO do
+  [C.exp| void { ImGui_ImplSDLRenderer2_RenderDrawData((ImDrawData*) $( void* ptr )) } |]