From 8aa16895bf1499c04d6a0c1c3ac7f96c6ade6ee7 Mon Sep 17 00:00:00 2001
From: Oliver Charles <ollie@ocharles.org.uk>
Date: Sun, 24 Jan 2021 19:50:21 +0000
Subject: [PATCH] Add a README

---
 README.md           | 105 ++++++++++++++++++++++++++++++++++++++++++++
 examples/Readme.hs  |  78 ++++++++++++++++++++++++++++++++
 hs-dear-imgui.cabal |   8 ++++
 3 files changed, 191 insertions(+)
 create mode 100644 README.md
 create mode 100644 examples/Readme.hs

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..05ebc6f
--- /dev/null
+++ b/README.md
@@ -0,0 +1,105 @@
+# Dear ImGui.hs
+
+> Dear ImGui is a **bloat-free graphical user interface library for C++**. It
+> outputs optimized vertex buffers that you can render anytime in your
+> 3D-pipeline enabled application. It is fast, portable, renderer agnostic and
+> self-contained (no external dependencies).
+
+This project contains Haskell bindings to the
+[ImGui](https://github.com/ocornut/imgui) project. This allows you to rapidly
+put together graphical user interfaces in Haskell, with a particular focus to
+games and graphics intensive applications.
+
+# Getting Started
+
+`dear-imgui.hs` can be used like a normal Haskell library. If you use Cabal,
+simply add `dear-imgui` to your `build-depends`. ImGui supports a variety of
+backends, and you will need to choose your backend at configuration time.
+Backends can be enabled using Cabal flags, and these can be set through the
+`cabal.project` file. For example, if you want to use a combination of SDL and
+OpenGL:
+
+```
+package dear-imgui
+  flags: +sdl +opengl
+```
+
+With this done, the following module is the "Hello, World!" of ImGui:
+
+``` haskell
+{-# language BlockArguments #-}
+{-# language LambdaCase #-}
+{-# language OverloadedStrings #-}
+
+module Main ( main ) where
+
+import Control.Exception
+import Control.Monad.IO.Class
+import Control.Monad.Managed
+import DearImGui
+import DearImGui.OpenGL
+import DearImGui.SDL
+import DearImGui.SDL.OpenGL
+import Graphics.GL
+import SDL
+
+main :: IO ()
+main = do
+  -- Initialize SDL
+  initializeAll
+
+  runManaged do
+    -- Create a window using SDL. As we're using OpenGL, we need to enable OpenGL too.
+    w <- do
+      let title = "Hello, Dear ImGui!"
+      let config = defaultWindow { windowGraphicsContext = OpenGLContext defaultOpenGL }
+      managed $ bracket (createWindow title config) destroyWindow
+
+    -- Create an OpenGL context
+    glContext <- managed $ bracket (glCreateContext w) glDeleteContext
+
+    -- Create an ImGui context
+    _ <- managed $ bracket createContext destroyContext
+
+    -- Initialize ImGui's SDL2 backend
+    _ <- managed_ $ bracket_ (sdl2InitForOpenGL w glContext) sdl2Shutdown
+
+    -- Initialize ImGui's OpenGL backend
+    _ <- managed_ $ bracket_ openGL2Init openGL2Shutdown
+
+    liftIO $ mainLoop w
+
+
+mainLoop :: Window -> IO ()
+mainLoop w = do
+  -- Process the event loop
+  untilNothingM pollEventWithImGui
+
+  -- Tell ImGui we're starting a new frame
+  openGL2NewFrame
+  sdl2NewFrame w
+  newFrame
+
+  -- Build the GUI
+  bracket_ (begin "Hello, ImGui!") end do
+    -- Add a text widget
+    text "Hello, ImGui!"
+
+    -- Add a button widget, and call 'putStrLn' when it's clicked
+    button "Clickety Click" >>= \case
+      False -> return ()
+      True  -> putStrLn "Ow!"
+
+  -- Render
+  glClear GL_COLOR_BUFFER_BIT
+
+  render
+  openGL2RenderDrawData =<< getDrawData
+
+  glSwapWindow w
+
+  mainLoop w
+
+  where
+    untilNothingM m = m >>= maybe (return ()) (\_ -> untilNothingM m)
+```
diff --git a/examples/Readme.hs b/examples/Readme.hs
new file mode 100644
index 0000000..97fe9cd
--- /dev/null
+++ b/examples/Readme.hs
@@ -0,0 +1,78 @@
+-- NOTE: If this is file is edited, please also copy and paste it into
+-- README.md.
+
+{-# language BlockArguments #-}
+{-# language LambdaCase #-}
+{-# language OverloadedStrings #-}
+
+module Main ( main ) where
+
+import Control.Exception
+import Control.Monad.IO.Class
+import Control.Monad.Managed
+import DearImGui
+import DearImGui.OpenGL
+import DearImGui.SDL
+import DearImGui.SDL.OpenGL
+import Graphics.GL
+import SDL
+
+main :: IO ()
+main = do
+  -- Initialize SDL
+  initializeAll
+
+  runManaged do
+    -- Create a window using SDL. As we're using OpenGL, we need to enable OpenGL too.
+    w <- do
+      let title = "Hello, Dear ImGui!"
+      let config = defaultWindow { windowGraphicsContext = OpenGLContext defaultOpenGL }
+      managed $ bracket (createWindow title config) destroyWindow
+
+    -- Create an OpenGL context
+    glContext <- managed $ bracket (glCreateContext w) glDeleteContext
+
+    -- Create an ImGui context
+    _ <- managed $ bracket createContext destroyContext
+
+    -- Initialize ImGui's SDL2 backend
+    _ <- managed_ $ bracket_ (sdl2InitForOpenGL w glContext) sdl2Shutdown
+
+    -- Initialize ImGui's OpenGL backend
+    _ <- managed_ $ bracket_ openGL2Init openGL2Shutdown
+
+    liftIO $ mainLoop w
+
+
+mainLoop :: Window -> IO ()
+mainLoop w = do
+  -- Process the event loop
+  untilNothingM pollEventWithImGui
+
+  -- Tell ImGui we're starting a new frame
+  openGL2NewFrame
+  sdl2NewFrame w
+  newFrame
+
+  -- Build the GUI
+  bracket_ (begin "Hello, ImGui!") end do
+    -- Add a text widget
+    text "Hello, ImGui!"
+
+    -- Add a button widget, and call 'putStrLn' when it's clicked
+    button "Clickety Click" >>= \case
+      False -> return ()
+      True  -> putStrLn "Ow!"
+
+  -- Render
+  glClear GL_COLOR_BUFFER_BIT
+
+  render
+  openGL2RenderDrawData =<< getDrawData
+
+  glSwapWindow w
+
+  mainLoop w
+
+  where
+    untilNothingM m = m >>= maybe (return ()) (\_ -> untilNothingM m)
diff --git a/hs-dear-imgui.cabal b/hs-dear-imgui.cabal
index 8218b68..682807b 100644
--- a/hs-dear-imgui.cabal
+++ b/hs-dear-imgui.cabal
@@ -83,3 +83,11 @@ executable test
   default-language: Haskell2010
   build-depends: base, sdl2, gl, dear-imgui
   ghc-options: -Wall
+
+
+executable readme
+  main-is: Readme.hs
+  hs-source-dirs: examples
+  default-language: Haskell2010
+  build-depends: base, sdl2, gl, dear-imgui, managed
+  ghc-options: -Wall