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