From b4bc36ca8979da0a3b5d7c35be78d87cfa12ae37 Mon Sep 17 00:00:00 2001
From: Alexander Bondarenko <486682+dpwiz@users.noreply.github.com>
Date: Tue, 14 Sep 2021 15:41:38 +0300
Subject: [PATCH] Update readme example (#103)

Fixes #68
---
 README.md          | 34 ++++++++++++++++++++++------------
 examples/Readme.hs | 20 +++++++++++++++-----
 2 files changed, 37 insertions(+), 17 deletions(-)

diff --git a/README.md b/README.md
index b32f884..3a57da4 100644
--- a/README.md
+++ b/README.md
@@ -54,38 +54,35 @@ main = do
 
   runManaged do
     -- Create a window using SDL. As we're using OpenGL, we need to enable OpenGL too.
-    w <- do
+    window <- 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
+    glContext <- managed $ bracket (glCreateContext window) glDeleteContext
 
     -- Create an ImGui context
     _ <- managed $ bracket createContext destroyContext
 
     -- Initialize ImGui's SDL2 backend
-    _ <- managed_ $ bracket_ (sdl2InitForOpenGL w glContext) sdl2Shutdown
+    _ <- managed_ $ bracket_ (sdl2InitForOpenGL window glContext) sdl2Shutdown
 
     -- Initialize ImGui's OpenGL backend
     _ <- managed_ $ bracket_ openGL2Init openGL2Shutdown
 
-    liftIO $ mainLoop w
+    liftIO $ mainLoop window
 
 
 mainLoop :: Window -> IO ()
-mainLoop w = do
-  -- Process the event loop
-  untilNothingM pollEventWithImGui
-
+mainLoop window = unlessQuit do
   -- Tell ImGui we're starting a new frame
   openGL2NewFrame
   sdl2NewFrame
   newFrame
 
   -- Build the GUI
-  bracket_ (begin "Hello, ImGui!") end do
+  withWindowOpen "Hello, ImGui!" do
     -- Add a text widget
     text "Hello, ImGui!"
 
@@ -103,12 +100,25 @@ mainLoop w = do
   render
   openGL2RenderDrawData =<< getDrawData
 
-  glSwapWindow w
+  glSwapWindow window
 
-  mainLoop w
+  mainLoop window
 
   where
-    untilNothingM m = m >>= maybe (return ()) (\_ -> untilNothingM m)
+    -- Process the event loop
+    unlessQuit action = do
+      shouldQuit <- checkEvents
+      if shouldQuit then pure () else action
+
+    checkEvents = do
+      pollEventWithImGui >>= \case
+        Nothing ->
+          return False
+        Just event ->
+          (isQuit event ||) <$> checkEvents
+
+    isQuit event =
+      SDL.eventPayload event == SDL.QuitEvent
 ```
 
 # Hacking
diff --git a/examples/Readme.hs b/examples/Readme.hs
index 405aa65..918ed13 100644
--- a/examples/Readme.hs
+++ b/examples/Readme.hs
@@ -45,10 +45,7 @@ main = do
 
 
 mainLoop :: Window -> IO ()
-mainLoop window = do
-  -- Process the event loop
-  untilNothingM pollEventWithImGui
-
+mainLoop window = unlessQuit do
   -- Tell ImGui we're starting a new frame
   openGL2NewFrame
   sdl2NewFrame
@@ -78,4 +75,17 @@ mainLoop window = do
   mainLoop window
 
   where
-    untilNothingM m = m >>= maybe (return ()) (\_ -> untilNothingM m)
+    -- Process the event loop
+    unlessQuit action = do
+      shouldQuit <- checkEvents
+      if shouldQuit then pure () else action
+
+    checkEvents = do
+      pollEventWithImGui >>= \case
+        Nothing ->
+          return False
+        Just event ->
+          (isQuit event ||) <$> checkEvents
+
+    isQuit event =
+      SDL.eventPayload event == SDL.QuitEvent