Add tab bar functions (#30)

Main.hs

@@ -5,6 +5,7 @@
 
 module Main (main) where
 
+import Control.Monad
 import Data.IORef
 import DearImGui
 import DearImGui.OpenGL
@@ -33,7 +34,9 @@ main = do
       pos <- newIORef $ ImVec2 64 64
       size' <- newIORef $ ImVec2 512 512
       selected <- newIORef 4
-      loop w checked color slider r pos size' selected
+      tab1 <- newIORef True
+      tab2 <- newIORef True
+      loop w checked color slider r pos size' selected tab1 tab2
 
       openGL2Shutdown
 
@@ -47,8 +50,10 @@ loop
   -> IORef ImVec2 
   -> IORef ImVec2
   -> IORef Int 
+  -> IORef Bool
+  -> IORef Bool
   -> IO ()
-loop w checked color slider r pos size' selected = do
+loop w checked color slider r pos size' selected tab1Ref tab2Ref = do
   quit <- pollEvents
 
   openGL2NewFrame
@@ -70,8 +75,22 @@ loop w checked color slider r pos size' selected = do
   setNextWindowBgAlpha 0.42
 
   begin "My Window"
+
   text "Hello!"
 
+  beginTabBar "My tab bar" ImGuiTabBarFlags_Reorderable >>= whenTrue do
+    beginTabItem "Tab 1" tab1Ref ImGuiTabBarFlags_None >>= whenTrue do
+      text "Tab 1 is currently selected."
+      endTabItem
+    beginTabItem "Tab 2" tab2Ref ImGuiTabBarFlags_None >>= whenTrue do
+      text "Tab 2 is selected now."
+      endTabItem
+    reOpen <- tabItemButton "ReopenTabs" ImGuiTabItemFlags_Trailing
+    when reOpen do
+      writeIORef tab1Ref True
+      writeIORef tab2Ref True
+    endTabBar
+
   listBox "Items" r [ "A", "B", "C" ]
 
   button "Click me" >>= \case
@@ -147,7 +166,7 @@ loop w checked color slider r pos size' selected = do
 
   glSwapWindow w
 
-  if quit then return () else loop w checked color slider r pos size' selected
+  if quit then return () else loop w checked color slider r pos size' selected tab1Ref tab2Ref
 
   where
 

src/DearImGui.hs

@@ -129,6 +129,14 @@ module DearImGui
   , endMenu
   , menuItem
 
+    -- ** Tabs, tab bar
+  , beginTabBar
+  , endTabBar
+  , beginTabItem
+  , endTabItem
+  , tabItemButton
+  , setTabItemClosed
+
     -- * Tooltips
   , beginTooltip
   , endTooltip
@@ -754,6 +762,57 @@ menuItem label = liftIO do
   withCString label \labelPtr ->
     (0 /=) <$> [C.exp| bool { MenuItem($(char* labelPtr)) } |]
 
+-- | Create a @TabBar@ and start appending to it.
+--
+-- Wraps @ImGui::BeginTabBar@.
+beginTabBar :: MonadIO m => String -> ImGuiTabBarFlags -> m Bool
+beginTabBar tabBarID flags = liftIO do
+  withCString tabBarID \ptr ->
+    (0 /=) <$> [C.exp| bool { BeginTabBar($(char* ptr), $(ImGuiTabBarFlags flags) ) } |]
+
+-- | Finish appending elements to a tab bar. Only call if 'beginTabBar' returns @True@.
+--
+-- Wraps @ImGui::EndTabBar@.
+endTabBar :: MonadIO m => m ()
+endTabBar = liftIO do
+  [C.exp| void { EndTabBar(); } |]
+
+-- | Create a new tab. Returns @True@ if the tab is selected.
+--
+-- Wraps @ImGui::BeginTabItem@.
+beginTabItem :: ( MonadIO m, HasGetter ref Bool, HasSetter ref Bool ) => String -> ref -> ImGuiTabBarFlags -> m Bool
+beginTabItem tabName ref flags = liftIO do
+  currentValue <- get ref
+  with ( bool 0 1 currentValue :: CBool ) \ refPtr -> do
+    open <- withCString tabName \ ptrName ->
+      (0 /=) <$> [C.exp| bool { BeginTabItem($(char* ptrName), $(bool* refPtr), $(ImGuiTabBarFlags flags) ) } |]
+    newValue <- (0 /=) <$> peek refPtr
+    ref $=! newValue
+    pure open
+
+-- | Finish appending elements to a tab. Only call if 'beginTabItem' returns @True@.
+--
+-- Wraps @ImGui::EndTabItem@.
+endTabItem :: MonadIO m => m ()
+endTabItem = liftIO do
+  [C.exp| void { EndTabItem(); } |]
+
+-- | Create a tab that behaves like a button. Returns @True@ when clicked. Cannot be selected in the tab bar.
+--
+-- Wraps @ImGui.TabItemButton@.
+tabItemButton :: MonadIO m => String -> ImGuiTabItemFlags -> m Bool
+tabItemButton tabName flags = liftIO do
+  withCString tabName \ namePtr ->
+    (0 /=) <$> [C.exp| bool { TabItemButton($(char* namePtr), $(ImGuiTabItemFlags flags) ) } |]
+
+-- | Notify the tab bar (or the docking system) that a tab/window is about to close.
+-- Useful to reduce visual flicker on reorderable tab bars.
+--
+-- __For tab-bar__: call after 'beginTabBar' and before tab submission. Otherwise, call with a window name.
+setTabItemClosed :: MonadIO m => String -> m ()
+setTabItemClosed tabName = liftIO do
+  withCString tabName \ namePtr ->
+    [C.exp| void { SetTabItemClosed($(char* namePtr)); } |]
 
 -- | Begin/append a tooltip window to create full-featured tooltip (with any
 -- kind of items).

src/DearImGui/Context.hs

@@ -30,6 +30,8 @@ imguiContext = mempty
       , ( TypeName "ImGuiCond", [t| ImGuiCond |] )
       , ( TypeName "ImGuiDir" , [t| ImGuiDir |] )
       , ( TypeName "ImGuiStyleVar"    , [t| ImGuiStyleVar |] )
+      , ( TypeName "ImGuiTabBarFlags" , [t| ImGuiTabBarFlags |] )
+      , ( TypeName "ImGuiTabItemFlags", [t| ImGuiTabItemFlags |] )
       , ( TypeName "ImVec2", [t| ImVec2 |] )
       , ( TypeName "ImVec3", [t| ImVec3 |] )
       , ( TypeName "ImVec4", [t| ImVec4 |] )