From 91eec219f6b9814c8065a1a33ca6ad3e088d4b58 Mon Sep 17 00:00:00 2001
From: Joonas Javanainen <joonas.javanainen@gmail.com>
Date: Sun, 27 Sep 2015 15:57:08 +0300
Subject: [PATCH] Unsafe function to get the "current UI" out of thin air

---
 src/lib.rs | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index cdb1528..e466456 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -233,7 +233,12 @@ impl ImGui {
             io.display_size.y = height as c_float;
             io.delta_time = delta_time;
         }
-        unsafe { imgui_sys::igNewFrame() };
+        unsafe {
+            imgui_sys::igNewFrame();
+            CURRENT_UI = Some(Ui {
+                imgui: mem::transmute(self as &'a ImGui)
+            });
+        }
         Ui {
             imgui: self
         }
@@ -243,11 +248,14 @@ impl ImGui {
 impl Drop for ImGui {
     fn drop(&mut self) {
         unsafe {
+            CURRENT_UI = None;
             imgui_sys::igShutdown();
         }
     }
 }
 
+static mut CURRENT_UI: Option<Ui<'static>> = None;
+
 #[cfg(feature = "sdl2")]
 impl ImGui {
     pub fn update_mouse(&mut self, mouse: &::sdl2::mouse::MouseUtil) {
@@ -315,7 +323,7 @@ impl<'ui> Ui<'ui> {
                 let mut im_draw_data = mem::zeroed();
                 RENDER_DRAW_LISTS_STATE.0 = &mut im_draw_data;
                 imgui_sys::igRender();
-                RENDER_DRAW_LISTS_STATE.0 = 0 as *mut imgui_sys::ImDrawData;
+                RENDER_DRAW_LISTS_STATE.0 = ptr::null_mut();
 
                 for &cmd_list in im_draw_data.cmd_lists() {
                     let draw_list =
@@ -326,6 +334,7 @@ impl<'ui> Ui<'ui> {
                         };
                     try!(f(draw_list));
                 }
+                CURRENT_UI = None;
             }
             Ok(())
         }
@@ -350,6 +359,12 @@ impl<'ui> Ui<'ui> {
     }
 }
 
+impl<'a> Ui<'a> {
+    pub unsafe fn current_ui() -> Option<&'a Ui<'a>> {
+        CURRENT_UI.as_ref()
+    }
+}
+
 // Window
 impl<'ui> Ui<'ui> {
     pub fn window<'p>(&self) -> Window<'ui, 'p> { Window::new() }