First try to find changed values

src/main.rs

@@ -18,6 +18,7 @@ mod shell;
 mod input;
 mod settings;
 mod cursor;
+mod shell_dlg;
 
 use std::thread;
 use std::env;

src/shell_dlg.rs

@@ -0,0 +1,62 @@
+use ui::{SH, Ui};
+use neovim_lib::{NeovimApi, CallError, Value};
+use gtk;
+use gtk_sys;
+use gtk::{Dialog, DialogExt};
+
+pub fn can_close_window(ui: &Ui) -> bool {
+    match get_changed_buffers() {
+        Ok(vec) => {
+            if !vec.is_empty() {
+                show_not_saved_dlg(ui, &vec)
+            } else {
+                true
+            }
+        },
+        Err(ref err) => {
+            println!("Error getting info from nvim: {}", err);
+            true
+        }
+    }
+}
+
+fn show_not_saved_dlg(ui: &Ui, changed_bufs: &Vec<String>) -> bool {
+    let flags = gtk::DIALOG_MODAL | gtk::DIALOG_DESTROY_WITH_PARENT;
+    let dlg = Dialog::new_with_buttons(Some("Question"), ui.window.as_ref(), flags, &[
+   ("_OK", gtk_sys::GTK_RESPONSE_ACCEPT as i32),
+                                       ("_Cancel",
+                                       gtk_sys::GTK_RESPONSE_REJECT as i32)
+    ]);
+
+    dlg.run();
+
+    true
+}
+
+fn get_changed_buffers() -> Result<Vec<String>, CallError> {
+    SHELL!(shell = {
+        let mut nvim = shell.nvim();
+        let buffers = nvim.get_buffers()?;
+
+        Ok(buffers.iter()
+            .map(|buf| {
+                (match buf.get_option(&mut nvim, "modified") {
+                     Ok(Value::Boolean(val)) => val,
+                     _ => {
+                         println!("Value must be boolean");
+                         false
+                     },
+                 },
+                 match buf.get_name(&mut nvim) {
+                     Ok(name) => name,
+                     Err(ref err) => {
+                         println!("Something going wrong while getting buffer name: {}", err);
+                         "<Error>".to_owned()
+                     },
+                 })
+            })
+            .filter(|e| e.0)
+            .map(|e| e.1)
+            .collect())
+    })
+}

src/ui.rs

@@ -13,6 +13,7 @@ use neovim_lib::NeovimApi;
 
 use settings;
 use shell::{Shell, NvimMode};
+use shell_dlg;
 use nvim::ErrorReport;
 
 macro_rules! ui_thread_var {
@@ -169,16 +170,17 @@ fn edit_save_all() {
     });
 }
 
-fn quit() {
-    UI.with(|ui_cell| {
-        let mut ui = ui_cell.borrow_mut();
-        ui.destroy();
-    });
-}
 
 fn gtk_delete(_: &ApplicationWindow, _: &Event) -> Inhibit {
-    quit();
-    Inhibit(false)
+    Inhibit(UI.with(|ui_cell| {
+        let mut ui = ui_cell.borrow_mut();
+        if shell_dlg::can_close_window(&ui) {
+            ui.destroy();
+            false
+        } else {
+            true
+        }
+    }))
 }