From f75177e9b64087ccefcf1b087d94bc4545df0afb Mon Sep 17 00:00:00 2001
From: Mirko Covizzi <mrkcvzz@gmail.com>
Date: Mon, 25 May 2020 22:15:58 +0200
Subject: [PATCH] Setup unique class naming for windows on Windows

---
 Cargo.toml        |  2 +-
 src/win/window.rs | 25 +++++++++++++++++++++++--
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index d1e864b..4af40fb 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,4 +9,4 @@ edition = "2018"
 [dependencies]
 
 [target.'cfg(windows)'.dependencies]
-winapi = { version = "0.3.8", features = ["libloaderapi", "winuser", "windef", "minwindef"] }
+winapi = { version = "0.3.8", features = ["libloaderapi", "winuser", "windef", "minwindef", "guiddef", "combaseapi"] }
diff --git a/src/win/window.rs b/src/win/window.rs
index 5c460cc..4684907 100644
--- a/src/win/window.rs
+++ b/src/win/window.rs
@@ -1,8 +1,10 @@
 extern crate winapi;
 
 use self::winapi::_core::mem::MaybeUninit;
+use self::winapi::shared::guiddef::GUID;
 use self::winapi::shared::minwindef::{LPARAM, LPVOID, LRESULT, UINT, WPARAM};
 use self::winapi::shared::windef::{HBRUSH, HICON, HMENU, HWND};
+use self::winapi::um::combaseapi::CoCreateGuid;
 use self::winapi::um::libloaderapi::GetModuleHandleA;
 use self::winapi::um::winuser::{
     CreateWindowExA, DefWindowProcA, DispatchMessageA, PeekMessageA, PostQuitMessage,
@@ -47,13 +49,31 @@ pub unsafe extern "system" fn wnd_proc(
 
 pub fn create_window(w: WindowOpenOptions) {
     unsafe {
+        // We generate a unique name for the new window class to prevent name collisions
+        let mut guid: GUID = MaybeUninit::uninit().assume_init();
+        CoCreateGuid(&mut guid);
+        let class_name = format!(
+            "Baseview-{}-{}-{}-{}{}{}{}{}{}{}{}\0",
+            guid.Data1,
+            guid.Data2,
+            guid.Data3,
+            guid.Data4[0],
+            guid.Data4[1],
+            guid.Data4[2],
+            guid.Data4[3],
+            guid.Data4[4],
+            guid.Data4[5],
+            guid.Data4[6],
+            guid.Data4[7]
+        );
+
         let hinstance = GetModuleHandleA(0 as *const i8);
         let wnd_class = WNDCLASSA {
             // todo: for OpenGL, will use it later
             style: CS_OWNDC | CS_HREDRAW | CS_VREDRAW,
             lpfnWndProc: Some(wnd_proc),
             hInstance: hinstance,
-            lpszClassName: "BaseviewClass\0".as_ptr() as *const i8,
+            lpszClassName: class_name.as_ptr() as *const i8,
             cbClsExtra: 0,
             cbWndExtra: 0,
             hIcon: 0 as HICON,
@@ -65,7 +85,8 @@ pub fn create_window(w: WindowOpenOptions) {
 
         let _hwnd = CreateWindowExA(
             0,
-            "BaseviewClass\0".as_ptr() as *const i8,
+            class_name.as_ptr() as *const i8,
+            // todo: change title based on options struct
             "Baseview\0".as_ptr() as *const i8,
             // todo: fine for now, will have to change with a parent
             WS_OVERLAPPEDWINDOW | WS_VISIBLE,