[Windows] Avoid GetModuleHandle(NULL) (#2301)

Use get_instance_handle() over GetModuleHandle(NULL)

Author: AronParker

src/platform_impl/windows/event_loop.rs

@@ -27,10 +27,7 @@ use windows_sys::Win32::{
         RDW_INTERNALPAINT, SC_SCREENSAVE,
     },
     Media::{timeBeginPeriod, timeEndPeriod, timeGetDevCaps, TIMECAPS, TIMERR_NOERROR},
-    System::{
-        LibraryLoader::GetModuleHandleW, Ole::RevokeDragDrop, Threading::GetCurrentThreadId,
-        WindowsProgramming::INFINITE,
-    },
+    System::{Ole::RevokeDragDrop, Threading::GetCurrentThreadId, WindowsProgramming::INFINITE},
     UI::{
         Controls::{HOVER_DEFAULT, WM_MOUSELEAVE},
         Input::{
@@ -647,7 +644,7 @@ fn create_event_target_window<T: 'static>() -> HWND {
             lpfnWndProc: Some(thread_event_target_callback::<T>),
             cbClsExtra: 0,
             cbWndExtra: 0,
-            hInstance: GetModuleHandleW(ptr::null()),
+            hInstance: util::get_instance_handle(),
             hIcon: 0,
             hCursor: 0, // must be null in order for cursor state to work properly
             hbrBackground: 0,
@@ -681,7 +678,7 @@ fn create_event_target_window<T: 'static>() -> HWND {
             0,
             0,
             0,
-            GetModuleHandleW(ptr::null()),
+            util::get_instance_handle(),
             ptr::null(),
         );
 

src/platform_impl/windows/icon.rs

@@ -1,10 +1,9 @@
-use std::{fmt, io, mem, path::Path, ptr, sync::Arc};
+use std::{fmt, io, mem, path::Path, sync::Arc};
 
 use windows_sys::{
     core::PCWSTR,
     Win32::{
         Foundation::HWND,
-        System::LibraryLoader::GetModuleHandleW,
         UI::WindowsAndMessaging::{
             CreateIcon, DestroyIcon, LoadImageW, SendMessageW, HICON, ICON_BIG, ICON_SMALL,
             IMAGE_ICON, LR_DEFAULTSIZE, LR_LOADFROMFILE, WM_SETICON,
@@ -111,7 +110,7 @@ impl WinIcon {
         let (width, height) = size.map(Into::into).unwrap_or((0, 0));
         let handle = unsafe {
             LoadImageW(
-                GetModuleHandleW(ptr::null()),
+                util::get_instance_handle(),
                 resource_id as PCWSTR,
                 IMAGE_ICON,
                 width as i32,

src/platform_impl/windows/util.rs

@@ -12,9 +12,12 @@ use std::{
 use windows_sys::{
     core::{HRESULT, PCWSTR},
     Win32::{
-        Foundation::{BOOL, HWND, RECT},
+        Foundation::{BOOL, HINSTANCE, HWND, RECT},
         Graphics::Gdi::{ClientToScreen, InvalidateRgn, HMONITOR},
-        System::LibraryLoader::{GetProcAddress, LoadLibraryA},
+        System::{
+            LibraryLoader::{GetProcAddress, LoadLibraryA},
+            SystemServices::IMAGE_DOS_HEADER,
+        },
         UI::{
             HiDpi::{DPI_AWARENESS_CONTEXT, MONITOR_DPI_TYPE, PROCESS_DPI_AWARENESS},
             Input::KeyboardAndMouse::GetActiveWindow,
@@ -205,6 +208,21 @@ pub fn is_focused(window: HWND) -> bool {
     window == unsafe { GetActiveWindow() }
 }
 
+pub fn get_instance_handle() -> HINSTANCE {
+    // Gets the instance handle by taking the address of the
+    // pseudo-variable created by the microsoft linker:
+    // https://devblogs.microsoft.com/oldnewthing/20041025-00/?p=37483
+
+    // This is preferred over GetModuleHandle(NULL) because it also works in DLLs:
+    // https://stackoverflow.com/questions/21718027/getmodulehandlenull-vs-hinstance
+
+    extern "C" {
+        static __ImageBase: IMAGE_DOS_HEADER;
+    }
+
+    unsafe { &__ImageBase as *const _ as _ }
+}
+
 impl CursorIcon {
     pub(crate) fn to_windows_cursor(self) -> PCWSTR {
         match self {

src/platform_impl/windows/window.rs

@@ -26,7 +26,6 @@ use windows_sys::Win32::{
         Com::{
             CoCreateInstance, CoInitializeEx, CoUninitialize, CLSCTX_ALL, COINIT_APARTMENTTHREADED,
         },
-        LibraryLoader::GetModuleHandleW,
         Ole::{OleInitialize, RegisterDragDrop},
     },
     UI::{
@@ -974,7 +973,7 @@ where
         CW_USEDEFAULT,
         parent.unwrap_or(0),
         pl_attribs.menu.unwrap_or(0),
-        GetModuleHandleW(ptr::null()),
+        util::get_instance_handle(),
         &mut initdata as *mut _ as *mut _,
     );
 
@@ -1013,7 +1012,7 @@ unsafe fn register_window_class<T: 'static>(
         lpfnWndProc: Some(super::event_loop::public_window_callback::<T>),
         cbClsExtra: 0,
         cbWndExtra: 0,
-        hInstance: GetModuleHandleW(ptr::null()),
+        hInstance: util::get_instance_handle(),
         hIcon: h_icon,
         hCursor: 0, // must be null in order for cursor state to work properly
         hbrBackground: 0,