Defer most initialisation until Scintilla window is created.

Previously, more initialisation was performed inside DllMain but some actions
such as loading libraries are unsafe inside DllMain.
Avoid listbox UnregisterClass if no attempt to register which will occur if
no Scintilla windows were created.
std::call_once is used to ensure initialisation is performed at most once.

1 files changed, 5 insertions, 3 deletions

diff --git a/win32/PlatWin.cxx b/win32/PlatWin.cxx
index a7bc5626c..96f642824 100644
--- a/win32/PlatWin.cxx
+++ b/win32/PlatWin.cxx
@@ -3243,8 +3243,10 @@ bool ListBoxX_Register() noexcept {
 	return ::RegisterClassEx(&wndclassc) != 0;
 }
 
-bool ListBoxX_Unregister() noexcept {
-	return ::UnregisterClass(ListBoxX_ClassName, hinstPlatformRes) != 0;
+void ListBoxX_Unregister() noexcept {
+	if (hinstPlatformRes) {
+		::UnregisterClass(ListBoxX_ClassName, hinstPlatformRes);
+	}
 }
 
 }
@@ -3374,7 +3376,7 @@ void Platform::Assert(const char *c, const char *file, int line) {
 	}
 }
 
-void Platform_Initialise(void *hInstance) {
+void Platform_Initialise(void *hInstance) noexcept {
 	hinstPlatformRes = static_cast<HINSTANCE>(hInstance);
 	LoadDpiForWindow();
 	ListBoxX_Register();