From 4be04e28bf0c382f53786f57954a05b28825f403 Mon Sep 17 00:00:00 2001
From: mlangkabel <malte.langkabel@gmail.com>
Date: Mon, 16 Jul 2018 12:54:17 +0200
Subject: [PATCH] ui: improved windows error handling for loading external dlls
 to display an error text

---
 src/lib/utility/utilityLibrary.h | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/src/lib/utility/utilityLibrary.h b/src/lib/utility/utilityLibrary.h
index 35b59079..ed1e1614 100644
--- a/src/lib/utility/utilityLibrary.h
+++ b/src/lib/utility/utilityLibrary.h
@@ -14,6 +14,7 @@
 #endif
 
 #include "utility/file/FilePath.h"
+#include "utility/utilityString.h"
 
 namespace utility
 {
@@ -26,9 +27,34 @@ namespace utility
 #ifdef _WIN32
 		const std::string libraryPathString = libraryPath.getBackslashedString();
 		HINSTANCE handle = LoadLibrary(libraryPathString.c_str());
-		if (handle == NULL)
+		if (handle == nullptr)
 		{
-			errorString = "Could not load library \"" + libraryPathString + "\"";
+			DWORD errorCode = GetLastError();
+			std::string errorReasonString;
+
+			LPSTR messageBuffer = nullptr;
+			const size_t size = FormatMessageA(
+				FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+				nullptr,
+				errorCode,
+				MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+				(LPSTR)&messageBuffer,
+				0,
+				nullptr
+			);
+			if (size > 0)
+			{
+				std::string message(messageBuffer, size);
+				errorReasonString = "error \"" + utility::trim(message) + "\" (code " + std::to_string(errorCode) + ").";
+			}
+			else
+			{
+				errorReasonString = "error code " + std::to_string(errorCode) + ".";
+			}
+
+			LocalFree(messageBuffer);
+
+			errorString = "Could not load library \"" + libraryPathString + "\" because of " + errorReasonString;
 			return std::function<Ret(Args...)>();
 		}