Improve error handling.

11 files changed, 161 insertions, 223 deletions

diff --git a/c/data.cpp b/c/data.cpp
index a75111a..32e059f 100644
--- a/c/data.cpp
+++ b/c/data.cpp
@@ -118,7 +118,7 @@ void WaitFor(Window& window, void (*f)(unsigned char*))
 
 	static auto procThread = [](void (*f)(unsigned char*)) noexcept -> void
 	{
-		SET_TERMINATE;
+		std::set_terminate(OnTerminate);
 		while (!(sig & READY))
 			Sleep(100);
 		sig = 0;
@@ -152,7 +152,8 @@ void WaitFor(Window& window, void (*f)(unsigned char*))
 	s_window = &window;
 	std::thread(procThread, f).detach();
 	s_window->Status(L".", 1);
-	Prefer(iTimer = SetTimer(nullptr, iTimer, 500, procTimer));
+	if (!(iTimer = SetTimer(nullptr, iTimer, 500, procTimer)))
+		throw Err(WINDOWS, L"Timer could not be started: %s");
 }
 
 void FetchData(unsigned char* sig)
diff --git a/c/drag.cpp b/c/drag.cpp
index b92429a..1622653 100644
--- a/c/drag.cpp
+++ b/c/drag.cpp
@@ -24,7 +24,8 @@ bool Dragger::IsDown() const
 bool Dragger::HandleLButtonDown()
 {
 	POINT pt;
-	Require(GetRelativeCursorPos(parent.hWnd, &pt));
+	if (!GetRelativeCursorPos(parent.hWnd, &pt))
+		throw Err(WINDOWS, L"Mouse cursor position could not be retrieved: %s");
 	if (!InDragArea(pt.x, pt.y)) return false;
 
 	if (IsDouble(GetMessageTime(), pt)) {
@@ -39,7 +40,8 @@ bool Dragger::HandleLButtonDown()
 bool Dragger::HandleSetCursor()
 {
 	POINT pt;
-	Require(GetRelativeCursorPos(parent.hWnd, &pt));
+	if (!GetRelativeCursorPos(parent.hWnd, &pt))
+		throw Err(WINDOWS, L"Mouse cursor position could not be retrieved: %s");
 
 	extern HCURSOR g_hcSizeNs;
 	bool r = true;
@@ -60,7 +62,8 @@ bool Dragger::HandleSetCursor()
 bool DlvDragger::InDragArea(const int x, const int y) const
 {
 	RECT rrDlv;
-	Require(GetRelativeRect(parent.dlv.hWnd, &rrDlv));
+	if (!GetRelativeRect(parent.dlv.hWnd, &rrDlv))
+		throw Err(WINDOWS, L"Data list view rectangle could not be retrieved: %s");
 
 	const int pad = EBIsThemeActive()? Dpi(6): 0;
 	const int extra = EBIsThemeActive()? 0: Dpi(2);
@@ -72,7 +75,8 @@ bool DlvDragger::InDragArea(const int x, const int y) const
 void DlvDragger::Drag(const int, const int y) const
 {
 	RECT rrDlv;
-	Require(GetRelativeRect(parent.dlv.hWnd, &rrDlv));
+	if (!GetRelativeRect(parent.dlv.hWnd, &rrDlv))
+		throw Err(WINDOWS, L"Data list view rectangle could not be retrieved: %s");
 
 	if (y < Dpi(50) || y > rrDlv.bottom-Dpi(20)) return;
 
diff --git a/c/episodelistview.cpp b/c/episodelistview.cpp
index b683114..db67ca9 100644
--- a/c/episodelistview.cpp
+++ b/c/episodelistview.cpp
@@ -162,7 +162,8 @@ LRESULT EpisodeListView::HandleNotify(const LPARAM lParam)
 			const ElvDataA& e = parent.fvElv.At(nm->nmcd.lItemlParam-1);
 			if (!e.bWatched) {
 				extern HFONT g_hfBold;
-				Require(SelectObject(nm->nmcd.hdc, g_hfBold));
+				if (!SelectObject(nm->nmcd.hdc, g_hfBold))
+					throw Err(WINDOWS, L"Bold font could not be selected: %s");
 				return CDRF_NEWFONT;
 			}
 			break;
@@ -183,8 +184,9 @@ LRESULT EpisodeListView::HandleNotify(const LPARAM lParam)
 	case NM_RCLICK:
 	    {
 		const DWORD pos = GetMessagePos();
-		Require(TrackPopupMenu(parent.hMenuPopup, TPM_RIGHTBUTTON,
-		    LOWORD(pos), HIWORD(pos), 0, parent.hWnd, nullptr));
+		if (!TrackPopupMenu(parent.hMenuPopup, TPM_RIGHTBUTTON,
+		    LOWORD(pos), HIWORD(pos), 0, parent.hWnd, nullptr))
+			throw Err(WINDOWS, L"Context menu could not be opened: %s");
 		return 0;
 	    }
 
diff --git a/c/err.cpp b/c/err.cpp
index fd35ddd..77bf394 100644
--- a/c/err.cpp
+++ b/c/err.cpp
@@ -77,11 +77,14 @@ std::wstring What(std::exception_ptr ex)
 		std::rethrow_exception(ex);
 	} catch (const Err& e) {
 		return e.what;
-	} catch (const WideException& e) {
-		return e.What();
 	} catch (const std::exception& e) {
 		return WideFromNarrow(e.what());
 	} catch (...) {
 		return L"Unknown exception";
 	}
 }
+
+void OnTerminate()
+{
+	EBMessageBox(What(), L"Fatal Error", MB_ICONERROR);
+}
diff --git a/c/err.h b/c/err.h
index d4a9976..4c6e829 100644
--- a/c/err.h
+++ b/c/err.h
@@ -4,6 +4,8 @@
 #include <exception>
 #include <string>
 
+#include "win32.h"
+
 enum ErrType : unsigned char
 {
 	GENERIC,
@@ -22,4 +24,34 @@ struct Err
 /* Return a wide string describing exception. */
 std::wstring What(std::exception_ptr e = std::current_exception());
 
+/* Exit gracefully on uncaught exception. */
+void OnTerminate();
+
+/* Exception-catching version of F that warns on exception. */
+template <auto F>
+auto Except = (decltype(F))[](auto... xs)
+{
+	try {
+		return F(xs...);
+	} catch (...) {
+		EBMessageBox(What(), L"Error");
+		if constexpr (!std::is_same_v<decltype(F(xs...)), void>)
+			return decltype(F(xs...)){};
+	}
+};
+
+/* Exception-catching version of F that exits on exception. */
+template <auto F>
+auto Noexcept = (decltype(F))[](auto... xs)
+{
+	try {
+		return F(xs...);
+	} catch (...) {
+		EBMessageBox(What(), L"Fatal Error", MB_ICONERROR);
+		exit(1);
+		if constexpr (!std::is_same_v<decltype(F(xs...)), void>)
+			return decltype(F(xs...)){};
+	}
+};
+
 #endif
diff --git a/c/listview.cpp b/c/listview.cpp
index b638f7b..0615ed0 100644
--- a/c/listview.cpp
+++ b/c/listview.cpp
@@ -2,6 +2,7 @@
 #include <commctrl.h>
 
 #include "drag.h"
+#include "err.h"
 #include "listview.h"
 #include "win32.h"
 #include "window.h"
@@ -14,17 +15,19 @@ ListView::ListView(Window& parent, const HMENU hMenu, const DWORD dwStyle) : par
 {
 	extern HFONT g_hfNormal;
 
-	hWnd = Require(CreateWindowExW(
+	if (!(hWnd = CreateWindowExW(
 	    WS_EX_CLIENTEDGE,
 	    WC_LISTVIEW,
 	    L"",
 	    dwStyle|WS_CHILD|WS_VISIBLE|WS_VSCROLL|WS_TABSTOP|LVS_REPORT|LVS_SHOWSELALWAYS,
 	    0, 0, 0, 0,
-	    parent.hWnd, hMenu, GetModuleHandle(nullptr), this));
+	    parent.hWnd, hMenu, GetModuleHandle(nullptr), this)))
+		throw Err(WINDOWS, L"List view could not be created: %s");
 	m_proc0 = reinterpret_cast<WNDPROC>(SetWindowLongPtr(
-	    hWnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(::WndProc)));
+	    hWnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(Except<::WndProc>)));
 
-	Require(SetPropW(hWnd, L"this", reinterpret_cast<HANDLE>(this)));
+	if (!SetPropW(hWnd, L"this", reinterpret_cast<HANDLE>(this)))
+		throw Err(WINDOWS, L"List view property could not be set: %s");
 	ListView_SetExtendedListViewStyle(hWnd, LVS_EX_FULLROWSELECT|LVS_EX_DOUBLEBUFFER);
 	SendMessageW(hWnd, WM_SETFONT, reinterpret_cast<WPARAM>(g_hfNormal), MAKELPARAM(FALSE, 0));
 }
diff --git a/c/main.cpp b/c/main.cpp
index f9d4a42..236b6d3 100644
--- a/c/main.cpp
+++ b/c/main.cpp
@@ -2,6 +2,7 @@
 #include <stdexcept>
 #include <windows.h>
 #include <commctrl.h>
+#include <shlobj.h>
 #include <libxml/xmlversion.h>
 
 #include "datalistview.h"
@@ -40,8 +41,8 @@ BOOL (__stdcall *IsThemeActive)();
 HRESULT (__stdcall *SetWindowTheme)(HWND, const wchar_t*, const wchar_t*);
 
 /* Initialize important global state on parent window creation. */
-static void InitializeMainWindow(HWND) noexcept;
-/* Process parent window commands. */
+static void InitializeMainWindow(HWND);
+/* Process main window commands. */
 static LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
 /* Handle messages to Help > About dialog. */
 static INT_PTR CALLBACK AboutDlgProc(HWND, UINT, WPARAM, LPARAM);
@@ -54,8 +55,7 @@ int WINAPI WinMain(
 	_In_ char* const,
 	_In_ const int nCmdShow)
 {
-	/* Exit gracefully on uncaught exception. */
-	SET_TERMINATE;
+	std::set_terminate(OnTerminate);
 
 	setbuf(stdout, nullptr);
 	LIBXML_TEST_VERSION;
@@ -63,12 +63,16 @@ int WINAPI WinMain(
 	INITCOMMONCONTROLSEX icc;
 	icc.dwSize = sizeof(icc);
 	icc.dwICC = ICC_WIN95_CLASSES;
-	Require(InitCommonControlsEx(&icc));
+	if (!InitCommonControlsEx(&icc))
+		throw Err(WINDOWS, L"Common controls could not be initialized: %s");
+
+	if (CoInitializeEx(nullptr, COINIT_APARTMENTTHREADED) != S_OK)
+		throw Err(GENERIC, L"COM library could not be initialized");
 
 	WNDCLASSEX wc;
 	memset(&wc, 0, sizeof(WNDCLASSEX));
 	wc.cbSize	 = sizeof(WNDCLASSEX);
-	wc.lpfnWndProc	 = WndProc;
+	wc.lpfnWndProc	 = Except<WndProc>;
 	wc.hInstance	 = hInstance;
 	wc.hIcon	 = LoadIconW(nullptr, IDI_APPLICATION);
 	wc.hCursor	 = g_hcArrow;
@@ -76,27 +80,31 @@ int WINAPI WinMain(
 	wc.lpszMenuName	 = MAKEINTRESOURCEW(IDR_MENU);
 	wc.lpszClassName = L"Episode Browser";
 	wc.hIconSm	 = LoadIconW(nullptr, IDI_APPLICATION);
-	Require(RegisterClassExW(&wc));
+	if (!RegisterClassExW(&wc))
+		throw Err(WINDOWS, L"Window class could not be registered: %s");
 
 	/* InitializeMainWindow is called before the first message is
 	 * sent to WndProc. This is important, as it initializes
 	 * global state on which WndProc relies. */
-	WithNextWindow(InitializeMainWindow);
-	const HWND hWnd = Require(CreateWindowExW(
+	WithNextWindow(Noexcept<InitializeMainWindow>);
+	HWND hWnd;
+	if (!(hWnd = CreateWindowExW(
 	    0,
 	    L"Episode Browser",
 	    L"Episode Browser",
 	    WS_OVERLAPPEDWINDOW|WS_CLIPCHILDREN,
 	    XMAIN, YMAIN, 0, 0,
-	    nullptr, nullptr, hInstance, nullptr));
+	    nullptr, nullptr, hInstance, nullptr)))
+		throw Err(WINDOWS, L"Main window could not be created: %s");
 
-	g_window->hWndStatus = Require(CreateWindowExW(
+	if (!(g_window->hWndStatus = CreateWindowExW(
 	    0,
 	    STATUSCLASSNAME,
 	    nullptr,
 	    WS_CHILD|WS_VISIBLE|SBARS_SIZEGRIP,
 	    0, 0, 0, 0,
-	    hWnd, reinterpret_cast<HMENU>(IDR_STATUS), hInstance, nullptr));
+	    hWnd, reinterpret_cast<HMENU>(IDR_STATUS), hInstance, nullptr)))
+		throw Err(WINDOWS, L"Status bar could not be created: %s");
 
 	ShowWindow(hWnd, nCmdShow);
 
@@ -119,7 +127,7 @@ int WINAPI WinMain(
 	return 0;
 }
 
-static void InitializeMainWindow_(const HWND hWnd)
+static void InitializeMainWindow(const HWND hWnd)
 {
 	/* This code is run ONCE, at the creation of the top-level
 	 * window -- before WndProc! This is important, as it
@@ -139,17 +147,22 @@ static void InitializeMainWindow_(const HWND hWnd)
 		m.cbSize -= 4;
 #endif
 
-		Require(SystemParametersInfoW(SPI_GETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICSW), &m, 0));
-		g_hfNormal = Require(CreateFontIndirectW(&m.lfMessageFont));
+		if (!SystemParametersInfoW(SPI_GETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICSW), &m, 0))
+			throw Err(WINDOWS, L"Non-client metrics could not be queried: %s");
+		if (!(g_hfNormal = CreateFontIndirectW(&m.lfMessageFont)))
+			throw Err(WINDOWS, L"System message font could not be loaded: %s");
 	} else
-		g_hfNormal = static_cast<HFONT>(Require(GetStockObject(DEFAULT_GUI_FONT)));
+		if (!(g_hfNormal = static_cast<HFONT>(GetStockObject(DEFAULT_GUI_FONT))))
+			    throw Err(WINDOWS, L"System GUI font could not be loaded: %s");
 
 	/* Load bold font. */
 	{
 		LOGFONTW lf;
-		Require(GetObjectW(g_hfNormal, sizeof(LOGFONTW), &lf));
+		if (!GetObjectW(g_hfNormal, sizeof(LOGFONTW), &lf))
+			throw Err(WINDOWS, L"Logical system font could not be loaded: %s");
 		lf.lfWeight = FW_BOLD;
-		g_hfBold = Require(CreateFontIndirectW(&lf));
+		if (!(g_hfBold = CreateFontIndirectW(&lf)))
+			throw Err(WINDOWS, L"Bold font could not be loaded: %s");
 	}
 
 	/* Load theme functions, if available. */
@@ -161,36 +174,21 @@ static void InitializeMainWindow_(const HWND hWnd)
 	g_window = new Window(hWnd);
 }
 
-void InitializeMainWindow(const HWND hWnd) noexcept
-{
-	try {
-		InitializeMainWindow_(hWnd);
-	} catch (...) {
-		EBMessageBox(What(), L"Initialization Error", MB_ICONERROR);
-		exit(1);
-	}
-}
-
 LRESULT CALLBACK WndProc(const HWND hWnd, const UINT uMsg, const WPARAM wParam, const LPARAM lParam)
 {
-	try {
-		return g_window->WndProc(hWnd, uMsg, wParam, lParam);
-	} catch (...) {
-		EBMessageBox(What(), L"Error");
-	}
-	return DefWindowProc(hWnd, uMsg, wParam, lParam);
+	return g_window->WndProc(hWnd, uMsg, wParam, lParam);
 }
 
 INT_PTR CALLBACK AboutDlgProc(const HWND hWnd, const UINT uMsg, const WPARAM wParam, const LPARAM)
 {
 	switch (uMsg) {
 	case WM_CLOSE:
-		EndDialog(hWnd, IDOK);
+		EndDialog(hWnd, IDCANCEL);
 		return TRUE;
 
 	case WM_COMMAND:
-		if (LOWORD(wParam) == IDOK)
-			EndDialog(hWnd, IDOK);
+		if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
+			EndDialog(hWnd, LOWORD(wParam));
 		return TRUE;
 
 	default:
@@ -200,19 +198,33 @@ INT_PTR CALLBACK AboutDlgProc(const HWND hWnd, const UINT uMsg, const WPARAM wPa
 
 INT_PTR CALLBACK PreferencesDlgProc(const HWND hWnd, const UINT uMsg, const WPARAM wParam, const LPARAM)
 {
-	switch (uMsg) {
-	case WM_CLOSE:
-		EndDialog(hWnd, IDOK);
+	if (uMsg == WM_CLOSE) {
+		EndDialog(hWnd, IDCANCEL);
 		return TRUE;
-
-	case WM_COMMAND:
-		if (LOWORD(wParam) == IDOK)
-			EndDialog(hWnd, IDOK);
+	} else if (uMsg == WM_COMMAND) {
+		switch (LOWORD(wParam)) {
+		case IDOK:
+		case IDCANCEL:
+			EndDialog(hWnd, LOWORD(wParam));
+			return TRUE;
+		case IDC_BROWSE:
+		    {
+			wchar_t path[MAX_PATH];
+			BROWSEINFOW bi = {hWnd, nullptr, path,
+					  L"Episode Browser will look for local episode files in the"
+					  L" chosen directory and its subdirectories.",
+					  BIF_EDITBOX|BIF_NEWDIALOGSTYLE|BIF_NONEWFOLDERBUTTON};
+			if (auto pidl = SHBrowseForFolderW(&bi)) {
+				if (!SHGetPathFromIDListW(pidl, path))
+					throw Err(GENERIC, L"Invalid path selected.");
+				EBMessageBox(path, L"You Chose");
+			}
+			return TRUE;
+		    }
+		}
 		return TRUE;
-
-	default:
+	} else
 		return FALSE;
-	}
 }
 
 LRESULT CALLBACK Window::WndProc(const HWND hWnd, const UINT uMsg, const WPARAM wParam, const LPARAM lParam)
@@ -265,11 +277,12 @@ LRESULT CALLBACK Window::WndProc(const HWND hWnd, const UINT uMsg, const WPARAM
 		/* Get new window position/size. */
 		{
 			const RECT* const r = reinterpret_cast<RECT*>(lParam);
-			Prefer(SetWindowPos(hWnd, nullptr,
+			if (!SetWindowPos(hWnd, nullptr,
 			    r->left, r->top,
 			    r->right-r->left,
 			    r->bottom-r->top,
-			    SWP_NOZORDER|SWP_NOACTIVATE));
+			    SWP_NOZORDER|SWP_NOACTIVATE))
+				throw Err(WINDOWS, L"");
 			UpdateLayout(r->right-r->left, r->bottom-r->top);
 		}
 		return 0;
@@ -395,7 +408,7 @@ void Window::HandleMainMenu(const HWND hWnd, const WORD command)
 		    GetModuleHandle(nullptr),
 		    MAKEINTRESOURCE(IDD_PREFERENCES),
 		    hWnd,
-		    PreferencesDlgProc);
+		    Except<PreferencesDlgProc>);
 		break;
 
 	case IDM_FILE_FETCH_DATA:
@@ -417,7 +430,7 @@ void Window::HandleMainMenu(const HWND hWnd, const WORD command)
 		    GetModuleHandle(nullptr),
 		    MAKEINTRESOURCE(IDD_ABOUT),
 		    hWnd,
-		    AboutDlgProc);
+		    Except<AboutDlgProc>);
 		break;
 
 	case IDM_VIEW_WATCHED:
@@ -465,16 +478,20 @@ void Window::UpdateLayout(int w, int h)
 
 	RECT rc, rrStatus;
 	if (w && h) rc = {0, 0, w, h};
-	else Require(GetClientRect(hWnd, &rc));
-	Require(GetRelativeRect(hWndStatus, &rrStatus));
+	else if (!GetClientRect(hWnd, &rc))
+		throw Err(WINDOWS, L"Window rectangle could not be retrieved: %s");
+	if (!GetRelativeRect(hWndStatus, &rrStatus))
+		throw Err(WINDOWS, L"Status bar rectangle could not be retrieved: %s");
 
 	SendMessageW(hWnd, WM_SETREDRAW, FALSE, 0);
 
 	/* Resize list views. */
 	const long pad = EBIsThemeActive()? Dpi(6): 0; /* Add padding in modern themes. */
 	const long cyDlv = rrStatus.top-dlv.Height()-pad;
-	Require(SetWindowRect(dlv.hWnd, pad, cyDlv, rc.right-pad, rrStatus.top-pad));
-	Require(SetWindowRect(elv.hWnd, pad, pad, rc.right-pad, cyDlv-pad));
+	if (!SetWindowRect(dlv.hWnd, pad, cyDlv, rc.right-pad, rrStatus.top-pad))
+		throw Err(WINDOWS, L"Data list view rectangle could not be updated: %s");
+	if (!SetWindowRect(elv.hWnd, pad, pad, rc.right-pad, cyDlv-pad))
+		throw Err(WINDOWS, L"Episode list view rectangle could not be updated: %s");
 	dlv.ResizeColumns(rc.right-pad-pad);
 	elv.ResizeColumns(rc.right-pad-pad);
 
diff --git a/c/util.h b/c/util.h
index 668d040..561e232 100644
--- a/c/util.h
+++ b/c/util.h
@@ -13,13 +13,6 @@
 #define CONCAT(a, b) CONCAT_IMPL(a, b)
 #define _ CONCAT(unused_, __LINE__)
 
-#define SET_TERMINATE							\
-	std::set_terminate([]() noexcept				\
-	{								\
-		EBMessageBox(What(), L"Fatal Error", MB_ICONERROR);	\
-		_Exit(1);						\
-	})
-
 /* Scope guard. */
 template <typename F>
 struct Finally
@@ -98,12 +91,12 @@ struct UniqueOk
 	T v;
 	UniqueOk(Unique<T, F>&& u) : v(std::move(u.v))
 	{
-		assert(u.ok, "UniqueOk may not be constructed from non-ok Unique");
+		assert(u.ok);
 		u.ok = false;
 	}
 	UniqueOk& operator =(Unique<T, F>&& u)
 	{
-		assert(u.ok, "UniqueOk may not be constructed from non-ok Unique");
+		assert(u.ok);
 		F(v);
 		v = std::move(u.v);
 		u.ok = false;
diff --git a/c/win32.cpp b/c/win32.cpp
index fa5116d..73316e8 100644
--- a/c/win32.cpp
+++ b/c/win32.cpp
@@ -32,17 +32,21 @@ void WithNextWindow(void (*proc)(HWND))
 
 	static thread_local void (*procNext)(HWND);
 	static thread_local HHOOK hHook;
-	procNext = proc;
-	hHook = Require(SetWindowsHookExW(WH_CBT, [](const int nCode,
+	static const auto procCBT = [](const int nCode,
 	    const WPARAM wParam, const LPARAM lParam) -> LRESULT CALLBACK
 	{
 		if (nCode == HCBT_CREATEWND) {
-			Require(UnhookWindowsHookEx(hHook));
+			if (!UnhookWindowsHookEx(hHook))
+				throw Err(WINDOWS, L"Window hook could not be removed: %s");
 			procNext(reinterpret_cast<HWND>(wParam));
 			return 0;
 		} else
 			return CallNextHookEx(0, nCode, wParam, lParam);
-	}, nullptr, GetCurrentThreadId()));
+	};
+
+	procNext = proc;
+	if (!(hHook = SetWindowsHookExW(WH_CBT, procCBT, nullptr, GetCurrentThreadId())))
+		throw Err(WINDOWS, L"Window hook could not be set: %s");
 }
 
 /* Display next created window in the center of given window. */
@@ -59,18 +63,16 @@ static void CenterNextWindow(HWND hWnd)
 	static thread_local HWND hWndParent;
 	static thread_local HWND hWndNext;
 	static thread_local HHOOK hHook;
-
-	hWndParent = hWnd;
-	hWndNext = nullptr;
-	hHook = Require(SetWindowsHookExW(WH_CBT, [](const int nCode,
-	    const WPARAM wParam, const LPARAM lParam) noexcept -> LRESULT CALLBACK
+	static const auto procCBT = [](const int nCode,
+	    const WPARAM wParam, const LPARAM lParam) -> LRESULT CALLBACK
 	{
 		if (!hWndNext && nCode == HCBT_CREATEWND) {
 			hWndNext = reinterpret_cast<HWND>(wParam);
 			return 0;
 		} else if (nCode == HCBT_ACTIVATE
 		    && reinterpret_cast<HWND>(wParam) == hWndNext) {
-			Require(UnhookWindowsHookEx(hHook));
+			if (!UnhookWindowsHookEx(hHook))
+				throw Err(WINDOWS, L"Window hook could not be removed: %s");
 
 			long lStyle = GetWindowLongW(hWndNext, GWL_STYLE);
 			if (!(lStyle & WS_POPUP)) return 0;
@@ -87,7 +89,12 @@ static void CenterNextWindow(HWND hWnd)
 			return 0;
 		} else
 			return CallNextHookEx(0, nCode, wParam, lParam);
-	}, nullptr, GetCurrentThreadId()));
+	};
+
+	hWndParent = hWnd;
+	hWndNext = nullptr;
+	if (!(hHook = SetWindowsHookExW(WH_CBT, procCBT, nullptr, GetCurrentThreadId())))
+		throw Err(WINDOWS, L"Window hook could not be set: %s");
 }
 
 int EBMessageBox(const std::wstring_view text, const std::wstring_view caption, const UINT uType)
@@ -112,84 +119,6 @@ int GetRelativeCursorPos(const HWND hWnd, POINT* const pt) noexcept
 	return 1;
 }
 
-Win32Error::Win32Error(const DWORD code, const HMODULE hModule) noexcept
-	: code(code), hModule(hModule) {}
-
-Win32Error::~Win32Error()
-{
-	if (m_szMsg)
-		HeapFree(GetProcessHeap(), 0, m_szMsg);
-	if (m_wszMsg)
-		HeapFree(GetProcessHeap(), 0, m_wszMsg);
-}
-
-const char* Win32Error::what() const noexcept
-{
-	if (!m_szMsg)
-		FormatMessageA(
-		    FORMAT_MESSAGE_ALLOCATE_BUFFER
-		    |FORMAT_MESSAGE_FROM_SYSTEM
-		    |FORMAT_MESSAGE_FROM_HMODULE
-		    |FORMAT_MESSAGE_IGNORE_INSERTS,
-		    hModule,
-		    code,
-		    MAKELANGID(LANG_ENGLISH, SUBLANG_ENGLISH_US),
-		    (char*)&m_szMsg,
-		    0, nullptr);
-	return m_szMsg? m_szMsg: "An unknown error occurred";
-}
-
-const wchar_t* Win32Error::What() const noexcept
-{
-	if (!m_wszMsg)
-		FormatMessageW(
-		    FORMAT_MESSAGE_ALLOCATE_BUFFER
-		    |FORMAT_MESSAGE_FROM_SYSTEM
-		    |FORMAT_MESSAGE_FROM_HMODULE
-		    |FORMAT_MESSAGE_IGNORE_INSERTS,
-		    hModule,
-		    code,
-		    MAKELANGID(LANG_ENGLISH, SUBLANG_ENGLISH_US),
-		    (wchar_t*)&m_wszMsg,
-		    0, nullptr);
-	return m_wszMsg? m_wszMsg: L"An unknown error occurred";
-}
-
-InternetError::InternetError(DWORD codeSystem)
-{
-	if (codeSystem != ERROR_INTERNET_EXTENDED_ERROR)
-		throw Win32Error(codeSystem, GetModuleHandle(L"wininet.dll"));
-
-	DWORD len, cch;
-	InternetGetLastResponseInfo(&code, nullptr, &len);
-
-	cch = len+1;
-	m_szMsg = new char[cch];
-	if (!InternetGetLastResponseInfoA(&code, m_szMsg, &cch))
-		throw Win32Error();
-
-	cch = len+1;
-	m_wszMsg = new wchar_t[cch];
-	if (!InternetGetLastResponseInfoW(&code, m_wszMsg, &len))
-		throw Win32Error();
-}
-
-InternetError::~InternetError()
-{
-	delete m_szMsg;
-	delete m_wszMsg;
-}
-
-const char* InternetError::what() const noexcept
-{
-	return m_szMsg;
-}
-
-const wchar_t* InternetError::What() const noexcept
-{
-	return m_wszMsg;
-}
-
 std::optional<Library> Library::Maybe(const wchar_t* const lib) noexcept
 {
 	HMODULE hModule = LoadLibraryW(lib);
diff --git a/c/win32.h b/c/win32.h
index c18e70f..0473f6c 100644
--- a/c/win32.h
+++ b/c/win32.h
@@ -6,8 +6,6 @@
 #include <windows.h>
 #include <commctrl.h>
 
-#include "err.h"
-
 /* Convert narrow to wide string. */
 std::wstring WideFromNarrow(const std::string_view src, const int cp = CP_UTF8);
 
@@ -23,39 +21,6 @@ int GetRelativeCursorPos(HWND hWnd, POINT* pt) noexcept;
 /* Cached values from GetSystemMetrics. */
 template <int I> auto Metric = GetSystemMetrics(I);
 
-struct WideException : public std::exception
-{
-	virtual const char* what() const noexcept = 0;
-	virtual const wchar_t* What() const noexcept = 0;
-};
-
-/* Exception for Windows API errors. */
-struct Win32Error : public WideException
-{
-	Win32Error(DWORD code = GetLastError(), HMODULE hModule = nullptr) noexcept;
-	~Win32Error() noexcept;
-	const char* what() const noexcept override;
-	const wchar_t* What() const noexcept override;
-	DWORD code;
-private:
-	HMODULE hModule;
-	char* m_szMsg = nullptr;
-	wchar_t* m_wszMsg = nullptr;
-};
-
-/* Exception for extended Wininet errors. */
-struct InternetError : public WideException
-{
-	InternetError(DWORD codeSystem = GetLastError());
-	~InternetError() noexcept;
-	const char* what() const noexcept override;
-	const wchar_t* What() const noexcept override;
-	DWORD code;
-private:
-	char* m_szMsg = nullptr;
-	wchar_t* m_wszMsg = nullptr;
-};
-
 /* Wrapper for loading and freeing dynamically linked libraries. */
 struct Library
 {
@@ -78,25 +43,6 @@ T* Library::GetProcAddress(const char* const szProc) noexcept
 	return (T*)(void*)::GetProcAddress(m_hModule, szProc);
 }
 
-/* Check result of Windows API call, throwing error on null. */
-template <typename T>
-inline T Require(const T x)
-{
-	if (!x) Err(WINDOWS, L"System error: %s");
-	return x;
-}
-
-/* Check result of Windows API call, showing a warning on null. */
-template <typename T>
-inline T Prefer(const T x)
-{
-	if (!x) {
-		EBMessageBox(Win32Error().What(), L"System Error", MB_ICONWARNING);
-		return (T)0;
-	}
-	return x;
-}
-
 /* Return integer scaled for current DPI. */
 inline int Dpi(const int i)
 {
diff --git a/c/window.h b/c/window.h
index daf7202..9d247ec 100644
--- a/c/window.h
+++ b/c/window.h
@@ -15,7 +15,15 @@ struct Window
 	HWND hWnd;
 	HWND hWndFocus = nullptr;
 	HWND hWndStatus = nullptr;
-	HMENU hMenuPopup = Require(GetSubMenu(Require(LoadMenuW(nullptr, MAKEINTRESOURCE(IDR_POPUPMENU))), 0));
+	const HMENU hMenuPopup = []()
+	{
+		HMENU hm;
+		if (!(hm = LoadMenuW(nullptr, MAKEINTRESOURCE(IDR_POPUPMENU))))
+			throw Err(WINDOWS, L"Context menu could not be loaded: %s");
+		if (!GetSubMenu(hm, 0))
+			throw Err(WINDOWS, L"Submenu could not be retrieved: %s");
+		return hm;
+	}();
 
 	/* File views. */
 	FileView<CfgA> fvCfg = FileView<CfgA>::Initialized(L"cfg.dat", 1);