1 files changed, 147 insertions, 0 deletions
diff --git a/c/win32.h b/c/win32.h
new file mode 100644
index 0000000..c4e57b7
--- /dev/null
+++ b/c/win32.h
@@ -0,0 +1,147 @@
+#ifndef WIN32_H
+#define WIN32_H
+
+#include <optional>
+#include <string_view>
+#include <windows.h>
+#include <commctrl.h>
+
+/* Convert narrow to wide string. */
+std::wstring WideFromNarrow(const std::string_view src, const int cp = CP_UTF8);
+
+/* Run given procedure at creation of next window. */
+void WithNextWindow(void (*proc)(HWND));
+
+/* Display message box centered in main window. */
+int EBMessageBox(std::wstring_view text, std::wstring_view data, UINT uType);
+
+/* Show message box for current exception. */
+void ShowException(
+    const wchar_t* fmt = L"An error occurred: %s",
+    const wchar_t* title = L"Error",
+    UINT uType = MB_ICONWARNING) noexcept;
+
+/* Retrieve mouse position relative to given window's client area. */
+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
+{
+	/* Non-throwing named constructor. */
+	static std::optional<Library> Maybe(const wchar_t* lib) noexcept;
+
+	Library(const wchar_t* lib);
+	~Library() noexcept;
+
+	template <class T> T* GetProcAddress(const char* szProc) noexcept;
+private:
+	/* Non-throwing constructor used by Maybe. */
+	Library(HMODULE hModule) noexcept;
+	HMODULE m_hModule;
+};
+
+template <typename T>
+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) throw Win32Error();
+	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)
+{
+	extern int g_dpi;
+	return MulDiv(i, g_dpi, 96);
+}
+
+/* Retrieve given window's rectangle relative to parent's client area. */
+inline BOOL GetRelativeRect(const HWND hWnd, RECT* const rr)
+{
+	if (!GetClientRect(hWnd, rr)) return 0;
+	return MapWindowPoints(hWnd, GetParent(hWnd), reinterpret_cast<POINT*>(rr), 2);
+}
+
+inline BOOL SetWindowRect(const HWND hWnd,
+    const long left, const long top, const long right, const long bottom)
+{
+	return MoveWindow(hWnd,
+	    left, top,
+	    right-left, bottom-top,
+	    TRUE);
+}
+
+inline BOOL SetWindowRect(const HWND hWnd, const RECT r)
+{
+	return SetWindowRect(hWnd, r.left, r.top, r.right, r.bottom);
+}
+
+/* The following two functions call uxtheme.dll functions, if
+ * uxtheme.dll exists, and otherwise do nothing. */
+inline BOOL EBIsThemeActive()
+{
+	extern BOOL (__stdcall *IsThemeActive)();
+	return IsThemeActive? IsThemeActive(): 0;
+}
+
+inline HRESULT EBSetWindowTheme(const HWND hWnd, const wchar_t* const pszSubAppName,
+    const wchar_t* const pszSubIdList)
+{
+	extern HRESULT (__stdcall *SetWindowTheme)(HWND, const wchar_t*, const wchar_t*);
+	return SetWindowTheme? SetWindowTheme(hWnd, pszSubAppName, pszSubIdList): 0;
+}
+
+#endif