sys/windows: add MessageBox procedures

core/sys/windows/types.odin

@@ -312,6 +312,65 @@ CREATESTRUCTW:: struct {
 	dwExStyle:      DWORD,
 }
 
+// MessageBox() Flags
+MB_OK                :: 0x00000000
+MB_OKCANCEL          :: 0x00000001
+MB_ABORTRETRYIGNORE  :: 0x00000002
+MB_YESNOCANCEL       :: 0x00000003
+MB_YESNO             :: 0x00000004
+MB_RETRYCANCEL       :: 0x00000005
+MB_CANCELTRYCONTINUE :: 0x00000006
+
+MB_ICONHAND        :: 0x00000010
+MB_ICONQUESTION    :: 0x00000020
+MB_ICONEXCLAMATION :: 0x00000030
+MB_ICONASTERISK    :: 0x00000040
+MB_USERICON        :: 0x00000080
+MB_ICONWARNING     :: MB_ICONEXCLAMATION
+MB_ICONERROR       :: MB_ICONHAND
+MB_ICONINFORMATION :: MB_ICONASTERISK
+MB_ICONSTOP        :: MB_ICONHAND
+
+MB_DEFBUTTON1 :: 0x00000000
+MB_DEFBUTTON2 :: 0x00000100
+MB_DEFBUTTON3 :: 0x00000200
+MB_DEFBUTTON4 :: 0x00000300
+
+MB_APPLMODAL   :: 0x00000000
+MB_SYSTEMMODAL :: 0x00001000
+MB_TASKMODAL   :: 0x00002000
+MB_HELP        :: 0x00004000 // Help Button
+
+MB_NOFOCUS              :: 0x00008000
+MB_SETFOREGROUND        :: 0x00010000
+MB_DEFAULT_DESKTOP_ONLY :: 0x00020000
+MB_TOPMOST              :: 0x00040000
+MB_RIGHT                :: 0x00080000
+MB_RTLREADING           :: 0x00100000
+
+MB_SERVICE_NOTIFICATION      :: 0x00200000
+MB_SERVICE_NOTIFICATION_NT3X :: 0x00040000
+
+MB_TYPEMASK :: 0x0000000F
+MB_ICONMASK :: 0x000000F0
+MB_DEFMASK  :: 0x00000F00
+MB_MODEMASK :: 0x00003000
+MB_MISCMASK :: 0x0000C000
+
+// Dialog Box Command IDs
+IDOK       :: 1
+IDCANCEL   :: 2
+IDABORT    :: 3
+IDRETRY    :: 4
+IDIGNORE   :: 5
+IDYES      :: 6
+IDNO       :: 7
+IDCLOSE    :: 8
+IDHELP     :: 9
+IDTRYAGAIN :: 10
+IDCONTINUE :: 11
+IDTIMEOUT  :: 32000
+
 CS_VREDRAW         : UINT : 0x0001
 CS_HREDRAW         : UINT : 0x0002
 CS_DBLCLKS         : UINT : 0x0008

core/sys/windows/user32.odin

@@ -120,6 +120,11 @@ foreign user32 {
 
 	GetKeyState :: proc(nVirtKey: c_int) -> SHORT ---
 	GetAsyncKeyState :: proc(vKey: c_int) -> SHORT ---
+
+	MessageBoxA :: proc(hWnd: HWND, lpText: LPCSTR, lpCaption: LPCSTR, uType: UINT) -> c_int ---
+	MessageBoxW :: proc(hWnd: HWND, lpText: LPCWSTR, lpCaption: LPCWSTR, uType: UINT) -> c_int ---
+	MessageBoxExA :: proc(hWnd: HWND, lpText: LPCSTR, lpCaption: LPCSTR, uType: UINT, wLanguageId: WORD) -> c_int ---
+	MessageBoxExW :: proc(hWnd: HWND, lpText: LPCWSTR, lpCaption: LPCWSTR, uType: UINT, wLanguageId: WORD) -> c_int ---
 }
 
 CreateWindowA :: #force_inline proc "stdcall" (