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 ;-------------------------------------------------------------------------------------------------------------------
 ; Hello, Windows!  in x86 ASM - (c) 2021 Dave's Garage - Use at your own risk, no warranty!
 ;-------------------------------------------------------------------------------------------------------------------
 
 ; Compiler directives and includes
 
 .386						; Full 80386 instruction set and mode
 .model flat, stdcall				; All 32-bit and later apps are flat. Used to include "tiny, etc"
 option casemap:none				; Preserve the case of system identifiers but not our own, more or less
 
 
 ; Include files - headers and libs that we need for calling the system dlls like user32, gdi32, kernel32, etc
 include \masm32\include\windows.inc		; Main windows header file (akin to Windows.h in C)
 include \masm32\include\user32.inc		; Windows, controls, etc
 include \masm32\include\kernel32.inc		; Handles, modules, paths, etc
 include \masm32\include\gdi32.inc		; Drawing into a device context (ie: painting)
 
 ; Libs - information needed to link ou binary to the system DLL callss
 
 includelib \masm32\lib\kernel32.lib		; Kernel32.dll
 includelib \masm32\lib\user32.lib		; User32.dll
 includelib \masm32\lib\gdi32.lib		; GDI32.dll
 
 ; Forward declarations - Our main entry point will call forward to WinMain, so we need to define it here
 
 WinMain proto :DWORD, :DWORD, :DWORD, :DWORD	; Forward decl for MainEntry
 
 ; Constants and Datra
 
 WindowWidth	equ 640				; How big we'd like our main window
 WindowHeight	equ 480
 
 .DATA
 
 ClassName    	db "MyWinClass", 0		; The name of our Window class
 AppName		db "Dave's Tiny App", 0		; The name of our main window
 
 .DATA?						; Uninitialized data - Basically just reserves address space
 
 hInstance	HINSTANCE ?			; Instance handle (like the process id) of our application
 CommandLine	LPSTR	  ?                     ; Pointer to the command line text we were launched with
 
 ;-------------------------------------------------------------------------------------------------------------------
 .CODE						; Here is where the program itself lives
 ;-------------------------------------------------------------------------------------------------------------------
 
 MainEntry proc
 
 	LOCAL	sui:STARTUPINFOA		; Reserve stack space so we can load and inspect the STARTUPINFO
 
 	push	NULL				; Get the instance handle of our app (NULL means ourselves)
 	call 	GetModuleHandle			; GetModuleHandle will return instance handle in EAX
 	mov	hInstance, eax			; Cache it in our global variable
 
 	call	GetCommandLineA			; Get the command line text ptr in EAX to pass on to main
 	mov	CommandLine, eax
 
 	; Call our WinMain and then exit the process with whatever comes back from it
 
 	; Please check this, I have only typed it, not tested it :-)
 
 	lea	eax, sui			; Get the STARTUPINFO for this process
 	push	eax
 	call	GetStartupInfoA			; Find out if wShowWindow should be used
 	test	sui.dwFlags, STARTF_USESHOWWINDOW
 	jz	@1
 	push	sui.wShowWindow			; If the show window flag bit was nonzero, we use wShowWindow
 	jmp	@2
 @1:
 	push	SW_SHOWDEFAULT			; Use the default
 @2:
 	push	CommandLine
 	push	NULL
 	push	hInstance
 	call	WinMain
 
 	push	eax
 	call	ExitProcess
 
 MainEntry endp
 
 ;
 ; WinMain - The traditional signature for the main entry point of a Windows programa
 ;
 
 WinMain proc hInst:HINSTANCE, hPrevInst:HINSTANCE, CmdLine:LPSTR, CmdShow:DWORD
 
 	LOCAL	wc:WNDCLASSEX			; Create these vars on the stack, hence LOCAL
 	LOCAL	msg:MSG
 	LOCAL	hwnd:HWND
 
 	mov	wc.cbSize, SIZEOF WNDCLASSEX		; Fill in the values in the members of our windowclass
 	mov	wc.style, CS_HREDRAW or CS_VREDRAW	; Redraw if resized in either dimension
 	mov	wc.lpfnWndProc, OFFSET WndProc		; Our callback function to handle window messages
 	mov	wc.cbClsExtra, 0			; No extra class data
 	mov	wc.cbWndExtra, 0			; No exttra window data
 	mov	eax, hInstance
 	mov	wc.hInstance, eax			; Our instance handle
 	mov	wc.hbrBackground, COLOR_3DSHADOW+1	; Default brush colors are color plus one
 	mov	wc.lpszMenuName, NULL			; No app menu
 	mov	wc.lpszClassName, OFFSET ClassName	; The window's class name
 
 	push	IDI_APPLICATION				; Use the default application icon
 	push	NULL
 	call 	LoadIcon
 	mov	wc.hIcon, eax
 	mov	wc.hIconSm, eax
 
 	push	IDC_ARROW				; Get the default "arrow" mouse cursor
 	push	NULL
 	call	LoadCursor
 	mov	wc.hCursor, eax
 
 	lea	eax, wc
 	push	eax
 	call	RegisterClassEx				; Register the window class
 
 	push	NULL					; Bonus data, but we have none, so null
 	push	hInstance				; Our app instance handle
 	push	NULL					; Menu handle
 	push	NULL					; Parent window (if we were a child window)
 	push	WindowHeight				; Our requested height
 	push	WindowWidth				; Our requested width
 	push	CW_USEDEFAULT				; Y
 	push	CW_USEDEFAULT				; X
 	push	WS_OVERLAPPEDWINDOW + WS_VISIBLE	; Window stytle (normal and visible)
 	push	OFFSET AppName				; The window title (our application name)
 	push	OFFSET ClassName			; The window class name of what we're creating
 	push	0					; Extended style bits, if any
 	call 	CreateWindowExA
 	cmp	eax, NULL
 	je	WinMainRet				; Fail and bail on NULL handle returned
 	mov	hwnd, eax				; Window handle is the result, returned in eax
 
 	push	eax					; Force a paint of our window
 	call	UpdateWindow
 
 MessageLoop:
 
 	push	0
 	push 	0
 	push	NULL
 	lea	eax, msg
 	push	eax
 	call	GetMessage				; Get a message from the application's message queue
 
 	cmp	eax, 0					; When GetMessage returns 0, it's time to exit
 	je	DoneMessages
 
 	lea	eax, msg				; Translate 'msg'
 	push	eax
 	call	TranslateMessage
 
 	lea	eax, msg				; Dispatch 'msg'
 	push	eax
 	call	DispatchMessage
 
 	jmp	MessageLoop
 
 DoneMessages:
 
 	mov	eax, msg.wParam				; Return wParam of last message processed
 
 WinMainRet:
 
 	ret
 
 WinMain endp
 
 ;
 ; WndProc - Our Main Window Procedure, handles painting and exiting
 ;
 
 WndProc proc hWnd:HWND, uMsg:UINT, wParam:WPARAM, lParam:LPARAM
 
 	LOCAL 	ps:PAINTSTRUCT				; Local stack variables
 	LOCAL	rect:RECT
 	LOCAL	hdc:HDC
 
 	cmp	uMsg, WM_DESTROY
 	jne	NotWMDestroy
 
 	push	0					; WM_DESTROY received, post our quit msg
 	call	PostQuitMessage				; Quit our application
 	xor	eax, eax				; Return 0 to indicate we handled it
 	ret
 
 NotWMDestroy:
 
 	cmp	uMsg, WM_PAINT
 	jne	NotWMPaint
 
 	lea	eax, ps					; WM_PAINT received
 	push	eax
 	push	hWnd
 	call	BeginPaint				; Go get a device context to paint into
 	mov	hdc, eax
 
 	push	TRANSPARENT
 	push	hdc
 	call	SetBkMode				; Make text have a transparent background
 
 	lea	eax, rect				; Figure out how big the client area is so that we
 	push	eax					;   can center our content over it
 	push	hWnd
 	call	GetClientRect
 
 	push	DT_SINGLELINE + DT_CENTER + DT_VCENTER
 	lea	eax, rect
 	push	eax
 	push	-1
 	push	OFFSET AppName
 	push	hdc
 	call	DrawText				; Draw text centered vertically and horizontally
 
 	lea	eax, ps
 	push	eax
 	push	hWnd
 	call	EndPaint				; Wrap up painting
 
 	xor	eax, eax				; Return 0 as no further processing needed
 	ret
 
 NotWMPaint:
 
 	push	lParam
 	push	wParam
 	push	uMsg
 	push	hWnd
 	call	DefWindowProc				; Forward message on to default processing and
 	ret						;   return whatever it does
 
 WndProc endp
 
 END MainEntry						; Specify entry point, else _WinMainCRTStartup is assumed