Draw_Rectangle_DllCall.ahk

; Draw rectangle via DllCall() (Not work with fullscreen applications!)
#NoEnv
SetBatchLines, -1
CoordMode, Mouse, Screen

OnMessage(0x14, "WM_ERASEBKGND")
Gui, -Caption +ToolWindow
Gui, +LastFound
WinSet, TransColor, Black
; Create the pen here so we don't need to create/delete it every time.
RedPen := DllCall("CreatePen", "int", PS_SOLID:=0, "int", BORDER_WIDTH:=1, "uint", 0xff)
return

WM_ERASEBKGND(wParam, lParam)
{
	global x1, y1, x2, y2, RedPen
	Critical 50
	if A_Gui = 1
	{
		; Retrieve stock brush.
		blackBrush := DllCall("GetStockObject", "int", BLACK_BRUSH:=0x4)
		; Select pen and brush.
		oldPen := DllCall("SelectObject", "uint", wParam, "uint", RedPen)
		oldBrush := DllCall("SelectObject", "uint", wParam, "uint", blackBrush)
		; Draw rectangle.
		DllCall("Rectangle", "uint", wParam, "int", 0, "int", 0, "int", x2-x1, "int", y2-y1)
		; Reselect original pen and brush (recommended by MS).
		DllCall("SelectObject", "uint", wParam, "uint", oldPen)
		DllCall("SelectObject", "uint", wParam, "uint", oldBrush)
		return 1
	}
}

+LButton::
MouseGetPos, xorigin, yorigin
SetTimer, rectangle, 10
return

rectangle:
MouseGetPos, x2, y2

; Has the mouse moved?
if (x1 y1) = (x2 y2)
	return

; Allow dragging to the left of the click point.
if (x2 < xorigin) {
	x1 := x2
	x2 := xorigin
} else
	x1 := xorigin

; Allow dragging above the click point.
if (y2 < yorigin) {
	y1 := y2
	y2 := yorigin
} else
	y1 := yorigin

Gui, Show, % "NA X" x1 " Y" y1 " W" x2-x1 " H" y2-y1
Gui, +LastFound
DllCall("RedrawWindow", "uint", WinExist(), "uint", 0, "uint", 0, "uint", 5)
return

+LButton Up::
SetTimer, rectangle, Off
Gui, Cancel
return

!x::ExitApp
!z::Reload