AutoHotkey Community

#NoEnv
CoordMode, Mouse ; Required: change coord mode to screen vs relative.
 
LetUserSelectRect(x1, y1, x2, y2)
MsgBox %x1%,%y1%  %x2%,%y2%

ExitApp
 
LetUserSelectRect(ByRef X1, ByRef Y1, ByRef X2, ByRef Y2)
{
    static r := 3
    ; Create the "selection rectangle" GUIs (one for each edge).
    Loop 4 {
        Gui, %A_Index%: -Caption +ToolWindow +AlwaysOnTop
        Gui, %A_Index%: Color, Red
    }
    ; Disable LButton.
    Hotkey, *LButton, lusr_return, On
    ; Wait for user to press LButton.
    KeyWait, LButton, D
    ; Get initial coordinates.
    MouseGetPos, xorigin, yorigin
    ; Set timer for updating the selection rectangle.
    SetTimer, lusr_update, 10
    ; Wait for user to release LButton.
    KeyWait, LButton
    ; Re-enable LButton.
    Hotkey, *LButton, Off
    ; Disable timer.
    SetTimer, lusr_update, Off
    ; Destroy "selection rectangle" GUIs.
    Loop 4
        Gui, %A_Index%: Destroy
    return
 
    lusr_update:
        MouseGetPos, x, y
        if (x = xlast && y = ylast)
            ; Mouse hasn't moved so there's nothing to do.
            return
        if (x < xorigin)
             x1 := x, x2 := xorigin
        else x2 := x, x1 := xorigin
        if (y < yorigin)
             y1 := y, y2 := yorigin
        else y2 := y, y1 := yorigin
        ; Update the "selection rectangle".
        Gui, 1:Show, % "NA X" x1 " Y" y1 " W" x2-x1 " H" r
        Gui, 2:Show, % "NA X" x1 " Y" y2-r " W" x2-x1 " H" r
        Gui, 3:Show, % "NA X" x1 " Y" y1 " W" r " H" y2-y1
        Gui, 4:Show, % "NA X" x2-r " Y" y1 " W" r " H" y2-y1
    lusr_return:
    return
}

#NoEnv
CoordMode, Mouse ; Required: change coord mode to screen vs relative.

LetUserSelectRect(x1, y1, x2, y2)
MsgBox %x1%,%y1%  %x2%,%y2%

LetUserSelectRect(ByRef aX1, ByRef aY1, ByRef aX2, ByRef aY2)
{
    ; Create red pen.
    redPen := DllCall("CreatePen", "int", 0, "int", 5, "uint", 0xff)
    ; Retrieve stock brush.
    blackBrush := DllCall("GetStockObject", "int", BLACK_BRUSH:=0x4)
    ; Create the "selection rectangle" GUI.
    Gui, -Caption +ToolWindow
    Gui, +LastFound
    WinSet, TransColor, Black
    ; Disable LButton.
    Hotkey, *LButton, lusr_return, On
    ; Wait for user to press LButton.
    KeyWait, LButton, D
    ; Get initial coordinates.
    MouseGetPos, xorigin, yorigin
    ; Set timer for updating the selection rectangle.
    SetTimer, lusr_update, 10
    ; Wait for user to release LButton.
    KeyWait, LButton
    ; Re-enable LButton.
    Hotkey, *LButton, Off
    ; Disable timer.
    SetTimer, lusr_update, Off
    ; Delete red pen.
    DllCall("DeleteObject", "uint", redPen)
    ; Destroy "selection rectangle" GUI.
    Gui, Destroy
    ; Set output parameters.
    if (x2 < xorigin)
         aX1 := x2, aX2 := xorigin
    else aX2 := x2, aX1 := xorigin
    if (y2 < yorigin)
         aY1 := y2, aY2 := yorigin
    else aY2 := y2, aY1 := yorigin
    return
   
    lusr_update:
        MouseGetPos, x2, y2
        if (x1 = x2 && y1 = y2)
            ; Mouse hasn't moved so there's nothing to do.
            return
        x1 := x2, y1 := y2
        ; Update the "selection rectangle" GUI.
        Gui, Show, % "NA X" . (x2<xorigin ? x2 : xorigin) . " Y" . (y2<yorigin ? y2 : yorigin)
                    . " W" . Abs(x2-xorigin) . " H" . Abs(y2-yorigin)
        Gui, +LastFound
        ; Get GDI device context for drawing.
        hdc := DllCall("GetDC", "uint", WinExist())
        ; Select pen and brush.
        oldPen := DllCall("SelectObject", "uint", hdc, "uint", redPen)
        oldBrush := DllCall("SelectObject", "uint", hdc, "uint", blackBrush)
        ; Draw rectangle.
        DllCall("Rectangle", "uint", hdc, "int", 0, "int", 0, "int", Abs(x2-xorigin), "int", Abs(y2-yorigin))
        ; Reselect original pen and brush (required for proper cleanup).
        DllCall("SelectObject", "uint", hdc, "uint", oldPen)
        DllCall("SelectObject", "uint", hdc, "uint", oldBrush)
        ; Clean up.
        DllCall("ReleaseDC", "uint", WinExist(), "uint", hdc)
    lusr_return:
    return
}