SysWin Finding Windows

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Finding windows

Finds a control's form, top-level windows, controls by id, and the windows of a process.

Windows are linked in two ways. A child window (a control, with WS_CHILD) has a parent: it lives inside the parent's client area. A top-level window can have an owner: it stays above its owner and is hidden with it, as a dialog stays above the main window. The functions here walk those links up, or search down for a control by its id, so a handler that only has one control's handle can reach the rest of its window.

Every process has an id; the last functions go from a window or a process id to the program that runs it.

Importing

#import "sys/win"
using win

Example

A window with an edit control and a button. The button's handler starts from the button alone: it finds the form, finds the edit control by its id, and fills it with the path of the program that owns the form:

#import "sys/win"
#import "sys/win/gui"
using win, gui

declare function WndProc( byval hwnd as HWND, byval uMsg as UINT, byval wParam as WPARAM, byval lParam as LPARAM ) as LRESULT

function main() as long
    SetProcessDpiAwareness( PROCESS_SYSTEM_DPI_AWARE )
    dim pWindow as CWindow = "FindDemo"
    dim hWin as HWND = pWindow.Create( NULL, "Finding windows", @WndProc )
    SetWindowClientSizeForDpi( hWin, 420, 110 )
    CenterWindow( hWin )
    pWindow.AddControl( "Edit", hWin, 101, "", 20, 20, 380, 24 )
    pWindow.AddControl( "Button", hWin, 100, "&Who owns this window?", 20, 60, 200, 30 )
    return pWindow.DoEvents( SW_NORMAL )
end function

function WndProc( byval hwnd as HWND, byval uMsg as UINT, byval wParam as WPARAM, byval lParam as LPARAM ) as LRESULT
    select case uMsg
        case WM_COMMAND
            if CBCTL( wParam, lParam ) = 100 andalso CBCTLMSG( wParam, lParam ) = BN_CLICKED then
                dim hButton as HWND = cast( HWND, lParam )
                dim hForm as HWND = GetFormHandle( hButton )
                dim hEdit as HWND = GetControlHandle( hButton, 101 )
                SetWindowText( hEdit, GetPathFromWindowHandle( hForm ) )
            end if
            return 0
        case WM_DESTROY
            PostQuitMessage( 0 )
            return 0
    end select
    return DefWindowProcW( hwnd, uMsg, wParam, lParam )
end function

end main()

Functions

Function	Does
ForceSetForegroundWindow	Brings a window to the front and gives it the keyboard, even from the background.
GetTopLevelWindow	Follows parents and owners up to the window at the top.
GetTopLevelParent	Follows parents up to the top-level window.
GetFormHandle	Returns the form or MDI child window a control is on.
GetControlHandle	Finds a control on a form by its id.
GetTopEnabledWindow	Returns the program's frontmost enabled, visible window.
GethWndFromPID	Returns a top-level window of a process.
GetPathFromProcessId	Returns the path of the program a process runs.
GetPathFromWindowHandle	Returns the path of the program that created a window.

Reference

ForceSetForegroundWindow

sub ForceSetForegroundWindow( byval hWin as HWND )

Brings a window to the front, activates it and gives it the keyboard focus. Windows refuses SetForegroundWindow to a program that is not in the foreground; this joins the calling thread's input to the thread of the current foreground window for the length of the call, which lets the request through.

Joining input queues can hang both threads if the other one is not responding, so keep it for the cases that need it, such as a second copy of a program handing over to the first.

Parameter	Meaning
hWin	The top-level window to bring forward.

Example

if IsIconic( hwnd ) then ShowWindow( hwnd, SW_RESTORE )
ForceSetForegroundWindow( hwnd )

Microsoft Learn: AttachThreadInput, SetForegroundWindow

GetTopLevelWindow

function GetTopLevelWindow( byval hWin as HWND ) as HWND

Walks up from a window to the one at the very top: from a child to its parent, and from a top-level window to its owner, until there is neither. From a control on a dialog owned by the main window, it returns the main window.

Returns the window at the top, which is hWin itself for an unowned top-level window, or NULL when hWin is not a window.

Example

dim hMain as HWND = GetTopLevelWindow( hCtrl )

Microsoft Learn: GetWindow

GetTopLevelParent

function GetTopLevelParent( byval hWin as HWND ) as HWND

Walks up from a window through GetParent until there is no parent. For a child window that is its top-level window. GetParent also returns the owner of a WS_POPUP window, so a popup's owner is followed; the owner of a top-level window without WS_POPUP is not, and the window itself is returned.

Returns the last window reached, or NULL when hWin is not a window.

Example

dim hTop as HWND = GetTopLevelParent( hCtrl )

Microsoft Learn: GetParent

GetFormHandle

function GetFormHandle( byval hWin as HWND ) as HWND

Returns the form a control is on: it walks up through the parents while the window has WS_CHILD, and stops at the first window that is not a child or that is an MDI child window (WS_EX_MDICHILD). A control nested in a group box or a tab page gives the form, not the container.

Returns the form or MDI child window, hWin itself for a top-level window, or NULL for NULL.

Example

dim hForm as HWND = GetFormHandle( hCtrl )
SetWindowText( hForm, "changed by a control" )

GetControlHandle

function GetControlHandle( byval hWin as HWND, byval wCtrlID as WORD ) as HWND

Finds the control with the id wCtrlID on a form. hWin can be the form or any control on it: the search starts from its form and looks at every window inside, nested ones included, returning the first whose id matches.

Parameter	Meaning
hWin	The form, or any control on it.
wCtrlID	The control id.

Returns the control, or NULL when there is none with that id.

Example

dim hEdit as HWND = GetControlHandle( hwnd, 101 )
if hEdit then SetFocus( hEdit )

Microsoft Learn: EnumChildWindows

GetTopEnabledWindow

function GetTopEnabledWindow() as HWND

Returns the frontmost top-level window of the calling program that is both enabled and visible, going down the Z order. Tooltip windows are skipped. A window disabled while a modal dialog is up is passed over, so the dialog is returned instead.

Returns the window, or NULL when the program has no such window (a console program without windows gets NULL).

Example

MsgBox( GetTopEnabledWindow(), "The download has finished." )

Microsoft Learn: EnumWindows

GethWndFromPID

function GethWndFromPID( byval PID as DWORD ) as HWND

Returns the first top-level window, going down the Z order, that belongs to the process with the id PID. The window can be hidden: a program keeps windows of its own that are never shown, so the window found is not always the main window.

Returns the window, or NULL when the process has no top-level window.

Example

dim hOther as HWND = GethWndFromPID( GetCurrentProcessId() )
if hOther then print "class "; GetWindowClassName( hOther )

Microsoft Learn: GetWindowThreadProcessId

GetPathFromProcessId

function GetPathFromProcessId( byval dwProcessId as DWORD ) as ustring

Returns the full path of the executable a process runs. The process is opened with query and read access, which fails for system processes and for processes of other users or with higher rights than the caller.

Returns the path, or an empty string when the process cannot be opened.

Example

print "this program: "; GetPathFromProcessId( GetCurrentProcessId() )

Microsoft Learn: GetModuleFileNameExW

GetPathFromWindowHandle

function GetPathFromWindowHandle( byval hWin as HWND ) as ustring

Returns the full path of the executable of the process that created a window: the window's process id passed to GetPathFromProcessId, with the same limits.

Returns the path, or an empty string for an invalid handle or a process that cannot be opened.

Example

print "the foreground window belongs to "; GetPathFromWindowHandle( GetForegroundWindow() )

See also

• Category: sys/win
• Window text and styles
• Window size and position
• CWindow