Draw line on windows

[nuclear112]

Draw Line On Windows
Does anyone know how to make it so that something draws a line on windows using the variables x1,x2,y1 and y2. e.g

drawLineWindows(x1,x2,y1,y2,color)

Picture below for example.


Thanks, Nuclear112

[nuclear112]

Can someone please give me a hand

[Paul M]

I believe you will need to use SetPixels or some other API i will see what i cna come up with

[westconn1]

you want to do this on the desktop (or form), or on an image or form within your program?

[Milk]

Here is a wonderfully messy method to draw non persistent lines on your desktop... This method is safe but by no means great, the only way to delete what you draw is to force a desktop refresh.

Option Explicit
Private Declare Function GetDesktopWindow Lib "user32" () As Long
Private Declare Function GetWindowDC Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function ReleaseDC Lib "user32" (ByVal hwnd As Long, ByVal hDC As Long) As Long
Private Declare Function MoveToEx Lib "gdi32" (ByVal hDC As Long, ByVal x As Long, ByVal y As Long, lpPoint As Any) As Long
Private Declare Function LineTo Lib "gdi32" (ByVal hDC As Long, ByVal x As Long, ByVal y As Long) As Long
Private Declare Function CreatePen Lib "gdi32" (ByVal nPenStyle As Long, ByVal nWidth As Long, ByVal crColor As Long) As Long
Private Declare Function SelectObject Lib "gdi32" (ByVal hDC As Long, ByVal hObject As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long

Private Sub Command1_Click()
  DrawLineOnDesktop 100, 100, 400, 400, vbRed, 5
End Sub

Private Sub DrawLineOnDesktop(ByVal X1 As Long, Y1 As Long, X2 As Long, Y2 As Long, Optional ByVal Colour As Long = -1, Optional ByVal Wdth As Long = 0)
Dim Wnd As Long, DC As Long
Dim hPen As Long, hOld As Long
 
  Wnd = GetDesktopWindow
  DC = GetWindowDC(Wnd)
  
  If Colour <> -1 Then
    hPen = CreatePen(0, Wdth, Colour) 'create a new pen
    hOld = SelectObject(DC, hPen) 'our new pen is selected, hOld is the old object handle
  End If

  MoveToEx DC, X1, Y1, ByVal &H0
  LineTo DC, X2, Y2
  
  If Colour <> -1 Then DeleteObject SelectObject(DC, hOld) 'delete new pen and reselect the old one
  ReleaseDC Wnd, DC
End Sub

An alternative and perhaps much better way would be to create a large borderless form and have that form pretend to be the desktop either by copying the desktop DC onto it or by creating a transparent form (SetWindowLayerAttributes win2k+)

[nuclear112]

Greats thanks for the code... Can someone edit this code so that the line can be deleted?

[nuclear112]

Can someone please help me?

[opus]

As Milk already stated

the only way to delete what you draw is to force a desktop refresh.

[nuclear112]

But isn't there way to rescript it so that it can turn it on and off?
Have have seen it done before...

[opus]

If have seen a line or something similar, drawn onto the desktop, which could be switched on and off, it was either not on the desktop (maybe an tranparent form) or the swichting-off was just the refreshing of the desktop!
The code presented by milk just drwas a line onto something (the dektop), it's not an control which has a .visible property!

[nuclear112]

Oh... Cause what im trying to achieve is... In my program I want the user to click and select a window and when they select the window a box will flash around the windows handle(hwnd).

[opus]

In my program I want the user to click and select a window and when they select the window a box will flash around the windows handle(hwnd).

I take it, you don't want to activate that window (in other words, your applications window is activated but the selected is "highlighted").

[nuclear112]

Na its ok if the other window gets activated

[opus]

OK, but why invent something new, windows does highlight the activated window, if you don't like the color of the the activated windowtitle just change the color-setting for that.
Or am I missing a point?

[nuclear112]

mmm, I think we are thinking about 2 different things

[RobCrombie]

Hi,

I am not sure this is the thread that I was trying to remember in my post -
http://www.vbforums.com/showthread.p...73#post2910573

But I will post a link to my text solution -
http://www.planet-source-code.com/vb...53509&lngWid=1
It may help, as it appears to be using similar API's

If someone can provide the tweak I mention in the top link (write over a form that was Topmost) , I would appreciate it.

[nuclear112]

Thanks you are heading on the right track... But can you make it so that it draws a line instead of text?