SelectObject API function

[Chris]

Juz a stupid Q, and take a look the code shown below:

    Dim hdc As Long
    Dim hPen As Long
    Dim hOldPen As Long
    Dim pt As POINTAPI
    
    hdc = GetDC(Form1.hwnd)
    hPen = CreatePen(PS_SOLID, RGB(0, 255, 255))
    hOldPen = SelectObject(hdc, hPen)
    Polyline hdc, pt(0), 5
    SelectObject hdc, hOldPen
    DeleteObject hPen
    ReleaseDC Form1.hwnd, hdc

Why there is a need to restore the old pen object into the device Context (DC)? What will happen if I does not restore it?

[gaffa]

A simple test for you:

Take out the restore pen code, then call the sub 1000000 times. Eventually you will run out of GDI handles, and the painting of all windows will go haywire

Basically, you need to restore the handles to pens and other objects just so your app doens't chew up all the avaialble system handles. It's annoying, but the consequences if you don't are even more annoying.

- gaffa

[Chris]

Thanks gaffa, I felt that after I change my code to restore the original pen object and now my app doesn't eat up all my memory