VII. Pengenalan Windows API (Application Programming Interface)

Window API merupakan kumpulan fungsi-fungsi eksternal yang disediakan library windows untuk mengatur kemampuan dan tingkah laku setiap element di Windows (dari tampilan di desktop hingga alokasi memory) sehingga dapat dimanfaatkan suatu program untuk meningkatkan kemampuan program tersebut, contohnya saja untuk pengaksesan registry windows dengan fasilitas built in visual basic sangat sukar dilakukan, tetapi dengn adanya fasilitas API untuk registry dari library advapi32.dll, pengaksesan tersebut menjadi lebih mudah. Untuk memasukkan Window API ke dalam proyek Visual Basic, cara yang paling mudah adalah dengan menggunakan program API Viewer yang terdapat di menubar Add-Ins yaitu Add-In Manager. Pilih Loaded API Viewer, lalu buka text file darinya, pilih Win32api.txt.

Project Sederhana Dengan Ekspresi

Program sederhana memanipulasi form standard Visual Basic 6.0

Menggunakan file resource gambarlayar.res diambil/diimport dari jendela explorer Visual Basic dari file: gambarlayar.res
Kontrol yang digunakan pada form1:
- picture1, dengan property visible=false
- command1
- image1, dengan property visible=true

Kode pada jendela form1:

Private Declare Function SendMessage Lib _
"user32" Alias "SendMessageA" _
(ByVal hwnd As Long, _
ByVal wMsg As Long, _
ByVal wParam As Long, _
lParam As Any) As Long

Private Const CCM_FIRST = &H2000
Private Const CCM_SETBKCOLOR = (CCM_FIRST + 1)
Private Const PBM_SETBKCOLOR = CCM_SETBKCOLOR
Private Const WM_USER = &H400
Private Const PBM_SETBARCOLOR = (WM_USER + 9)

Private Declare Sub ReleaseCapture Lib "user32" ()

Const WM_NCLBUTTONDOWN = &HA1
Const HTCAPTION = 2

Public Function prosesLAH()
Me.MousePointer = 11
Me.Hide
DoEvents
Set Picture1.Picture = LoadResPicture(101, Bitmap)
Picture1.ScaleMode = vbPixels
Picture1.AutoRedraw = True
Picture1.AutoSize = True
Picture1.BorderStyle = vbBSNone
Me.Width = Picture1.Width
Me.Height = Picture1.Height
WindowRegion = BuatRegion(Picture1)
SetWindowRgn Me.hwnd, WindowRegion, True
Me.Show
Me.Refresh
Me.MousePointer = 0
End Function

Private Sub Command1_Click()
Unload Me
End Sub
Private Sub Form_Load()
Me.BackColor = RGB(214, 219, 191)
Set Image1.Picture = LoadResPicture(101, Bitmap)
Call prosesLAH
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, _
x As Single, y As Single)
Dim lngReturnValue As Long

If Button = 1 Then
Call ReleaseCapture
lngReturnValue = SendMessage(Me.hwnd, WM_NCLBUTTONDOWN, _
HTCAPTION, 0&)
End If
End Sub

Public ask As Boolean
Public DE As Integer

Buat module dengan nama module1, Masukkan kode program pada jendela kode module, sebagai berikut:

Public Declare Function SetWindowPos Lib "user32" _
(ByVal hwnd As Long, _
ByVal hWndInsertAfter As Long, _
ByVal x As Long, ByVal y As Long, _
ByVal cx As Long, ByVal cy As Long, _
ByVal wFlags As Long) As Long
Public Const SWP_NOMOVE = &H2
Public Const SWP_NOSIZE = &H1
Public Const HWND_TOPMOST = -1
Public Const HWND_NOTOPMOST = -2

Public withFrameFlag As Boolean
Public Declare Function GetPixel Lib "gdi32" (ByVal hDC As Long, ByVal x As Long, ByVal y As Long) As Long
Public Declare Function SetWindowRgn Lib "user32" (ByVal hwnd As Long, ByVal hRgn As Long, ByVal bRedraw As Boolean) As Long
Public Declare Function CreateRectRgn Lib "gdi32" (ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long
Public Declare Function CombineRgn Lib "gdi32" (ByVal hDestRgn As Long, ByVal hSrcRgn1 As Long, ByVal hSrcRgn2 As Long, ByVal nCombineMode As Long) As Long
Public Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Public Const RGN_OR = 2
Public xpos As Long
Public ypos As Long
Public Function BuatRegion(skinGbr As PictureBox) As Long
Dim x As Long, y As Long, awalBrsX As Long
Dim RegionSemua As Long, BrsRegion As Long
Dim TransparentColor As Long
Dim pdAwalRegion As Boolean
Dim BrsPada As Boolean
Dim hDC As Long
Dim LebarGbr As Long
Dim TinggiGbr As Long
hDC = skinGbr.hDC
LebarGbr = skinGbr.ScaleWidth
TinggiGbr = skinGbr.ScaleHeight

pdAwalRegion = True: BrsPada = False
x = y = awalBrsX = 0
warnaTransparan = GetPixel(hDC, 0, 0)
For y = 0 To TinggiGbr - 1
For x = 0 To LebarGbr - 1
If GetPixel(hDC, x, y) = warnaTransparan Or x = LebarGbr Then
If BrsPada Then
BrsPada = False
BrsRegion = CreateRectRgn(awalBrsX, y, x, y + 1)

If pdAwalRegion Then
RegionSemua = BrsRegion
pdAwalRegion = False
Else
CombineRgn RegionSemua, RegionSemua, BrsRegion, RGN_OR
DeleteObject BrsRegion
End If
End If
Else
If Not BrsPada Then
BrsPada = True
awalBrsX = x
End If
End If
Next
Next 
BuatRegion = RegionSemua
End Function