Tech Note 39: Using APIs to create Popup Forms and Dialogs

May 28, 2008

© NSB Corporation. All rights reserved.

Contributed by Alex Yakhnin, Software Developer, Morganville, NJ. Updated in 2008 by Manfred from Germany.


NSBasic Visual Designer allows developers to create different 'logical' forms in the application by assigning controls to an array and hiding or showing the controls during the run-time. But these 'logical' forms doesn't allow to create a Popup forms or Dialogs that don't take the whole screen area. The purpose of this article is to show how to implement this functionality using API object (NSBWin32.dll).

More Information

Almost every object in the Windows operating system is a window, i.e. forms, buttons, labels, textboxes etc..., that are created with the certain attributes or styles. It is possible, though, to change those window styles during the run-time and get the look and behavior that are needed for the application. The NSBasic.win32.api object implements .WindowLong method that wraps up SetWindowLong and GetWindowLong API calls and could be used for these purposes. The steps to create a Popup form will be to change the existing control to behave like a form and assign to it all other controls that we want to show on the form. We can achieve the latter using .WindowParent method of the API object, changing the 'parent' for these controls. I see that Label control will be the perfect candidate for the 'parent' form. So we are armed enough to create a simple popup form that asks for a string to search:


Sample 1

'***  25.01.08 ML, Dialogbox Testing
'***  Based on old Tech Note 39: Using APIs to create Popup Forms and Dialogs
'***  requires NSBWIN32 to be installed on PPC
'***  tested with MDE2.0 (WM5) and HP iPAQ rx1950 (WM5)
Option Explicit

ShowOKButton True
Call Setup_Form
Call Setup_DBox
Call Setup_DBox2

'Activate WS_CAPTION, which normally should be the default
CB1.Value = True
CB2.Value = True
CB3.Value = True
Call BApply_Click

'***************** Setup Form **********************************************
Sub Setup_Form
   AddObject "CheckBox","CB1",0,0,100,16
   CB1.Caption = "BORDER"
   AddObject "CheckBox","CB2",0,16,100,16
   CB2.FontSize = 8
   CB2.Caption = "CAPTION"
   CB2.Enabled = False
   AddObject "CheckBox","CB3",0,32,100,16
   CB3.Caption = "DLGFRAME"
   AddObject "CheckBox","CB4",0,48,100,16
   CB4.Caption = "SYSMENU !!"
   AddObject "CheckBox","CB5",0,64,100,16
   CB5.Caption = "THICKFRAME"
   AddObject "CheckBox","CB6",0,80,100,16
   CB6.Caption = "VSCROLL"
   AddObject "CheckBox","CB7",0,96,100,16
   CB7.Caption = "HSCROLL"

   AddObject "CheckBox","CB11",0,120,100,16
   CB11.Caption = "CLIENTEDGE"
   AddObject "CheckBox","CB12",0,136,100,16
   CB12.Caption = "CAPTIONOKBTN"

   AddObject "Label","LB1",100,0,140,32
   LB1.BackColor = &HC0C0C0
   LB1.Caption   = "Check desired options and Click Apply"
   LB1.Fontsize  = 8

   AddObject "CommandButton","BApply",0,160,100,18
   BApply.Caption = "Apply"
   AddObject "CommandButton","BShow",0,190,100,18
   BShow.Caption = "Show DBox"

   AddObject "CommandButton","BShow2",0,210,100,18
   BShow2.Caption = "Show DBox2"

   AddObject "NSBasic.win32.API", "API"
End Sub

'****************** Form Events ********************************************

'Window styles
Const WS_BORDER      = &H800000     'Has Border
Const WS_CAPTION     = &HC00000     'Has Titlebar = BORDER + DLGFRAME, movable
Const WS_DLGFRAME    = &H400000     'Dialogbox
Const WS_SYSMENU     = &H80000      'x-Button, pressing destroys Window
Const WS_POPUP       = &H80000000   'hangs system, need warmstart
Const WS_THICKFRAME  = &H40000      'user sizable + movable Window
Const WS_VSCROLL     = &H200000     'scrollbar, but somehow not functional
Const WS_HSCROLL     = &H100000     'scrollbar, but somehow not functional

'Extended window styles winuser.h
Const WS_EX_CLIENTEDGE   = &H200      'user movable Window
Const WS_EX_CAPTIONOKBTN = &H80000000 'Ok-Button in title, raises frmFind_Click

' Style Flags
Const GWL_STYLE   = (-16)
Const GWL_EXSTYLE = (-20)

Dim Style, ExStyle, oBox

Sub BApply_Click
   If DBox.Visible Then 
      Set oBox = Dbox
      Set oBox = Dbox2
   End If
   Style = CLng(0)
   If CB1.Value Then Style = Style Or WS_BORDER
   If CB2.Value Then Style = Style Or WS_CAPTION
   If CB3.Value Then Style = Style Or WS_DLGFRAME
   If CB4.Value Then Style = Style Or WS_SYSMENU
   If CB5.Value Then Style = Style Or WS_THICKFRAME
   If CB6.Value Then Style = Style Or WS_VSCROLL
   If CB7.Value Then Style = Style Or WS_HSCROLL
   API.WindowLong(oBox.hWnd, GWL_STYLE) = Style
   If (Style And WS_CAPTION) = WS_CAPTION Then
      'Title bar is present, we hide the labeltext, but not the title ;)
      oBox.ForeColor = oBox.BackColor
      oBox.ForeColor = vbBlack
   End If

   ExStyle = CLng(0)
   If CB11.Value Then ExStyle = ExStyle Or WS_EX_CLIENTEDGE
   If CB12.Value Then ExStyle = ExStyle Or WS_EX_CAPTIONOKBTN
   API.WindowLong(oBox.hWnd, GWL_EXSTYLE) = ExStyle
End Sub

Sub BShow_Click
   If     DBox2.Visible Then DBox2.Hide
   If Not DBox.Visible  Then Dbox.Show
End Sub

Sub BShow2_Click
   If     DBox.Visible  Then DBox.Hide
   If Not DBox2.Visible Then Dbox2.Show
End Sub

Sub CB1_Click
   CB2.value = CB1.value And CB3.value
End Sub

Sub CB3_Click
   CB2.value = CB1.value And CB3.value
End Sub

'***************** Setup Dialogbox *****************************************
Sub Setup_DBox
   AddObject "Label",         "DBox",     100,100,140,140
   DBox.BackColor = vbYellow
   DBox.Caption   = "I'am the DBox"
   AddObject "Label",         "DboxFind",  10, 15,100, 18, DBox
   DboxFind.BackColor = 12632256
   DboxFind.Caption   = "Enter Text:"
   AddObject "TextBox",       "DboxInput", 10, 40,115, 18, DBox
   DboxInput.BorderStyle = 1
   AddObject "CommandButton", "DboxOk",    10, 70, 55, 18, DBox
   DboxOk.BackColor = 12632256
   DboxOk.Caption = "&OK"      '& doesn't make much sense on PPCs
   AddObject "CommandButton", "DboxCancel",80, 70, 55, 18, DBox
   DboxCancel.BackColor = 12632256
   DboxCancel.Caption = "&Cancel"
End Sub

'***************** Dialogbox Events *****************************************
Sub DboxOk_Click
   'When no text was entered the msgbox hides instead of DBox ??
   If DboxInput.Text <> "" Then MsgBox DboxInput.Text
End Sub

Sub DboxCancel_Click
End Sub

Sub DBox_Click
   If (Style And WS_DLGFRAME) = 0 Then
      MsgBox "No Title Bar present, clicked anywhere in Box"
      MsgBox "Clicked Ok-Button in titlebar"
   End If
End Sub

Sub DBOX_GotFocus
   'Never happens
   MsgBox "DBOX_GotFocus"
End Sub

'***************** Setup Dialogbox2 *****************************************
'***************** Setup Dialogbox2 (Progressbar) ***************************
Sub Setup_DBox2
   AddObject "Label",         "DBox2",     100,100,140,140
   DBox2.BackColor = vbYellow
   DBox2.Caption   = "DBox2-Progressbar"
   AddObject "Label",         "Dbox2Info",  10, 15,110, 18, DBox2
   Dbox2Info.BackColor = vbmagenta
   Dbox2Info.Caption   = "Info"
   Call PBar_Init(10, 40, 125, 18, DBox2)
   AddObject "CommandButton", "Dbox2Start",   10, 70, 55, 18, DBox2
   Dbox2Start.BackColor = &HC0C0C0
   Dbox2Start.Caption = "Start"
   AddObject "CommandButton", "Dbox2Cancel",  80, 70, 55, 18, DBox2
   Dbox2Cancel.BackColor = &HC0C0C0
   Dbox2Cancel.Caption = "Cancel"
   AddObject "CommandButton", "Dbox2Stop",    10, 90, 55, 18, DBox2
   Dbox2Stop.BackColor = &HC0C0C0
   Dbox2Stop.Caption = "Stop"
   Call ButtonEnable(DBox2Stop,False)
End Sub

Sub ButtonEnable(ByRef ctl, enable)
   ctl.enabled = enable
   If ctl.Tag = "" Then ctl.Tag = ctl.BackColor
   If enable Then
      'ctl.Backcolor = &Hc0c0c0
      ctl.Backcolor = ctl.Tag
      ctl.Backcolor = vbblack
   End If
End Sub

'***************** Dialogbox2 Events *****************************************
Sub DBox2_Click
   If (Style And WS_DLGFRAME) = 0 Then
      MsgBox "No Title Bar present, clicked anywhere in Box"
      MsgBox "Clicked Ok-Button in titlebar"
   End If
End Sub

Sub Dbox2Cancel_Click
End Sub

Const Maxrounds = 100
Dim Rounds
Sub DBox2Start_Click()
   DBox2Start.Timer = 200
   Call ButtonEnable(DBox2Stop, True)
   Call ButtonEnable(DBox2Start,False)
   Rounds = 0
   Call PBAR_Show()
End Sub

Sub DBox2Start_Timer()
   Rounds = Rounds + 1
   If Rounds > MaxRounds Then
      Call DBox2Stop_Click()
      exit Sub
   End If
   Call PBar_Progress(Rounds * 100 / Maxrounds, "")
End Sub

Sub DBox2Stop_Click()
   DBox2Start.Timer = 0
   Call ButtonEnable(DBox2Stop, False)
   Call ButtonEnable(DBox2Start,True)
End Sub

'***	23.01.08 Poor Man's Progressbar ML
Dim GPB1, GPB2

Public Sub PBar_Hide
   GPB1.Visible = False
   GPB2.Visible = GPB1.Visible
End Sub

Public Sub PBar_Init(ByVal Left, ByVal Top, ByVal Width, ByVal Height,ByRef Parent)
   AddObject "Label", "GPB1", Left, Top, Width, Height, Parent
   GPB1.Visible     = False
   GPB1.BorderStyle = 1
   AddObject "Label", "GPB2", Left+1, Top+1, Width-2, Height-1, Parent
   GPB2.Visible     = GPB1.Visible
   GPB2.BackColor   = vbBlue
   GPB2.ForeColor   = vbWhite
End Sub

Public Sub PBar_Progress(ByVal Percent, ByVal txt)
   If GPB1.Visible = False Then Call PBar_Show
   If txt = "" Then
      GPB2.Caption   = Percent & "%"
      GPB2.Caption = txt
   End If
   GPB2.Width = (GPB1.Width - 2) * Percent / 100
   'very strange, this has to be done when WS_BORDER is active
   'if not the Label will walk out of the box downwards
   'Demo: you can watch this when you Check "BORDER" without "DLGFRAME"
   If (Style And WS_CAPTION) = WS_CAPTION Then
      GPB2.Left = GPB1.Left-1
      GPB2.Top = GPB1.Top-24
   End If
End Sub

Public Sub PBar_Show
   GPB1.Visible = True
   GPB2.Width   = 0
   GPB2.Visible = GPB1.Visible
   GPB2.Left    = GPB1.Left + 1
   GPB2.Top     = GPB1.Top + 1
End Sub

The following options have an effect on WM5 devices:
BORDER Draws a thin border around the box
CAPTION (= BORDER + DLGFRAME) layout like MsgBox with titlebar, makes box movable
SYSMENU Displays X-button in the titlebar, pressing this button destroys the box-window
THICKFRAME Draws 3D-border around the box, makes box sizable
SCROLL Displays scrollbars in the box, but scrolling does not seem to work (perhaps someone wants to investigate that further)
CLIENTEDGE Draws 3D-border around the box, but not sizable
CAPTIONOKBTN Displays Ok-button in the titlebar (CAPTION must be set), clicking fires Dbox_Click event

All buttons actually work! We are even able to catch the click on the "OK" button: frmFind_Click event will be working. But, we will have some problems with the "X" (Close) button: If you click on this button our form will be actually destroyed by the Windows without giving us any chance to do a clean up work and it is not possible to catch this event. Plus, our application wouldn't know that the controls where destroyed and will not allow us to recreate them with the same name. So, I suggest you do not use this feature.

Alex Yakhnin, Software Developer, Morganville, NJ and Manfred, somewhere in Germany.