Liberty BASIC Programmer's Encyc - Retrieving Information from Textboxes

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JanetTerra Feb 9, 2007

Retrieving Information from Textboxes

The Native Liberty BASIC Command

Liberty BASIC has a native command for retrieving textbox contents -

 Print #main.tbx1, "!Contents? text$"

In most instances, this is all the code programs require.

 WindowWidth = 400 
 WindowHeight = 300 
 UpperLeftX = Int((DisplayWidth - WindowWidth) /2) 
 UpperLeftY = Int((DisplayHeight - WindowHeight) /2) 
 Statictext #main.stx1, "What is your name?", 20, 34, 70, 60 
 Textbox #main.tbx1, 100, 50, 200, 30 
 Button #main.default, " OK ", GetName, UL, 320, 50 
 Open "Retrieving Textbox Contents" for Dialog as #main 
 #main, "Trapclose XbyTrap" 
 #main, "Font Times_New_Roman 12 Bold" 
 
 
 Wait 
 
 Sub XbyTrap handle$ 
 Close #handle$ 
 End 
 End Sub 
 
 Sub GetName handle$ 
 #main.tbx1, "!Contents? name$" 
 Notice "Hello, ";name$ 
 End Sub

 CallDLL #user32, "SendMessageA", _ 
 hText as Ulong, _ ' handle of the textbox 
 _EM_GETLINECOUNT as Long, _ ' message to be passed 
 0 as Long, _ ' no further information to be passed 
 0 as Long, _ ' no further information to be passed 
 result as Long ' Windows returns the number of lines

Here is a demo to get the number of lines in a textbox. The mainwindow is kept visible for the printing of returned information. You may need to reposition your GUI window to see this information.

 ' Define a textbox 
 Textbox #main.tb, 10, 20, 150, 68 
 
 ' Stylebits for word wrapping and vertical scrolling 
 Stylebits #main.tb, _WS_VSCROLL OR _ES_MULTILINE, _ES_AUTOHSCROLL, 0, 0 
 
 ' Define text 
 demoText$ = "All Gaul is divided into three parts, one of " + _ 
 "which the Belgae inhabit, the Aquitani another, those who " + _ 
 "in their own language are called Celts, in our Gauls, the third. " + _ 
 "All these differ from each other in language, customs, and laws." 
 
 Open "Lines of Multiline Textbox" for Window as #main 
 #main, "Trapclose XbyTrap" 
 #main, "Font Times_New_Roman 10 bold" 
 
 ' Print the text in the textbox 
 #main.tb, demoText$ 
 
 ' Get the handle of the textbox 
 hText=hWnd(#main.tb) 
 
 ' Pass the required arguments to SendMessageA API 
 nLines = ReturnedMessage(hText, _EM_GETLINECOUNT, 0, 0) 
 Print "There are ";nLines;" lines in this textbox." 
 
 Wait 
 
 ' Program ends here 
 Sub XbyTrap handle$ 
 Close #handle$ 
 End 
 End Sub 
 
 ' SendMessageA Function 
 Function ReturnedMessage(handle, Msg, wParam, lParam) 
 CallDLL #user32, "SendMessageA", _ 
 handle as Ulong, _ 
 Msg as Long, _ 
 wParam as Long, _ 
 lParam as Long, _ 
 ReturnedMessage as Long 
 End Function

Get the Number of Characters in Each Line of Text

SendMessageA will not return the actual text string. Instead, it returns the number of characters in that string. This next demo is the same as the previous demo, with a function added to get the number of characters at the end of each line. It is important to recognize that the function does not return the number of characters in that line, but the number of characters from the beginning of the text to the end of that line . Again using the API call SendMessageA , the handle of the textbox is passed as well as the message _EM_LINEINDEX . SendMessageA also needs to know which line is being questioned. The first available extra information argument, wParam , passes the line number to be queried. There is no additional information needed, so the second informational argument, lParam , remains 0.

 CallDLL #user32, "SendMessageA", _ 
 hText as Ulong, _ ' handle of the textbox 
 _EM_LINEINDEX as Long, _ ' message to be passed 
 lineNumber as Long, _ ' the queried line number 
 0 as Long, _ ' no further information to be passed 
 result as Long ' Windows returns the number of lines

Since the last line is treated a little differently, the loop must terminate at the next to the last line For i = 1 to nLines - 1 . The code for the last line immediately follows the loop.

 ' Define a textbox 
 Textbox #main.tb, 10, 20, 150, 68 
 
 ' Stylebits for word wrapping and vertical scrolling 
 Stylebits #main.tb, _WS_VSCROLL OR _ES_MULTILINE, _ES_AUTOHSCROLL, 0, 0 
 
 ' Define text 
 demoText$ = "All Gaul is divided into three parts, one of " + _ 
 "which the Belgae inhabit, the Aquitani another, those who " + _ 
 "in their own language are called Celts, in our Gauls, the third. " + _ 
 "All these differ from each other in language, customs, and laws." 
 
 Open "Lines of Multiline Textbox" for Window as #main 
 #main, "Trapclose XbyTrap" 
 #main, "Font Times_New_Roman 10 bold" 
 
 ' Print the text in the textbox 
 #main.tb, demoText$ 
 
 ' Get the handle of the textbox 
 hText=hWnd(#main.tb) 
 
 ' Pass the required arguments to SendMessageA API 
 nLines = ReturnedMessage(hText, _EM_GETLINECOUNT, 0, 0) 
 Print "There are ";nLines;" lines in this textbox." 
 
 ' Get the total number of characters at the end of each line 
 For i = 1 to nLines - 1 
 nCharacters = ReturnedMessage(hText, _EM_LINEINDEX, i, 0) 
 Print "Line #";i;": ";nCharacters;" Characters" 
 Next i 
 
 Wait 
 
 ' Program ends here 
 Sub XbyTrap handle$ 
 Close #handle$ 
 End 
 End Sub 
 
 ' SendMessageA Function 
 Function ReturnedMessage(handle, Msg, wParam, lParam) 
 CallDLL #user32, "SendMessageA", _ 
 handle as Ulong, _ 
 Msg as Long, _ 
 wParam as Long, _ 
 lParam as Long, _ 
 ReturnedMessage as Long 
 End Function

How will knowing what the total number of characters reveal the actual number of characters in each line? By keeping track of how many characters were used in preceding lines, the number of characters already assigned is known. Subtract that number from the number of characters up to and including the selected line. The difference is the number of characters in just the selected line. Start the position, startPos , as 1.

 ' Define a textbox 
 Textbox #main.tb, 10, 20, 150, 68 
 
 ' Stylebits for word wrapping and vertical scrolling 
 Stylebits #main.tb, _WS_VSCROLL OR _ES_MULTILINE, _ES_AUTOHSCROLL, 0, 0 
 
 ' Define text 
 demoText$ = "All Gaul is divided into three parts, one of " + _ 
 "which the Belgae inhabit, the Aquitani another, those who " + _ 
 "in their own language are called Celts, in our Gauls, the third. " + _ 
 "All these differ from each other in language, customs, and laws." 
 
 Open "Lines of Multiline Textbox" for Window as #main 
 #main, "Trapclose XbyTrap" 
 #main, "Font Times_New_Roman 10 bold" 
 
 ' Print the text in the textbox 
 #main.tb, demoText$ 
 textLength = Len(demoText$) 
 
 ' Get the handle of the textbox 
 hText=hWnd(#main.tb) 
 
 ' Pass the required arguments to SendMessageA API 
 nLines = ReturnedMessage(hText, _EM_GETLINECOUNT, 0, 0) 
 Print "There are ";nLines;" lines in this textbox" 
 
 ' The starting position is 1 
 startPos = 1 
 
 For i = 1 to nLines - 1 
 ' Get the total number of characters in each line 
 nCharacters = ReturnedMessage(hText, _EM_LINEINDEX, i, 0) 
 ' The characters in that line start with startPos and continue through to nCharacters 
 Print "Line ";i;": Characters ";startPos;" - ";nCharacters 
 ' startPos moves up to the nCharacters pos for the next line 
 startPos = nCharacters + 1 
 Next i 
 ' Get the number of characters in the last line by subtracting the nCharacters 
 ' found thus far from the Length of the entire text 
 nCharacters = textLength - nCharacters 
 Print "Line ";i;": Characters ";startPos;" - ";textLength 
 
 'Wait for button to be pushed 
 Wait 
 
 ' Program ends here 
 Sub XbyTrap handle$ 
 Close #handle$ 
 End 
 End Sub 
 
 ' SendMessageA Function 
 Function ReturnedMessage(handle, Msg, wParam, lParam) 
 CallDLL #user32, "SendMessageA", _ 
 handle as Ulong, _ 
 Msg as Long, _ 
 wParam as Long, _ 
 lParam as Long, _ 
 ReturnedMessage as Long 
 End Function

Liberty BASIC's Mid$() Function

Now that the starting and ending character position number is known, the Liberty BASIC Mid$() function can be used to extract that one line. The Mid$() function has 3 elements

The whole text to be parsed (demoText$)
The starting position (startPos)
The number of characters to be extracted from the starting position to the right (nCharacters - startPos)

A simple demo of the Liberty BASIC Mid$() function -

 txt$ = "trouble" 
 m$ = Mid$(txt$, 4, 3) 
 Print m$ 
 End

Executing this code prints ubl , where u is the character in the fourth position of the string trouble , and ubl are the three characters in sequence beginning in this fourth position.

In this textbox demo, startPos becomes the start position and nCharacters - startPos becomes the sequence range of characters. Here is the code again, this time extracting and printing each line of text.

 ' Define a textbox 
 Textbox #main.tb, 10, 20, 150, 68 
 
 ' Stylebits for word wrapping and vertical scrolling 
 Stylebits #main.tb, _WS_VSCROLL OR _ES_MULTILINE, _ES_AUTOHSCROLL, 0, 0 
 
 ' Define text 
 demoText$ = "All Gaul is divided into three parts, one of " + _ 
 "which the Belgae inhabit, the Aquitani another, those who " + _ 
 "in their own language are called Celts, in our Gauls, the third. " + _ 
 "All these differ from each other in language, customs, and laws." 
 
 Open "Lines of Multiline Textbox" for Window as #main 
 #main, "Trapclose XbyTrap" 
 #main, "Font Times_New_Roman 10 bold" 
 
 ' Print the text in the textbox 
 #main.tb, demoText$ 
 textLength = Len(demoText$) 
 
 ' Get the handle of the textbox 
 hText=hWnd(#main.tb) 
 
 ' Pass the required arguments to SendMessageA API 
 nLines = ReturnedMessage(hText, _EM_GETLINECOUNT, 0, 0) 
 Print "There are ";nLines;" lines in this textbox" 
 
 ' The starting position is 1 
 startPos = 1 
 
 For i = 1 to nLines - 1 
 ' Get the total number of characters in each line 
 nCharacters = ReturnedMessage(hText, _EM_LINEINDEX, i, 0) 
 ' Print that line of text using the Mid$() function 
 Print Mid$(demoText$, startPos, nCharacters - startPos) 
 ' startPos moves up to the nCharacters pos for the next line 
 startPos = nCharacters + 1 
 Next i 
 ' Get the number of characters in the last line by subtracting the nCharacters 
 ' found thus far from the Length of the entire text 
 nCharacters = textLength - nCharacters 
 Print Mid$(demoText$, startPos, nCharacters) 
 
 'Wait for button to be pushed 
 Wait 
 
 ' Program ends here 
 Sub XbyTrap handle$ 
 Close #handle$ 
 End 
 End Sub 
 
 ' SendMessageA Function 
 Function ReturnedMessage(handle, Msg, wParam, lParam) 
 CallDLL #user32, "SendMessageA", _ 
 handle as Ulong, _ 
 Msg as Long, _ 
 wParam as Long, _ 
 lParam as Long, _ 
 ReturnedMessage as Long 
 End Function

You may never need to extract single lines of text in a multiline textbox, but at least you know you can.