31 December 2012

Printing a listing on another printer

If you are running a Windows Vista or Windows 7 operating system, then the procedure to select different printers has changed from earlier versions of Windows. Starting with Windows Vista the "Printer ..." button is missing from the common dialog Page Setup dialog box. This is a consequence of the newer Windows operating systems. Now if you want to change printers or print drivers, you must change the default printer from the “Devices and Printers” window

How does this affect printing from GFA-BASIC 32?
To print a listing you can select Print in the File submenu. Depending on the presence of a text-selection, Gfa_Print will either print the entire listing or the current selection only. The text is printed immediately, without an option to select a different printer or to cancel the print job.

Initially, when you haven't printed before, the listing is sent to the default printer using default settings. At very first time, on my default printer, this produces lines in a vey hard to read small font size printed in the upper left corner of the paper.
Now I'm aware of this behavior, I make sure to set the printer page options before I  start printing for the first time.
The printer settings are available in the Printer Tab in the GFA-BASIC 32 Properties dialog box. The top two buttons are used to customize GB32's printing options.

GB32 Properties Printer

Selecting the top button labeled 'Page Setup' will bring up the Page Setup common dialog box. The Page Setup dialog box allows the user to set the paper size, source, orientation, and margins for printing. Starting with Windows Vista the common dialog box that pops up in GFA-BASIC 32 looks like this. The margin settings are initialized to zero, so it is logical that the listing is printed in the top-left corner of the paper.

GB32 PageSetup

After changing the page settings and selecting OK, GFA-BASIC 32 updates the top button in the Printer Tab with the name of the Printer (here Lexmark).

  • Due to a bug in the GFA-BASICs English string data the button text isn't shown properly. Rather than providing the printer name it only shows the word 'Printer'. (The first image shows a fixed version of the IDE.)

Applying new settings
The Page Setup values aren't applied before selecting the OK button in the GFA-BASIC Properties dialog box. The same is true for values from the other tabs (Editor and Compiler). 
The printer settings are applied to some global application variables and stored in 4 registry values in 'HCKU\Software\GFA\Basic' register sub keys:

Printer String containing DEVNAMES values
PrinterDMF Data containing relevant DEVMODE values
PrinterFont Compressed LOGFONT structure
PrinterPage Margins, MarginMetrics, Options. Used to initialize the Properties Print Page

At the next start the GFA-BASIC IDE reads back the "PrinterPage" values from the registry and assigns them to the global Printer Page variables. These values are used to initialize the controls of the Printer Properties Page (hence the name PrinterPage).

The "Printer" and "PrinterDMF" registry values contain device specific information. When the actual process of printing is started these values are used to create a printer device context. In case the values are missing or corrupted GFA-BASIC will obtain a device context for the default printer and starts printing without any user intervention.

How changes affect GB32
If you paid attention, you will have noticed that GFA-BASIC 32 supports the logic for using different printer than the default printer, but lacks the possibility to select one. How come? Well in all their wisdom Microsoft decided to change the Page Setup common dialog box starting with Windows Vista. Previously, until Windows XP, the Page Setup common dialog box contained a third button labeled 'Printer ...". It was this button that allowed the user to select a different printer from the Page Setup dialog box.

Workaround? Hardly!
When GFA-BASIC 32 was released it could not be known that MS would remove the "Printer ..." button. GB32's printer selection logic was build entirely around this button in the Page Setup dialog. That was - and still is - the only way to select a different printer. The only remaining option is to set another printer as the default printer from the Control Panel, although that wouldn't suffice. You should also remove the registry settings "Printer" and "PrinterDMF".

By providing this background information I'm hoping for some input as of how to get an actually working hotfix.

29 December 2012

Memory Leak with Form.Picture Object

When you assign an image to the Picture property of a Form Ocx, and don't release the Picture explicitly, a memory leak occurs when the Form is destroyed.

An image can be assigned using the Form-Editor Properties window in the sidebar. For a Form object the Properties window shows a Picture property that can be assigned an image (bitmap, icon, cursor, GIF, JPEG, and metafiles) by double clicking in the value column. Behind the scenes the LoadForm command - that is used to load a Form created with the Form-Editor - will create a COM Picture object on behalf of the Form. The dynamically allocated Picture COM object is then assigned to the Form.Picture property. 
However, a program may also set a Picture object to the Form.Picture property explicitly in code.

The memory leak occurs when the Form is closed. In the process of destroying all resources the Picture object is simply forgotten. The memory for the image is never released and the reference count on the COM object never reaches zero. Not only the memory necessary to store the image, but the memory allocated for the COM object will remain occupied. The memory used to store a bitmap can be of a considerable size and after some time you may even run out of memory. This most likely will present itself after RUNning a program multiple times within the IDE.

The best place to set the Picture Object to Nothing is within the Form_Destroy() event sub. A program cannot release the object when the Form has gone (==Nothing).

The leaked memory can never be reclaimed, because after the Form is destroyed the pointer to the Picture's COM Object is zeroed out. Selecting 'Cleanup Resources' from the Project menu will not work.

16 November 2012

Windows 8: Download WinHlp32.exe

GFA-BASIC 32 for Windows works perfectly well under Windows 8 (Win32/COM). GB32 is the ultimate professional BASIC to write native Windows 32 desktop programs to be compatible with older OSes and the latest Windows OS Win 8.

However to be useful with Windows 8 you will need to display the older-formatted help file using WinHlp32.exe. This program is required to display 32-bit Help files that have the ".hlp" file name extension. To view .hlp files on Windows 8, you need to install this application.

Download it from Microsoft Download Center.

11 October 2012

An owned Form

Until of the older set of chm MSDN Library files (<= October 2001) were replaced by the newer MSHELP, the MSDN contained an article called "Win32 Window Hierarchy and Styles" by Kyle Marsh, September 29, 1993. This article explains how top-level windows (aka Forms) relate to each other.

Form is a top-level window
A Form window, whether is is created using OpenW, Dialog, or Form, is a top-level window by default. A top-level window is any window that is not a child window. Top-level windows do not have the WS_CHILD style. All top-level windows are also connected to the desktop window through the parent window handle, GetParent(). Top-level windows are connected to the desktop window as if they were child windows of the desktop, and can be considered children of the desktop in that parent/child navigation techniques can be used to move between a top-level window and the desktop window. All top-level windows are displayed in the client area of the desktop window and thus behave as if they were children of the desktop for display purposes.

The parent window
Each window, being a top-level or a child window, has a parent window. The desktop window occupies the first level of the windows hierarchy and top-level windows occupy the second level. Child windows, which are windows created with the WS_CHILD style, occupy all other levels. Child windows connect to their parent window in the same way top-level windows connect to the desktop window.

The owned window
Top-level windows can own or be owned by other top-level windows. One Form can own another Form. An owned window is always displayed above its owner in the Z order and is hidden when its owner is minimized. Try this and see what happens, you cannot display Form Win_1 on top of Form Win_2:

OpenW 1
Me.Caption = Me.Name
OpenW Owner Win_1 , 2
Me.Caption = Me.Name
Until Me Is Nothing

Win_2 is owned by Win_1. Owned windows are not hidden when their owner is hidden. Thus, if window #1 is minimized, window #2 is hidden as well.
BTW you can set the owner using the designer in the Properties window. A Form has a an Owned property that can be set to True. After loading the Form using LoadForm the current active Form as referenced by Me will be set as the owner.

On the API level an owned window relationship is created by passing the window handle to the owner window in the hwndParent parameter of the CreateWindow() function. GB32 passes the window handle of the Form object specified in the Owner clause in the OpenW statement. To top-level window #2, window #1 is the owner, but not its parent window. The parent window for both Forms is the desktop window.
The GetParent() API function is not used to obtain the owner of a top-level window, that would return the desktop window handle. Insert the following lines before the start of the message loop. Both will return Null (0).

Print GetParent(Win_1.hWnd)
Print GetParent(Win_2.hWnd)

To obtain the owner GetWindow(hWnd, GW_OWNER) API function should be used. Insert these lines as well, and see how their results differ.

Print GetWindow(Win_1.hWnd, GW_OWNER)
Print GetWindow(Win_2.hWnd, GW_OWNER)

Finally, closing the owned top-level Win_2 won't automatically close Win_1. After Win_2 has been destroyed the current Form Me is set to Win_1. The global message loop will not end until Me == Nothing, which will not happen until Win_1 has been closed.

25 July 2012

Desktop Applications Again

PCWorld featured an article on changing habits of users of desktop, web, and smartphone software. Some quotes.

Cloud computing
"We had a thesis that people did not want to install software; that the cloud meant that people could use a browser to interact with software and would never have to install anything. We were completely wrong,” Jones says. “People love installing software"

The Web is out
No more Web-based applications: "But given what developers have discovered firsthand, we may see users clamor for native desktop apps, where they previously deemed Web apps to be sufficient."

Also read the blogs referenced in this article. GFA-BASIC 32 survived its time.

18 July 2012

How does GB32 define a word?

Did you ever realize how GB32 defines a word? Is it consistent across the different editor operations? Does a Ctrl-Left keyboard shortcut point to same word start as Ctrl-F? The Ctrl-F accelerator shows the Find Dialog Box where the Find What edit text control defaults to the current word. Is this the same word that is used in Ctrl-Left and Ctrl-Right actions? And what about the mouse double-click? What word does the editor use for the FindNextWord, to locate the next occurrence of that word? An example.

Global iVar1% = $4DC41C
Dim dd As Double = 2.45!

The next table shows the result of the 'current word' used to start the operation.

Word Ctrl Right Find Dlg Double Click
Global Global Global Global
iVar1% iVar1% iVar1 iVar1%
$4DC41C 4DC41C 4DC41C $4DC41C
2.45! 2.45! 2 2 or 45, depending on the position of the caret

Disturbing? At least confusing, because it isn't consistent. To me the whole module containing the editor's find and replace code seems a bit clumsy. (Maybe Frank Ostrowski was somewhat distracted during its development.) I can only guess what leaded to this inconsistency. The $AutoPostFix directive may have caused the decision to use the variable name without a postfix with the Find Dialog. Anyway, I don't like it. In my opinion all operations that determine a word should select the same word and the green marked words seem to be best candidate.

If there would be separate functions that return the current word, it would give me a starting point. Unfortunately, all operations mentioned above have their own getcurrentword algorithm. Another set back, by now I hoped to have had implemented the COM support I promised.

16 July 2012

Efficiently building a String

If you need to build a string by adding lots of pieces together, GFA-BASIC's string handling is relative slow because a new string is created in memory every time a new piece is added.

Often, alternatives are used like string builder functions. String builders allocate a string chunk and then uses memory copy methods to manipulate the data within the same string's memory. You'll find them in all frameworks and libraries of popular programming languages.

GB32 offers an efficient string builder as well, although it is bit hidden. The sprintf() function reserves a chunk of stack memory and uses memory copy functions to copy characters form the source string to a destination string. When it hits on a data placeholder in the source string it copies the data into destination string. Only when all characters and data are copied to destination buffer, the stack buffer in converted to a an actual String.

The difference between the two methods is illustrated below:

Dim sEdPos As String
' Assemble a caret position in a long
Dim EdPos As Long = MakeLong(12, 1)
' Put the string together
sEdPos = "Line: " + Dec(HiWord(EdPos)) + _
  " Column: " + Dec(LoWord(EdPos))
' Or use sprintf()
sEdPos = sprintf("Line: %d Column: %d", _
  HiWord(EdPos), LoWord(EdPos))

12 July 2012

(GB/VB)BASIC isn't dead

You are invited to visit "TIOBE Programming Community Index" at : http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html

See the trends in computer language. Right now plain C enjoys the first position, with Java and C++ slowly going down and Objective-C going up. (Visual) Basic remains steady at position 6. Don't confuse it with VB.NET, which is located at position 15. But VB.NET has an increasing audience also.

07 July 2012

Write # or Print #

Why does the GB32 Hash type use Write to save the data from a hash table (= dictionary)?

The correct answer is: In contrast with Print #, Write # uses a non-locale format. In Basic we often choose Print # over Write #, but both have their own goal. It has even been suggested that Write is a relic from prehistoric BASICs. However, this isn't true. To be able to correctly read data from a file into variables using Input #, use the Write # statement instead of the Print # statement to write the data to the files. Using Write # ensures each separate data field is properly delimited.

Both, the Print # and Write # commands, can be used to write data to a sequential text file, however the commands cause the information to be written to the text file differently.

The Write # statement is used to write raw data to the text file as comma- delimited and has the following syntax:

Write #filenumber[,outputlist]

All data written to the file using Print # is internationally aware; that is, the data is properly formatted/converted using the appropriate decimal separator. The syntax is similar, but the result quite different.

Print #filenumber[,outputlist]

Difference 1 – Quotation marks
The Write# command places quotation marks around all text values (strings), but not numeric data. The Date fields are surrounded with #s (pound signs). 
The Input# command is used to retrieve values from a text-only file created with the Write# statement (removes quotation marks from strings).

The Print# command does not enclose the data in quotation marks.

Difference 2 – Delimiter
The Write # command separates two or more values on the same command line with commas.The Print # command separates two or more values on the same command line (separated by a comma) with a tab character.

Print # writes an image of the data to the file, you must delimit the data yourself so it prints correctly. If you use Tab (or a comma) with no arguments to move the print position to the next print zone, Print # also writes the spaces between print fields to the file.

Advantages of Write
When using Write # to write data to a file, several universal assumptions are followed so the data can always be read and correctly interpreted using Input #, regardless of locale:

  • Numeric data is always written using the period as the decimal separator.
  • For Boolean data, either #True# or #False# is printed. The True and False keywords are not translated, regardless of locale.
  • Date data is written to the file using the universal date format. When either the date or the time component is missing or zero, only the part provided gets written to the file.
  • Nothing is written to the file if outputlist data is Empty. However, for data, #Null# is written.
  • If outputlist data is Null data, #Null# is written to the file.
  • For Error data, the output appears as #Error errorcode#. The Error keyword is not translated, regardless of locale.

To get your memory refreshed, look at the following code:

OpenW 1
Write App.Name          // "NoName"
Write CFloat(3.2)       // 3.2
Write CDate(Now)        // #2012-07-11 12:42:33
Write CBool(0)          // #False#
Write CHandle(0)        // #Null#
Write CFloat(3.2), Date // 3.2,#2012-07-11 12:42:33

' Print inserts a space at the front of a number
Print App.Name          // NoName
Print CFloat(3.2)       //  3.2
Print CDate(Now)        // 11-7-2012 12:42:33
Print CBool(0)          // False
Print CHandle(0)        //  0
Print CFloat(3.2), Date // 3.2      #2012-07-11 12:42:33

Unlike the Print # statement, the Write # statement inserts commas between items and quotation marks around strings as they are written to the file. You don't have to put explicit delimiters in the list. Write # inserts a newline character, that is, a carriage return–linefeed (Chr(13) + Chr(10), after it has written the final character in outputlist to the file.

If, at some future time, you want to read the data from a file using the Input # statement, use the Write # statement instead of the Print # statement to write the data to the file. Using Write # ensures the integrity of each separate data field by properly delimiting it, so it can be read back in using Input #. Using Write # also ensures it can be correctly read in any locale.

12 April 2012

Ocx background color

Not all OCX controls support a .BackColor property to change the background color, although the control itself allows changing it. Here GB32 conforms to VB too much. Rather than adding a property to the implementation – which would require another patch in executable code – we can use a different approach.

All OCX controls share a user-defined structure to store the current settings of the wrapped control. Setting and getting property values is sometimes nothing more than changing and setting a member of the structure. Setting and obtaining the background value is one of them. The BackColor property stores its value in the member at offset $B8 of the start of object’s data block. The following code changes the background of a StatusBar Ocx.

Form frm1
Ocx StatusBar sb1
Trace SetBkColorControl(sb1, RGB(23, 56, 229))
Until Me Is Nothing

Function SetBkColorControl(Ctrl As Control, Color As Long) As Long
  Const OffBackColor = $B8
  Local Long ObjPtr  = Long{*Ctrl}
  SetBkColorControl  = Long{ObjPtr + OffBackColor}
  {ObjPtr + OffBackColor} = Color
  ~InvalidateRect(Ctrl.hwnd, 0, 1)

  ' Notes
  ' 1 Using the IDispatch interface does not work
  '   when the GetTypeInfo doesn't support the
  '   the .BackColor property.
  ' BackColor is not a property of StatusBar
  If 0 Then Ctrl.BackColor = Color

  ' 2 When using XP Visual Themes the Visual Style
  '   theme takes over and gets precedence over
  '   GB OCX propery settings.

Note – Not all controls let their background set this way. Just experiment. 

03 April 2012

ImageList error signals missing manifest

When an application adds an Ocx ImageList to a Form using the Form-Editor an error might occur after compilation to EXE.

When the EXE is started the application stops executing displaying an ImageList loading error. This error occurs when the application is developed using a GfaWin32.Exe.manifest file. The manifest file forces the executable (named in its file name) to use the newer comctl32.dll version 6.x to apply more appealing visual styles. This DLL contains an updated load and save function for Image List common controls. When your application is compiled to a stand-alone the ImageList data is saved within the EXE using the ImageList_Write() API from the comctl32.dll version 6. Now when you launch the stand-alone EXE without a reference to the newer common control DLL, the ImageList_Read() from the older DLL is used. And, well… these functions are not compatible.

After compiling an application to a stand-alone EXE, a manifest file for the stand-alone EXE must be included, otherwise the executable will start without using the newer comctl32.dll. So, if you name your application “myapp.exe” you must include a “myapp.exe.manifest” file along with the EXE. You can easily copy the GfaWin32.exe.manifest file to the application’s directory and rename it by replacing the first part to the name of your application. A GB32 project would then include the following files:


Note - It doesn’t hurt to include a manifest file for systems that don’t support comctl32 version 6.

05 February 2012

How a GLL Dialog # is created

The Dialog command used in a GLL editor extension is quite different than the Dialog in a normal GB32 application. How is that possible?

When one or more GLLs is loaded in memory, the IDE assigns the compiled GLL an array with pointers to the GB32 library functions in the runtime DLL (or Ocx). This is the same array with pointers each application gets when it is loaded. This way a call to a library function like Left$(), Dialog, or OpenW, etc, will reference the appropriate function in the runtime. When the GLL is loaded some of these pointers are replaced by addresses of functions inside the IDE executable. This way when the GLL invokes a dialog related function it will call the function inside the IDE, rather than in the runtime. All the dialog box related functions and commands are replaced. Examples are the Control command and the names of standard and common controls. You'll find an overview of the valid GB32 dialog box related statements and functions in the help file.

The GB32 dialog box related statements and functions are GfaBasic for Windows 16-bit-compatible. However, the window styles specified in the Dialog # command may come as a surprise. When you omit the style GB32 uses a default window style. GB32 processes as follows:

' Create a dialog box
Local Long dwStyle = 0
Dialog # 1, 200, 200, 536, 400, "" , dwStyle

' How GB32 sets the Dialog window styles.
If (dwStyle %& DS_MODALFRAME) Then

Else If dwStyle == 0                  ' Default Style?
  If Len(szTitle) == 0                ' No Title?
dwStyle  |= DS_SYSMODAL       ' Top Most

The system creates the window (dialog box) with the WS_EX_TOPMOST style using CreateWindowEx(). The dialog has no owner or parent. It is modeless because it exist parallel to the Gfa_hWnd IDE window.
The WS_EX_TOPMOST style does not prevent the user from accessing other windows on the desktop.
This gives you the tools puzzle the appearance of GLL dialog box and might explain its unexpected visual style.

29 January 2012

Gfa_Setting() returns extra #0

Gfa_Setting is available as a statement and as a function. They are used as follows:

' Set/Create a subkey
Gfa_Setting("MySubKey") = mysetting$
' Get subkey value ($)
mysetting$ = Gfa_Setting("MySubKey")
' Delete a subkey
Gfa_Setting("MySubKey") = ""

The Gfa_Setting(subkey$) reads a value from the subkey under HKEY_CURRENT_USER\Software\GFA\Basic using the RegQueryValueEx() API function that retrieves the data for a specified value name associated with an open registry key. The advantage of using this API is that it doesn't require a data type. Even better, the function returns a code indicating the type of data stored in the specified value. The possible type codes are:

Const REG_NONE  = 0
Const REG_SZ  = 1
Const REG_EXPAND_SZ  = 2
Const REG_BINARY  = 3
Const REG_DWORD  = 4
Const REG_LINK  = 6
Const REG_MULTI_SZ  = 7

After invoking RegQueryValueEx GB32 checks the value in the type parameter and than decides how to copy the data to the GB32 variable used in the var$ = Gfa_Setting(subkey$) code. When the type value returned is REG_SZ or REG_EXPAND_SZ or REG_BINARY then GB32 uses the StrPeek(addr, size) function to create and copy the data to the string. The size of the data is also returned by RegQueryValueEx. Simple enough. But there is a catch that is overlooked:

"If the data has the REG_SZ, REG_MULTI_SZ or REG_EXPAND_SZ type, then the data will also include the size of the terminating null character or characters."

GB32 uses the size value to invoke StrPeek and stores the terminating #0 character inside the string and sets the length of the string to the size of data + 1 for the #0 character. GB32 uses the same function for Gfa_BinSetting() and does not care for the value of the size.

Now, when you apply a string concatenation (str & str2) the second string doesn't seem to be appended to the first string. The including #0 character in the last position of the string makes the use of string functions awkward. When you pass that string to a function that expects a C-string the string data is read to the first #0 character. Internally, and externally on the API level, many functions expect a C-string and stop processing the string at first occurrence of a #0 character.  

For now, you best use ZTrim() on the return value of Gfa_Setting(). It seems not to predict how many #0 characters will be included. See underlined words in the quotation.

' Get subkey string value
mysetting$ = ZTrim(Gfa_Setting("MySubKey"))

20 January 2012

Gfa_Line doesn't always redraw the caret

The GFA-BASIC implementation of the editor-extension contains a large set of Gfa_* functions and commands. However, in contrast with the term 'editor extension', the Gfa_* statements are not restricted to the (text) editor only. The GFA-BASIC IDE application itself is divided into several entities such as an application part, a form-editor, a compiler, and a text-editor. Only a part of the Gfa_ statements apply to the text-editor only, and the most important terms in this respect are 'text-selection' and 'insertion point'.

The active point
The text-selection represents a selection in the code text in the editor window. Note that a selection can be a single point (the insertion point) or a contiguous range of text. Using Gfa_ commands you can move the insertion point, control which text is selected, and modify the contents of the selection. When the text-selection is restricted to a single point, Gfa_Line and Gfa_Col return its position. Also, since there is no selection, Gfa_Line equals Gfa_SelLine and Gfa_Col equals Gfa_SelCol.

Whether or not the text is selected, the Gfa_Line and Gfa_Col always indicate the active point. This is the point where all other text actions are performed. When a range of text is selected the insertion point can be located at the beginning or at the end of the selection.

Command Description
Gfa_Line Gets/sets the line where the insertion point is.
Gfa_Col Gets/sets the column where the insertion point is.
Gfa_SelLine Gets/sets the line at the bottom of a selection. The bottom line is not necessarily at the active end of the selection.
Gfa_SelCol Gets/sets the column at the bottom of a selection. The bottom line is not necessarily at the active end of the selection.

Moving the caret
The insertion point is represented by a caret, is a blinking line, block, or bitmap in the client area of a window. The caret typically indicates the place at which text (or graphics) will be inserted. The caret is a system resource and controlled by invoking Windows system API calls such as ShowCaret() and SetCaretPosition(). Each time the caret is moved SetCaretPosition() is invoked.
Programmatically, you move the caret using one of the following Gfa_ commands:

Command Key Press
Gfa_Left [count ] LEFT ARROW
Gfa_Right [count] RIGHT ARROW
Gfa_Down [count] DOWN ARROW
Gfa_Up [count] UP ARROW
Gfa_PageDown PAGE DOWN
Gfa_PageUp PAGE UP

count is optional. A Long that specifies the number of times you want to repeat this action. The default is one.

  • When executing one of these commands (or pressing the key(s)) the current selection is canceled before the action is performed.
  • These are relative movements. They move the caret relative to the current active insertion point represented by Gfa_Col and Gfa_Line.
  • Many key press actions are not represented by a Gfa_ command. For instance: word-left, word-right; end-of-line, start-of-line; etc.

So, how do you move the caret to an absolute position, rather than to a relative one? Within a text line the Gfa_Col = newcolumn command will do the trick. It cancels any selection and updates the caret position. By assigning 0 to Gfa_Col the caret moves to the start-of-the-line and by setting it to some large number (_maxInt) is moves to the end-of-the-line. Consequently, you expect Gfa_Line to do the same for lines. Well it does modify the current line, but it sometimes 'forget" to update the caret visually. Meaning, it forgets to put the caret into its new position.

Gfa_Line = doesn't redraw caret
The Gfa_Line = command differs in two aspects from all other commands. First it doesn't cancel a selection, and, secondly, it doesn't always redraw the caret in it's new position. It does however change the current line used for text operations, which is important because some text operations are line oriented. So, without displaying the caret at the new position (combined with a possible scrolling) the current active line can be changed to perform actions on the text line (Gfa_Update, Gfa_Text = , delete and insert lines, setting a bookmark, clipboard actions, etc). The problem is that the editor extension implementation lacks a command to update the caret explicitly.

Workaround to redraw caret
To explicitly make the caret visible after invoking Gfa_Line = we must take into account that as portion of the text maybe selected. So, first we must cancel any selection and after invoking Gfa_Line =  we must redraw the caret ourselves.

Global Gfa_SetCaret As Pointer Byte
Pointer(Gfa_SetCaret)       = $4DC41C
Global Const Ed_SetCaretPos = $409B99

' Cancel selection (if any)
Gfa_Col = 0 ' Set/Goto new line Gfa_Line = iGotoLine ' Set global flag (when in OnWMCommand) Gfa_SetCaret = 1 ' Or call directly ~StdCall(Ed_SetCaretPos)()

Most (if not all) IDE commands are processed in the IDE's OnWMCommand() function. This is a central routine to execute all accelerator key commands, menu commands, and the GLL's key and menu events. Besides this, it adds the commands to the UNDO-buffer and stores them in a keyboard macro when Gfa_IsRecording = True. At the end of IDE's OnWMCommand() function the global variable Gfa_IsCaret is checked to see if any of the executed commands did set this flag (to have the caret redrawn). If so, before returning from OnWMCommand() the IDE's Ed_SetCaretPos() function is invoked to redraw the caret and Gfa_SetCaret is cleared.

Now you have some background knowledge of Gfa_Line you have the tools to properly redraw the caret.