[SOLVED] How to scroll a TMemo to it's end (Windows+Linux)

[Hartmut]

When searching the Forum for this question, I found endless matches, but unfortunately none of them worked for me:

Code: Pascal  [Select][+][-]

1. procedure showMemo(SL: TStringList);
2.    var MM: TMemo;
3.    begin
4.    MM:=Form1.Memo1; {abbreviation}
5.    MM.Lines.Assign(SL); {assigns a StringList to TMemo 'MM'}
6.  
7. // MM.ScrollBars:=ssVertical;
8. // MM.VertScrollBar.Position:=MaxLongInt;
9.  
10. // MM.SelStart:=length(MM.Lines.Text);
11. // MM.SelStart:=length(MM.Lines.Text)-1;
12. // MM.SelStart:=MaxLongInt;
13. // MM.SelLength:=0; {used always after a 'MM.SelStart:=...'}
14.  
15. // MM.CaretPos := Point(0, MM.Lines.Count-1);
16.  
17.    Form1.ShowModal; {shows the Form which contains TMemo 'MM'}
18.    end;
19.  

As you can see, I assign the contens of a StringList to a TMemo 'MM', then I try to scroll it to the end (but this does nothing) and then show the Form which contains TMemo 'MM'. Result: the Form with the Memo ist displayed and the content of the Memo is correct (the content of the StringList), but the Memo shows it's beginning and not it's end. A vertical scrollbar is displayed.

I tried all of the above alternatives, one by one (only 'MM.SelLength:=0' always after one of the 'MM.SelStart:=...').

Until now I only tried on Linux (Ubuntu 24.04 GTK2 with Lazarus 3.4.0 and FPC 3.2.2).
I want solutions for Windows and Linux.
Thanks in advance.

[cdbc]

Hi
You can try this:

Code: Pascal  [Select][+][-]

1. MM.Selstart:= UTF8Length(MM.Caption);

I do see, that you tried that, but here with me it works as advertized...
Regards Benny

[Hartmut]

Thanks Benny, but unfortunately it does not work (as the other 'MM.Selstart:=...' I tried before).

[cdbc]

Here you go.
Works like a charm on PCLinuxOS with QT6, got no way of testing on GTKx
Regards Benny

[Remy Lebeau]

I don't know if this works the same for FPC/LCL, but in Delphi VCL on Windows I use this:

Code: Pascal  [Select][+][-]

1. Memo1.SelStart := Memo1.GetTextLen;
2. Memo1.SelLength := 0;
3. // alternatively:
4. // var len: Integer := Memo1.GetTextLen;
5. // Memo1.Perform(EM_SETSEL, len, len);
6.  
7. Memo1.Perform(EM_SCROLLCARET, 0, 0); // <-- the magic happens here

[Hartmut]

Thanks Remy Lebeau. As said my current problem is on Linux. Because there I did not find EM_SETSEL and EM_SCROLLCARET, I stole them from Windows (don't know if this is legal) and tried this 2 alternatives:

Code: Pascal  [Select][+][-]

1. const EM_SCROLLCARET = 183; {from /.../fpcsrc/rtl/win/wininc/messages.inc}
2. MM.SelStart := MM.GetTextLen;
3. MM.SelLength := 0;
4. MM.Perform(EM_SCROLLCARET, 0, 0); // <-- the magic happens here

and:

Code: Pascal  [Select][+][-]

1. const EM_SETSEL = 177;      {from /.../fpcsrc/rtl/win/wininc/messages.inc}
2.       EM_SCROLLCARET = 183; {from /.../fpcsrc/rtl/win/wininc/messages.inc}
3. var len: Integer;
4. len:=MM.GetTextLen;
5. MM.Perform(EM_SETSEL, len, len);
6. MM.Perform(EM_SCROLLCARET, 0, 0); // <-- the magic happens here

Unfortunately both alternatives did not work (did not scroll).


Thanks a lot Benny for your demo. The good news is, it works (Linux Ubuntu 24.04 GTK2 with Lazarus 3.4.0 and FPC 3.2.2). But you have a main difference: you scroll in Button3Click(), which is during ShowModal(), while I need scrolling before calling ShowModal() as showed in my 1st post, because I want an automatic scroll and don't want the need to press a button each and every time to see the end of the Memo.

So I modified your demo by adding a FormCreate-Event:

Code: Pascal  [Select][+][-]

1. procedure TForm1.FormCreate(Sender: TObject);
2.    begin
3.    writeln('FormCreate');
4.    Memo1.Lines.LoadFromFile('unit1.pas');
5.    Memo1.SelStart:= UTF8Length(Memo1.Caption);
6. // Memo1.SelLength:=0; // did not help
7.    end;

Unfortunately now your demo does not work anymore.

In my real code (which is a common unit, used by many programs):
 - the Form is created dynamically by CreateNew(Application)
 - then everything else is initialized
 - then the data is assigned from a StringList 'SL' to the Memo 'MM' via MM.Lines.Assign(SL)
 - then ShowModal() is called.

How can I cause a scroll to the Memo's end before calling ShowModal() - on Windows+Linux?

[CM630]

Have you tried TRichMemo?

[Hartmut]

Hello CM630, I tried TRichMemo earlier in another context and faced a lot of problems.

In my real code (which is a common unit, used by many programs)

As said, I'm searching for a solution for a common unit, used by many programs, where I don't want to set everything upside down by replacing a TMemo by a TRichMemo - which a) would require endless effort for many many tests (double for Windows and for Linux) and would b) for sure cause a couple of other problems - even if scrolling would work there before calling ShowModal().

[cdbc]

Hi
Hmmm... TMemo reacts to / manipulates the 'Viewport' when visible...
· Take a look at 'Application.QueueAsyncCall'
· Create a 'procedure HandleAsync(aData: ptrint);'
·· in this proc you call "MM.SelStart:= UTF8Length(MM.Caption);"
· Create a 'FormShow' event-handler
· In that handler call QueueAsyncCall(@HandleAsync,0), to get a small delay

The above ought to do the trick 
Regards Benny

[Zvoni]

Thanks a lot Benny for your demo. The good news is, it works (Linux Ubuntu 24.04 GTK2 with Lazarus 3.4.0 and FPC 3.2.2). But you have a main difference: you scroll in Button3Click(), which is during ShowModal(), while I need scrolling before calling ShowModal() as showed in my 1st post, because I want an automatic scroll and don't want the need to press a button each and every time to see the end of the Memo.

So I modified your demo by adding a FormCreate-Event:

Code: Pascal  [Select][+][-]

1. procedure TForm1.FormCreate(Sender: TObject);
2.    begin
3.    writeln('FormCreate');
4.    Memo1.Lines.LoadFromFile('unit1.pas');
5.    Memo1.SelStart:= UTF8Length(Memo1.Caption);
6. // Memo1.SelLength:=0; // did not help
7.    end;

Unfortunately now your demo does not work anymore.

In my real code (which is a common unit, used by many programs):
 - the Form is created dynamically by CreateNew(Application)
 - then everything else is initialized
 - then the data is assigned from a StringList 'SL' to the Memo 'MM' via MM.Lines.Assign(SL)
 - then ShowModal() is called.

How can I cause a scroll to the Memo's end before calling ShowModal() - on Windows+Linux?

*sigh*.... and have you tried the OnShow-Event instead of the OnCreate, hmm?
If something works DURING the Form is shown, but not before........

In my real code (which is a common unit, used by many programs):
 - the Form is created dynamically by CreateNew(Application)
 - then everything else is initialized
 - then the data is assigned from a StringList 'SL' to the Memo 'MM' via MM.Lines.Assign(SL)
 - then ShowModal() is called.
 - In OnShow do the Scrolling

Alternative might be OnActivation (since that one fires after OnShow), though with a Blocking-Variable "FirstRun" or something like that

[Hartmut]

Short intermediate info: the solution from cdbc with QueueAsyncCall() in FormShow-Event works on Linux! Will test on Windows soon and report then.

@Zvoni: yes, I had already tried OnShow-Event and OnActivation before I started this Topic, but both had not worked (without QueueAsyncCall).

[Hartmut]

Meanwhile I tested, the solution from cdbc with QueueAsyncCall() in Event FormShow() works on Windows too. The problem is solved.
Thanks a lot to all who tried to help me, especially Benny.