RichMemo/WorkArounds

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Revision as of 05:05, 29 September 2020 by Dbannon (talk | contribs) (note about cocoa.)
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RichMemo is a great component, but its not finished. This page lists some work arounds for some incomplete RichMemo functions. Its important to note that the things mentioned here are NOT official characteristics of RichMemo. They are things found to work in the current release. Its likely they will change in the future, please don't assume that they will continue to work or even that they will even continue to be needed.

If you use any of these work arounds, mark your code accordingly and test carefully when you update RichMemo ! If you don't need a work around, get rid of it, some of these here are quite ugly !

Observed Issues

GetTextAttributes()

Status : Linux - OK; Windows - needs patch; Mac - Needs Patch.

The problem : An issue of RichMemo.GetTextAttributes() not detecting an out of range first param was fixed early 2020. However, that fix introduced a bug in macOS that stops GetTextAttribute working altogether and therefore much of RichMemo.

The problem relates to the use of GetTextLen() in TCustomRichMemo.isValidCharOfs(), #1128 of RichMemo.pas and can be easily fixed by adding some ifdefs that use UTF8Length() instead. make the function look like this - 

function TCustomRichMemo.isValidCharOfs(TextStart: integer): Boolean;
begin
  // TextStart, where TextStart = GetTextLen, is a location at the end of the text
  // it's technically a valid character offset (position)
  // Because it's where the entry should occur
  {$ifdef LCLCOCOA}Result := (TextStart >= 0) and (TextStart < length(Text));
  {$else}Result := (TextStart >= 0) and (TextStart <= GetTextLen);{$endif}    // DRB 2020-09-25
end;

The unpatched function works fine under Linux and Windows.

Documented at RichMemo#GetTextAttributes

Logged https://bugs.freepascal.org/view.php?id=32296

Search() fails under Cocoa

Status : Linux,Windows - OK; Mac Cocoa fails.

The Problem : On Cocoa, always returns false.

Logged :

Documented at RichMemo#Search

The Test : 

var
    Start, len : longint;
begin
    RichMemo1.Clear;
    RichMemo1.Append('This is some text to search');
    if Richmemo1.Search('some', 1, 25, [], Start, Len) then
        showmessage('found ' + inttostr(Start) + ' ' + inttostr(Len))
    else showmessage('Failed to find');
end;

Tells us it found nothing.

The Fix : Nothing tested, it should/could be possible to search RichMemo1.Text, as its a Mac only issue and Mac has single char line ending, reasonably fast and easy ?

OnLinkAction does not set LinkStart and LinkLen on Win10

Problem : OnLinkAction does not set LinkStart and LinkLen on Win10. A call back procedure, eg Form1.RichMemo1LinkAction(..) has those two parameters to indicate where the link the user clicked is. However, on Win10 (at least) they are set randomly.

The test : On a Form, put a RichMemo and a button. Make the Button's Click event look like this - 

procedure TForm1.ButtonLinkClick(Sender: TObject);
begin
    RichMemo1.Clear;
    RichMemo1.Append('A Link OK ? (give it a click)');
    RichMemo1.SetLink(2, 4, True);
end;

Then make the RichMemo's OnLinkAction event look like - 

procedure TForm1.RichMemo1LinkAction(Sender: TObject; ALinkAction: TLinkAction;
  const info: TLinkMouseInfo; LinkStart, LinkLen: Integer);
begin
     Showmessage('clicked [' + RichMemo1.GetText(LinkStart, LinkLen) + '] at ' + inttostr(LinkStart) + ' '	+ inttostr(LinkLen));
end;

Then run it, click the button, click the link.

The Fix : Fortunately, SelStart is set to where the user clicked, must be somewhere on the link. 

procedure TEditBoxForm.RichMemo1LinkAction(Sender: TObject;
    ALinkAction: TLinkAction; const info: TLinkMouseInfo; LinkStart,
    LinkLen: Integer);
var
     Index, Len : longint;
begin
    Index := RichMemo1.SelStart;
    Len := 0;
    while RichMemo1.IsLink(Index) do dec(Index);
    inc(Index);
    While RichMemo1.isLink(Index + Len) do inc(Len);
    Showmessage('clicked [' + RichMemo1.GetText(Index, Len) + '] at ' + inttostr(Index) + ' '	+ inttostr(Len));
end;

I Cannot determine the system default or application font.

The Problem : Cannot determine the system default or application font. Maybe someone else can suggest a more elegant way to find out this information, I cannot ! And it turns out that we need to know that font because a call to SetLink() changes the in use font to that one !

The Fix : Well, this is tacky but works. Make a call to SetLink() from OnShow(..), record the font and then clear it. Should work on all systems. 

procedure TEditBoxForm.FormShow(Sender: TObject);
var
  FP :  TFontParams;
begin
    RichMemo1.Clear;                     
    RichMemo1.Append('a line of text');
    Richmemo1.SetLink(2, 4, true);       
    RichMemo1.GetTextAttributes(4, FP);
    Showmessage('Looks like we are using ' + inttostr(FP.Size) + ' ' + FP.Name);
    RichMemo1.Clear;
 end;

SetLink() Fails on Linux

Status : Linux - needs patch; Windows - OK; Mac - Not Working.

The Problem : SetLink() Fails on Linux.

Reported : http://forum.lazarus.freepascal.org/index.php/topic,37850.0.html

Seems that if there is an existing tag covering the spot where we want to put a link, it fails. But if we clear any tags in that area first, all good. This may not suit all applications however ! Add a line to GTK2RichMemo, #1349 in class procedure Gtk2WSCustomRichMemo.SetTextUIParams(...) just before the call to gtk_text_buffer_apply_tag_by_name(...) - 

gtk_text_buffer_remove_all_tags(buffer,  @istart, @iend);

This will clear all tags and so gtk_text_buffer_apply_tag_by_name(...) has no problem setting 'link'. I am afraid I do not know why this is necessary and, yes, it will obviously clear tags on that text you may want there so, I don't think its a great solution, just one that suits me and is, perhaps, better than the existing behaviour.

SetLink() sometimes changes the font

The Problem : SetLink() sometimes changes the font. This happens when, for example, your code has detected that the user has just typed in a link address, SetLink() is called but as the user continues to type the font may look different. Its because after the call, the in use font is changed to be the system or application font. But before that call, it was what ever font RichMemwas using.

Documented : Not officially. This function, eg RichMemo1.SetLink(Start, Len, True), marks an existing section of text as being a 'Link'. Start is the zero based position of the character of the link, Len is the number of characters in the link, True means make a link, False means remove an existing link. An optional forth parameter is "LinkData" (that might be returned to the event) however, I could not get that to work and did not need it anyway...

The Fix : One solution to this problem is to make sure we are using the System Font all along. See above item on this page ....

GetStyleRange(..) does not count changes in background colour

The Problem : GetStyleRange(..) does not count changes in background colour when determining range boundaries under Windows. This function is documented at RichMemo#GetStyleRange

The Fix : Its trivial to make a new version of GetStyleRange(..) to replace the one built into RichMemo as long as you have already patched RichMemo1.GetTextAttributes(Index, FPr), as detailed above. 

function Form1.FPisEqual(const FP, FPRef : TFontParams) : boolean;
begin
  Result := false;
  if FP.name  FPRef.name then exit();
  if FP.size  FPRef.size then exit();
  if FP.bkColor  FPRef.bkcolor then exit();
  if FP.style  FPRef.style then exit();
  if FP.HasBkClr  FPRef.HasBkClr then exit();
  Result := true
end;

function Form1.GetStyleRange(const Index : longint; out Start, Len : longint) : boolean;
var
        FP, FPr :  TFontParams;
begin
    Result := false;
    Start := Index;
    if not RichMemo1.GetTextAttributes(Index, FPr) then exit();
    repeat
    	dec(Start);
        if not RichMemo1.GetTextAttributes(Start, FP) then break;
    until not FPisEqual(FP, FPr);
    inc(Start);
    Len := 0;
    repeat
        inc(Len);
        if not RichMemo1.GetTextAttributes(Start + Len, FP) then break;
    until not FPisEqual(FP, FPr);
    Result := True;
end;

So, instead of calling RichMemo1.GetStyleRange(..) just use GetStyleRange(..). The above fix has been added to CocoaRichMemo, trunk.

Sometimes newly typed characters are not made visible, Windows

Status : Linux - OK; Windows - Needs Workaround; Mac - OK.

The Problem : Newly typed characters are not made visible, Windows. Seems to happen for exmple when you scan over the document after each keypress by hooking into the OnChange(..) event. Or you write something into the RichEdit and immediatly call (eg) GetTextAttributes(). Wiping over with the mouse or moving the control makes the newly written text visible again. Strange.

The Test : On a form, put a RichText and a button. Make the Button's Click event look like - 

procedure TForm1.ButtonCheckVisibleClick(Sender: TObject);
var
	FP :  TFontParams;
begin
    RichMemo1.Append('Can you see this line of text ?');
    RichMemo1.GetTextAttributes(1, FP);              
end;


The Fix : (I warned you some of these are pretty ugly) I found that a call to SetLink(..) will refresh things ! Passing it 'false' says turn the link off, there is not one there anyway so all good. So make the above look like this - 

procedure TForm1.ButtonCheckVisibleClick(Sender: TObject);
var
	FP :  TFontParams;
begin
    RichMemo1.Append('Can you see this line of text ?');
    RichMemo1.GetTextAttributes(1, FP);
    RichMemo1.SetLink(0, 1, False);          
end;

This is not necessary under Linux or Mac but it does no real harm, technically its a waste of cycles so you may want to use an $IFDEF

Working on a Mac, macOS

On the associated Discussion page there is a table and some notes about my experiences with RichMemo on the Mac in August/September 2017. The results there are a bit confronting and I have chosen, at this stage, not to move them to the main page. At least until someone with some more Mac experience can confirm what I found.

In the mean time, anyone thinking of developing a cross platform application using RichMemo is advised to test their work quite early on the Mac. And, perhaps, share their experiences.


See Also

Retrieved from "http://wiki.freepascal.org/index.php?title=RichMemo/WorkArounds&oldid=140309"