[SOLVED] Placholder on TMemo
lazarus / 31-LCL

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pmesquita · 2021-11-08 19:48

Guys... I'm trying to modernize the ICU in my application one of the
items is: PlaceHolder as in html

I'm creating a canvas in TMemo to be able to write well in a primitive
way because I don't usually work with it but the text is only
"written" if the memo or has the focus or the mouse over it... but I
have no idea what it could be...

any tips..

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   TMemo =
class(StdCtrls.TMemo)   private     FH: String;     FSidecolor:
TColor;     FSideColorWidth: Integer;     FAskForAttention: Boolean; 
  FCanvas: TCanvas;     procedure SetH(const AValue: String);   
 procedure WMPaint(var Message: TWMPaint); message WM_PAINT;   
 Constructor Create(AOwner: TComponent); override;     Destructor
Destroy; override;    published     Property H: String  read FH  
Write SetH;   end;    ...{ TMemo } Constructor TMemo.Create(AOwner:
TComponent); begin  inherited Create(AOwner);  FCanvas:=
Tcanvas.Create; end; Destructor TMemo.Destroy; begin 
FreeAndNil(FCanvas);  inherited Destroy; End; procedure
TMemo.WMPaint(var Message: TWMPaint);var  Canvas:
TControlCanvas; begin  inherited;    Canvas := TControlCanvas.Create; 
  try      Canvas.Control := Self;     
Canvas.Font.Assign(Self.Font);      Canvas.TextOut(10, 10, FH);   
finally      Canvas.Free;    end; end; procedure TMemo.SetH(const
AValue: String); Begin  FH:= AValue;  Invalidate; End;

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jamie · 2021-11-08 22:49

Trying to decode your message here..

From what I get I think you are having update issues ?

Invalidate is a late comer but if you use Repaint after a change it
may update sooner for you.

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pmesquita · 2021-11-08 23:19

Hello,
I've attached a small example of the code I posted...
I tried using repaint but the problem persists... the text is only
displayed if the focus is on the memo or the mouse goes over it...

FPC: 3.2.2
Lazarus: 2.0.12

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jamie · 2021-11-09 01:01

Please look at this source directly here.

Its your original but I have added a delayed message because when the
OS WM_Paint returns it processes the DefaultWindowProc
which is when the memo updates if it needs updating.

 Your attempt was correct but out of sync with how windows processes
Memos and how the WM_PAINT handler is done..

 I suppose you can call the defaultWindowPRoc within your code then do
your canvas code afterwards and return the message as being handled
but what I have here should work across the pond ...


Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
Unit1; {$mode objfpc}{$H+} interface uses  Windows,Classes, SysUtils,
Forms, Controls, Graphics, Dialogs,
StdCtrls,LMessages,lclType,lclintf; type   { TForm1 } TMemo =
class(StdCtrls.TMemo)   private     FH: String;     FSidecolor:
TColor;     FSideColorWidth: Integer;     FAskForAttention: Boolean; 
  FCanvas: TCanvas;     procedure SetH(const AValue: String);   
 procedure WMPaint(var Message: TWMPaint); message WM_PAINT;   
 procedure Paint(Var Msssage); message LM_USER+1;     Constructor
Create(AOwner: TComponent); override;     Destructor Destroy;
override;    published     Property H: String  read FH   Write SetH; 
 end;  TForm1 = class(TForm)    Edit1: TEdit;    Memo1: TMemo;   
procedure Edit1Change(Sender: TObject);  private   public   end; var 
Form1: TForm1; implementation {$R *.lfm} { TForm1 }procedure
TMemo.Paint(Var Msssage);Var  C:TControlCanvas;Begin     C :=
TControlCanvas.Create;    try      C.Control := Self;     
C.Font.Assign(Self.Font);      C.TextOut(10, 10, FH);    finally     
C.Free;    end;end; procedure TForm1.Edit1Change(Sender:
TObject);begin  memo1.H:=Edit1.Text;end; Constructor
TMemo.Create(AOwner: TComponent); begin  inherited Create(AOwner); 
FCanvas:= Tcanvas.Create; end; Destructor TMemo.Destroy; begin 
FreeAndNil(FCanvas);  inherited Destroy; End; procedure
TMemo.WMPaint(var Message: TWMPaint); begin  inherited; 
PostMessage(Self.Handle,WM_USER+1, 0,0); //Post a later
message... end; procedure TMemo.SetH(const AValue: String); Begin 
FH:= AValue;  Invalidate; End;end.

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pmesquita · 2021-11-09 12:55

Jamie...

Thank you very much for the help and explanations and with this I was
able to do what I needed...
Attached is an example and a little improved...

Long live Lazarus/FPC