How to set required Edit fields with a red border? - delphi

Question

I want to require a little fields. And when they will not be filled in that they will be red and needed to fill in.
before the post can be done
Here is a screenshot of what do I want to achieve:

Answer 1

I would add a TShape, which can draw a red line around your edit box. If you want the red border to replace the normal TEdit border you can modify the properties of your Edit control so it has no Border.
If you want the shape to be unfilled, change brush style to bsClear

Answer 2

You might hook the WM_Paint message and draw a rectangle on the ControlCanvas if required. One way to do this could look like this:
unit Edit_WithFrame_If_Needed_But_Empty;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TEdit = Class(StdCtrls.TEdit)
procedure WMPaint(var Message: TWMPaint); message WM_PAINT;
procedure CMTextChanged(var Message: TMessage); message CM_TEXTCHANGED;
procedure WMKEYUP(var Message: TWMPaint); message WM_KEYUP;
private
FPaintedRed: Boolean;
FRequired: Boolean;
procedure CheckForInvalidate;
published
public
Property Required: Boolean read FRequired Write FRequired;
End;
TForm2 = class(TForm)
Button1: TButton;
Edit1: TEdit;
Edit2: TEdit;
Edit3: TEdit;
procedure FormCreate(Sender: TObject);
private
{ Private-Deklarationen }
public
{ Public-Deklarationen }
end;
var
Form2: TForm2;
implementation
{$R *.dfm}
{ TEdit }
procedure TEdit.CheckForInvalidate;
begin
if Required and (Length(Trim(Text)) = 0) then
begin
if not FPaintedRed then
Invalidate;
end
else if FPaintedRed then
Invalidate;
end;
procedure TEdit.CMTextChanged(var Message: TMessage);
begin
inherited;
CheckForInvalidate;
end;
procedure TEdit.WMKEYUP(var Message: TWMPaint);
begin
CheckForInvalidate;
end;
procedure TEdit.WMPaint(var Message: TWMPaint);
var
CC: TControlCanvas;
begin
inherited;
if Required and (Length(Trim(Text)) = 0) then
begin
FPaintedRed := true;
CC := TControlCanvas.Create;
try
CC.Control := Self;
CC.Pen.Color := clRed;
CC.Pen.Width := 3;
CC.Rectangle(ClientRect);
finally
CC.Free;
end;
end
else
FPaintedRed := false;
end;
procedure TForm2.FormCreate(Sender: TObject);
begin
Edit1.Required := true;
Edit3.Required := true;
end;
end.