Changing the color of Edit Controls with VCL Styles Enabled

February 6, 2012 by Rodrigo 42 Comments

The Issue

The last weeks I found a couple questions and QC reports(100645, 101822, 102984) regarding to how change the color of a Edit Control (TEdit, TMaskEdit, TMemo and so on) when the VCL Styles are enabled. So today I will show you how you can change the colors of these controls even with the VCL Styles activated.

In a Standard VCL Form application you can change the Color property of Edit controls

But when the Vcl Styles Are applied these colors are not used, and the controls are painted using the colors of the current VCl Style.

The Solution

So what is the solution? well the answer is : Create a new TStyleHook (read this article to learn more about Style Hooks) . All the TWinControls uses a TStyleHook to paint the control when the vcl styles are actived, so you can modify the TStyleHook of a particular control to modify the way of how the component is painted.

Implementation

Before to implement a Custom Style hook you must be aware which this new TStyleHook will affect to all the controls of the same type used in the RegisterStyleHook method, because the Style hooks are implemented for a particular class type and not for an instance.

First let’s create a style hook for the TCustomEdit descendents, using the TEditStyleHook class, this new style hook can be used with controls like TEdit, TMaskEdit, TLabeledEdit and so on.

Check the next commented code

  TEditStyleHookColor = class(TEditStyleHook)
  private
    procedure UpdateColors;
  protected
    procedure WndProc(var Message: TMessage); override;
  public
    constructor Create(AControl: TWinControl); override;
  end;

uses
  Vcl.Styles;

type
 TWinControlH= class(TWinControl);

constructor TEditStyleHookColor.Create(AControl: TWinControl);
begin
  inherited;
  //call the UpdateColors method to use the custom colors
  UpdateColors;
end;

//Here you set the colors of the style hook
procedure TEditStyleHookColor.UpdateColors;
var
  LStyle: TCustomStyleServices;
begin
 if Control.Enabled then
 begin
  Brush.Color := TWinControlH(Control).Color; //use the Control color
  FontColor   := TWinControlH(Control).Font.Color;//use the Control font color
 end
 else
 begin
  //if the control is disabled use the colors of the style
  LStyle := StyleServices;
  Brush.Color := LStyle.GetStyleColor(scEditDisabled);
  FontColor := LStyle.GetStyleFontColor(sfEditBoxTextDisabled);
 end;
end;

//Handle the messages of the control
procedure TEditStyleHookColor.WndProc(var Message: TMessage);
begin
  case Message.Msg of
    CN_CTLCOLORMSGBOX..CN_CTLCOLORSTATIC:
      begin
        //Get the colors
        UpdateColors;
        SetTextColor(Message.WParam, ColorToRGB(FontColor));
        SetBkColor(Message.WParam, ColorToRGB(Brush.Color));
        Message.Result := LRESULT(Brush.Handle);
        Handled := True;
      end;
    CM_ENABLEDCHANGED:
      begin
        //Get the colors
        UpdateColors;
        Handled := False;
      end
  else
    inherited WndProc(Message);
  end;
end;

Now a style hook for the TCustomMemo using the TMemoStyleHook class.

  TMemoStyleHookColor = class(TMemoStyleHook)
  private
    procedure UpdateColors;
  protected
    procedure WndProc(var Message: TMessage); override;
  public
    constructor Create(AControl: TWinControl); override;
  end;

constructor TMemoStyleHookColor.Create(AControl: TWinControl);
begin
  inherited;
  //call the UpdateColors method to use the custom colors
  UpdateColors;
end;

//Set the colors to be used by the Style hook
procedure TMemoStyleHookColor.UpdateColors;
var
  LStyle: TCustomStyleServices;
begin
 if Control.Enabled then
 begin
  Brush.Color := TWinControlH(Control).Color;
  FontColor   := TWinControlH(Control).Font.Color;
 end
 else
 begin
  //if the control is disabled use the current style colors
  LStyle := StyleServices;
  Brush.Color := LStyle.GetStyleColor(scEditDisabled);
  FontColor := LStyle.GetStyleFontColor(sfEditBoxTextDisabled);
 end;
end;

//handle the messages
procedure TMemoStyleHookColor.WndProc(var Message: TMessage);
begin
  case Message.Msg of
    CN_CTLCOLORMSGBOX..CN_CTLCOLORSTATIC:
      begin
        //get the colors
        UpdateColors;
        SetTextColor(Message.WParam, ColorToRGB(FontColor));
        SetBkColor(Message.WParam, ColorToRGB(Brush.Color));
        Message.Result := LRESULT(Brush.Handle);
        Handled := True;
      end;

    CM_COLORCHANGED,
    CM_ENABLEDCHANGED:
      begin
        //get the colors
        UpdateColors;
        Handled := False;
      end
  else
    inherited WndProc(Message);
  end;
end;

Finally to apply the above code you must call the TStyleManager.Engine.RegisterStyleHook method in this way (ideally in the initialization part of you unit)

 TStyleManager.Engine.RegisterStyleHook(TEdit, TEditStyleHookColor);
 TStyleManager.Engine.RegisterStyleHook(TMaskEdit, TEditStyleHookColor);
 TStyleManager.Engine.RegisterStyleHook(TLabeledEdit, TEditStyleHookColor);
 TStyleManager.Engine.RegisterStyleHook(TButtonedEdit, TEditStyleHookColor);

 TStyleManager.Engine.RegisterStyleHook(TMemo, TMemoStyleHookColor);

Trick : If you only want apply these new hooks to the controls of a particular form, you can use a interposer class in the begining of your unit

type
  TEdit= Class (Vcl.StdCtrls.TEdit);
  TMemo= Class (Vcl.StdCtrls.TMemo);
  TButtonedEdit= Class (Vcl.ExtCtrls.TButtonedEdit);
  TLabeledEdit= Class (Vcl.ExtCtrls.TLabeledEdit);

The final result

Now look how the forms with the vcl styles can have custom colors in the Edit controls

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Check the full source code on Github.