Make dialogs compatible with "large fonts". [duplicate]

Question

Which do you think are best practices for making a windows dialog compatible both with standard fonts (96 dpi) and "large fonts" setting (120 dpi) so that objects don't overlap or get cut off?

BTW: Just in case it's relevant, I'm interested in doing this for Delphi dialogs.

Thanks in advance!

Answer 1

In general one should use layout managers for this purpose. That what they are designed for.

Delphi (did not work with it for a long time) does not have such managers but is able to handle different dpi ever since. You have to use the autosize propery of the components to ensure that they have the right size for the text they display. To prevent overlapping of components arrange them on the form using the alignment and anchor properties. Eventually you have to group components in containers to achieve a proper layout.

Answer 2

There's a pretty good article in the D2007 help file, under "Considerations When Dynamically Resizing Forms and Controls" (note that the URL is to the help file itself, and not a web page as such).

The same topic, under the same name, can be found in the D2010 help file (same caveat about the URL as above), or on the docwiki.

It also is worthwhile (at least a little bit) to examine TForm.Scaled and TForm.ScaleBy.

Answer 3

This is how I try to deal with Delphi VCL's pixels regardless of Window's font size setting.

unit App.Screen;

interface

uses Controls;

type
  TAppScreen = class(TObject)
  private
    FDefaultPixelsPerInch: integer;
    FPixelsPerInch: integer;
    function GetPixelsPerInch: integer;
    procedure SetPixelsPerInch(const Value: integer);
  public
    procedure AfterConstruction; override;
    function DefaultPixelsPerInch: integer;
    function InAcceptableRange(const aPPI: integer): boolean;
    procedure ScaleControl(const aControl: TWinControl);
    property PixelsPerInch: integer read GetPixelsPerInch write SetPixelsPerInch;
  end;

  TAppScreenHelper = class helper for TAppScreen
  private
    class var FInstance: TAppScreen;
    class function GetInstance: TAppScreen; static;
  public
    class procedure Setup;
    class procedure TearDown;
    class property Instance: TAppScreen read GetInstance;
  end;

implementation

uses
  TypInfo, Windows, SysUtils, Forms, Graphics;

type
  TScreenEx = class(TScreen)
  published
    property PixelsPerInch;
  end;

  TScreenHelper = class helper for TScreen
  public
    procedure SetPixelsPerInch(Value: integer);
  end;

procedure TScreenHelper.SetPixelsPerInch(Value: integer);
begin
  PInteger(Integer(Self) + (Integer(GetPropInfo(TScreenEx, 'PixelsPerInch').GetProc) and $00FFFFFF))^ := Value;
end;

procedure TAppScreen.AfterConstruction;
begin
  inherited;
  FDefaultPixelsPerInch := Screen.PixelsPerInch;
  FPixelsPerInch := FDefaultPixelsPerInch;
end;

function TAppScreen.DefaultPixelsPerInch: integer;
begin
  Result := FDefaultPixelsPerInch;
end;

function TAppScreen.GetPixelsPerInch: integer;
begin
  Result := FPixelsPerInch;
end;

function TAppScreen.InAcceptableRange(const aPPI: integer): boolean;
begin
  if DefaultPixelsPerInch > aPPI then
    Result := DefaultPixelsPerInch * 0.55 < aPPI
  else if DefaultPixelsPerInch < aPPI then
    Result := DefaultPixelsPerInch * 1.55 > aPPI
  else
    Result := True;
end;

procedure TAppScreen.ScaleControl(const aControl: TWinControl);
begin
  aControl.ScaleBy(PixelsPerInch, DefaultPixelsPerInch);
end;

procedure TAppScreen.SetPixelsPerInch(const Value: integer);
begin
  FPixelsPerInch := Value;
  Screen.SetPixelsPerInch(FPixelsPerInch);
end;

class function TAppScreenHelper.GetInstance: TAppScreen;
begin
  if FInstance = nil then
    FInstance := TAppScreen.Create;
  Result := FInstance;
end;

class procedure TAppScreenHelper.Setup;
begin
  TAppScreen.Instance;
end;

class procedure TAppScreenHelper.TearDown;
begin
  FInstance.Free;
  FInstance := nil;
end;

initialization
  TAppScreen.Setup;
finalization
  TAppScreen.TearDown;
end.

Try the following to test the effects of different pixels value:

TAppScreen.Instance.PixelsPerInch := 120;
TAppScreen.Instance.PixelsPerInch := 96;
TAppScreen.Instance.PixelsPerInch := 150;

You should change the PixelsPerInch before instantiate TForm's descendant including Delphi's VCL dialogs.