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.