Dark theme

From Lazarus wiki
Revision as of 09:05, 29 August 2020 by Trev (talk | contribs) (Opting out of dark mode: Link Info.plist)

How to detect whether the operating system is using a dark theme?

Universal method

Example 1

// by "Alextp" from Lazarus forum
function IsDarkTheme: boolean;
const
  cMax = $A0;
var
  N: TColor;
begin
  N:= ColorToRGB(clWindow);
  Result:= (Red(N)<cMax) and (Green(N)<cMax) and (Blue(N)<cMax);
end;

Example 2

// by "dbannon" from Lazarus forum
function IsDarkTheme(F: TForm): boolean;
var
  Col : string;
begin
  // if char 3, 5 and 7 are all 'A' or above, we are not in a DarkTheme
  Col := HexStr(qword(F.GetRGBColorResolvingParent()), 8);
  Result := (Col[3] < 'A') and (Col[5] < 'A') and (Col[7] < 'A');
end;

Windows method

Example 1

// by "jwdietrich" from Lazarus forum
uses
  Windows, Win32Proc, Registry;
     
// IsDarkTheme: Detects if the Dark Theme (true) has been enabled or not (false)
function IsDarkTheme: boolean;
const
  KEYPATH = '\Software\Microsoft\Windows\CurrentVersion\Themes\Personalize';
  KEYNAME = 'AppsUseLightTheme';
var
  LightKey: boolean;
  Registry: TRegistry;
begin
  Result := false;
  Registry := TRegistry.Create;
  try
    Registry.RootKey := HKEY_CURRENT_USER;
    if Registry.OpenKeyReadOnly(KEYPATH) then
      begin
        if Registry.ValueExists(KEYNAME) then
          LightKey := Registry.ReadBool(KEYNAME)
        else
          LightKey := true;
      end
    else
      LightKey := true;
    Result := not LightKey
  finally
    Registry.Free;
  end;
end;

macOS method

Example 1

// by "jwdietrich" from Lazarus forum
uses
  MacOSAll;
     
function IsMinMacOS(Maj, Min: integer): boolean;
  { returns true, if this app runs on a macOS version as specified or newer }
var
  Major, Minor: SInt32;
  theError: SInt16;
begin
  result := false;
  theError := Gestalt(gestaltSystemVersionMajor, Major);
  if theError = 0 then
    theError := Gestalt(gestaltSystemVersionMinor, Minor);
  if theError = 0 then
    if (Major = Maj) and (Minor >= Min) or (Major > Maj) then
      Result := True;
end;
     
function MojaveOrNewer: boolean;
  { returns true, if this app runs on macOS X 10.14 Mojave or newer }
begin
  result := IsMinMacOS(10, 14);
end;
     
{ The following two functions were suggested by Hansaplast at https://forum.lazarus.freepascal.org/index.php/topic,43111.msg304366.html }
     
// Retrieve key's string value from user preferences. Result is encoded using NSStrToStr's default encoding.
function GetPrefString(const KeyName : string) : string;
begin
  Result := NSStringToString(NSUserDefaults.standardUserDefaults.stringForKey(NSStr(@KeyName[1])));
end;
     
// IsDarkTheme: Detects if the Dark Theme (true) has been enabled or not (false)
function IsDarkTheme: boolean;
begin
  Result := false;
  if MojaveOrNewer then
    Result := pos('DARK',UpperCase(GetPrefString('AppleInterfaceStyle'))) > 0;
end;

Demo

unit Unit1;

{$mode objfpc}{$H+}
{$modeswitch objectivec1}

interface

uses
  Classes, Forms, Dialogs, StdCtrls, SysUtils,
  CocoaAll, CocoaUtils, MacOSAll;

type

  { TForm1 }

  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private

  public

  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{ TForm1 }

function IsMinMacOS(Maj, Min: integer): boolean;
  { returns true, if this app runs on a macOS version as specified or newer }
var
  Major, Minor: SInt32;
  theError: SInt16;
begin
  result := false;
  theError := Gestalt(gestaltSystemVersionMajor, Major);
  if theError = 0 then
    theError := Gestalt(gestaltSystemVersionMinor, Minor);
  if theError = 0 then
    if (Major = Maj) and (Minor >= Min) or (Major > Maj) then
      Result := True;
end;

function MojaveOrNewer: boolean;
  { returns true, if this app runs on macOS X 10.14 Mojave or newer }
begin
  result := IsMinMacOS(10, 14);
end;

function GetPrefString(const KeyName : string) : string;
begin
  Result := NSStringToString(NSUserDefaults.standardUserDefaults.stringForKey(NSStr(@KeyName[1])));
end;

function IsDarkTheme: boolean;
begin
  Result := false;
  if MojaveOrNewer then
    Result := pos('DARK',UpperCase(GetPrefString('AppleInterfaceStyle'))) > 0;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if(IsDarkTheme) then
    ShowMessage('Dark mode')
  else
    ShowMessage('Light mode');
end;

end.

Example 2

Catalina added an "Auto" option where the computer switches between Light and Dark modes depending on time of day. The 'AppleInterfaceStyle' method apparently doesn't work if auto is enabled.

The solution is to get the NSApp.effectiveAppearance string which will be one of a number of values including 'NSAppearanceNameAqua' (standard light mode) and 'NSAppearanceNameDarkAqua' (standard dark mode). Google these to see the whole list which includes other light and dark modes with added contrast. The effectiveAppearance is correct in all modes including when auto mode kicks in.

Tested on Mojave, Catalina, Big Sur.

// by "Clover" from Lazarus forum
function IsMacDarkMode: Boolean;
var
  sMode: string;
begin
  //sMode := CFStringToStr( CFStringRef( NSUserDefaults.StandardUserDefaults.stringForKey( NSSTR('AppleInterfaceStyle') ))); // Doesn't work in auto mode
  sMode  := CFStringToStr( CFStringRef( NSApp.effectiveAppearance.name ));
  Result := Pos('Dark', sMode) > 0;
end;

Demo

unit Unit1;

{$mode objfpc}{$H+}
{$modeswitch objectivec1}

interface

uses
  Classes, Forms, Dialogs, StdCtrls,
  CocoaAll, CocoaUtils, MacOSAll;

type

  { TForm1 }

  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private

  public

  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{ TForm1 }

function IsMacDarkMode: Boolean;
var
  sMode: string;
begin
  sMode  := CFStringToStr( CFStringRef( NSApp.effectiveAppearance.name ));
  Result := Pos('Dark', sMode) > 0;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if(IsMacDarkMode) then
    ShowMessage('Dark mode')
  else
    ShowMessage('Light mode');
end;

end.

Opting out of dark mode

Mac systems automatically opt in any application linked against the macOS 10.14 or later SDK to both light and dark appearances. You can opt out of dark mode by including the NSRequiresAquaSystemAppearance key (with a value of YES) in your application’s Info.plist property list file. Setting this key to YES causes the system to ignore the user's preference and always apply a light appearance to your application.

Opting in to dark mode

If you build your application against an earlier SDK but still want to support Dark Mode, include the NSRequiresAquaSystemAppearance key (with a value of NO) in your applications's Info.plist file. Do so only if your applications's appearance looks correct when running in macOS 10.14 and later with Dark Mode enabled.

See also

External links