Dark theme
Detect Dark Theme
How to detect whether the operating system is using a dark theme?
Universal method
The following method is based on the GUI colors. It works on all platforms but those colors are not updated when the theme is changed while the application is running. Thus it cannot allow to detect if the dark mode is toggled.
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 "Hansaplast" & "Alextp" from Lazarus forum
function IsDarkTheme: boolean;
function _Level(C: TColor): double;
begin
Result:= Red(C)*0.3 + Green(C)*0.59 + Blue(C)*0.11;
end;
begin
Result:= _Level(ColorToRGB(clWindow)) < _Level(ColorToRGB(clWindowText));
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 "trev" from Lazarus forum
{ returns true, if this app runs on macOS 10.14.0 Mojave or newer }
function MojaveOrNewer: boolean;
var
minOsVer: NSOperatingSystemVersion;
begin
//Setup minimum version (Mojave)
minOsVer.majorVersion:= 10;
minOsVer.minorVersion:= 14;
minOsVer.patchVersion:= 0;
// Check minimum version
if(NSProcessInfo.ProcessInfo.isOperatingSystemAtLeastVersion(minOSVer)) then
Result := True
else
Result := False;
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
{$R *.lfm}
{ TForm1 }
{ returns true, if this app runs on macOS 10.14 Mojave or newer }
function MojaveOrNewer: boolean;
var
minOsVer: NSOperatingSystemVersion;
begin
// Setup minimum version (Mojave)
minOsVer.majorVersion:= 10;
minOsVer.minorVersion:= 14;
minOsVer.patchVersion:= 0;
// Check minimum version
if(NSProcessInfo.ProcessInfo.isOperatingSystemAtLeastVersion(minOSVer)) then
Result := True
else
Result := False;
end;
function GetPrefString(const KeyName : string) : string;
begin
Result := NSStringToString(NSUserDefaults.standardUserDefaults.stringForKey(NSStr(@KeyName[1])));
end;
function IsDarkTheme: boolean;
begin
Result := false;
if MojaveOrNewer then
Result := pos('DARK',UpperCase(GetPrefString('AppleInterfaceStyle'))) > 0;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
if(IsDarkTheme) then
ShowMessage('Dark mode')
else
ShowMessage('Light mode');
end;
end.
Example 2
Catalina added an "Auto" option where the computer switches between Light and Dark modes depending on time of day. The 'AppleInterfaceStyle' method apparently doesn't work if auto is enabled.
The solution is to get the NSApp.effectiveAppearance string which will be one of a number of values including 'NSAppearanceNameAqua' (standard light mode) and 'NSAppearanceNameDarkAqua' (standard dark mode). Google these to see the whole list which includes other light and dark modes with added contrast. The effectiveAppearance is correct in all modes including when auto mode kicks in.
Tested on Mojave, Catalina, Big Sur.
// by "Clover" from Lazarus forum
function IsMacDarkMode: Boolean;
var
sMode: string;
begin
//sMode := CFStringToStr( CFStringRef( NSUserDefaults.StandardUserDefaults.stringForKey( NSSTR('AppleInterfaceStyle') ))); // Doesn't work in auto mode
sMode := CFStringToStr( CFStringRef( NSApp.effectiveAppearance.name ));
Result := Pos('Dark', sMode) > 0;
end;
Demo
unit Unit1;
{$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 application's Info.plist property list file. Do so only if your application's appearance looks correct when running in macOS 10.14 and later with Dark Mode enabled.
Dark Windows title bar
For Windows 10 and higher versions it is possible to activate dark title bar of the application window.
uses LCLType;
function IsWindows10OrGreater(BuildNumber: Integer): Boolean;
begin
Result := (Win32MajorVersion >= 10) and (Win32BuildNumber >= BuildNumber);
end;
procedure SetDarkModeTitleBar(AForm: TForm; Active: Bool);
type
TDwmSetWindowAttribute = function(hwnd: HWND; dwAttribute: DWORD; pvAttribute: Pointer; cbAttribute: DWORD): HRESULT; stdcall;
const
DwmapiLibName = 'dwmapi.dll';
DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1 = 19;
DWMWA_USE_IMMERSIVE_DARK_MODE = 20;
var
DwmapiLib: TLibHandle;
DwmSetWindowAttribute: TDwmSetWindowAttribute;
Attr: DWord;
begin
DwmapiLib := LoadLibrary(DwmapiLibName);
if DwmapiLib <> 0 then DwmSetWindowAttribute := GetProcAddress(DwmapiLib, 'DwmSetWindowAttribute')
else DwmSetWindowAttribute := nil;
if Assigned(DwmSetWindowAttribute) and IsWindows10OrGreater(17763) then begin
Attr := DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1;
if IsWindows10OrGreater(18985) then Attr := DWMWA_USE_IMMERSIVE_DARK_MODE;
DwmSetWindowAttribute(AForm.Handle, Attr, @Active, SizeOf(Active));
end;
if DwmapiLib <> 0 then FreeLibrary(DwmapiLib);
end;
Activate Dark Theme
Windows IDE
To make the Lazarus IDE in dark themed, you can use the package metadarkstyledsgn.lpk. At the time of writing 17th Oct 2024 the version in the online package manager is broken. Use the git version metadarkstyle.
MacOS
- On Intel Macs you need to compile with -WM10.14 to support dark mode. Better use -WM11 to also support modern style form.
- For the IDE: add it to the Tools / Configure "Build Lazarus" / Options
- For a project: add it to Project / Project Options / Compiler Options / Custom Options
