diff --git a/source/apphelpers.pas b/source/apphelpers.pas
index 872418e8..0c92623b 100644
--- a/source/apphelpers.pas
+++ b/source/apphelpers.pas
@@ -356,7 +356,6 @@ type
   function GetCurrentPackageFullName(out Len: Cardinal; Name: PWideChar): Integer; stdcall; external kernel32 delayed;
   function GetUwpFullName: String;
   function RunningAsUwp: Boolean;
-  function DpiScaleFactor(Form: TForm): Double;
   function GetThemeColor(Color: TColor): TColor;
   function ThemeIsDark(ThemeName: String): Boolean;
   function ProcessExists(pid: Cardinal): Boolean;
@@ -2935,12 +2934,6 @@ begin
 end;
 
 
-function DpiScaleFactor(Form: TForm): Double;
-begin
-  Result := Form.Monitor.PixelsPerInch / Form.PixelsPerInch;
-end;
-
-
 function GetThemeColor(Color: TColor): TColor;
 begin
   // Not required with vcl-style-utils:
diff --git a/source/extra_controls.pas b/source/extra_controls.pas
index 215dadd1..e927c900 100644
--- a/source/extra_controls.pas
+++ b/source/extra_controls.pas
@@ -4,17 +4,19 @@ interface
 
 uses
   Classes, SysUtils, Forms, Windows, Messages, System.Types, StdCtrls, Clipbrd,
-  SizeGrip, SizeGripThemed, apphelpers, Vcl.Graphics;
+  SizeGrip, SizeGripThemed, apphelpers, Vcl.Graphics, Vcl.Dialogs;
 
 type
   // Form with a sizegrip in the lower right corner, without the need for a statusbar
   TExtForm = class(TForm)
     private
       FFontSet: Boolean;
+      FPixelsPerInchOnDefaultMonitor: Integer;
     public
       constructor Create(AOwner: TComponent); override;
       procedure AddSizeGrip;
-      class procedure InheritFont(AFont: TFont; Form: TForm);
+      function DpiScaleFactor(Form: TForm=nil): Double;
+      procedure InheritFont(AFont: TFont);
     protected
       procedure DoShow; override;
   end;
@@ -33,6 +35,7 @@ implementation
 
 constructor TExtForm.Create(AOwner: TComponent);
 begin
+  FPixelsPerInchOnDefaultMonitor := Screen.Monitors[0].PixelsPerInch;
   inherited;
   FFontSet := False;
 end;
@@ -43,7 +46,7 @@ begin
   // Expect the window to be on the wanted monitor now, so we can scale fonts according
   // to the screen's DPI setting
   if not FFontSet then begin
-    InheritFont(Font, Self);
+    InheritFont(Font);
     FFontSet := True;
   end;
   inherited;
@@ -61,7 +64,13 @@ begin
 end;
 
 
-class procedure TExtForm.InheritFont(AFont: TFont; Form: TForm);
+function TExtForm.DpiScaleFactor(Form: TForm=nil): Double;
+begin
+  Result := Monitor.PixelsPerInch / FPixelsPerInchOnDefaultMonitor;
+end;
+
+
+procedure TExtForm.InheritFont(AFont: TFont);
 var
   LogFont: TLogFont;
   GUIFontName: String;
@@ -75,12 +84,12 @@ begin
     // Apply user specified font
     AFont.Name := GUIFontName;
     // Set size on top of automatic dpi-increased size
-    AFont.Size := Round(AppSettings.ReadInt(asGUIFontSize) * DpiScaleFactor(Form));
+    AFont.Size := Round(AppSettings.ReadInt(asGUIFontSize) * DpiScaleFactor);
   end else begin
     // Apply system font. See issue #3204.
     // Code taken from http://www.gerixsoft.com/blog/delphi/system-font
     if SystemParametersInfo(SPI_GETICONTITLELOGFONT, SizeOf(TLogFont), @LogFont, 0) then begin
-      AFont.Height := Round(LogFont.lfHeight * DpiScaleFactor(Form));
+      AFont.Height := Round(LogFont.lfHeight * DpiScaleFactor);
       AFont.Orientation := LogFont.lfOrientation;
       AFont.Charset := TFontCharset(LogFont.lfCharSet);
       AFont.Name := PChar(@LogFont.lfFaceName);
diff --git a/source/loginform.pas b/source/loginform.pas
index cbe86ebc..2987db0e 100644
--- a/source/loginform.pas
+++ b/source/loginform.pas
@@ -4,10 +4,10 @@ interface
 
 uses
   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
-  Dialogs, StdCtrls, ExtCtrls, gnugettext, System.UITypes;
+  Dialogs, StdCtrls, ExtCtrls, gnugettext, System.UITypes, extra_controls;
 
 type
-  TfrmLogin = class(TForm)
+  TfrmLogin = class(TExtForm)
     btnOK: TButton;
     pnlBackground: TPanel;
     lblPrompt: TLabel;
diff --git a/source/main.pas b/source/main.pas
index 4f33a4ad..db9116e1 100644
--- a/source/main.pas
+++ b/source/main.pas
@@ -1830,7 +1830,7 @@ begin
 
   Delimiter := AppSettings.ReadString(asDelimiter);
 
-  InheritFont(SynCompletionProposal.Font, Self);
+  InheritFont(SynCompletionProposal.Font);
   // Simulated link label, has non inherited blue font color
   lblExplainProcess.Font.Color := clBlue;
   lblExplainProcessAnalyzer.Font.Color := clBlue;
@@ -1849,7 +1849,7 @@ begin
   QueryTab.spltHelpers := spltQueryHelpers;
   QueryTab.spltQuery := spltQuery;
   QueryTab.tabsetQuery := tabsetQuery;
-  InheritFont(QueryTab.tabsetQuery.Font, Self);
+  InheritFont(QueryTab.tabsetQuery.Font);
   QueryTab.ResultTabs := TResultTabs.Create(True);
 
   QueryTabs := TObjectList<TQueryTab>.Create(True);
@@ -10752,7 +10752,7 @@ begin
   // Prevent various problems with alignment of controls. See http://www.heidisql.com/forum.php?t=18924
   QueryTab.tabsetQuery.Top := QueryTab.spltQuery.Top + QueryTab.spltQuery.Height;
   QueryTab.tabsetQuery.Align := tabsetQuery.Align;
-  InheritFont(QueryTab.tabsetQuery.Font, Self);
+  InheritFont(QueryTab.tabsetQuery.Font);
   QueryTab.tabsetQuery.Images := tabsetQuery.Images;
   QueryTab.tabsetQuery.Style := tabsetQuery.Style;
   QueryTab.tabsetQuery.TabHeight := tabsetQuery.TabHeight;
diff --git a/source/routine_editor.pas b/source/routine_editor.pas
index a6516afe..a3e3ebcc 100644
--- a/source/routine_editor.pas
+++ b/source/routine_editor.pas
@@ -184,11 +184,11 @@ begin
   btnSave.Enabled := Modified;
   btnDiscard.Enabled := Modified;
   // Buttons are randomly moved, since VirtualTree update, see #440
-  btnSave.Top := Height - btnSave.Height - Round(3 * DpiScaleFactor(MainForm));
+  btnSave.Top := Height - btnSave.Height - Round(3 * MainForm.DpiScaleFactor);
   btnHelp.Top := btnSave.Top;
   btnDiscard.Top := btnSave.Top;
   btnRunProc.Top := btnSave.Top;
-  btnRunProc.Left := Width - btnRunProc.Width - Round(3 * DpiScaleFactor(MainForm));
+  btnRunProc.Left := Width - btnRunProc.Width - Round(3 * MainForm.DpiScaleFactor);
   Mainform.actRunRoutines.Enabled := DBObject.Name <> '';
   Mainform.ShowStatusMsg;
   Screen.Cursor := crDefault;
diff --git a/source/table_editor.pas b/source/table_editor.pas
index 20a42f55..4cfbeae5 100644
--- a/source/table_editor.pas
+++ b/source/table_editor.pas
@@ -353,7 +353,7 @@ begin
   AlterCodeValid := False;
   PageControlMainChange(Self); // Foreign key editor needs a hit
   // Buttons are randomly moved, since VirtualTree update, see #440
-  btnSave.Top := Height - btnSave.Height - Round(3 * DpiScaleFactor(MainForm));
+  btnSave.Top := Height - btnSave.Height - Round(3 * MainForm.DpiScaleFactor);
   btnHelp.Top := btnSave.Top;
   btnDiscard.Top := btnSave.Top;
   UpdateSQLCode;
diff --git a/source/trigger_editor.pas b/source/trigger_editor.pas
index 0b22be94..aac34cf9 100644
--- a/source/trigger_editor.pas
+++ b/source/trigger_editor.pas
@@ -164,7 +164,7 @@ begin
     end;
   end;
   // Buttons are randomly moved, since VirtualTree update, see #440
-  btnSave.Top := Height - btnSave.Height - Round(3 * DpiScaleFactor(MainForm));
+  btnSave.Top := Height - btnSave.Height - Round(3 * MainForm.DpiScaleFactor);
   btnHelp.Top := btnSave.Top;
   btnDiscard.Top := btnSave.Top;
   Modification(Self);