diff --git a/lcl/interfaces/qt5/qtlclintf.inc b/lcl/interfaces/qt5/qtlclintf.inc
index 2d3078a696..03060ef68c 100644
--- a/lcl/interfaces/qt5/qtlclintf.inc
+++ b/lcl/interfaces/qt5/qtlclintf.inc
@@ -290,11 +290,15 @@ var
   QtDC: TQtDeviceContext absolute DC;
   X, Y: Integer;
   W, H: Integer;
+  P: TPoint;
 begin
   if not IsValidDC(DC) then
     exit;
   QtDC.save;
   try
+    P := Point(0, 0);
+    SetWindowOrgEx(DC, 0, 0, @P);
+
     W := (R.Right - R.Left - 1) div DX;
     H := (R.Bottom - R.Top - 1) div DY;
 
diff --git a/lcl/interfaces/qt5/qtwidgets.pas b/lcl/interfaces/qt5/qtwidgets.pas
index 743dc7f522..095eeab912 100644
--- a/lcl/interfaces/qt5/qtwidgets.pas
+++ b/lcl/interfaces/qt5/qtwidgets.pas
@@ -20114,8 +20114,15 @@ begin
     Msg.PaintStruct^.hdc := FDesignContext;
 
     P := getClientOffset;
+
+    {$IFDEF QTSCROLLABLEFORMS}
+    inc(P.X, -ScrollArea.horizontalScrollBar.getValue);
+    inc(P.Y, -ScrollArea.verticalScrollBar.getValue);
+    {$ELSE}
     inc(P.X, FScrollX);
     inc(P.Y, FScrollY);
+    {$ENDIF}
+
     TQtDeviceContext(Msg.DC).translate(P.X, P.Y);
 
     // send paint message
@@ -20157,9 +20164,13 @@ var
 begin
   if FDesignControl = nil then
     Exit;
-  // FDesignControl must be same as form area,
-  // since we use QWidget, not QMainWindow in design time.
+  {$IFDEF QTSCROLLABLEFORMS}
+  QWidget_contentsRect(ScrollArea.viewportWidget, @R);
+  R.Width := R.Width + ScrollArea.horizontalScrollBar.getMax;
+  R.Height := R.Height + ScrollArea.verticalScrollBar.getMax;
+  {$ELSE}
   QWidget_contentsRect(Widget, @R);
+  {$ENDIF}
   with R do
   begin
     QWidget_move(FDesignControl, Left, Top);
@@ -20309,9 +20320,7 @@ begin
                 {$IFDEF QTSCROLLABLEFORMS}
                 else
                 if (aWidget is TQtWindowArea) then
-                begin
                   TQtWindowArea(aWidget).scroll(XStep, YStep);
-                end;
                 {$ENDIF}
               end else
               begin
@@ -20397,7 +20406,11 @@ begin
           end;
         end;
       end;
-      QEventPaint: SlotDesignControlPaint(Sender, Event);
+      QEventPaint:
+      begin
+        SlotDesignControlPaint(Sender, Event);
+        Result := True;
+      end;
       QEventContextMenu: SlotContextMenu(Sender, Event);
     end;
   finally
diff --git a/lcl/interfaces/qt5/qtwinapi.inc b/lcl/interfaces/qt5/qtwinapi.inc
index 98b9cb4e86..2dcfcc2676 100644
--- a/lcl/interfaces/qt5/qtwinapi.inc
+++ b/lcl/interfaces/qt5/qtwinapi.inc
@@ -2829,7 +2829,8 @@ function TQtWidgetSet.GetDCOriginRelativeToWindow(PaintDC: HDC;
 var
   QtDC: TQtDeviceContext absolute PaintDC;
   Matrix: QTransformH;
-  P: TPoint;
+  DCScreenOrigin, P: TPoint;
+  Pt1, Pt2: TQtPoint;
 begin
   {$ifdef VerboseQtWinAPI}
     WriteLn('[WinAPI GetDCOriginRelativeToWindow] PaintDC ' + dbghex(PaintDC));
@@ -2840,13 +2841,26 @@ begin
   Matrix := QPainter_transform(QtDC.Widget);
   OriginDiff := Point(0, 0);
   P := Point(0, 0);
+  DCScreenOrigin := Point(0, 0);
+  if (QtDC.Parent <> nil) then
+  begin
+    Pt2.X := 0;
+    Pt2.y := 0;
+    QWidget_mapToGlobal(QtDC.Parent, @Pt1, @Pt2);
+    DCScreenOrigin.X := Pt1.X;
+    DCScreenOrigin.Y := Pt1.Y;
+  end;
   if WindowHandle <> 0 then
+  begin
     P := TQtWidget(WindowHandle).getClientOffset;
+    P := TQtWidget(WindowHandle).MapToGlobal(P, False);
+  end;
   if Matrix <> nil then
   begin
-    OriginDiff.X := Round(QTransform_Dx(Matrix)) - P.X;
-    OriginDiff.Y := Round(QTransform_Dy(Matrix)) - P.Y;
+    OriginDiff.X := DCScreenOrigin.X - P.X;
+    OriginDiff.Y := DCScreenOrigin.Y - P.Y;
   end;
+  Result := True;
 end;
 
 {------------------------------------------------------------------------------
diff --git a/lcl/interfaces/qt6/qtlclintf.inc b/lcl/interfaces/qt6/qtlclintf.inc
index 0221d3ed4e..1e0e30838f 100644
--- a/lcl/interfaces/qt6/qtlclintf.inc
+++ b/lcl/interfaces/qt6/qtlclintf.inc
@@ -290,11 +290,15 @@ var
   QtDC: TQtDeviceContext absolute DC;
   X, Y: Integer;
   W, H: Integer;
+  P: TPoint;
 begin
   if not IsValidDC(DC) then
     exit;
   QtDC.save;
   try
+    P := Point(0, 0);
+    SetWindowOrgEx(DC, 0, 0, @P);
+
     W := (R.Right - R.Left - 1) div DX;
     H := (R.Bottom - R.Top - 1) div DY;
 
diff --git a/lcl/interfaces/qt6/qtwidgets.pas b/lcl/interfaces/qt6/qtwidgets.pas
index a99adea855..60bb8cca32 100644
--- a/lcl/interfaces/qt6/qtwidgets.pas
+++ b/lcl/interfaces/qt6/qtwidgets.pas
@@ -20035,8 +20035,15 @@ begin
     Msg.PaintStruct^.hdc := FDesignContext;
 
     P := getClientOffset;
+
+    {$IFDEF QTSCROLLABLEFORMS}
+    inc(P.X, -ScrollArea.horizontalScrollBar.getValue);
+    inc(P.Y, -ScrollArea.verticalScrollBar.getValue);
+    {$ELSE}
     inc(P.X, FScrollX);
     inc(P.Y, FScrollY);
+    {$ENDIF}
+
     TQtDeviceContext(Msg.DC).translate(P.X, P.Y);
 
     // send paint message
@@ -20078,9 +20085,13 @@ var
 begin
   if FDesignControl = nil then
     Exit;
-  // FDesignControl must be same as form area,
-  // since we use QWidget, not QMainWindow in design time.
+  {$IFDEF QTSCROLLABLEFORMS}
+  QWidget_contentsRect(ScrollArea.viewportWidget, @R);
+  R.Width := R.Width + ScrollArea.horizontalScrollBar.getMax;
+  R.Height := R.Height + ScrollArea.verticalScrollBar.getMax;
+  {$ELSE}
   QWidget_contentsRect(Widget, @R);
+  {$ENDIF}
   with R do
   begin
     QWidget_move(FDesignControl, Left, Top);
@@ -20230,9 +20241,7 @@ begin
                 {$IFDEF QTSCROLLABLEFORMS}
                 else
                 if (aWidget is TQtWindowArea) then
-                begin
                   TQtWindowArea(aWidget).scroll(XStep, YStep);
-                end;
                 {$ENDIF}
               end else
               begin
@@ -20318,7 +20327,11 @@ begin
           end;
         end;
       end;
-      QEventPaint: SlotDesignControlPaint(Sender, Event);
+      QEventPaint:
+      begin
+        SlotDesignControlPaint(Sender, Event);
+        Result := True;
+      end;
       QEventContextMenu: SlotContextMenu(Sender, Event);
     end;
   finally
diff --git a/lcl/interfaces/qt6/qtwinapi.inc b/lcl/interfaces/qt6/qtwinapi.inc
index 787253a17f..adaa831b72 100644
--- a/lcl/interfaces/qt6/qtwinapi.inc
+++ b/lcl/interfaces/qt6/qtwinapi.inc
@@ -2825,7 +2825,8 @@ function TQtWidgetSet.GetDCOriginRelativeToWindow(PaintDC: HDC;
 var
   QtDC: TQtDeviceContext absolute PaintDC;
   Matrix: QTransformH;
-  P: TPoint;
+  DCScreenOrigin, P: TPoint;
+  Pt1, Pt2: TQtPoint;
 begin
   {$ifdef VerboseQtWinAPI}
     WriteLn('[WinAPI GetDCOriginRelativeToWindow] PaintDC ' + dbghex(PaintDC));
@@ -2836,13 +2837,26 @@ begin
   Matrix := QPainter_transform(QtDC.Widget);
   OriginDiff := Point(0, 0);
   P := Point(0, 0);
+  DCScreenOrigin := Point(0, 0);
+  if (QtDC.Parent <> nil) then
+  begin
+    Pt2.X := 0;
+    Pt2.y := 0;
+    QWidget_mapToGlobal(QtDC.Parent, @Pt1, @Pt2);
+    DCScreenOrigin.X := Pt1.X;
+    DCScreenOrigin.Y := Pt1.Y;
+  end;
   if WindowHandle <> 0 then
+  begin
     P := TQtWidget(WindowHandle).getClientOffset;
+    P := TQtWidget(WindowHandle).MapToGlobal(P, False);
+  end;
   if Matrix <> nil then
   begin
-    OriginDiff.X := Round(QTransform_Dx(Matrix)) - P.X;
-    OriginDiff.Y := Round(QTransform_Dy(Matrix)) - P.Y;
+    OriginDiff.X := DCScreenOrigin.X - P.X;
+    OriginDiff.Y := DCScreenOrigin.Y - P.Y;
   end;
+  Result := True;
 end;
 
 {------------------------------------------------------------------------------