TScrollBox: make opaque for ParentColor=False and ParentBackground=False. Issue #40047

lcl/controls.pp

@@ -1431,6 +1431,7 @@ type
   protected
     procedure Changed;
     function  GetPalette: HPalette; virtual;
+    function GetParentBackground: Boolean;
     function ChildClassAllowed(ChildClass: TClass): Boolean; virtual;
     procedure ReadState(Reader: TReader); override; // called
     procedure Loaded; override;
@@ -1453,6 +1454,7 @@ type
     procedure SetHint(const Value: TTranslateString); virtual;
     procedure SetName(const Value: TComponentName); override;
     procedure SetParent(NewParent: TWinControl); virtual;
+    procedure SetParentBackground(const AParentBackground: Boolean); virtual;
     procedure SetParentComponent(NewParentComponent: TComponent); override;
     procedure WndProc(var TheMessage: TLMessage); virtual;
     procedure ParentFormHandleInitialized; virtual; // called by ChildHandlesCreated of parent form
@@ -1504,6 +1506,7 @@ type
     property DragKind: TDragKind read FDragKind write FDragKind default dkDrag;
     property DragMode: TDragMode read FDragMode write SetDragMode default dmManual;
     property MouseCapture: Boolean read GetMouseCapture write SetMouseCapture;
+    property ParentBackground: Boolean read GetParentBackground write SetParentBackground;
     property ParentColor: Boolean read FParentColor write SetParentColor default True;
     property ParentFont: Boolean  read FParentFont write SetParentFont default True;
     property ParentShowHint: Boolean read FParentShowHint write SetParentShowHint default True;
@@ -2219,7 +2222,6 @@ type
     function  GetClientRect: TRect; override;
     function  GetControlOrigin: TPoint; override;
     function  GetDeviceContext(var WindowHandle: HWND): HDC; override;
-    function GetParentBackground: Boolean;
     function  IsControlMouseMsg(var TheMessage): Boolean;
     procedure CreateHandle; virtual;
     procedure CreateParams(var Params: TCreateParams); virtual;
@@ -2243,7 +2245,6 @@ type
     procedure SetBorderStyle(NewStyle: TBorderStyle); virtual;
     procedure SetColor(Value: TColor); override;
     procedure SetChildZPosition(const AChild: TControl; const APosition: Integer);
-    procedure SetParentBackground(const AParentBackground: Boolean); virtual;
     procedure ShowControl(AControl: TControl); virtual;
     procedure UpdateControlState;
     procedure UpdateShowing; virtual; // checks control's handle visibility, called by DoAllAutoSize and UpdateControlState
@@ -2255,7 +2256,6 @@ type
     property BorderStyle: TBorderStyle read GetBorderStyle write SetBorderStyle default bsNone;
     property OnGetSiteInfo: TGetSiteInfoEvent read FOnGetSiteInfo write FOnGetSiteInfo;
     property OnGetDockCaption: TGetDockCaptionEvent read FOnGetDockCaption write FOnGetDockCaption;
-    property ParentBackground: Boolean read GetParentBackground write SetParentBackground;
   public
     // properties which are supported by all descendents
     property BorderWidth: TBorderWidth read FBorderWidth write SetBorderWidth default 0;

lcl/forms.pp

@@ -205,6 +205,12 @@ type
   TScrollBox = class(TScrollingWinControl)
   protected
     class procedure WSRegisterClass; override;
+
+    procedure SetParentBackground(const AParentBackground: Boolean); override;
+
+    procedure CMParentColorChanged(var Message: TLMessage); message CM_PARENTCOLORCHANGED;
+    procedure Loaded; override;
+    procedure UpdateParentColorChange;
   public
     constructor Create(AOwner: TComponent); override;
   published
@@ -227,7 +233,7 @@ type
     property Enabled;
     property Color nodefault;
     property Font;
-    property ParentBackground default False;
+    property ParentBackground default True;
     property ParentBiDiMode;
     property ParentColor;
     property ParentFont;

lcl/include/control.inc

@@ -1343,6 +1343,11 @@ begin
   Result:=0;
 end;
 
+function TControl.GetParentBackground: Boolean;
+begin
+  Result := csParentBackground in ControlStyle;
+end;
+
 function TControl.ChildClassAllowed(ChildClass: TClass): Boolean;
 begin
   Result:=false;
@@ -1837,6 +1842,7 @@ begin
   begin
     FColor := Value;
     ParentColor := False;
+    ParentBackground := False;
     Perform(CM_COLORCHANGED, 0, 0);
     Invalidate;
   end;
@@ -4422,6 +4428,18 @@ begin
   end;
 end;
 
+procedure TControl.SetParentBackground(const AParentBackground: Boolean);
+begin
+  if ParentBackground = AParentBackground then
+    Exit;
+
+  if AParentBackground then
+    ControlStyle := ControlStyle + [csParentBackground]
+  else
+    ControlStyle := ControlStyle - [csParentBackground];
+  Invalidate;
+end;
+
 {------------------------------------------------------------------------------
   TControl SetParentComponent
 ------------------------------------------------------------------------------}

lcl/include/scrollbox.inc

@@ -19,9 +19,38 @@ constructor TScrollBox.Create(AOwner: TComponent);
 begin
   Inherited Create(AOwner);
   fCompStyle:= csScrollBox;
-  ControlStyle := ControlStyle + [csCaptureMouse];
+  ControlStyle := ControlStyle + [csCaptureMouse]
+    - [csOpaque] + [csParentBackground]; // we need the default background
   AutoScroll := True;
   BorderStyle := bsSingle;
 end;
 
+procedure TScrollBox.CMParentColorChanged(var Message: TLMessage);
+begin
+  UpdateParentColorChange;
+  inherited;
+end;
+
+procedure TScrollBox.Loaded;
+begin
+  inherited Loaded;
+  UpdateParentColorChange;
+end;
+
+procedure TScrollBox.SetParentBackground(const AParentBackground: Boolean);
+begin
+  if ParentBackground=AParentBackground then
+    Exit;
+  inherited;
+  UpdateParentColorChange;
+end;
+
+procedure TScrollBox.UpdateParentColorChange;
+begin
+  if ParentColor or ParentBackground then
+    ControlStyle := ControlStyle - [csOpaque]
+  else
+    ControlStyle := ControlStyle + [csOpaque];
+end;
+
 // included by forms.pp

lcl/include/wincontrol.inc

@@ -6529,18 +6529,6 @@ begin
   InvalidatePreferredSize;
 end;
 
-procedure TWinControl.SetParentBackground(const AParentBackground: Boolean);
-begin
-  if ParentBackground = AParentBackground then
-    Exit;
-
-  if AParentBackground then
-    ControlStyle := ControlStyle + [csParentBackground]
-  else
-    ControlStyle := ControlStyle - [csParentBackground];
-  Invalidate;
-end;
-
 procedure TWinControl.SetParentDoubleBuffered(Value: Boolean);
 begin
   if FParentDoubleBuffered <> Value then
@@ -7730,11 +7718,6 @@ begin
   Result:=HandleAllocated and (GetCaptureControl=Self);
 end;
 
-function TWinControl.GetParentBackground: Boolean;
-begin
-  Result := csParentBackground in ControlStyle;
-end;
-
 {------------------------------------------------------------------------------
   function TWinControl.ParentHandlesAllocated: boolean;