diff --git a/src/dropdown.cpp b/src/dropdown.cpp
index a328c69896..e424d79ad6 100644
--- a/src/dropdown.cpp
+++ b/src/dropdown.cpp
@@ -132,7 +132,7 @@ struct DropdownWindow : Window {
 
 		/* Set flag on parent widget to indicate that we have just closed. */
 		NWidgetCore *nwc = this->parent->GetWidget<NWidgetCore>(this->parent_button);
-		if (nwc != nullptr) SetBit(nwc->disp_flags, NDB_DROPDOWN_CLOSED);
+		if (nwc != nullptr) nwc->disp_flags.Set(NWidgetDisplayFlag::DropdownClosed);
 	}
 
 	void OnFocusLost(bool closing) override
@@ -410,7 +410,7 @@ void ShowDropDownList(Window *w, DropDownList &&list, int selected, WidgetID but
 	Colours wi_colour = nwi->colour;
 
 	if ((nwi->type & WWT_MASK) == NWID_BUTTON_DROPDOWN) {
-		nwi->disp_flags |= ND_DROPDOWN_ACTIVE;
+		nwi->disp_flags.Set(NWidgetDisplayFlag::DropdownActive);
 	} else {
 		nwi->SetLowered(true);
 	}
diff --git a/src/news_gui.cpp b/src/news_gui.cpp
index bef04fe83a..1c29471c77 100644
--- a/src/news_gui.cpp
+++ b/src/news_gui.cpp
@@ -396,11 +396,11 @@ struct NewsWindow : Window {
 			} else {
 				nvp->InitializeViewport(this, GetReferenceTile(ni->reftype1, ni->ref1), ScaleZoomGUI(ZOOM_LVL_NEWS));
 			}
-			if (this->ni->flags & NF_NO_TRANSPARENT) nvp->disp_flags |= ND_NO_TRANSPARENCY;
+			if (this->ni->flags & NF_NO_TRANSPARENT) nvp->disp_flags.Set(NWidgetDisplayFlag::NoTransparency);
 			if ((this->ni->flags & NF_INCOLOUR) == 0) {
-				nvp->disp_flags |= ND_SHADE_GREY;
+				nvp->disp_flags.Set(NWidgetDisplayFlag::ShadeGrey);
 			} else if (this->ni->flags & NF_SHADE) {
-				nvp->disp_flags |= ND_SHADE_DIMMED;
+				nvp->disp_flags.Set(NWidgetDisplayFlag::ShadeDimmed);
 			}
 		}
 
diff --git a/src/widget.cpp b/src/widget.cpp
index 4ea993f7c6..5149181d1d 100644
--- a/src/widget.cpp
+++ b/src/widget.cpp
@@ -194,7 +194,7 @@ static void ScrollbarClickPositioning(Window *w, NWidgetScrollbar *sb, int x, in
 	}
 	if (pos < mi + button_size) {
 		/* Pressing the upper button? */
-		SetBit(sb->disp_flags, NDB_SCROLLBAR_UP);
+		sb->disp_flags.Set(NWidgetDisplayFlag::ScrollbarUp);
 		if (_scroller_click_timeout <= 1) {
 			_scroller_click_timeout = 3;
 			changed = sb->UpdatePosition(rtl ? 1 : -1);
@@ -202,7 +202,7 @@ static void ScrollbarClickPositioning(Window *w, NWidgetScrollbar *sb, int x, in
 		w->mouse_capture_widget = sb->GetIndex();
 	} else if (pos >= ma - button_size) {
 		/* Pressing the lower button? */
-		SetBit(sb->disp_flags, NDB_SCROLLBAR_DOWN);
+		sb->disp_flags.Set(NWidgetDisplayFlag::ScrollbarDown);
 
 		if (_scroller_click_timeout <= 1) {
 			_scroller_click_timeout = 3;
@@ -2401,7 +2401,7 @@ void NWidgetViewport::Draw(const Window *w)
 {
 	if (this->current_x == 0 || this->current_y == 0) return;
 
-	if (this->disp_flags & ND_NO_TRANSPARENCY) {
+	if (this->disp_flags.Test(NWidgetDisplayFlag::NoTransparency)) {
 		TransparencyOptionBits to_backup = _transparency_opt;
 		_transparency_opt &= (1 << TO_SIGNS) | (1 << TO_TEXT); // Disable all transparency, except textual stuff
 		w->DrawViewport();
@@ -2411,8 +2411,8 @@ void NWidgetViewport::Draw(const Window *w)
 	}
 
 	/* Optionally shade the viewport. */
-	if (this->disp_flags & (ND_SHADE_GREY | ND_SHADE_DIMMED)) {
-		GfxFillRect(this->GetCurrentRect(), (this->disp_flags & ND_SHADE_DIMMED) ? PALETTE_TO_TRANSPARENT : PALETTE_NEWSPAPER, FILLRECT_RECOLOUR);
+	if (this->disp_flags.Any({NWidgetDisplayFlag::ShadeGrey, NWidgetDisplayFlag::ShadeDimmed})) {
+		GfxFillRect(this->GetCurrentRect(), this->disp_flags.Test(NWidgetDisplayFlag::ShadeDimmed) ? PALETTE_TO_TRANSPARENT : PALETTE_NEWSPAPER, FILLRECT_RECOLOUR);
 	}
 
 	DrawOutline(w, this);
@@ -2626,9 +2626,9 @@ void NWidgetScrollbar::Draw(const Window *w)
 	const DrawPixelInfo *dpi = _cur_dpi;
 	if (dpi->left > r.right || dpi->left + dpi->width <= r.left || dpi->top > r.bottom || dpi->top + dpi->height <= r.top) return;
 
-	bool up_lowered = HasBit(this->disp_flags, NDB_SCROLLBAR_UP);
-	bool down_lowered = HasBit(this->disp_flags, NDB_SCROLLBAR_DOWN);
-	bool middle_lowered = !(this->disp_flags & ND_SCROLLBAR_BTN) && w->mouse_capture_widget == this->index;
+	bool up_lowered = this->disp_flags.Test(NWidgetDisplayFlag::ScrollbarUp);
+	bool down_lowered = this->disp_flags.Test(NWidgetDisplayFlag::ScrollbarDown);
+	bool middle_lowered = !this->disp_flags.Any({NWidgetDisplayFlag::ScrollbarUp, NWidgetDisplayFlag::ScrollbarDown}) && w->mouse_capture_widget == this->index;
 
 	if (this->type == NWID_HSCROLLBAR) {
 		DrawHorizontalScrollbar(r, this->colour, up_lowered, middle_lowered, down_lowered, this);
@@ -3091,7 +3091,7 @@ void NWidgetLeaf::Draw(const Window *w)
 		case NWID_BUTTON_DROPDOWN:
 		case NWID_PUSHBUTTON_DROPDOWN:
 			if (this->index >= 0) w->SetStringParameters(this->index);
-			DrawButtonDropdown(r, this->colour, clicked, (this->disp_flags & ND_DROPDOWN_ACTIVE) != 0, this->GetString(), this->align);
+			DrawButtonDropdown(r, this->colour, clicked, this->disp_flags.Test(NWidgetDisplayFlag::DropdownActive), this->GetString(), this->align);
 			break;
 
 		default:
diff --git a/src/widget_type.h b/src/widget_type.h
index 79296cc929..0394abec1e 100644
--- a/src/widget_type.h
+++ b/src/widget_type.h
@@ -323,36 +323,28 @@ public:
 };
 
 /** Nested widget flags that affect display and interaction with 'real' widgets. */
-enum NWidgetDisplay : uint16_t {
+enum NWidgetDisplayFlag : uint8_t {
 	/* Generic. */
-	NDB_LOWERED         = 0, ///< Widget is lowered (pressed down) bit.
-	NDB_DISABLED        = 1, ///< Widget is disabled (greyed out) bit.
-	/* Viewport widget. */
-	NDB_NO_TRANSPARENCY = 2, ///< Viewport is never transparent.
-	NDB_SHADE_GREY      = 3, ///< Shade viewport to grey-scale.
-	NDB_SHADE_DIMMED    = 4, ///< Display dimmed colours in the viewport.
-	/* Button dropdown widget. */
-	NDB_DROPDOWN_ACTIVE = 5, ///< Dropdown menu of the button dropdown widget is active. @see #NWID_BUTTON_DROPDOWN
-	/* Scrollbar widget. */
-	NDB_SCROLLBAR_UP    = 6, ///< Up-button is lowered bit.
-	NDB_SCROLLBAR_DOWN  = 7, ///< Down-button is lowered bit.
-	/* Generic. */
-	NDB_HIGHLIGHT       = 8, ///< Highlight of widget is on.
-	NDB_DROPDOWN_CLOSED = 9, ///< Dropdown menu of the dropdown widget has closed.
+	Lowered, ///< Widget is lowered (pressed down) bit.
+	Disabled, ///< Widget is disabled (greyed out) bit.
 
-	ND_LOWERED  = 1 << NDB_LOWERED,                ///< Bit value of the lowered flag.
-	ND_DISABLED = 1 << NDB_DISABLED,               ///< Bit value of the disabled flag.
-	ND_HIGHLIGHT = 1 << NDB_HIGHLIGHT,             ///< Bit value of the highlight flag.
-	ND_NO_TRANSPARENCY = 1 << NDB_NO_TRANSPARENCY, ///< Bit value of the 'no transparency' flag.
-	ND_SHADE_GREY      = 1 << NDB_SHADE_GREY,      ///< Bit value of the 'shade to grey' flag.
-	ND_SHADE_DIMMED    = 1 << NDB_SHADE_DIMMED,    ///< Bit value of the 'dimmed colours' flag.
-	ND_DROPDOWN_ACTIVE = 1 << NDB_DROPDOWN_ACTIVE, ///< Bit value of the 'dropdown active' flag.
-	ND_SCROLLBAR_UP    = 1 << NDB_SCROLLBAR_UP,    ///< Bit value of the 'scrollbar up' flag.
-	ND_SCROLLBAR_DOWN  = 1 << NDB_SCROLLBAR_DOWN,  ///< Bit value of the 'scrollbar down' flag.
-	ND_SCROLLBAR_BTN   = ND_SCROLLBAR_UP | ND_SCROLLBAR_DOWN, ///< Bit value of the 'scrollbar up' or 'scrollbar down' flag.
-	ND_DROPDOWN_CLOSED = 1 << NDB_DROPDOWN_CLOSED, ///< Bit value of the 'dropdown closed' flag.
+	/* Viewport widget. */
+	NoTransparency, ///< Viewport is never transparent.
+	ShadeGrey, ///< Shade viewport to grey-scale.
+	ShadeDimmed, ///< Display dimmed colours in the viewport.
+
+	/* Button dropdown widget. */
+	DropdownActive, ///< Dropdown menu of the button dropdown widget is active. @see #NWID_BUTTON_DROPDOWN
+
+	/* Scrollbar widget. */
+	ScrollbarUp, ///< Up-button is lowered bit.
+	ScrollbarDown, ///< Down-button is lowered bit.
+
+	/* Generic. */
+	Highlight, ///< Highlight of widget is on.
+	DropdownClosed, ///< Dropdown menu of the dropdown widget has closed.
 };
-DECLARE_ENUM_AS_BIT_SET(NWidgetDisplay)
+using NWidgetDisplayFlags = EnumBitSet<NWidgetDisplayFlag, uint16_t>;
 
 /** Container with the data associated to a single widget. */
 struct WidgetData {
@@ -397,7 +389,7 @@ public:
 	TextColour GetHighlightColour() const override;
 	void SetHighlighted(TextColour highlight_colour) override;
 
-	NWidgetDisplay disp_flags; ///< Flags that affect display and interaction with the widget.
+	NWidgetDisplayFlags disp_flags; ///< Flags that affect display and interaction with the widget.
 	Colours colour;            ///< Colour of this widget.
 protected:
 	const WidgetID index;      ///< Index of the nested widget (\c -1 means 'not used').
@@ -419,14 +411,14 @@ protected:
  */
 inline void NWidgetCore::SetHighlighted(TextColour highlight_colour)
 {
-	this->disp_flags = highlight_colour != TC_INVALID ? SETBITS(this->disp_flags, ND_HIGHLIGHT) : CLRBITS(this->disp_flags, ND_HIGHLIGHT);
+	highlight_colour != TC_INVALID ? this->disp_flags.Set(NWidgetDisplayFlag::Highlight) : this->disp_flags.Reset(NWidgetDisplayFlag::Highlight);
 	this->highlight_colour = highlight_colour;
 }
 
 /** Return whether the widget is highlighted. */
 inline bool NWidgetCore::IsHighlighted() const
 {
-	return HasBit(this->disp_flags, NDB_HIGHLIGHT);
+	return this->disp_flags.Test(NWidgetDisplayFlag::Highlight);
 }
 
 /** Return the colour of the highlight. */
@@ -441,13 +433,13 @@ inline TextColour NWidgetCore::GetHighlightColour() const
  */
 inline void NWidgetCore::SetLowered(bool lowered)
 {
-	this->disp_flags = lowered ? SETBITS(this->disp_flags, ND_LOWERED) : CLRBITS(this->disp_flags, ND_LOWERED);
+	lowered ? this->disp_flags.Set(NWidgetDisplayFlag::Lowered) : this->disp_flags.Reset(NWidgetDisplayFlag::Lowered);
 }
 
 /** Return whether the widget is lowered. */
 inline bool NWidgetCore::IsLowered() const
 {
-	return HasBit(this->disp_flags, NDB_LOWERED);
+	return this->disp_flags.Test(NWidgetDisplayFlag::Lowered);
 }
 
 /**
@@ -456,13 +448,13 @@ inline bool NWidgetCore::IsLowered() const
  */
 inline void NWidgetCore::SetDisabled(bool disabled)
 {
-	this->disp_flags = disabled ? SETBITS(this->disp_flags, ND_DISABLED) : CLRBITS(this->disp_flags, ND_DISABLED);
+	this->disp_flags = disabled ? this->disp_flags.Set(NWidgetDisplayFlag::Disabled) : this->disp_flags.Reset(NWidgetDisplayFlag::Disabled);
 }
 
 /** Return whether the widget is disabled. */
 inline bool NWidgetCore::IsDisabled() const
 {
-	return HasBit(this->disp_flags, NDB_DISABLED);
+	return this->disp_flags.Test(NWidgetDisplayFlag::Disabled);
 }
 
 
diff --git a/src/window.cpp b/src/window.cpp
index ad61dce045..63f63f3c2d 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -296,7 +296,7 @@ void Window::OnDropdownClose(Point pt, WidgetID widget, int index, bool instant_
 	/* Raise the dropdown button */
 	NWidgetCore *nwi2 = this->GetWidget<NWidgetCore>(widget);
 	if ((nwi2->type & WWT_MASK) == NWID_BUTTON_DROPDOWN) {
-		nwi2->disp_flags &= ~ND_DROPDOWN_ACTIVE;
+		nwi2->disp_flags.Reset(NWidgetDisplayFlag::DropdownActive);
 	} else {
 		this->RaiseWidget(widget);
 	}
@@ -607,7 +607,7 @@ static void DispatchLeftClickEvent(Window *w, int x, int y, int click_count)
 	WidgetType widget_type = (nw != nullptr) ? nw->type : WWT_EMPTY;
 
 	/* Allow dropdown close flag detection to work. */
-	if (nw != nullptr) ClrBit(nw->disp_flags, NDB_DROPDOWN_CLOSED);
+	if (nw != nullptr) nw->disp_flags.Reset(NWidgetDisplayFlag::DropdownClosed);
 
 	bool focused_widget_changed = false;
 	/* If clicked on a window that previously did not have focus */
@@ -642,7 +642,7 @@ static void DispatchLeftClickEvent(Window *w, int x, int y, int click_count)
 	}
 
 	/* Dropdown window of this widget was closed so don't process click this time. */
-	if (HasBit(nw->disp_flags, NDB_DROPDOWN_CLOSED)) return;
+	if (nw->disp_flags.Test(NWidgetDisplayFlag::DropdownClosed)) return;
 
 	if ((widget_type & ~WWB_PUSHBUTTON) < WWT_LAST && (widget_type & WWB_PUSHBUTTON)) w->HandleButtonClick(widget_index);
 
@@ -1830,8 +1830,8 @@ static void DecreaseWindowCounters()
 				NWidgetBase *nwid = pair.second;
 				if (nwid->type == NWID_HSCROLLBAR || nwid->type == NWID_VSCROLLBAR) {
 					NWidgetScrollbar *sb = static_cast<NWidgetScrollbar*>(nwid);
-					if (sb->disp_flags & (ND_SCROLLBAR_UP | ND_SCROLLBAR_DOWN)) {
-						sb->disp_flags &= ~(ND_SCROLLBAR_UP | ND_SCROLLBAR_DOWN);
+					if (sb->disp_flags.Any({NWidgetDisplayFlag::ScrollbarUp, NWidgetDisplayFlag::ScrollbarDown})) {
+						sb->disp_flags.Reset(NWidgetDisplayFlag::ScrollbarUp).Reset(NWidgetDisplayFlag::ScrollbarDown);
 						w->mouse_capture_widget = -1;
 						sb->SetDirty(w);
 					}
@@ -2297,10 +2297,10 @@ static void HandleScrollbarScrolling(Window *w)
 		i = _cursor.pos.y - _cursorpos_drag_start.y;
 	}
 
-	if (sb->disp_flags & ND_SCROLLBAR_BTN) {
+	if (sb->disp_flags.Any({NWidgetDisplayFlag::ScrollbarUp, NWidgetDisplayFlag::ScrollbarDown})) {
 		if (_scroller_click_timeout == 1) {
 			_scroller_click_timeout = 3;
-			if (sb->UpdatePosition(rtl == HasBit(sb->disp_flags, NDB_SCROLLBAR_UP) ? 1 : -1)) w->SetDirty();
+			if (sb->UpdatePosition(rtl == sb->disp_flags.Test(NWidgetDisplayFlag::ScrollbarUp) ? 1 : -1)) w->SetDirty();
 		}
 		return;
 	}