Scroll most lists by finger dragging list contents

src/object_gui.cpp

@@ -86,7 +86,7 @@ public:
 		this->vscroll->SetCount(ObjectClass::GetUIClassCount());
 
 		NWidgetMatrix *matrix = this->GetWidget<NWidgetMatrix>(WID_BO_SELECT_MATRIX);
-		matrix->SetScrollbar(this->GetScrollbar(WID_BO_SELECT_SCROLL));
+		matrix->SetScrollbar(this->GetScrollbar(WID_BO_SELECT_SCROLL), WID_BO_SELECT_SCROLL);
 
 		this->SelectOtherClass(_selected_object_class);
 		if (this->CanRestoreSelectedObject()) {

src/rail_gui.cpp

@@ -1031,7 +1031,7 @@ public:
 			this->vscroll->SetPosition(Clamp(_railstation.station_class - 2, 0, max(this->vscroll->GetCount() - this->vscroll->GetCapacity(), 0)));
 
 			NWidgetMatrix *matrix = this->GetWidget<NWidgetMatrix>(WID_BRAS_MATRIX);
-			matrix->SetScrollbar(this->vscroll2);
+			matrix->SetScrollbar(this->vscroll2, this->vscroll2 ? WID_BRAS_MATRIX_SCROLL : -1);
 			matrix->SetCount(_railstation.station_count);
 			matrix->SetClicked(_railstation.station_type);
 		}
@@ -1851,7 +1851,7 @@ struct BuildRailWaypointWindow : PickerWindowBase {
 		this->CreateNestedTree();
 
 		NWidgetMatrix *matrix = this->GetWidget<NWidgetMatrix>(WID_BRW_WAYPOINT_MATRIX);
-		matrix->SetScrollbar(this->GetScrollbar(WID_BRW_SCROLL));
+		matrix->SetScrollbar(this->GetScrollbar(WID_BRW_SCROLL), WID_BRW_SCROLL);
 
 		this->FinishInitNested(TRANSPORT_RAIL);
 

src/widget.cpp

@@ -101,6 +101,17 @@ static void ScrollbarClickPositioning(Window *w, NWidgetScrollbar *sb, int x, in
 		pos = y;
 		button_size = NWidgetScrollbar::GetVerticalDimension().height;
 	}
+
+	if (_scrollbar_finger_drag) {
+		w->mouse_capture_widget = sb->index;
+		_cursorpos_drag_start.x = x;
+		_cursorpos_drag_start.y = y;
+		_scrollbar_size = max(1, (int) sb->current_y * sb->GetCount() / sb->GetCapacity());
+		_scrollbar_start_pos = sb->GetPosition() * _scrollbar_size / sb->GetCount();
+		w->SetDirty();
+		return;
+	}
+
 	if (pos < mi + button_size) {
 		/* Pressing the upper button? */
 		SetBit(sb->disp_flags, NDB_SCROLLBAR_UP);
@@ -1748,9 +1759,20 @@ void NWidgetMatrix::SetCount(int count)
  * Assign a scrollbar to this matrix.
  * @param sb The scrollbar to assign to us.
  */
-void NWidgetMatrix::SetScrollbar(Scrollbar *sb)
+void NWidgetMatrix::SetScrollbar(Scrollbar *sb, int index)
 {
 	this->sb = sb;
+	this->sb_index = index;
+}
+
+Scrollbar *NWidgetMatrix::GetScrollbar()
+{
+	return this->sb;
+}
+
+int NWidgetMatrix::GetScrollbarWidget()
+{
+	return this->sb_index;
 }
 
 void NWidgetMatrix::SetupSmallestSize(Window *w, bool init_array)

src/widget_type.h

@@ -520,7 +520,9 @@ public:
 	void SetColour(Colours colour);
 	void SetClicked(int clicked);
 	void SetCount(int count);
-	void SetScrollbar(Scrollbar *sb);
+	void SetScrollbar(Scrollbar *sb, int index);
+	Scrollbar *GetScrollbar();
+	int GetScrollbarWidget();
 
 	void SetupSmallestSize(Window *w, bool init_array);
 	void AssignSizePosition(SizingType sizing, uint x, uint y, uint given_width, uint given_height, bool rtl);
@@ -534,6 +536,7 @@ protected:
 	int clicked;    ///< The currently clicked widget.
 	int count;      ///< Amount of valid widgets.
 	Scrollbar *sb;  ///< The scrollbar we're associated with.
+	int sb_index;   ///< The scrollbar widget index.
 private:
 	int widget_w;   ///< The width of the child widget including inter spacing.
 	int widget_h;   ///< The height of the child widget including inter spacing.

src/window.cpp

@@ -78,6 +78,7 @@ Point _cursorpos_drag_start;
 
 int _scrollbar_start_pos;
 int _scrollbar_size;
+bool _scrollbar_finger_drag;
 byte _scroller_click_timeout = 0;
 
 bool _scrolling_viewport;  ///< A viewport is being scrolled with the mouse.
@@ -2113,9 +2114,34 @@ static void HandleMouseDragNoTitlebars()
 		_focused_window->window_class != WC_MAIN_TOOLBAR_RIGHT &&
 		_focused_window->window_class != WC_BUILD_CONFIRMATION &&
 		FindWindowByClass(WC_DROPDOWN_MENU) == NULL) {
-		StartWindowDrag(_focused_window);
+		if (abs(_cursor.pos.x - _left_button_down_pos.x) < abs(_cursor.pos.y - _left_button_down_pos.y)) {
-		_drag_delta.x += _cursor.pos.x - _left_button_down_pos.x;
+			int widgetId = GetWidgetFromPos(_focused_window, _left_button_down_pos.x - _focused_window->left, _left_button_down_pos.y - _focused_window->top);
-		_drag_delta.y += _cursor.pos.y - _left_button_down_pos.y;
+			if (widgetId >= 0) {
+				NWidgetBase *widget = _focused_window->GetWidget<NWidgetBase>(widgetId);
+				NWidgetScrollbar *scroll = NULL;
+				if (widget && widget->type == WWT_MATRIX) {
+					NWidgetLeaf *list = _focused_window->GetWidget<NWidgetLeaf>(widgetId);
+					if (list && list->scrollbar_index >= 0) {
+						scroll = _focused_window->GetWidget<NWidgetScrollbar>(list->scrollbar_index);
+					}
+				}
+				if (widget && widget->type == NWID_MATRIX) {
+					NWidgetMatrix *list = _focused_window->GetWidget<NWidgetMatrix>(widgetId);
+					if (list && list->GetScrollbar() && list->GetScrollbarWidget() >= 0) {
+						scroll = _focused_window->GetWidget<NWidgetScrollbar>(list->GetScrollbarWidget());
+					}
+				}
+				if (scroll && scroll->IsVertical() && scroll->GetCount() > scroll->GetCapacity()) {
+					_scrollbar_finger_drag = true;
+					ScrollbarClickHandler(_focused_window, scroll, _left_button_down_pos.x, _left_button_down_pos.y);
+				}
+			}
+		}
+		if (_focused_window->mouse_capture_widget == -1) {
+			StartWindowDrag(_focused_window);
+			_drag_delta.x += _cursor.pos.x - _left_button_down_pos.x;
+			_drag_delta.y += _cursor.pos.y - _left_button_down_pos.y;
+		}
 	}
 }
 
@@ -2593,6 +2619,9 @@ static void HandleScrollbarScrolling(Window *w)
 	} else {
 		i = _cursor.pos.y - _cursorpos_drag_start.y;
 	}
+	if (_scrollbar_finger_drag) {
+		i = -i;
+	}
 
 	if (sb->disp_flags & ND_SCROLLBAR_BTN) {
 		if (_scroller_click_timeout == 1) {
@@ -2624,6 +2653,7 @@ static EventState HandleActiveWidget()
 			/* Abort if no button is clicked any more. */
 			if (!_left_button_down) {
 				w->mouse_capture_widget = -1;
+				_scrollbar_finger_drag = false;
 				w->SetDirty();
 				return ES_HANDLED;
 			}

src/window_gui.h

@@ -906,6 +906,7 @@ extern Point _cursorpos_drag_start;
 
 extern int _scrollbar_start_pos;
 extern int _scrollbar_size;
+extern bool _scrollbar_finger_drag;
 extern byte _scroller_click_timeout;
 enum {
 	SCROLLER_CLICK_DELAY = 6 ///< Delay in video frames between scrollbar doing scroll, we don't want to get to the bottom of the list in an instant

todo.txt

@@ -5,7 +5,5 @@
 
 - Misclicking station from orders dialog should hide the dialog for 3 times.
 
-- Draggable combo boxes.
-
 - Create auto-save when the app is put to background, and load it on the next start.