(svn r20922) -Fix [FS#4071]: accidentally moving the mouse of the scrollbar arrows while pressing it clicks the button next to the arrow

src/widget.cpp

@@ -89,7 +89,7 @@ static void ScrollbarClickPositioning(Window *w, NWidgetScrollbar *sb, int x, in
 			_scroller_click_timeout = 3;
 			sb->UpdatePosition(rtl ? 1 : -1);
 		}
-		_left_button_clicked = false;
+		w->scrolling_scrollbar = sb->index;
 	} else if (pos >= ma - 10) {
 		/* Pressing the lower button? */
 		SetBit(sb->disp_flags, NDB_SCROLLBAR_DOWN);
@@ -98,7 +98,7 @@ static void ScrollbarClickPositioning(Window *w, NWidgetScrollbar *sb, int x, in
 			_scroller_click_timeout = 3;
 			sb->UpdatePosition(rtl ? -1 : 1);
 		}
-		_left_button_clicked = false;
+		w->scrolling_scrollbar = sb->index;
 	} else {
 		Point pt = HandleScrollbarHittest(sb, mi, ma, sb->type == NWID_HSCROLLBAR);
 
@@ -1686,7 +1686,7 @@ void NWidgetScrollbar::Draw(const Window *w)
 
 	bool up_lowered = HasBit(this->disp_flags, NDB_SCROLLBAR_UP);
 	bool down_lowered = HasBit(this->disp_flags, NDB_SCROLLBAR_DOWN);
-	bool middle_lowered = (w->scrolling_scrollbar == this->index);
+	bool middle_lowered = !(this->disp_flags & ND_SCROLLBAR_BTN) && w->scrolling_scrollbar == this->index;
 
 	if (this->type == NWID_HSCROLLBAR) {
 		DrawHorizontalScrollbar(r, this->colour, up_lowered, middle_lowered, down_lowered, this);

src/widget_type.h

@@ -262,6 +262,7 @@ enum NWidgetDisplay {
 	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.
 };
 DECLARE_ENUM_AS_BIT_SET(NWidgetDisplay)
 

src/window.cpp

@@ -1861,6 +1861,15 @@ static EventState HandleScrollbarScrolling()
 				i = _cursor.pos.y - _cursorpos_drag_start.y;
 			}
 
+			if (sb->disp_flags & ND_SCROLLBAR_BTN) {
+				if (_scroller_click_timeout == 1) {
+					_scroller_click_timeout = 3;
+					sb->UpdatePosition(rtl == HasBit(sb->disp_flags, NDB_SCROLLBAR_UP) ? 1 : -1);
+					w->SetDirty();
+				}
+				return ES_HANDLED;
+			}
+
 			/* Find the item we want to move to and make sure it's inside bounds. */
 			int pos = min(max(0, i + _scrollbar_start_pos) * sb->GetCount() / _scrollbar_size, max(0, sb->GetCount() - sb->GetCapacity()));
 			if (rtl) pos = max(0, sb->GetCount() - sb->GetCapacity() - pos);