BScrollBar: Add lines and dots knob styles to scroll bar

Fixes #9137

Move scroll bar drawing into HaikuControlLook

Added B_SCROLLABLE flag to BControlLook

Update FakeScrollBar in Appearance to also draw using HaikuControlLook.

Focus works on scroll bars again, used by FakeScrollBar... and probably
nowhere else.

Added private _ScrollingEnabled() convenience method to BScrollBar and
use it in a few places making.

Create ScrollBarPrivate.h header to share a couple of scroll bar related
enums with HaikuControlLook that come from BeOS Scroll Bar prefs.

Stuff arrow_direction enum into BScrollBar::Private as it has been
succeeded by a similar enum already present in BControlLook and is only
around now for BScrollBar::Private::DrawScrollBarButton.

Change-Id: Idc31ee41de091ba45ded2f0315a004af00143803

headers/private/interface/HaikuControlLook.h

@@ -157,15 +157,17 @@ public:
 									const rgb_color& base,
 									uint32 flags = 0);
 
-	virtual	void				DrawScrollBarBackground(BView* view,
-									BRect& rect1, BRect& rect2,
+	virtual	void				DrawScrollBar(BView* view, BRect& rect,
 									const BRect& updateRect,
 									const rgb_color& base, uint32 flags,
-									orientation orientation);
-	virtual	void				DrawScrollBarBackground(BView* view,
-									BRect& rect, const BRect& updateRect,
+									orientation orientation,
+									bool doubleArrows = false,
+									int32 buttonDown = -1);
+	virtual	void				DrawScrollBarThumb(BView* view, BRect& rect,
+									BRect& thumbRect, const BRect& updateRect,
 									const rgb_color& base, uint32 flags,
-									orientation orientation);
+									orientation orientation,
+									uint32 knobStyle = 0);
 
 	virtual	void				DrawScrollViewFrame(BView* view,
 									BRect& rect, const BRect& updateRect,
@@ -559,6 +561,26 @@ protected:
 									const rgb_color& base, rgb_color& color,
 									uint32 flags) const;
 
+			void				_DrawScrollBarBackground(BView* view,
+									BRect& rect1, BRect& rect2,
+									const BRect& updateRect,
+									const rgb_color& base, uint32 flags,
+									orientation orientation);
+			void				_DrawScrollBarBackground(BView* view,
+									BRect& rect, const BRect& updateRect,
+									const rgb_color& base, uint32 flags,
+									orientation orientation);
+			void				_DrawDisabledScrollBarBackground(BView* view,
+									BRect rect, orientation orientation,
+									const rgb_color& light,
+									const rgb_color& dark,
+									const rgb_color& fill);
+			void				_DrawScrollBarArrowButton(BView* view,
+									BRect rect, const BRect& updateRect,
+									const rgb_color& base, uint32 flags,
+									int32 direction, orientation orientation,
+									bool doubleArrows, bool down);
+
 private:
 			bool				fCachedOutline;
 };

headers/private/interface/ScrollBarPrivate.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2018 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		John Scipione, [email protected]
+ */
+#ifndef _SCROLL_BAR_PRIVATE_H
+#define _SCROLL_BAR_PRIVATE_H
+
+// Constants for determining which arrow is down and are defined with respect
+// to double arrow mode. ARROW_1 and ARROW_4 refer to the outer pair of arrows
+// while ARROW_2 and ARROW_3 refer to the inner ones. ARROW_1 point left/up
+// and ARROW_4 points right/down. THUMB is the scroll bar thumb.
+enum {
+	SCROLL_NO_ARROW = -1,
+	SCROLL_ARROW_1,
+	SCROLL_ARROW_2,
+	SCROLL_ARROW_3,
+	SCROLL_ARROW_4,
+	SCROLL_THUMB
+};
+
+// constants for determining which knob style to draw on scroll bar
+typedef enum {
+	KNOB_NONE = 0,
+	KNOB_DOTS,
+	KNOB_LINES
+} knob_style;
+
+
+#endif // _SCROLL_BAR_PRIVATE_H