UI: Hide & shrink scroll-bars based on cursor position

Scroll-bars are now hidden unless the cursor approaches them, in which case they
smoothly grow and become more & more visible. Note that since 0d309144020168e55,
scroll-bars are drawn on top of editor contents. There's no more jumping of
buttons when scroll-bars appear.

Technical notes:
* AZones are used to adjust scrollbars based on mouse movements

  We may want to support screen level AZones if we want scrollbars to also
  smoothly appear when approaching them from a different area.
  I also plan to make further changes to AZones to clean up stuff a bit.
* Had to move AZone handling to a post ARegion init stage, since we need the
  updated View2D data from there.
* View2D masks and scroller rectangles are now updated on every redraw. It's
  cheap to do that though.

1 files changed, 5 insertions, 0 deletions

diff --git a/source/blender/makesdna/DNA_view2d_types.h b/source/blender/makesdna/DNA_view2d_types.h
index 3319fed8cdd..a0480aa361b 100644
--- a/source/blender/makesdna/DNA_view2d_types.h
+++ b/source/blender/makesdna/DNA_view2d_types.h
@@ -64,6 +64,11 @@ typedef struct View2D {
 	int tab_num;					/* number of tabs stored */
 	int tab_cur;					/* current tab */
 
+	/* Usually set externally (as in, not in view2d files). */
+	char alpha_vert, alpha_hor;		/* alpha of vertical and horizontal scrollbars (range is [0, 255]) */
+	short size_vert, size_hor;		/* Dynamic size for scrollers without scale markers (no V2D_SCROLL_SCALE_FOO) */
+	short pad;
+
 	/* animated smooth view */
 	struct SmoothView2DStore *sms;
 	struct wmTimer *smooth_timer;