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, 30 insertions, 7 deletions

diff --git a/source/blender/editors/interface/view2d.c b/source/blender/editors/interface/view2d.c
index 8342387f956..2a687118eaa 100644
--- a/source/blender/editors/interface/view2d.c
+++ b/source/blender/editors/interface/view2d.c
@@ -152,10 +152,11 @@ static void view2d_masks(View2D *v2d, bool check_scrollers)
 	 *	- if they overlap, they must not occupy the corners (which are reserved for other widgets)
 	 */
 	if (scroll) {
-		const int scroll_width = (v2d->scroll & V2D_SCROLL_SCALE_VERTICAL) ?
-		                             V2D_SCROLL_WIDTH_TEXT : V2D_SCROLL_WIDTH;
-		const int scroll_height = (v2d->scroll & V2D_SCROLL_SCALE_HORIZONTAL) ?
-		                              V2D_SCROLL_HEIGHT_TEXT : V2D_SCROLL_HEIGHT;
+		int scroll_width  = (v2d->scroll & V2D_SCROLL_SCALE_VERTICAL) ?   V2D_SCROLL_WIDTH_TEXT  : v2d->size_vert;
+		int scroll_height = (v2d->scroll & V2D_SCROLL_SCALE_HORIZONTAL) ? V2D_SCROLL_HEIGHT_TEXT : v2d->size_hor;
+
+		CLAMP_MIN(scroll_width, V2D_SCROLL_WIDTH_MIN);
+		CLAMP_MIN(scroll_height, V2D_SCROLL_HEIGHT_MIN);
 
 		/* vertical scroller */
 		if (scroll & V2D_SCROLL_LEFT) {
@@ -357,6 +358,11 @@ void UI_view2d_region_reinit(View2D *v2d, short type, int winx, int winy)
 	/* set masks (always do), but leave scroller scheck to totrect_set */
 	view2d_masks(v2d, 0);
 	
+	if (do_init) {
+		/* Visible by default. */
+		v2d->alpha_hor = v2d->alpha_vert = 255;
+	}
+	
 	/* set 'tot' rect before setting cur? */
 	/* XXX confusing stuff here still - I made this function not check scroller hide - that happens in totrect_set */
 	if (tot_changed)
@@ -1641,6 +1647,9 @@ View2DScrollers *UI_view2d_scrollers_calc(
 	/* scrollers is allocated here... */
 	scrollers = MEM_callocN(sizeof(View2DScrollers), "View2DScrollers");
 	
+	/* Always update before drawing (for dynamically sized scrollers). */
+	view2d_masks(v2d, false);
+	
 	vert = v2d->vert;
 	hor = v2d->hor;
 	
@@ -1804,9 +1813,11 @@ static void scroll_printstr(Scene *scene, float x, float y, float val, int power
 /* Draw scrollbars in the given 2d-region */
 void UI_view2d_scrollers_draw(const bContext *C, View2D *v2d, View2DScrollers *vs)
 {
+	bTheme *btheme = UI_GetTheme();
 	Scene *scene = CTX_data_scene(C);
 	rcti vert, hor;
-	int scroll = view2d_scroll_mapped(v2d->scroll);
+	const int scroll = view2d_scroll_mapped(v2d->scroll);
+	const char emboss_alpha = btheme->tui.widget_emboss[3];
 	unsigned char scrollers_back_color[4];
 
 	/* Color for scrollbar backs */
@@ -1818,8 +1829,8 @@ void UI_view2d_scrollers_draw(const bContext *C, View2D *v2d, View2DScrollers *v
 	
 	/* horizontal scrollbar */
 	if (scroll & V2D_SCROLL_HORIZONTAL) {
-		bTheme *btheme = UI_GetTheme();
 		uiWidgetColors wcol = btheme->tui.wcol_scroll;
+		const float alpha_fac = v2d->alpha_hor / 255.0f;
 		rcti slider;
 		int state;
 		
@@ -1830,6 +1841,11 @@ void UI_view2d_scrollers_draw(const bContext *C, View2D *v2d, View2DScrollers *v
 		
 		state = (v2d->scroll_ui & V2D_SCROLL_H_ACTIVE) ? UI_SCROLL_PRESSED : 0;
 		
+		wcol.inner[3]   *= alpha_fac;
+		wcol.item[3]    *= alpha_fac;
+		wcol.outline[3] *= alpha_fac;
+		btheme->tui.widget_emboss[3] *= alpha_fac; /* will be reset later */
+		
 		/* show zoom handles if:
 		 *	- zooming on x-axis is allowed (no scroll otherwise)
 		 *	- slider bubble is large enough (no overdraw confusion)
@@ -1916,9 +1932,9 @@ void UI_view2d_scrollers_draw(const bContext *C, View2D *v2d, View2DScrollers *v
 	
 	/* vertical scrollbar */
 	if (scroll & V2D_SCROLL_VERTICAL) {
-		bTheme *btheme = UI_GetTheme();
 		uiWidgetColors wcol = btheme->tui.wcol_scroll;
 		rcti slider;
+		const float alpha_fac = v2d->alpha_vert / 255.0f;
 		int state;
 		
 		slider.xmin = vert.xmin;
@@ -1928,6 +1944,11 @@ void UI_view2d_scrollers_draw(const bContext *C, View2D *v2d, View2DScrollers *v
 		
 		state = (v2d->scroll_ui & V2D_SCROLL_V_ACTIVE) ? UI_SCROLL_PRESSED : 0;
 		
+		wcol.inner[3]   *= alpha_fac;
+		wcol.item[3]    *= alpha_fac;
+		wcol.outline[3] *= alpha_fac;
+		btheme->tui.widget_emboss[3] *= alpha_fac; /* will be reset later */
+		
 		/* show zoom handles if:
 		 *	- zooming on y-axis is allowed (no scroll otherwise)
 		 *	- slider bubble is large enough (no overdraw confusion)
@@ -1990,6 +2011,8 @@ void UI_view2d_scrollers_draw(const bContext *C, View2D *v2d, View2DScrollers *v
 		}
 	}
 	
+	/* Was changed above, so reset. */
+	btheme->tui.widget_emboss[3] = emboss_alpha;
 }
 
 /* free temporary memory used for drawing scrollers */