st/scroll-view-fade: Add :extend-fade-area property

Since commit f60a469a34e, everything outside the fade area is painted
fully transparent. That is required for the fade effect during app
grid navigation, to prevent unfaded parts of surrounding pages
becoming visible on wide-screen displays.

However in most other cases, that behavior is the exact opposite
of what we want: Elements outside the fade area (like scroll bars)
should never fade.

In order to fix the regular case, hide the new behavior behind a
property.

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/4234

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1831>

diff --git a/src/st/st-scroll-view-fade.c b/src/st/st-scroll-view-fade.c
index b387e384a56883ed467dbe93023c21bb504b947e..6c0176f5d9bac23031201bb9e8af8195d8cc2de2 100644 (file)
--- a/src/st/st-scroll-view-fade.c
+++ b/src/st/st-scroll-view-fade.c
@@ -45,6 +45,7 @@ struct _StScrollViewFade
   StAdjustment *hadjustment;
 
   guint fade_edges : 1;
+  guint extend_fade_area: 1;
 
   ClutterMargin fade_margins;
 };
@@ -58,6 +59,7 @@ enum {
 
   PROP_FADE_MARGINS,
   PROP_FADE_EDGES,
+  PROP_EXTEND_FADE_AREA,
 
   N_PROPS
 };
@@ -168,6 +170,7 @@ st_scroll_view_fade_paint_target (ClutterOffscreenEffect *effect,
                                      value <= 1.0 :
                                      (rtl ? value > 0.0 : value < 1.0));
 
+  clutter_shader_effect_set_uniform (shader, "extend_fade_area", G_TYPE_INT, 1, self->extend_fade_area);
   clutter_shader_effect_set_uniform (shader, "fade_offset_top", G_TYPE_FLOAT, 1, ABS (self->fade_margins.top));
   clutter_shader_effect_set_uniform (shader, "fade_offset_bottom", G_TYPE_FLOAT, 1, ABS (self->fade_margins.bottom));
   clutter_shader_effect_set_uniform (shader, "fade_offset_left", G_TYPE_FLOAT, 1, ABS (self->fade_margins.left));
@@ -325,6 +328,21 @@ st_scroll_view_fade_set_fade_edges (StScrollViewFade *self,
   g_object_thaw_notify (G_OBJECT (self));
 }
 
+static void
+st_scroll_view_fade_set_extend_fade_area (StScrollViewFade *self,
+                                          gboolean          extend_fade_area)
+{
+  if (self->extend_fade_area == extend_fade_area)
+    return;
+
+  self->extend_fade_area = extend_fade_area;
+
+  if (self->actor != NULL)
+    clutter_actor_queue_redraw (self->actor);
+
+  g_object_notify_by_pspec (G_OBJECT (self), props[PROP_EXTEND_FADE_AREA]);
+}
+
 static void
 st_scroll_view_fade_set_property (GObject *object,
                                   guint prop_id,
@@ -341,6 +359,9 @@ st_scroll_view_fade_set_property (GObject *object,
     case PROP_FADE_EDGES:
       st_scroll_view_fade_set_fade_edges (self, g_value_get_boolean (value));
       break;
+    case PROP_EXTEND_FADE_AREA:
+      st_scroll_view_fade_set_extend_fade_area (self, g_value_get_boolean (value));
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -363,6 +384,9 @@ st_scroll_view_fade_get_property (GObject *object,
     case PROP_FADE_EDGES:
       g_value_set_boolean (value, self->fade_edges);
       break;
+    case PROP_EXTEND_FADE_AREA:
+      g_value_set_boolean (value, self->extend_fade_area);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -414,6 +438,18 @@ st_scroll_view_fade_class_init (StScrollViewFadeClass *klass)
                           FALSE,
                           ST_PARAM_READWRITE);
 
+  /**
+   * StScrollViewFade:extend-fade-area:
+   *
+   * Whether faded edges should extend beyond the faded area of the #StScrollViewFade.
+   */
+  props[PROP_EXTEND_FADE_AREA] =
+    g_param_spec_boolean ("extend-fade-area",
+                          "Extend Fade Area",
+                          "Whether faded edges should extend beyond the faded area",
+                          FALSE,
+                          ST_PARAM_READWRITE);
+
   g_object_class_install_properties (gobject_class, N_PROPS, props);
 }
 

diff --git a/src/st/st-scroll-view-fade.glsl b/src/st/st-scroll-view-fade.glsl
index 0d8812b0788b6875009ec5800fb71f0b113a1070..39ed6a34500c26de9f5c92067eea3992a0aad40c 100644 (file)
--- a/src/st/st-scroll-view-fade.glsl
+++ b/src/st/st-scroll-view-fade.glsl
@@ -28,6 +28,7 @@ uniform bool  fade_edges_top;
 uniform bool  fade_edges_right;
 uniform bool  fade_edges_bottom;
 uniform bool  fade_edges_left;
+uniform bool  extend_fade_area;
 
 uniform vec2 fade_area_topleft;
 uniform vec2 fade_area_bottomright;
@@ -38,11 +39,11 @@ void main ()
 
     float y = height * cogl_tex_coord_in[0].y;
     float x = width * cogl_tex_coord_in[0].x;
+    float ratio = 1.0;
 
     if (x > fade_area_topleft[0] && x < fade_area_bottomright[0] &&
         y > fade_area_topleft[1] && y < fade_area_bottomright[1])
     {
-        float ratio = 1.0;
         float fade_top_start = fade_area_topleft[1] + fade_offset_top;
         float fade_left_start = fade_area_topleft[0] + fade_offset_left;
         float fade_bottom_start = fade_area_bottomright[1] - fade_offset_bottom;
@@ -67,9 +68,14 @@ void main ()
         if (fade_right) {
             ratio *= (fade_area_bottomright[0] - x) / (fade_area_bottomright[0] - fade_right_start);
         }
-
-        cogl_color_out *= ratio;
-    } else {
-        cogl_color_out *= 0.0;
+    } else if (extend_fade_area) {
+        if (x <= fade_area_topleft[0] && fade_edges_left ||
+            x >= fade_area_bottomright[0] && fade_edges_right ||
+            y <= fade_area_topleft[1] && fade_edges_top ||
+            y >= fade_area_bottomright[1] && fade_edges_bottom) {
+            ratio = 0.0;
+        }
     }
+
+    cogl_color_out *= ratio;
 }