[gnome-shell/wip/carlosg/weak-ref-source: 2/6] st/scroll-view: Make fade effect take ClutterMargin

[Carlos Garnacho <carlosg src gnome org>]

commit b25ef170ca7ae99e1ef7ad794b556d28ed9cf424
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Feb 3 12:07:34 2021 +0100

    st/scroll-view: Make fade effect take ClutterMargin
    
    Instead of taking just vertical/horizontal offsets, take a ClutterMargin
    to allow us set the fade offsets on each direction specifically. Also,
    handle negative values in margins, the fade effect will run in the negative
    space left by the scrollview padding instead. Another difference now is
    that areas outside the extents of the effect will be transparent, instead
    of the effect ending abruptly past the given extents.
    
    This will be used by the app grid, in order to selectively let see either
    of next/prev pages while navigating.
    
    While at it, fix code style issues in st_scroll_view_update_fade_effect(),
    and clean up unused variables from the GLSL code.

 js/ui/appDisplay.js             |   9 +++-
 src/st/st-scroll-view-fade.c    | 105 +++++++++++++++-------------------------
 src/st/st-scroll-view-fade.glsl |  27 +++++------
 src/st/st-scroll-view.c         |  49 ++++++++++---------
 src/st/st-scroll-view.h         |   5 +-
 5 files changed, 90 insertions(+), 105 deletions(-)
---
diff --git a/js/ui/appDisplay.js b/js/ui/appDisplay.js
index 69b4d0fff5..fe2c3f1004 100644
--- a/js/ui/appDisplay.js
+++ b/js/ui/appDisplay.js
@@ -264,7 +264,14 @@ var BaseAppView = GObject.registerClass({
                 return;
         }
 
-        this._scrollView.update_fade_effect(vOffset, hOffset);
+        this._scrollView.update_fade_effect(
+            new Clutter.Margin({
+                left: hOffset,
+                right: hOffset,
+                top: vOffset,
+                bottom: vOffset
+            })
+        );
     }
 
     _createGrid() {
diff --git a/src/st/st-scroll-view-fade.c b/src/st/st-scroll-view-fade.c
index a0bb85bda8..eec36a8839 100644
--- a/src/st/st-scroll-view-fade.c
+++ b/src/st/st-scroll-view-fade.c
@@ -46,8 +46,7 @@ struct _StScrollViewFade
 
   guint fade_edges : 1;
 
-  float vfade_offset;
-  float hfade_offset;
+  ClutterMargin fade_margins;
 };
 
 G_DEFINE_TYPE (StScrollViewFade,
@@ -57,8 +56,7 @@ G_DEFINE_TYPE (StScrollViewFade,
 enum {
   PROP_0,
 
-  PROP_VFADE_OFFSET,
-  PROP_HFADE_OFFSET,
+  PROP_FADE_MARGINS,
   PROP_FADE_EDGES,
 
   N_PROPS
@@ -136,6 +134,15 @@ st_scroll_view_fade_paint_target (ClutterOffscreenEffect *effect,
   if (h_scroll_visible)
       fade_area_bottomright[1] -= clutter_actor_get_height (hscroll);
 
+  if (self->fade_margins.left < 0)
+    fade_area_topleft[0] -= ABS (self->fade_margins.left);
+  if (self->fade_margins.right < 0)
+    fade_area_bottomright[0] += ABS (self->fade_margins.right);
+  if (self->fade_margins.top < 0)
+    fade_area_topleft[1] -= ABS (self->fade_margins.top);
+  if (self->fade_margins.bottom < 0)
+    fade_area_bottomright[1] += ABS (self->fade_margins.bottom);
+
   st_adjustment_get_values (self->vadjustment, &value, &lower, &upper, NULL, NULL, &page_size);
   value = (value - lower) / (upper - page_size - lower);
   clutter_shader_effect_set_uniform (shader, "fade_edges_top", G_TYPE_INT, 1, self->fade_edges ? value >= 
0.0 : value > 0.0);
@@ -146,8 +153,10 @@ st_scroll_view_fade_paint_target (ClutterOffscreenEffect *effect,
   clutter_shader_effect_set_uniform (shader, "fade_edges_left", G_TYPE_INT, 1, self->fade_edges ? value >= 
0.0 : value > 0.0);
   clutter_shader_effect_set_uniform (shader, "fade_edges_right", G_TYPE_INT, 1, self->fade_edges ? value <= 
1.0 : value < 1.0);
 
-  clutter_shader_effect_set_uniform (shader, "vfade_offset", G_TYPE_FLOAT, 1, self->vfade_offset);
-  clutter_shader_effect_set_uniform (shader, "hfade_offset", G_TYPE_FLOAT, 1, self->hfade_offset);
+  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));
+  clutter_shader_effect_set_uniform (shader, "fade_offset_right", G_TYPE_FLOAT, 1, ABS 
(self->fade_margins.right));
   clutter_shader_effect_set_uniform (shader, "tex", G_TYPE_INT, 1, 0);
   clutter_shader_effect_set_uniform (shader, "height", G_TYPE_FLOAT, 1, clutter_actor_get_height 
(self->actor));
   clutter_shader_effect_set_uniform (shader, "width", G_TYPE_FLOAT, 1, clutter_actor_get_width 
(self->actor));
@@ -266,39 +275,21 @@ st_scroll_view_fade_dispose (GObject *gobject)
 }
 
 static void
-st_scroll_view_vfade_set_offset (StScrollViewFade *self,
-                                 float fade_offset)
-{
-  if (self->vfade_offset == fade_offset)
-    return;
-
-  g_object_freeze_notify (G_OBJECT (self));
-
-  self->vfade_offset = fade_offset;
-
-  if (self->actor != NULL)
-    clutter_actor_queue_redraw (self->actor);
-
-  g_object_notify_by_pspec (G_OBJECT (self), props[PROP_VFADE_OFFSET]);
-  g_object_thaw_notify (G_OBJECT (self));
-}
-
-static void
-st_scroll_view_hfade_set_offset (StScrollViewFade *self,
-                                 float fade_offset)
+st_scroll_view_set_fade_margins (StScrollViewFade *self,
+                                 ClutterMargin    *fade_margins)
 {
-  if (self->hfade_offset == fade_offset)
+  if (self->fade_margins.left == fade_margins->left &&
+      self->fade_margins.right == fade_margins->right &&
+      self->fade_margins.top == fade_margins->top &&
+      self->fade_margins.bottom == fade_margins->bottom)
     return;
 
-  g_object_freeze_notify (G_OBJECT (self));
-
-  self->hfade_offset = fade_offset;
+  self->fade_margins = *fade_margins;
 
   if (self->actor != NULL)
     clutter_actor_queue_redraw (self->actor);
 
-  g_object_notify_by_pspec (G_OBJECT (self), props[PROP_HFADE_OFFSET]);
-  g_object_thaw_notify (G_OBJECT (self));
+  g_object_notify_by_pspec (G_OBJECT (self), props[PROP_FADE_MARGINS]);
 }
 
 static void
@@ -329,11 +320,8 @@ st_scroll_view_fade_set_property (GObject *object,
 
   switch (prop_id)
     {
-    case PROP_VFADE_OFFSET:
-      st_scroll_view_vfade_set_offset (self, g_value_get_float (value));
-      break;
-    case PROP_HFADE_OFFSET:
-      st_scroll_view_hfade_set_offset (self, g_value_get_float (value));
+    case PROP_FADE_MARGINS:
+      st_scroll_view_set_fade_margins (self, g_value_get_boxed (value));
       break;
     case PROP_FADE_EDGES:
       st_scroll_view_fade_set_fade_edges (self, g_value_get_boolean (value));
@@ -354,11 +342,8 @@ st_scroll_view_fade_get_property (GObject *object,
 
   switch (prop_id)
     {
-    case PROP_HFADE_OFFSET:
-      g_value_set_float (value, self->hfade_offset);
-      break;
-    case PROP_VFADE_OFFSET:
-      g_value_set_float (value, self->vfade_offset);
+    case PROP_FADE_MARGINS:
+      g_value_set_boxed (value, &self->fade_margins);
       break;
     case PROP_FADE_EDGES:
       g_value_set_boolean (value, self->fade_edges);
@@ -391,29 +376,15 @@ st_scroll_view_fade_class_init (StScrollViewFadeClass *klass)
   offscreen_class->paint_target = st_scroll_view_fade_paint_target;
 
   /**
-   * StScrollViewFade:vfade-offset:
-   *
-   * The height of area which is faded at the top and bottom edges of the
-   * #StScrollViewFade.
-   */
-  props[PROP_VFADE_OFFSET] =
-    g_param_spec_float ("vfade-offset",
-                        "Vertical Fade Offset",
-                        "The height of the area which is faded at the edge",
-                        0.f, G_MAXFLOAT, DEFAULT_FADE_OFFSET,
-                        ST_PARAM_READWRITE);
-
-  /**
-   * StScrollViewFade:hfade-offset:
+   * StScrollViewFade:fade-margins:
    *
-   * The height of area which is faded at the left and right edges of the
-   * #StScrollViewFade.
+   * The margins widths that are faded.
    */
-  props[PROP_HFADE_OFFSET] =
-    g_param_spec_float ("hfade-offset",
-                        "Horizontal Fade Offset",
-                        "The width of the area which is faded at the edge",
-                        0.f, G_MAXFLOAT, DEFAULT_FADE_OFFSET,
+  props[PROP_FADE_MARGINS] =
+    g_param_spec_boxed ("fade-margins",
+                        "Fade margins",
+                        "The margin widths that are faded",
+                        CLUTTER_TYPE_MARGIN,
                         ST_PARAM_READWRITE);
 
   /**
@@ -434,8 +405,12 @@ st_scroll_view_fade_class_init (StScrollViewFadeClass *klass)
 static void
 st_scroll_view_fade_init (StScrollViewFade *self)
 {
-  self->vfade_offset = DEFAULT_FADE_OFFSET;
-  self->hfade_offset = DEFAULT_FADE_OFFSET;
+  self->fade_margins = (ClutterMargin) {
+    DEFAULT_FADE_OFFSET,
+    DEFAULT_FADE_OFFSET,
+    DEFAULT_FADE_OFFSET,
+    DEFAULT_FADE_OFFSET
+  };
 }
 
 /**
diff --git a/src/st/st-scroll-view-fade.glsl b/src/st/st-scroll-view-fade.glsl
index 2eacfd9af5..6e82ff5469 100644
--- a/src/st/st-scroll-view-fade.glsl
+++ b/src/st/st-scroll-view-fade.glsl
@@ -20,8 +20,10 @@
 uniform sampler2D tex;
 uniform float height;
 uniform float width;
-uniform float vfade_offset;
-uniform float hfade_offset;
+uniform float fade_offset_top;
+uniform float fade_offset_bottom;
+uniform float fade_offset_left;
+uniform float fade_offset_right;
 uniform bool  fade_edges_top;
 uniform bool  fade_edges_right;
 uniform bool  fade_edges_bottom;
@@ -37,23 +39,19 @@ void main ()
     float y = height * cogl_tex_coord_in[0].y;
     float x = width * cogl_tex_coord_in[0].x;
 
-    /*
-     * We cannot just return here due to a bug in llvmpipe see:
-     * https://bugzilla.freedesktop.org/show_bug.cgi?id=62357
-     */
     if (x > fade_area_topleft[0] && x < fade_area_bottomright[0] &&
-        y > fade_area_topleft[1] && y < fade_area_bottomright[1]) {
+        y > fade_area_topleft[1] && y < fade_area_bottomright[1])
+    {
         float ratio = 1.0;
-        float fade_top_start = fade_area_topleft[1] + vfade_offset;
-        float fade_left_start = fade_area_topleft[0] + hfade_offset;
-        float fade_bottom_start = fade_area_bottomright[1] - vfade_offset;
-        float fade_right_start = fade_area_bottomright[0] - hfade_offset;
-        bool fade_top = y < vfade_offset && fade_edges_top;
+        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;
+        float fade_right_start = fade_area_bottomright[0] - fade_offset_right;
+        bool fade_top = y < fade_top_start && fade_edges_top;
         bool fade_bottom = y > fade_bottom_start && fade_edges_bottom;
         bool fade_left = x < fade_left_start && fade_edges_left;
         bool fade_right = x > fade_right_start && fade_edges_right;
 
-        float vfade_scale = height / vfade_offset;
         if (fade_top) {
             ratio *= (fade_area_topleft[1] - y) / (fade_area_topleft[1] - fade_bottom_start);
         }
@@ -62,7 +60,6 @@ void main ()
             ratio *= (fade_area_bottomright[1] - y) / (fade_area_bottomright[1] - fade_bottom_start);
         }
 
-        float hfade_scale = width / hfade_offset;
         if (fade_left) {
             ratio *= (fade_area_topleft[0] - x) / (fade_area_topleft[0] - fade_left_start);
         }
@@ -72,5 +69,7 @@ void main ()
         }
 
         cogl_color_out *= ratio;
+    } else {
+        cogl_color_out *= 0;
     }
 }
diff --git a/src/st/st-scroll-view.c b/src/st/st-scroll-view.c
index 0cf48adafc..32a2ab5245 100644
--- a/src/st/st-scroll-view.c
+++ b/src/st/st-scroll-view.c
@@ -164,42 +164,41 @@ st_scroll_view_get_property (GObject    *object,
 /**
  * st_scroll_view_update_fade_effect:
  * @scroll: a #StScrollView
- * @vfade_offset: The length of the vertical fade effect, in pixels.
- * @hfade_offset: The length of the horizontal fade effect, in pixels.
+ * @fade_margins: a #ClutterMargin defining the vertical fade effects, in pixels.
  *
- * Sets the height of the fade area area in pixels. A value of 0
+ * Sets the fade effects in all four edges of the view. A value of 0
  * disables the effect.
  */
 void
-st_scroll_view_update_fade_effect (StScrollView *scroll,
-                                   float         vfade_offset,
-                                   float         hfade_offset)
+st_scroll_view_update_fade_effect (StScrollView  *scroll,
+                                   ClutterMargin *fade_margins)
 {
   StScrollViewPrivate *priv = ST_SCROLL_VIEW (scroll)->priv;
 
-  /* A fade amount of more than 0 enables the effect. */
-  if (vfade_offset > 0. || hfade_offset > 0.)
+  /* A fade amount of other than 0 enables the effect. */
+  if (fade_margins->left != 0. || fade_margins->right != 0. ||
+      fade_margins->top != 0. || fade_margins->bottom != 0.)
     {
-      if (priv->fade_effect == NULL) {
-        priv->fade_effect = g_object_new (ST_TYPE_SCROLL_VIEW_FADE, NULL);
+      if (priv->fade_effect == NULL)
+        {
+          priv->fade_effect = g_object_new (ST_TYPE_SCROLL_VIEW_FADE, NULL);
 
-        clutter_actor_add_effect_with_name (CLUTTER_ACTOR (scroll), "fade",
-                                            CLUTTER_EFFECT (priv->fade_effect));
-      }
+          clutter_actor_add_effect_with_name (CLUTTER_ACTOR (scroll), "fade",
+                                              CLUTTER_EFFECT (priv->fade_effect));
+        }
 
       g_object_set (priv->fade_effect,
-                    "vfade-offset", vfade_offset,
-                    NULL);
-      g_object_set (priv->fade_effect,
-                    "hfade-offset", hfade_offset,
+                    "fade-margins", fade_margins,
                     NULL);
     }
    else
     {
-      if (priv->fade_effect != NULL) {
-        clutter_actor_remove_effect (CLUTTER_ACTOR (scroll), CLUTTER_EFFECT (priv->fade_effect));
-        priv->fade_effect = NULL;
-      }
+      if (priv->fade_effect != NULL)
+        {
+          clutter_actor_remove_effect (CLUTTER_ACTOR (scroll),
+                                       CLUTTER_EFFECT (priv->fade_effect));
+          priv->fade_effect = NULL;
+        }
     }
 
   clutter_actor_queue_redraw (CLUTTER_ACTOR (scroll));
@@ -744,7 +743,13 @@ st_scroll_view_style_changed (StWidget *widget)
   StThemeNode *theme_node = st_widget_get_theme_node (widget);
   gdouble vfade_offset = st_theme_node_get_length (theme_node, "-st-vfade-offset");
   gdouble hfade_offset = st_theme_node_get_length (theme_node, "-st-hfade-offset");
-  st_scroll_view_update_fade_effect (self, vfade_offset, hfade_offset);
+  st_scroll_view_update_fade_effect (self,
+                                     &(ClutterMargin){
+                                       vfade_offset,
+                                       vfade_offset,
+                                       hfade_offset,
+                                       hfade_offset,
+                                     });
 
   st_widget_style_changed (ST_WIDGET (priv->hscroll));
   st_widget_style_changed (ST_WIDGET (priv->vscroll));
diff --git a/src/st/st-scroll-view.h b/src/st/st-scroll-view.h
index 2f2c31d6c9..e2acaca2f5 100644
--- a/src/st/st-scroll-view.h
+++ b/src/st/st-scroll-view.h
@@ -82,9 +82,8 @@ gboolean      st_scroll_view_get_overlay_scrollbars (StScrollView *scroll);
 void          st_scroll_view_set_policy          (StScrollView   *scroll,
                                                   StPolicyType    hscroll,
                                                   StPolicyType    vscroll);
-void          st_scroll_view_update_fade_effect  (StScrollView *scroll,
-                                                  float vfade_offset,
-                                                  float hfade_offset);
+void          st_scroll_view_update_fade_effect  (StScrollView  *scroll,
+                                                  ClutterMargin *fade_margins);
 
 G_END_DECLS