scroll-view-fade: Do the offset math in the shader

This doesn't (or shouldn't) change the visual appearance of the fade
effect, but does do all the testing math inside the shader, rather
than on the CPU. This will make fading the offset much easier in
the future.

https://bugzilla.gnome.org/show_bug.cgi?id=689249

diff --git a/src/st/st-scroll-view-fade.c b/src/st/st-scroll-view-fade.c
index 5093e7d191fa5a306fa11c8add1867ae1fd53c15..1a9ff1db341fb064f4f3d3f103cac4f32700d405 100644 (file)
--- a/src/st/st-scroll-view-fade.c
+++ b/src/st/st-scroll-view-fade.c
@@ -53,10 +53,10 @@ struct _StScrollViewFade
   gint height_uniform;
   gint width_uniform;
   gint fade_area_uniform;
-  gint offset_top_uniform;
-  gint offset_bottom_uniform;
-  gint offset_left_uniform;
-  gint offset_right_uniform;
+  gint vfade_offset_uniform;
+  gint hfade_offset_uniform;
+  gint vvalue_uniform;
+  gint hvalue_uniform;
 
   StAdjustment *vadjustment;
   StAdjustment *hadjustment;
@@ -121,14 +121,14 @@ st_scroll_view_fade_pre_paint (ClutterEffect *effect)
         cogl_program_get_uniform_location (self->program, "width");
       self->fade_area_uniform =
         cogl_program_get_uniform_location (self->program, "fade_area");
-      self->offset_top_uniform =
-        cogl_program_get_uniform_location (self->program, "offset_top");
-      self->offset_bottom_uniform =
-        cogl_program_get_uniform_location (self->program, "offset_bottom");
-      self->offset_left_uniform =
-        cogl_program_get_uniform_location (self->program, "offset_left");
-      self->offset_right_uniform =
-        cogl_program_get_uniform_location (self->program, "offset_right");
+      self->vfade_offset_uniform =
+        cogl_program_get_uniform_location (self->program, "vfade_offset");
+      self->hfade_offset_uniform =
+        cogl_program_get_uniform_location (self->program, "hfade_offset");
+      self->vvalue_uniform =
+        cogl_program_get_uniform_location (self->program, "vvalue");
+      self->hvalue_uniform =
+        cogl_program_get_uniform_location (self->program, "hvalue");
     }
 
   parent_class = CLUTTER_EFFECT_CLASS (st_scroll_view_fade_parent_class);
@@ -207,38 +207,24 @@ st_scroll_view_fade_paint_target (ClutterOffscreenEffect *effect)
   if (h_scroll_visible)
       fade_area[1][1] -= clutter_actor_get_height (hscroll);
 
-  st_adjustment_get_values (self->vadjustment, &value, &lower, &upper, NULL, NULL, &page_size);
+  if (self->vvalue_uniform > -1)
+    {
+      st_adjustment_get_values (self->vadjustment, &value, &lower, &upper, NULL, NULL, &page_size);
+      value = (value - lower) / (upper - page_size - lower);
+      cogl_program_set_uniform_1f (self->program, self->vvalue_uniform, value);
+    }
 
-  if (self->offset_top_uniform > -1) {
-    if (value > lower + 0.1)
-      cogl_program_set_uniform_1f (self->program, self->offset_top_uniform, self->vfade_offset);
-    else
-      cogl_program_set_uniform_1f (self->program, self->offset_top_uniform, 0.0f);
-  }
-
-  if (self->offset_bottom_uniform > -1) {
-    if (value < upper - page_size - 0.1)
-      cogl_program_set_uniform_1f (self->program, self->offset_bottom_uniform, self->vfade_offset);
-    else
-      cogl_program_set_uniform_1f (self->program, self->offset_bottom_uniform, 0.0f);
-  }
-
-  st_adjustment_get_values (self->hadjustment, &value, &lower, &upper, NULL, NULL, &page_size);
-
-  if (self->offset_left_uniform > -1) {
-    if (value > lower + 0.1)
-      cogl_program_set_uniform_1f (self->program, self->offset_left_uniform, self->hfade_offset);
-    else
-      cogl_program_set_uniform_1f (self->program, self->offset_left_uniform, 0.0f);
-  }
-
-  if (self->offset_right_uniform > -1) {
-    if (value < upper - page_size - 0.1)
-      cogl_program_set_uniform_1f (self->program, self->offset_right_uniform, self->hfade_offset);
-    else
-      cogl_program_set_uniform_1f (self->program, self->offset_right_uniform, 0.0f);
-  }
+  if (self->hvalue_uniform > -1)
+    {
+      st_adjustment_get_values (self->hadjustment, &value, &lower, &upper, NULL, NULL, &page_size);
+      value = (value - lower) / (upper - page_size - lower);
+      cogl_program_set_uniform_1f (self->program, self->hvalue_uniform, value);
+    }
 
+  if (self->vfade_offset_uniform > -1)
+    cogl_program_set_uniform_1f (self->program, self->vfade_offset_uniform, self->vfade_offset);
+  if (self->hfade_offset_uniform > -1)
+    cogl_program_set_uniform_1f (self->program, self->hfade_offset_uniform, self->hfade_offset);
   if (self->tex_uniform > -1)
     cogl_program_set_uniform_1i (self->program, self->tex_uniform, 0);
   if (self->height_uniform > -1)
@@ -517,8 +503,10 @@ st_scroll_view_fade_init (StScrollViewFade *self)
   self->height_uniform = -1;
   self->width_uniform = -1;
   self->fade_area_uniform = -1;
-  self->offset_top_uniform = -1;
-  self->offset_bottom_uniform = -1;
+  self->vfade_offset_uniform = -1;
+  self->hfade_offset_uniform = -1;
+  self->vvalue_uniform = -1;
+  self->hvalue_uniform = -1;
   self->vfade_offset = DEFAULT_FADE_OFFSET;
   self->hfade_offset = DEFAULT_FADE_OFFSET;
 

diff --git a/src/st/st-scroll-view-fade.glsl b/src/st/st-scroll-view-fade.glsl
index 4b07642adad3beea2999893a1137c601d9116e5a..7897c7b80adebbc0f219955827f367e7852e341b 100644 (file)
--- a/src/st/st-scroll-view-fade.glsl
+++ b/src/st/st-scroll-view-fade.glsl
@@ -22,10 +22,10 @@
 uniform sampler2D tex;
 uniform float height;
 uniform float width;
-uniform float offset_bottom;
-uniform float offset_top;
-uniform float offset_right;
-uniform float offset_left;
+uniform float vfade_offset;
+uniform float hfade_offset;
+uniform float vvalue;
+uniform float hvalue;
 
 /*
  * Used to pass the fade area to the shader
@@ -50,17 +50,16 @@ void main ()
         return;
 
     float ratio = 1.0;
-    float fade_bottom_start = fade_area[1][1] - offset_bottom;
-    float fade_right_start = fade_area[1][0] - offset_right;
-    float ratio_top = y / offset_top;
+    float fade_bottom_start = fade_area[1][1] - vfade_offset;
+    float fade_right_start = fade_area[1][0] - hfade_offset;
+    float ratio_top = y / vfade_offset;
     float ratio_bottom = (fade_area[1][1] - y)/(fade_area[1][1] - fade_bottom_start);
-    float ratio_left = x / offset_left;
+    float ratio_left = x / hfade_offset;
     float ratio_right = (fade_area[1][0] - x)/(fade_area[1][0] - fade_right_start);
-    bool in_scroll_area = fade_area[0][0] <= x && fade_area[1][0] >= x;
-    bool fade_top = y < offset_top;
-    bool fade_bottom = y > fade_bottom_start;
-    bool fade_left = x < offset_left;
-    bool fade_right = x > fade_right_start;
+    bool fade_top = y < vfade_offset && vvalue > 0;
+    bool fade_bottom = y > fade_bottom_start && vvalue < 1;
+    bool fade_left = x < hfade_offset && hvalue > 0;
+    bool fade_right = x > fade_right_start && hvalue < 1;
 
     if (fade_top) {
         ratio *= ratio_top;