[gnome-shell/T29763: 25/249] st: Implement more CSS gradient options

[Matthew Leeds <mwleeds src gnome org>]

commit 574b4dd591b7d1a117754a1bdc1f9cd6eea1b661
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Fri Dec 8 17:29:36 2017 -0200

    st: Implement more CSS gradient options
    
    In order to implement the Endless Toggle Button with the curved
    edge, the currently supported gradient CSS properties are not
    enough.
    
    This commit implements three new CSS gradient-related properties:
    
     - background-gradient-radius
     - background-gradient-stop
     - background-gradient-position
    
    This is obviously deviating from the CSS specs, but so it is the
    current CSS properties. This is just the absolute minimum we need
    in order to implement the Endless Toggle Button with curved edges.
    
    https://phabricator.endlessm.com/T20325

 src/st/st-theme-node-drawing.c | 34 ++++++++++++++++++++++++++++++----
 src/st/st-theme-node-private.h |  6 ++++++
 src/st/st-theme-node.c         | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+), 4 deletions(-)
---
diff --git a/src/st/st-theme-node-drawing.c b/src/st/st-theme-node-drawing.c
index c2d4ccf839..f8c336cd5f 100644
--- a/src/st/st-theme-node-drawing.c
+++ b/src/st/st-theme-node-drawing.c
@@ -605,11 +605,25 @@ create_cairo_pattern_of_background_gradient (StThemeNode *node,
     pattern = cairo_pattern_create_linear (0, 0, width, 0);
   else
     {
-      gdouble cx, cy;
+      gdouble cx, cy, radius;
 
-      cx = width / 2.;
-      cy = height / 2.;
-      pattern = cairo_pattern_create_radial (cx, cy, 0, cx, cy, MIN (cx, cy));
+      if (node->background_gradient_position_set)
+        {
+          cx = node->background_gradient_position_x;
+          cy = node->background_gradient_position_y;
+        }
+      else
+        {
+          cx = width / 2.;
+          cy = height / 2.;
+        }
+
+      if (node->background_gradient_radius != -1)
+        radius = node->background_gradient_radius;
+      else
+        radius = MIN (width / 2., height / 2.);
+
+      pattern = cairo_pattern_create_radial (cx, cy, 0, cx, cy, radius);
     }
 
   cairo_pattern_add_color_stop_rgba (pattern, 0,
@@ -617,6 +631,18 @@ create_cairo_pattern_of_background_gradient (StThemeNode *node,
                                      node->background_color.green / 255.,
                                      node->background_color.blue / 255.,
                                      node->background_color.alpha / 255.);
+
+  /* Add an intermediate stop when any is set */
+  if (node->background_gradient_stop_position != -1)
+    {
+      cairo_pattern_add_color_stop_rgba (pattern,
+                                         CLAMP (((float) node->background_gradient_stop_position) / width, 
0., 1.),
+                                         node->background_color.red / 255.,
+                                         node->background_color.green / 255.,
+                                         node->background_color.blue / 255.,
+                                         node->background_color.alpha / 255.);
+    }
+
   cairo_pattern_add_color_stop_rgba (pattern, 1,
                                      node->background_gradient_end.red / 255.,
                                      node->background_gradient_end.green / 255.,
diff --git a/src/st/st-theme-node-private.h b/src/st/st-theme-node-private.h
index 57f3bd6d8f..1fe154d604 100644
--- a/src/st/st-theme-node-private.h
+++ b/src/st/st-theme-node-private.h
@@ -44,6 +44,12 @@ struct _StThemeNode {
   StGradientType background_gradient_type;
   ClutterColor background_gradient_end;
 
+  guint background_gradient_position_set : 1;
+  int background_gradient_position_x;
+  int background_gradient_position_y;
+  int background_gradient_stop_position;
+  int background_gradient_radius;
+
   int background_position_x;
   int background_position_y;
 
diff --git a/src/st/st-theme-node.c b/src/st/st-theme-node.c
index 31057b0129..7ea9c74a32 100644
--- a/src/st/st-theme-node.c
+++ b/src/st/st-theme-node.c
@@ -46,6 +46,8 @@ static void
 st_theme_node_init (StThemeNode *node)
 {
   node->transition_duration = -1;
+  node->background_gradient_stop_position = -1;
+  node->background_gradient_radius = -1;
 
   st_theme_node_paint_state_init (&node->cached_state);
 }
@@ -2149,6 +2151,45 @@ _st_theme_node_ensure_background (StThemeNode *node)
         {
           get_color_from_term (node, decl->value, &node->background_gradient_end);
         }
+      else if (strcmp (property_name, "-gradient-position") == 0)
+        {
+          GetFromTermResult result = get_length_from_term_int (node, decl->value, FALSE, 
&node->background_gradient_position_x);
+          if (result == VALUE_NOT_FOUND)
+            {
+              node->background_gradient_position_set = FALSE;
+              continue;
+            }
+          else
+            node->background_gradient_position_set = TRUE;
+
+          result = get_length_from_term_int (node, decl->value->next, FALSE, 
&node->background_gradient_position_y);
+
+          if (result == VALUE_NOT_FOUND)
+            {
+              node->background_gradient_position_set = FALSE;
+              continue;
+            }
+          else
+            node->background_gradient_position_set = TRUE;
+        }
+      else if (strcmp (property_name, "-gradient-stop") == 0)
+        {
+          GetFromTermResult result = get_length_from_term_int (node, decl->value, FALSE, 
&node->background_gradient_stop_position);
+          if (result == VALUE_NOT_FOUND)
+            {
+              node->background_gradient_stop_position = -1;
+              continue;
+            }
+        }
+      else if (strcmp (property_name, "-gradient-radius") == 0)
+        {
+          GetFromTermResult result = get_length_from_term_int (node, decl->value, FALSE, 
&node->background_gradient_radius);
+          if (result == VALUE_NOT_FOUND)
+            {
+              node->background_gradient_radius = -1;
+              continue;
+            }
+        }
     }
 }