cssimage: Implement proper cross-fades for gradients

This is intended mainly to speed up the current situation with spinners
on debug kernels. Because we now don't use a cross-fade to draw the
transition but instead have a real gradient that we draw, we don't need
to use the slow cross-fade code.

https://bugzilla.gnome.org/show_bug.cgi?id=684639

4 files changed, 227 insertions, 1 deletions

diff --git a/gtk/gtkcssimagegradient.c b/gtk/gtkcssimagegradient.c
index 30bfab35e9..4085719585 100644
--- a/gtk/gtkcssimagegradient.c
+++ b/gtk/gtkcssimagegradient.c
@@ -48,6 +48,136 @@ gtk_css_image_gradient_compute (GtkCssImage             *image,
   return GTK_CSS_IMAGE (copy);
 }
 
+cairo_pattern_t *
+fade_pattern (cairo_pattern_t *pattern,
+              double           opacity)
+{
+  double x0, y0, x1, y1, r0, r1;
+  cairo_pattern_t *result;
+  int i, n;
+
+  switch (cairo_pattern_get_type (pattern))
+    {
+    case CAIRO_PATTERN_TYPE_LINEAR:
+      cairo_pattern_get_linear_points (pattern, &x0, &y0, &x1, &y1);
+      result = cairo_pattern_create_linear (x0, y0, x1, y1);
+      break;
+    case CAIRO_PATTERN_TYPE_RADIAL:
+      cairo_pattern_get_radial_circles (pattern, &x0, &y0, &r0, &x1, &y1, &r1);
+      result = cairo_pattern_create_radial (x0, y0, r0, x1, y1, r1);
+      break;
+    default:
+      g_return_val_if_reached (NULL);
+    }
+
+  cairo_pattern_get_color_stop_count (pattern, &n);
+  for (i = 0; i < n; i++)
+    {
+      double o, r, g, b, a;
+
+      cairo_pattern_get_color_stop_rgba (pattern, i, &o, &r, &g, &b, &a);
+      cairo_pattern_add_color_stop_rgba (result, o, r, g, b, a * opacity);
+    }
+
+  return pattern;
+}
+
+cairo_pattern_t *
+transition_pattern (cairo_pattern_t *start,
+                    cairo_pattern_t *end,
+                    double           progress)
+{
+  double sx0, sy0, sx1, sy1, sr0, sr1, ex0, ey0, ex1, ey1, er0, er1;
+  cairo_pattern_t *result;
+  int i, n;
+
+  progress = CLAMP (progress, 0.0, 1.0);
+
+  if (end == NULL)
+    return fade_pattern (start, 1.0 - progress);
+
+  g_assert (cairo_pattern_get_type (start) == cairo_pattern_get_type (end));
+
+  switch (cairo_pattern_get_type (start))
+    {
+    case CAIRO_PATTERN_TYPE_LINEAR:
+      cairo_pattern_get_linear_points (start, &sx0, &sy0, &sx1, &sy1);
+      cairo_pattern_get_linear_points (start, &ex0, &ey0, &ex1, &ey1);
+      result = cairo_pattern_create_linear ((1 - progress) * sx0 + progress * ex0,
+                                            (1 - progress) * sx1 + progress * ex1,
+                                            (1 - progress) * sy0 + progress * ey0,
+                                            (1 - progress) * sy1 + progress * ey1);
+      break;
+    case CAIRO_PATTERN_TYPE_RADIAL:
+      cairo_pattern_get_radial_circles (start, &sx0, &sy0, &sr0, &sx1, &sy1, &sr1);
+      cairo_pattern_get_radial_circles (start, &ex0, &ey0, &er0, &ex1, &ey1, &er1);
+      result = cairo_pattern_create_radial ((1 - progress) * sx0 + progress * ex0,
+                                            (1 - progress) * sy0 + progress * ey0,
+                                            (1 - progress) * sr0 + progress * er0,
+                                            (1 - progress) * sx1 + progress * ex1,
+                                            (1 - progress) * sy1 + progress * ey1,
+                                            (1 - progress) * sr1 + progress * er1);
+      break;
+    default:
+      g_return_val_if_reached (NULL);
+    }
+
+  cairo_pattern_get_color_stop_count (start, &n);
+  for (i = 0; i < n; i++)
+    {
+      double so, sr, sg, sb, sa, eo, er, eg, eb, ea;
+
+      cairo_pattern_get_color_stop_rgba (start, i, &so, &sr, &sg, &sb, &sa);
+      cairo_pattern_get_color_stop_rgba (start, i, &eo, &er, &eg, &eb, &ea);
+
+      cairo_pattern_add_color_stop_rgba (result,
+                                         (1 - progress) * so + progress * eo,
+                                         (1 - progress) * sr + progress * er,
+                                         (1 - progress) * sg + progress * eg,
+                                         (1 - progress) * sb + progress * eb,
+                                         (1 - progress) * sa + progress * ea);
+    }
+
+  return result;
+}
+
+GtkCssImage *
+gtk_css_image_gradient_transition (GtkCssImage *start_image,
+                                   GtkCssImage *end_image,
+                                   guint        property_id,
+                                   double       progress)
+{
+  GtkGradient *start_gradient, *end_gradient, *gradient;
+  cairo_pattern_t *start_pattern, *end_pattern;
+  GtkCssImageGradient *result;
+
+  start_gradient = GTK_CSS_IMAGE_GRADIENT (start_image)->gradient;
+  start_pattern = GTK_CSS_IMAGE_GRADIENT (start_image)->pattern;
+  if (end_image == NULL)
+    {
+      end_gradient = NULL;
+      end_pattern = NULL;
+    }
+  else
+    {
+      if (!GTK_IS_CSS_IMAGE_GRADIENT (end_image))
+        return GTK_CSS_IMAGE_CLASS (_gtk_css_image_gradient_parent_class)->transition (start_image, end_image, property_id, progress);
+
+      end_gradient = GTK_CSS_IMAGE_GRADIENT (end_image)->gradient;
+      end_pattern = GTK_CSS_IMAGE_GRADIENT (end_image)->pattern;
+    }
+
+  gradient = _gtk_gradient_transition (start_gradient, end_gradient, property_id, progress);
+  if (gradient == NULL)
+    return GTK_CSS_IMAGE_CLASS (_gtk_css_image_gradient_parent_class)->transition (start_image, end_image, property_id, progress);
+
+  result = g_object_new (GTK_TYPE_CSS_IMAGE_GRADIENT, NULL);
+  result->gradient = gradient;
+  result->pattern = transition_pattern (start_pattern, end_pattern, progress);
+
+  return GTK_CSS_IMAGE (result);
+}
+
 static gboolean
 gtk_css_image_gradient_draw_circle (GtkCssImageGradient *image,
                                     cairo_t              *cr,
@@ -169,6 +299,7 @@ _gtk_css_image_gradient_class_init (GtkCssImageGradientClass *klass)
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
 
   image_class->compute = gtk_css_image_gradient_compute;
+  image_class->transition = gtk_css_image_gradient_transition;
   image_class->draw = gtk_css_image_gradient_draw;
   image_class->parse = gtk_css_image_gradient_parse;
   image_class->print = gtk_css_image_gradient_print;
diff --git a/gtk/gtkgradient.c b/gtk/gtkgradient.c
index ee57066116..3c16fca5a7 100644
--- a/gtk/gtkgradient.c
+++ b/gtk/gtkgradient.c
@@ -440,3 +440,91 @@ gtk_gradient_to_string (GtkGradient *gradient)
 
   return g_string_free (str, FALSE);
 }
+
+static GtkGradient *
+gtk_gradient_fade (GtkGradient *gradient,
+                   double       opacity)
+{
+  GtkGradient *faded;
+  guint i;
+
+  faded = g_slice_new (GtkGradient);
+  faded->stops = g_array_new (FALSE, FALSE, sizeof (ColorStop));
+
+  faded->x0 = gradient->x0;
+  faded->y0 = gradient->y0;
+  faded->x1 = gradient->x1;
+  faded->y1 = gradient->y1;
+  faded->radius0 = gradient->radius0;
+  faded->radius1 = gradient->radius1;
+
+  faded->ref_count = 1;
+
+  for (i = 0; i < gradient->stops->len; i++)
+    {
+      GtkSymbolicColor *color;
+      ColorStop *stop;
+
+      stop = &g_array_index (gradient->stops, ColorStop, i);
+      color = gtk_symbolic_color_new_alpha (stop->color, opacity);
+      gtk_gradient_add_color_stop (gradient, stop->offset, color);
+      gtk_symbolic_color_unref (color);
+    }
+
+  return faded;
+}
+
+GtkGradient *
+_gtk_gradient_transition (GtkGradient *start,
+                          GtkGradient *end,
+                          guint        property_id,
+                          double       progress)
+{
+  GtkGradient *gradient;
+  guint i;
+
+  g_return_val_if_fail (start != NULL, NULL);
+
+  if (end == NULL)
+    return gtk_gradient_fade (start, 1.0 - CLAMP (progress, 0.0, 1.0));
+
+  if (start->stops->len != end->stops->len)
+    return NULL;
+
+  /* check both are radial/linear */
+  if ((start->radius0 == 0 && start->radius1 == 0) != (end->radius0 == 0 && end->radius1 == 0))
+    return NULL;
+
+  gradient = g_slice_new (GtkGradient);
+  gradient->stops = g_array_new (FALSE, FALSE, sizeof (ColorStop));
+
+  gradient->x0 = (1 - progress) * start->x0 + progress * end->x0;
+  gradient->y0 = (1 - progress) * start->y0 + progress * end->y0;
+  gradient->x1 = (1 - progress) * start->x1 + progress * end->x1;
+  gradient->y1 = (1 - progress) * start->y1 + progress * end->y1;
+  gradient->radius0 = (1 - progress) * start->radius0 + progress * end->radius0;
+  gradient->radius1 = (1 - progress) * start->radius1 + progress * end->radius1;
+
+  gradient->ref_count = 1;
+
+  for (i = 0; i < start->stops->len; i++)
+    {
+      ColorStop *start_stop, *end_stop;
+      GtkSymbolicColor *color;
+      double offset;
+
+      start_stop = &g_array_index (start->stops, ColorStop, i);
+      end_stop = &g_array_index (end->stops, ColorStop, i);
+
+      offset = (1 - progress) * start_stop->offset + progress * end_stop->offset;
+      color = (GtkSymbolicColor *) _gtk_css_value_transition ((GtkCssValue *) start_stop->color,
+                                                              (GtkCssValue *) end_stop->color,
+                                                              property_id,
+                                                              progress);
+      g_assert (color);
+      gtk_gradient_add_color_stop (gradient, offset, color);
+      gtk_symbolic_color_unref (color);
+    }
+
+  return gradient;
+}
diff --git a/gtk/gtkgradientprivate.h b/gtk/gtkgradientprivate.h
index 1ad2eef2ec..9cd37f2e71 100644
--- a/gtk/gtkgradientprivate.h
+++ b/gtk/gtkgradientprivate.h
@@ -29,6 +29,11 @@ cairo_pattern_t *       _gtk_gradient_resolve_full            (GtkGradient
                                                                GtkCssComputedValues    *parent_values,
                                                                GtkCssDependencies      *dependencies);
 
+GtkGradient *           _gtk_gradient_transition              (GtkGradient             *start,
+                                                               GtkGradient             *end,
+                                                               guint                    property_id,
+                                                               double                   progress);
+
 G_END_DECLS
 
 #endif /* __GTK_STYLE_PROPERTIES_PRIVATE_H__ */
diff --git a/gtk/gtksymboliccolor.c b/gtk/gtksymboliccolor.c
index 53409f100f..5e96c254e0 100644
--- a/gtk/gtksymboliccolor.c
+++ b/gtk/gtksymboliccolor.c
@@ -249,7 +249,9 @@ gtk_css_value_symbolic_transition (GtkCssValue *start,
                                    guint        property_id,
                                    double       progress)
 {
-  return NULL;
+  return (GtkCssValue *) gtk_symbolic_color_new_mix ((GtkSymbolicColor *) start,
+                                                     (GtkSymbolicColor *) end,
+                                                     progress);
 }
 
 static void