csscolorvalue: Fix percentage ranges for relative colors

Add tests as well, now that they can be computed at parse time.

gtk/gtkcsscolor.c

@@ -225,6 +225,60 @@ gtk_css_color_space_get_coord_name (GtkCssColorSpace color_space,
     }
 }
 
+void
+gtk_css_color_space_get_coord_range (GtkCssColorSpace  color_space,
+                                     gboolean          legacy_rgb_scale,
+                                     guint             coord,
+                                     float            *lower,
+                                     float            *upper)
+{
+  if (coord == 3)
+    {
+      *lower = 0;
+      *upper = 1;
+      return;
+    }
+
+  switch (color_space)
+    {
+    case GTK_CSS_COLOR_SPACE_SRGB:
+      *lower = 0;
+      *upper = legacy_rgb_scale ? 255 : 1;
+      return;
+    case GTK_CSS_COLOR_SPACE_SRGB_LINEAR:
+      *lower = 0;
+      *upper = 1;
+      return;
+    case GTK_CSS_COLOR_SPACE_HSL:
+    case GTK_CSS_COLOR_SPACE_HWB:
+      switch (coord)
+        {
+        case 0: *lower = *upper = NAN; return;
+        case 1:
+        case 2: *lower = 0; *upper = 100; return;
+        default: g_assert_not_reached ();
+        }
+    case GTK_CSS_COLOR_SPACE_OKLAB:
+      switch (coord)
+        {
+        case 0: *lower = 0; *upper = 1; return;
+        case 1:
+        case 2: *lower = -0.4; *upper = 0.4; return;
+        default: g_assert_not_reached ();
+        }
+    case GTK_CSS_COLOR_SPACE_OKLCH:
+      switch (coord)
+        {
+        case 0: *lower = 0; *upper = 1; return;
+        case 1: *lower = 0; *upper = 0.4; return;
+        case 2: *lower = *upper = NAN; return;
+        default: g_assert_not_reached ();
+        }
+    default:
+      g_assert_not_reached ();
+    }
+}
+
 static gboolean
 color_space_is_polar (GtkCssColorSpace color_space)
 {

gtk/gtkcsscolorprivate.h

@@ -114,6 +114,12 @@ void    gtk_css_color_interpolate (const GtkCssColor      *from,
 const char * gtk_css_color_space_get_coord_name (GtkCssColorSpace color_space,
                                                  guint            coord);
 
+void gtk_css_color_space_get_coord_range (GtkCssColorSpace  color_space,
+                                          gboolean          legacy_rgb_scale,
+                                          guint             coord,
+                                          float            *lower,
+                                          float            *upper);
+
 gboolean gtk_css_color_interpolation_method_parse (GtkCssParser           *parser,
                                                    GtkCssColorSpace       *in,
                                                    GtkCssHueInterpolation *interp);

gtk/gtkcsscolorvalue.c

@@ -605,8 +605,16 @@ resolve_relative (GtkCssValue      *values[4],
     {
       if (values[i])
         {
+          float lower, upper;
+
+          gtk_css_color_space_get_coord_range (color_space, legacy_rgb_scale,
+                                               i, &lower, &upper);
+
           m[i] = FALSE;
-          v[i] = gtk_css_number_value_get_canonical (values[i], 1);
+          v[i] = gtk_css_number_value_get_canonical (values[i], upper - lower);
+
+          if (gtk_css_number_value_has_percent (values[i]))
+            v[i] += lower;
         }
       else
         {

testsuite/css/parser/relative-color.css

@@ -26,3 +26,39 @@ f {
 g {
   color: rgb(from currentColor r g 100 / 50%);
 }
+
+h {
+  color: rgb(from white 100% 100% 100% / 100%);
+}
+
+i {
+  color: color(from white srgb 100% 100% 100% / 100%);
+}
+
+j {
+  color: color(from white srgb-linear 100% 100% 100% / 100%);
+}
+
+k {
+  color: hsl(from white 0 100% 100% / 100%);
+}
+
+l {
+  color: hwb(from white 0 100% 0% / 100%);
+}
+
+m {
+  color: hwb(from white 0 0% 100% / 100%);
+}
+
+n {
+  color: oklch(from white 100% 100% 0 / 100%);
+}
+
+o {
+  color: oklab(from white 100% 0% 0% / 100%);
+}
+
+p {
+  color: oklab(from white 100% 100% 100% / 100%);
+}

testsuite/css/parser/relative-color.ref.css

@@ -22,3 +22,39 @@ f {
 g {
   color: color(from currentcolor srgb r g 100 / 50%);
 }
+
+h {
+  color: color(srgb 1 1 1);
+}
+
+i {
+  color: color(srgb 1 1 1);
+}
+
+j {
+  color: color(srgb-linear 1 1 1);
+}
+
+k {
+  color: color(srgb 1 1 1);
+}
+
+l {
+  color: color(srgb 1 1 1);
+}
+
+m {
+  color: color(srgb 0 0 0);
+}
+
+n {
+  color: oklch(1 0.4 0);
+}
+
+o {
+  color: oklab(1 -0.4 -0.4);
+}
+
+p {
+  color: oklab(1 0.4 0.4);
+}