[IMP] web_editor, *: automatically increase default link color contrast

*: website

Inside a color combination (or outside, as considered the same as inside
color combination number 1), the link color can be configured. It is
set by themes to one of the 5 theme colors. Sometimes, no color of
those 5 colors contrast enough with the color combination's background
and we accepted that before, relying on the fact the user can change the
link color if he wants too. Now we automatically increase the contrast
of those link colors, except if the user overrides it.

This system might be extended to all foreground colors in the future but
the system has to be improved for that.

closes odoo/odoo#58538

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/addons/web_editor/static/src/scss/web_editor.variables.scss b/addons/web_editor/static/src/scss/web_editor.variables.scss
index 321adeb7024..00d7884f4f7 100644
--- a/addons/web_editor/static/src/scss/web_editor.variables.scss
+++ b/addons/web_editor/static/src/scss/web_editor.variables.scss
@@ -576,6 +576,36 @@ $o-color-extras-nesting-selector: '&, .o_colored_level &';
     }
 }
 
+// Function which returns if a color has contrast enough in comparaison to
+// another given color.
+@function has-enough-contrast($color1, $color2) {
+    $r: (max(red($color1), red($color2))) - (min(red($color1), red($color2)));
+    $g: (max(green($color1), green($color2))) - (min(green($color1), green($color2)));
+    $b: (max(blue($color1), blue($color2))) - (min(blue($color1), blue($color2)));
+    $sum-rgb: $r + $g + $b;
+    @return ($sum-rgb >= 500);
+}
+
+// Function which transforms a color to increase its contrast in comparison to
+// another given color.
+@function increase-contrast($color1, $color2) {
+    @if not $color1 or not $color2 {
+        @return null;
+    }
+    $luma-c1: luma($color1);
+    $luma-c2: luma($color2);
+    $lightness-c1: lightness($color1);
+    $lightness-inc: if($luma-c1 < $luma-c2, -1%, 1%);
+    $i: 0;
+    // Max 15% lightness change even if not contrasted enough
+    @while ($lightness-c1 > 0.1% and $lightness-c1 < 99.9% and $i < 15 and not has-enough-contrast($color1, $color2)) {
+        $color1: adjust-color($color1, $lightness: $lightness-inc);
+        $lightness-c1: $lightness-c1 + $lightness-inc;
+        $i: $i + 1;
+    }
+    @return $color1;
+}
+
 // Print a document property the right way (depending on the type of the printed
 // variable).
 @mixin print-variable($key, $value) {