From cfc99666546a82c40286ad732474f675e60817a5 Mon Sep 17 00:00:00 2001
From: MacDue <macdue@dueutil.tech>
Date: Sun, 19 Mar 2023 23:55:03 +0000
Subject: [PATCH] LibWeb: Add scaleable checkboxes (with theme/accent-color
 support)

This reworks checkboxes to use a tiny 16x16 SDF for the tick icon along
with an antialiased background/border.

The checkbox now works well at any scale, shows the various checkbox
state (enabled, disabled, being pressed), and supports using the colors
from the active system theme and/or the accent-color property.
---
 Userland/Libraries/LibWeb/CSS/Default.css     |  27 ----
 .../LibWeb/Painting/CheckBoxPaintable.cpp     | 128 +++++++++++++++++-
 .../LibWeb/Painting/CheckBoxPaintable.h       |   2 +
 3 files changed, 129 insertions(+), 28 deletions(-)

diff --git a/Userland/Libraries/LibWeb/CSS/Default.css b/Userland/Libraries/LibWeb/CSS/Default.css
index 8224e05ad87..c42ad126400 100644
--- a/Userland/Libraries/LibWeb/CSS/Default.css
+++ b/Userland/Libraries/LibWeb/CSS/Default.css
@@ -64,33 +64,6 @@ button:hover, input[type=submit]:hover, input[type=button]:hover, input[type=res
     background-color: -libweb-palette-hover-highlight;
 }
 
-input[type=checkbox] {
-    display: inline-block;
-    width: 12px;
-    height: 12px;
-    margin: 2px;
-    border: 1px solid -libweb-palette-threed-shadow1;
-    background-repeat: no-repeat;
-    background-size: cover;
-}
-
-input[type=checkbox]:checked {
-    /*
-    This roughly resembles ClassicStylePainter's paint_check_box() while uncoupling the styling from LibGfx, similar to
-    <button> above. This is a simple checkmark that still looks ok at 2x scale.
-    Eventually we should respect the `accent-color` property here, which may require going back to an implementation via
-    CheckBoxPaintable::paint().
-    */
-    image-rendering: pixelated;
-    background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAwAAAAMCAYAAABWdVznAAAABHNCSVQICAgIfAhkiAAAAEhJREFUKFNjYBgs4D/MIYxEuAiuGKiWkZAGFMUgw5mQbECWBAljKAYJwmxAl0Tnw81FdhK6DcgGYtWA0xlw1TgY2GzCoZQWwgCU1woFwvnCFQAAAABJRU5ErkJggg==);
-}
-
-input[type=checkbox]:indeterminate {
-    image-rendering: pixelated;
-    /* FIXME: Eventually respect the `accent-color` property here. */
-    background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAwAAAAMCAYAAABWdVznAAAAAXNSR0IArs4c6QAAACZJREFUKFNjZCARMJKonmGQa/hPwD9g5yP7gWQNRAXYIA8lovwAAHYYAg3vRihbAAAAAElFTkSuQmCC);
-}
-
 option {
     display: none;
 }
diff --git a/Userland/Libraries/LibWeb/Painting/CheckBoxPaintable.cpp b/Userland/Libraries/LibWeb/Painting/CheckBoxPaintable.cpp
index 22c95bdf8df..9ab7e6d5b2b 100644
--- a/Userland/Libraries/LibWeb/Painting/CheckBoxPaintable.cpp
+++ b/Userland/Libraries/LibWeb/Painting/CheckBoxPaintable.cpp
@@ -1,10 +1,14 @@
 /*
  * Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2023, MacDue <macdue@dueutil.tech>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #include <LibGUI/Event.h>
+#include <LibGfx/AntiAliasingPainter.h>
+#include <LibGfx/Bitmap.h>
+#include <LibGfx/GrayscaleBitmap.h>
 #include <LibWeb/HTML/BrowsingContext.h>
 #include <LibWeb/HTML/HTMLImageElement.h>
 #include <LibWeb/Layout/CheckBox.h>
@@ -13,7 +17,60 @@
 
 namespace Web::Painting {
 
-JS::NonnullGCPtr<CheckBoxPaintable> CheckBoxPaintable::create(Layout::CheckBox const& layout_box)
+// A 16x16 signed distance field for the checkbox's tick (slightly rounded):
+static Array<u8, 16 * 16> s_check_mark_sdf {
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 251, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 231, 194, 189, 218, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 245, 193, 142, 131, 165, 205, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 209, 156, 105, 78, 116, 174, 237,
+    254, 254, 254, 254, 254, 254, 254, 254, 226, 173, 120, 69, 79, 132, 185, 243,
+    254, 254, 254, 254, 254, 254, 254, 243, 190, 138, 85, 62, 115, 167, 219, 254,
+    254, 254, 227, 203, 212, 249, 254, 207, 154, 102, 50, 98, 149, 202, 254, 254,
+    254, 225, 180, 141, 159, 204, 224, 171, 119, 67, 81, 134, 186, 238, 254, 254,
+    243, 184, 135, 90, 113, 157, 188, 136, 84, 64, 116, 169, 221, 254, 254, 254,
+    237, 174, 118, 71, 68, 113, 153, 100, 48, 100, 152, 204, 254, 254, 254, 254,
+    254, 208, 162, 116, 71, 67, 107, 65, 83, 135, 187, 240, 254, 254, 254, 254,
+    254, 251, 206, 162, 116, 71, 43, 66, 119, 171, 223, 254, 254, 254, 254, 254,
+    254, 254, 251, 206, 162, 116, 73, 102, 154, 207, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 251, 206, 162, 124, 139, 190, 242, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 251, 210, 187, 194, 229, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 251, 254, 254, 254, 254, 254, 254, 254, 254, 254
+};
+
+// A 16x16 signed distance field for an indeterminate checkbox (rounded line)
+// Note: We could use the AA fill_rect_with_rounded_corners() for this in future,
+// though right now it can't draw at subpixel accuracy (so is misaligned and jitters when scaling).
+static Array<u8, 16 * 16> s_check_indeterminate {
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 239, 211, 209, 209, 209, 209, 209, 209, 211, 237, 254, 254, 254,
+    254, 254, 252, 195, 151, 145, 145, 145, 145, 145, 145, 150, 193, 250, 254, 254,
+    254, 254, 243, 179, 115, 81, 81, 81, 81, 81, 81, 113, 177, 241, 254, 254,
+    254, 254, 243, 179, 115, 79, 79, 79, 79, 79, 79, 113, 177, 241, 254, 254,
+    254, 254, 251, 194, 149, 143, 143, 143, 143, 143, 143, 148, 192, 250, 254, 254,
+    254, 254, 254, 237, 210, 207, 207, 207, 207, 207, 207, 209, 236, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254,
+    254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254, 254
+};
+
+static constexpr Gfx::GrayscaleBitmap check_mark_sdf()
+{
+    return Gfx::GrayscaleBitmap(s_check_mark_sdf, 16, 16);
+}
+
+static constexpr Gfx::GrayscaleBitmap check_indeterminate_sdf()
+{
+    return Gfx::GrayscaleBitmap(s_check_indeterminate, 16, 16);
+}
+
+JS::NonnullGCPtr<CheckBoxPaintable>
+CheckBoxPaintable::create(Layout::CheckBox const& layout_box)
 {
     return layout_box.heap().allocate_without_realm<CheckBoxPaintable>(layout_box);
 }
@@ -33,4 +90,73 @@ Layout::CheckBox& CheckBoxPaintable::layout_box()
     return static_cast<Layout::CheckBox&>(layout_node());
 }
 
+void CheckBoxPaintable::paint(PaintContext& context, PaintPhase phase) const
+{
+    if (!is_visible())
+        return;
+
+    PaintableBox::paint(context, phase);
+
+    if (phase != PaintPhase::Foreground)
+        return;
+
+    auto const& checkbox = static_cast<HTML::HTMLInputElement const&>(layout_box().dom_node());
+    bool enabled = layout_box().dom_node().enabled();
+    Gfx::AntiAliasingPainter painter { context.painter() };
+    auto checkbox_rect = context.enclosing_device_rect(absolute_rect()).to_type<int>();
+    auto checkbox_radius = checkbox_rect.width() / 5;
+
+    auto& palette = context.palette();
+
+    auto shade = [&](Color color, float amount) {
+        return color.mixed_with(palette.is_dark() ? Color::Black : Color::White, amount);
+    };
+
+    auto modify_color = [&](Color color) {
+        if (being_pressed() && enabled)
+            return shade(color, 0.3f);
+        return color;
+    };
+
+    auto base_text_color = palette.color(ColorRole::BaseText);
+    auto accent = computed_values().accent_color().value_or(palette.color(ColorRole::Accent));
+    auto base = shade(base_text_color.inverted(), 0.8f);
+    auto dark_gray = shade(base_text_color, 0.3f);
+    auto gray = shade(dark_gray, 0.4f);
+    auto mid_gray = shade(gray, 0.3f);
+    auto light_gray = shade(mid_gray, 0.3f);
+
+    auto increase_contrast = [&](Color color, Color background) {
+        auto constexpr min_contrast = 2;
+        if (color.contrast_ratio(background) < min_contrast) {
+            color = color.inverted();
+            if (color.contrast_ratio(background) > min_contrast)
+                return color;
+        }
+        return color;
+    };
+
+    // Little heuristic that smaller things look better with more smoothness.
+    float smoothness = 1.0f / (max(checkbox_rect.width(), checkbox_rect.height()) / 2);
+    if (checkbox.checked() && !checkbox.indeterminate()) {
+        auto background_color = enabled ? accent : mid_gray;
+        painter.fill_rect_with_rounded_corners(checkbox_rect, modify_color(background_color), checkbox_radius);
+        auto tick_color = increase_contrast(base, background_color);
+        if (!enabled)
+            tick_color = shade(tick_color, 0.5f);
+        context.painter().draw_signed_distance_field(checkbox_rect, tick_color, check_mark_sdf(), smoothness);
+    } else {
+        auto background_color = enabled ? base : light_gray;
+        auto border_thickness = max(1, checkbox_rect.width() / 10);
+        painter.fill_rect_with_rounded_corners(checkbox_rect, modify_color(enabled ? gray : mid_gray), checkbox_radius);
+        painter.fill_rect_with_rounded_corners(checkbox_rect.shrunken(border_thickness, border_thickness, border_thickness, border_thickness),
+            enabled ? base : light_gray, max(0, checkbox_radius - border_thickness));
+        if (checkbox.indeterminate()) {
+            auto dash_color = increase_contrast(dark_gray, background_color);
+            context.painter().draw_signed_distance_field(checkbox_rect,
+                modify_color(enabled ? dash_color : shade(dash_color, 0.3f)), check_indeterminate_sdf(), smoothness);
+        }
+    }
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/Painting/CheckBoxPaintable.h b/Userland/Libraries/LibWeb/Painting/CheckBoxPaintable.h
index 4c1a91e34d6..0b9d85cd08a 100644
--- a/Userland/Libraries/LibWeb/Painting/CheckBoxPaintable.h
+++ b/Userland/Libraries/LibWeb/Painting/CheckBoxPaintable.h
@@ -20,6 +20,8 @@ public:
     Layout::CheckBox const& layout_box() const;
     Layout::CheckBox& layout_box();
 
+    virtual void paint(PaintContext&, PaintPhase) const override;
+
 private:
     CheckBoxPaintable(Layout::CheckBox const&);
 };