tor-browser

commit 88016633b31bbc3fa5e7c1b17dcf27fc961a3496
parent f289eebba9194e9f22fce14b4e97c2da7a6e7c31
Author: Emilio Cobos Álvarez <emilio@crisal.io>
Date:   Thu, 30 Oct 2025 22:53:12 +0000

Bug 1993820 - Tweak checked radio rendering to minimize snapping artifacts. r=dholbert

We're drawing it as a background circle, and an inner background +
border circle, which means that the outer background can snap
differently.

Draw it as an outer background + border, and an inner circle instead, so
as to minimize snapping artifacts on the outer border.

Differential Revision: https://phabricator.services.mozilla.com/D270477

Diffstat:
M
widget/Theme.cpp
 | 
39
+++++++++++++++++++++------------------

1 file changed, 21 insertions(+), 18 deletions(-)
diff --git a/widget/Theme.cpp b/widget/Theme.cpp
@@ -633,26 +633,29 @@ void Theme::PaintRadioControl(PaintBackendData& aPaintData,
                               DPIRatio aDpiRatio) {
   auto [backgroundColor, borderColor, checkColor] =
       ComputeCheckboxColors(aState, StyleAppearance::Radio, aColors);
+  const bool isChecked = aState.HasState(ElementState::CHECKED);
   {
-    CSSCoord borderWidth = kCheckboxRadioBorderWidth;
-    if (backgroundColor == borderColor) {
-      borderWidth = 0.0f;
+    CSSCoord outerBorderWidth = kCheckboxRadioBorderWidth;
+    auto effectiveBackground = isChecked ? checkColor : backgroundColor;
+    if (effectiveBackground == borderColor) {
+      outerBorderWidth = 0.0f;
     }
-    PaintStrokedCircle(aPaintData, aRect, backgroundColor, borderColor,
-                       borderWidth, aDpiRatio);
-  }
-
-  if (aState.HasState(ElementState::CHECKED)) {
-    // See bug 1951930 and bug 1941755 for some discussion on this chunk of
-    // code.
-    const CSSCoord kOuterBorderWidth = 1.0f;
-    const CSSCoord kInnerBorderWidth = 2.0f;
-    LayoutDeviceRect rect(aRect);
-    auto width = LayoutDeviceCoord(
-        ThemeDrawing::SnapBorderWidth(kOuterBorderWidth, aDpiRatio));
-    rect.Deflate(width);
-    PaintStrokedCircle(aPaintData, rect, backgroundColor, checkColor,
-                       kInnerBorderWidth, aDpiRatio);
+    PaintStrokedCircle(aPaintData, aRect, effectiveBackground, borderColor,
+                       outerBorderWidth, aDpiRatio);
+  }
+
+  if (isChecked) {
+    // See bug 1951930 / bug 1941755 for discussion on this chunk of code.
+    constexpr CSSCoord kInnerBorderWidth = 2.0f;
+    LayoutDeviceRect innerCircleBounds(aRect);
+    // It's important that these are two different calls so that the snapping of
+    // the inner rect matches the one PaintStrokedCircle above does.
+    innerCircleBounds.Deflate(
+        ThemeDrawing::SnapBorderWidth(kCheckboxRadioBorderWidth, aDpiRatio));
+    innerCircleBounds.Deflate(
+        ThemeDrawing::SnapBorderWidth(kInnerBorderWidth, aDpiRatio));
+    PaintStrokedCircle(aPaintData, innerCircleBounds, backgroundColor,
+                       sTransparent, 0.0f, aDpiRatio);
   }
 
   if (aState.HasState(ElementState::FOCUSRING)) {