Bug 1720792: Add MozNativevisitedhyperlinktext color, use it to style visited links r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D120657

layout/style/PreferenceSheet.cpp

@@ -112,18 +112,29 @@ void PreferenceSheet::Prefs::Load(bool aIsChrome) {
         useStandins ? ColorID::Window : ColorID::WindowBackground, scheme,
         standins, mColors.mDefaultBackground);
     mColors.mLink = LookAndFeel::Color(ColorID::MozNativehyperlinktext, scheme,
-                                    standins, mColors.mLink);
+                                       standins, mColors.mLink);
+
+    if (auto color = LookAndFeel::GetColor(
+            ColorID::MozNativevisitedhyperlinktext, scheme, standins)) {
+      // If the system provides a visited link color, we should use it.
+      mColors.mVisitedLink = *color;
+    } else if (mUseAccessibilityTheme) {
+      // The fallback visited link color on HCM (if the system doesn't provide
+      // one) is produced by preserving the foreground's green and averaging the
+      // foreground and background for the red and blue.  This is how IE and
+      // Edge do it too.
+      mColors.mVisitedLink = NS_RGB(AVG2(NS_GET_R(mColors.mDefault),
+                                         NS_GET_R(mColors.mDefaultBackground)),
+                                    NS_GET_G(mColors.mDefault),
+                                    AVG2(NS_GET_B(mColors.mDefault),
+                                         NS_GET_B(mColors.mDefaultBackground)));
+    } else {
+      // Otherwise we keep the default visited link color
+    }
   }
 
   if (mUseAccessibilityTheme && !useStandins) {
     mColors.mActiveLink = mColors.mLink;
-    // Visited link color is produced by preserving the foreground's green
-    // and averaging the foreground and background for the red and blue.
-    // This is how IE and Edge do it too.
-    mColors.mVisitedLink = NS_RGB(
-        AVG2(NS_GET_R(mColors.mDefault), NS_GET_R(mColors.mDefaultBackground)),
-        NS_GET_G(mColors.mDefault),
-        AVG2(NS_GET_B(mColors.mDefault), NS_GET_B(mColors.mDefaultBackground)));
   } else {
     GetColor("browser.active_color", mColors.mActiveLink);
     GetColor("browser.visited_color", mColors.mVisitedLink);

layout/style/test/test_non_content_accessible_values.html

@@ -11,6 +11,7 @@ const NON_CONTENT_ACCESSIBLE_VALUES = {
     "-moz-colheadertext",
     "-moz-system-color(highlight, light)",
     "-moz-system-color(highlight, dark)",
+    "-moz-nativevisitedhyperlinktext",
     "text-select-foreground",
     "text-select-background",
     "text-select-background-disabled",

servo/components/style/values/specified/color.rs

@@ -362,6 +362,10 @@ pub enum SystemColor {
     /// colors.
     MozNativehyperlinktext,
 
+    /// As above, but visited link color.
+    #[css(skip)]
+    MozNativevisitedhyperlinktext,
+
     #[parse(aliases = "-moz-hyperlinktext")]
     Linktext,
     #[parse(aliases = "-moz-activehyperlinktext")]

widget/cocoa/SDKDeclarations.h

@@ -25,6 +25,11 @@
 
 using NSAppearanceName = NSString*;
 
+@interface NSColor (NSColor10_13)
+// "Available in 10.10", but not present in any SDK less than 10.13
+@property(class, strong, readonly) NSColor* systemPurpleColor NS_AVAILABLE_MAC(10_10);
+@end
+
 #endif
 
 #if !defined(MAC_OS_X_VERSION_10_14) || MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_14

widget/cocoa/nsLookAndFeel.mm

@@ -22,6 +22,7 @@
 #include "SDKDeclarations.h"
 
 #import <Cocoa/Cocoa.h>
+#import <AppKit/NSColor.h>
 
 // This must be included last:
 #include "nsObjCExceptions.h"
@@ -337,6 +338,9 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme, nscolor
     case ColorID::MozNativehyperlinktext:
       color = GetColorFromNSColor(NSColor.linkColor);
       break;
+    case ColorID::MozNativevisitedhyperlinktext:
+      color = GetColorFromNSColor(NSColor.systemPurpleColor);
+      break;
     // The following colors are supposed to be used as font-smoothing background
     // colors, in the chrome-only -moz-font-smoothing-background-color property.
     // This property is used for text on "vibrant" -moz-appearances.

widget/nsXPLookAndFeel.cpp

@@ -303,6 +303,7 @@ static const char sColorPrefs[][41] = {
     "ui.-moz-win-mediatext",
     "ui.-moz-win-communicationstext",
     "ui.-moz-nativehyperlinktext",
+    "ui.-moz-nativevisitedhyperlinktext",
     "ui.-moz-hyperlinktext",
     "ui.-moz-activehyperlinktext",
     "ui.-moz-visitedhyperlinktext",
@@ -579,6 +580,7 @@ nscolor nsXPLookAndFeel::GetStandinForNativeColor(ColorID aID) {
     COLOR(MozWinMediatext, 0xFF, 0xFF, 0xFF)
     COLOR(MozWinCommunicationstext, 0xFF, 0xFF, 0xFF)
     COLOR(MozNativehyperlinktext, 0x00, 0x66, 0xCC)
+    COLOR(MozNativevisitedhyperlinktext, 0x55, 0x1A, 0x8B)
     COLOR(MozComboboxtext, 0x00, 0x00, 0x00)
     COLOR(MozCombobox, 0xFF, 0xFF, 0xFF)
     default:

widget/uikit/nsLookAndFeel.mm

@@ -248,6 +248,11 @@ nsresult nsLookAndFeel::NativeGetColor(ColorID, ColorScheme, nscolor& aResult) {
       // There appears to be no available system defined color. HARDCODING to the appropriate color.
       aResult = NS_RGB(0x14, 0x4F, 0xAE);
       break;
+    case ColorID::MozNativevisitedhyperlinktext:
+      // Safari defaults to the MacOS color implementation for visited links, which in turn uses
+      // systemPurpleColor, so we do the same here.
+      aResult = GetColorFromUIColor([UIColor systemPurpleColor]);
+      break;
     default:
       NS_WARNING("Someone asked nsILookAndFeel for a color I don't know about");
       aResult = NS_RGB(0xff, 0xff, 0xff);