inverse color to match dark/light appearance

SquirrelPanel.m

@@ -1907,6 +1907,14 @@ - (void)hideStatus:(NSTimer *)timer {
           colorWithAlphaComponent:foregroundColor.alphaComponent];
 }
 
+static inline NSColor *inverseColor(NSColor *color) {
+  return [NSColor colorWithColorSpace:color.colorSpace
+                                  hue:color.hueComponent
+                           saturation:color.saturationComponent
+                           brightness:1-color.brightnessComponent
+                                alpha:color.alphaComponent];
+}
+
 static NSFontDescriptor *getFontDescriptor(NSString *fullname) {
   if (fullname == nil) {
     return nil;
@@ -2266,6 +2274,26 @@ + (void)updateTheme:(SquirrelTheme *)theme withConfig:(SquirrelConfig *)config f
   highlightedTextColor = highlightedTextColor ? highlightedTextColor : [NSColor selectedTextColor];
   highlightedBackColor = highlightedBackColor ? highlightedBackColor : isNative ? [NSColor selectedTextBackgroundColor] : nil;
 
+  if (@available(macOS 10.14, *)) {
+    if (theme.translucency > 0 &&
+        ((backgroundColor.brightnessComponent >= 0.5 && isDark) ||
+         (backgroundColor.brightnessComponent < 0.5 && !isDark))) {
+      backgroundColor = inverseColor(backgroundColor);
+      borderColor = borderColor ? inverseColor(borderColor) : nil;
+      preeditBackgroundColor = preeditBackgroundColor ? inverseColor(preeditBackgroundColor) : nil;
+      candidateTextColor = inverseColor(candidateTextColor);
+      highlightedCandidateTextColor = [inverseColor(highlightedCandidateTextColor) highlightWithLevel:highlightedCandidateTextColor.brightnessComponent];
+      highlightedCandidateBackColor = highlightedCandidateBackColor ? [inverseColor(highlightedCandidateBackColor) shadowWithLevel:1-highlightedCandidateBackColor.brightnessComponent] : nil;
+      candidateLabelColor = inverseColor(candidateLabelColor);
+      highlightedCandidateLabelColor = [inverseColor(highlightedCandidateLabelColor) highlightWithLevel:highlightedCandidateLabelColor.brightnessComponent];
+      commentTextColor = inverseColor(commentTextColor);
+      highlightedCommentTextColor = [inverseColor(highlightedCommentTextColor) highlightWithLevel:highlightedCommentTextColor.brightnessComponent];
+      textColor = inverseColor(textColor);
+      highlightedTextColor = [inverseColor(highlightedTextColor) highlightWithLevel:highlightedTextColor.brightnessComponent];
+      highlightedBackColor = highlightedBackColor ? [inverseColor(highlightedBackColor) shadowWithLevel:1-highlightedBackColor.brightnessComponent] : nil;
+    }
+  }
+
   attrs[NSForegroundColorAttributeName] = candidateTextColor;
   highlightedAttrs[NSForegroundColorAttributeName] = highlightedCandidateTextColor;
   labelAttrs[NSForegroundColorAttributeName] = candidateLabelColor;