feat: adjust opacity settings (#631)

# Summary

Fixes:
#627
Do not apply additional opacity if user specified it manually. 

## Test Plan

First scenario:
- Run the app
- Adjust `htmlStyle` to use color with opacity
- Notice additional opacity is not applied

Second scenario:
- Run the app
- Adjust `htmlStyle` to use color without opacity
- Notice that additional opacity is applied

## Screenshots / Videos

n/a

## Compatibility

| OS      | Implemented |
| ------- | :---------: |
| iOS     |    ✅     |
| Android |    ✅     |

## Checklist

- [x] E2E tests are passing
- [ ] Required E2E tests have been added (if applicable)

Author: exploIF

android/src/main/java/com/swmansion/enriched/text/EnrichedTextStyle.kt

@@ -155,7 +155,7 @@ data class EnrichedTextStyle(
       opacity: Int,
     ): Int {
       val color = parseColor(context, map, key)
-      if (Color.alpha(color) == 0) return color
+      if (Color.alpha(color) != 255) return color
       return (color and 0x00FFFFFF) or (opacity.coerceIn(0, 255) shl 24)
     }
 

android/src/main/java/com/swmansion/enriched/textinput/styles/HtmlStyle.kt

@@ -197,8 +197,7 @@ class HtmlStyle : EnrichedStyle {
     color: Int,
     alpha: Int,
   ): Int {
-    // Do not apply opacity to transparent color
-    if (Color.alpha(color) == 0) return color
+    if (Color.alpha(color) != 255) return color
     val a = alpha.coerceIn(0, 255)
     return (color and 0x00FFFFFF) or (a shl 24)
   }

ios/extensions/ColorExtension.h

@@ -3,5 +3,6 @@
 
 @interface UIColor (ColorExtension)
 - (BOOL)isEqualToColor:(UIColor *)otherColor;
-- (UIColor *)colorWithAlphaIfNotTransparent:(CGFloat)newAlpha;
+- (UIColor *)colorWithResolvedAlpha;
+- (UIColor *)colorWithResolvedAlpha:(CGFloat)newAlpha;
 @end

ios/extensions/ColorExtension.mm

@@ -27,10 +27,20 @@ - (BOOL)isEqualToColor:(UIColor *)otherColor {
   return [selfColor isEqual:otherColor];
 }
 
-- (UIColor *)colorWithAlphaIfNotTransparent:(CGFloat)newAlpha {
+// Default fallback alpha of 0.4 — opaque colors get this applied so the text
+// cursor remains visible through the highlight. If the caller already set a
+// custom alpha (anything below 1.0), we respect that value instead.
+- (UIColor *)colorWithResolvedAlpha {
+  return [self colorWithResolvedAlpha:0.4];
+}
+
+- (UIColor *)colorWithResolvedAlpha:(CGFloat)newAlpha {
   CGFloat alpha = 0.0;
   [self getRed:nil green:nil blue:nil alpha:&alpha];
-  if (alpha > 0.0) {
+  // alpha == 1.0 means the color was never given a custom transparency, so
+  // apply newAlpha. Any other value means the caller explicitly chose it —
+  // leave it untouched.
+  if (alpha >= 1.0) {
     return [self colorWithAlphaComponent:newAlpha];
   }
   return self;

ios/extensions/LayoutManagerExtension.mm

@@ -73,8 +73,7 @@ - (void)drawCodeBlocks:(id<EnrichedViewHost>)host
   NSArray<StylePair *> *allCodeBlocks = [codeBlockStyle all:visibleCharRange];
   NSArray<StylePair *> *mergedCodeBlocks =
       [self mergeContiguousStylePairs:allCodeBlocks];
-  UIColor *bgColor =
-      [[host.config codeBlockBgColor] colorWithAlphaIfNotTransparent:0.4];
+  UIColor *bgColor = [[host.config codeBlockBgColor] colorWithResolvedAlpha];
   CGFloat radius = [host.config codeBlockBorderRadius];
   [bgColor setFill];
 

ios/styles/InlineCodeStyle.mm

@@ -29,7 +29,7 @@ - (void)applyStyling:(NSRange)range {
     [self.host.textView.textStorage
         addAttribute:NSBackgroundColorAttributeName
                value:[[self.host.config inlineCodeBgColor]
-                         colorWithAlphaIfNotTransparent:0.4]
+                         colorWithResolvedAlpha]
                range:subRange];
     [self.host.textView.textStorage
         addAttribute:NSForegroundColorAttributeName

ios/styles/MentionStyle.mm

@@ -54,7 +54,7 @@ - (void)applyStyling:(NSRange)range {
     NSUnderlineColorAttributeName : styleProps.color,
     NSStrikethroughColorAttributeName : styleProps.color,
     NSBackgroundColorAttributeName :
-        [styleProps.backgroundColor colorWithAlphaIfNotTransparent:0.4],
+        [styleProps.backgroundColor colorWithResolvedAlpha],
   } mutableCopy];
 
   if (styleProps.decorationLine == DecorationUnderline) {

ios/utils/EnrichedTextTouchHandler.mm

@@ -115,7 +115,7 @@ - (void)updateVisualsPressed:(BOOL)pressed {
     }
     if (bgColor) {
       newAttrs[NSBackgroundColorAttributeName] =
-          [bgColor colorWithAlphaIfNotTransparent:0.4];
+          [bgColor colorWithResolvedAlpha];
     }
 
     [self.view.textView.textStorage addAttributes:newAttrs range:_activeRange];