Add title bar for code blocks in the Demo app CodeSyntaxHighlightView (#249)

Author: moophis

Examples/Demo/Demo/CodeSyntaxHighlightView.swift

@@ -26,7 +26,7 @@ struct CodeSyntaxHighlightView: View {
       }
 
       func highlightCode(_ content: String, language: String?) -> Text {
-        guard language?.lowercased() == "swift" else {
+        guard language != nil else {
           return Text(content)
         }
 
@@ -50,15 +50,92 @@ struct CodeSyntaxHighlightView: View {
         .markdownCodeSyntaxHighlighter(.splash(theme: .sunset(withFont: .init(size: 16))))
     }
     ```
+
+    More languages to render:
+
+    ```
+    A plain code block without the specifying a language name.
+    ```
+
+    ```cpp
+    #include <iostream>
+    #include <vector>
+
+    int main() {
+        std::vector<std::string> fruits = {"apple", "banana", "orange"};
+        for (const std::string& fruit : fruits) {
+            std::cout << "I love " << fruit << "s!" << std::endl;
+        }
+        return 0;
+    }
+    ```
+
+    ```typescript
+    interface Person {
+      name: string;
+      age: number;
+    }
+
+    const person = Person();
+    ```
+
+    ```ruby
+    fruits = ["apple", "banana", "orange"]
+    fruits.each do |fruit|
+      puts "I love #{fruit}s!"
+    end
+    ```
+
     """#
 
   var body: some View {
     DemoView {
       Markdown(self.content)
+        .markdownBlockStyle(\.codeBlock) {
+          codeBlock($0)
+        }
         .markdownCodeSyntaxHighlighter(.splash(theme: self.theme))
     }
   }
 
+  @ViewBuilder
+  private func codeBlock(_ configuration: CodeBlockConfiguration) -> some View {
+    VStack(spacing: 0) {
+      HStack {
+        Text(configuration.language ?? "plain text")
+          .font(.system(.caption, design: .monospaced))
+          .fontWeight(.semibold)
+          .foregroundColor(Color(theme.plainTextColor))
+        Spacer()
+
+        Image(systemName: "clipboard")
+          .onTapGesture {
+            copyToClipboard(configuration.content)
+          }
+      }
+      .padding(.horizontal)
+      .padding(.vertical, 8)
+      .background {
+        Color(theme.backgroundColor)
+      }
+
+      Divider()
+
+      ScrollView(.horizontal) {
+        configuration.label
+          .relativeLineSpacing(.em(0.25))
+          .markdownTextStyle {
+            FontFamilyVariant(.monospaced)
+            FontSize(.em(0.85))
+          }
+          .padding()
+      }
+    }
+    .background(Color(.secondarySystemBackground))
+    .clipShape(RoundedRectangle(cornerRadius: 8))
+    .markdownMargin(top: .zero, bottom: .em(0.8))
+  }
+
   private var theme: Splash.Theme {
     // NOTE: We are ignoring the Splash theme font
     switch self.colorScheme {
@@ -68,6 +145,17 @@ struct CodeSyntaxHighlightView: View {
       return .sunset(withFont: .init(size: 16))
     }
   }
+
+  private func copyToClipboard(_ string: String) {
+#if os(macOS)
+    if let pasteboard = NSPasteboard.general {
+      pasteboard.clearContents()
+      pasteboard.setString(string, forType: .string)
+    }
+#elseif os(iOS)
+    UIPasteboard.general.string = string
+#endif
+  }
 }
 
 struct CodeSyntaxHighlightView_Previews: PreviewProvider {

Examples/Demo/Demo/SyntaxHighlighter/SplashCodeSyntaxHighlighter.swift

@@ -10,7 +10,7 @@ struct SplashCodeSyntaxHighlighter: CodeSyntaxHighlighter {
   }
 
   func highlightCode(_ content: String, language: String?) -> Text {
-    guard language?.lowercased() == "swift" else {
+    guard language != nil else {
       return Text(content)
     }