Accept color name "magenta" instead of "purple" (#13261)

When loading color schemes from Json, check if GetValueForKey failed. If
it did, and we were searching for the colors "purple"/"brightPurple",
swap out the color name with "magenta"/"brightMagenta" and try again.
This was tested manually by creating a new color scheme using the colors
"magenta"/"brightMagenta" and loading it, then printing colored text in
the terminal to assure that the colors were correctly assigned as
purple.

This changes the color loader to use an index pair table to add support
for alternate color names.

## Validation Steps Performed
- Manually edit settings.json, creating a new color scheme with colors
  "magenta" and "brightMagenta"
- View the color scheme in settings - the colors will appear as "purple"
  and "brightPurple" in the UI
- Run a program that prints colored text, purple and brightPurple text
  will appear in the colors defined as magenta and brightMagenta
- Modify the color scheme in the settings UI and save it, the colors
  will be saved as "purple" and "brightPurple" *(I think this is the
  right behavior, since calling them "magenta" is technically a
  mistake)*
- Repeat the steps above with a normal color scheme - colors named
  "purple" and "brightPurple" still load properly

Closes #11456

src/cascadia/TerminalSettingsModel/ColorScheme.cpp

@@ -21,24 +21,30 @@ static constexpr std::string_view BackgroundKey{ "background" };
 static constexpr std::string_view SelectionBackgroundKey{ "selectionBackground" };
 static constexpr std::string_view CursorColorKey{ "cursorColor" };
 
-static constexpr std::array<std::string_view, 16> TableColors = {
-    "black",
-    "red",
-    "green",
-    "yellow",
-    "blue",
-    "purple",
-    "cyan",
-    "white",
-    "brightBlack",
-    "brightRed",
-    "brightGreen",
-    "brightYellow",
-    "brightBlue",
-    "brightPurple",
-    "brightCyan",
-    "brightWhite"
-};
+static constexpr size_t ColorSchemeExpectedSize = 16;
+static constexpr std::array<std::pair<std::string_view, size_t>, 18> TableColorsMapping{ {
+    // Primary color mappings
+    { "black", 0 },
+    { "red", 1 },
+    { "green", 2 },
+    { "yellow", 3 },
+    { "blue", 4 },
+    { "purple", 5 },
+    { "cyan", 6 },
+    { "white", 7 },
+    { "brightBlack", 8 },
+    { "brightRed", 9 },
+    { "brightGreen", 10 },
+    { "brightYellow", 11 },
+    { "brightBlue", 12 },
+    { "brightPurple", 13 },
+    { "brightCyan", 14 },
+    { "brightWhite", 15 },
+
+    // Alternate color mappings (GH#11456)
+    { "magenta", 5 },
+    { "brightMagenta", 13 },
+} };
 
 ColorScheme::ColorScheme() noexcept :
     ColorScheme{ winrt::hstring{} }
@@ -98,11 +104,18 @@ bool ColorScheme::_layerJson(const Json::Value& json)
     JsonUtils::GetValueForKey(json, CursorColorKey, _CursorColor);
 
     // Required fields
-    for (unsigned int i = 0; i < TableColors.size(); ++i)
+    size_t colorCount = 0;
+    for (const auto& [key, index] : TableColorsMapping)
     {
-        isValid &= JsonUtils::GetValueForKey(json, til::at(TableColors, i), til::at(_table, i));
+        colorCount += JsonUtils::GetValueForKey(json, key, til::at(_table, index));
+        if (colorCount == ColorSchemeExpectedSize)
+        {
+            break;
+        }
     }
 
+    isValid &= (colorCount == 16); // Valid schemes should have exactly 16 colors
+
     return isValid;
 }
 
@@ -122,9 +135,10 @@ Json::Value ColorScheme::ToJson() const
     JsonUtils::SetValueForKey(json, SelectionBackgroundKey, _SelectionBackground);
     JsonUtils::SetValueForKey(json, CursorColorKey, _CursorColor);
 
-    for (unsigned int i = 0; i < TableColors.size(); ++i)
+    for (size_t i = 0; i < ColorSchemeExpectedSize; ++i)
     {
-        JsonUtils::SetValueForKey(json, til::at(TableColors, i), til::at(_table, i));
+        const auto& key = til::at(TableColorsMapping, i).first;
+        JsonUtils::SetValueForKey(json, key, til::at(_table, i));
     }
 
     return json;