Allow negative rgb and rgba values and clamp them to range 0-255 (#1129)

When converting rgb and rgba strings to colors, browsers tolerate numbers out of the acceptable color range but BabylonNative does not.

This change updates the color string regex to accept negative numbers and clamps them to the acceptable color range of 0 to 255.

Author: docEdub

Polyfills/Canvas/Source/Colors.h

@@ -212,19 +212,19 @@ namespace Babylon::Polyfills::Internal
             }
 
             // matches strings of the form rgb(#,#,#) or rgba(#,#,#,#)
-            static const std::regex rgbRegex("rgba?\\(\\s*(\\d{1,3})\\s*,\\s*(\\d{1,3})\\s*,\\s*(\\d{1,3})\\s*(?:,\\s*(\\d{1,3}))?\\s*\\)");
+            static const std::regex rgbRegex("rgba?\\(\\s*(-?\\d{1,3})\\s*,\\s*(-?\\d{1,3})\\s*,\\s*(-?\\d{1,3})\\s*(?:,\\s*(-?\\d{1,3}))?\\s*\\)");
             std::smatch rgbMatch;
             if (std::regex_match(str, rgbMatch, rgbRegex))
             {
                 if (rgbMatch.size() == 5)
                 { 
                     if (rgbMatch[4].matched)
                     {
-                        return nvgRGBA(std::stoi(rgbMatch[1]), std::stoi(rgbMatch[2]), std::stoi(rgbMatch[3]), std::stoi(rgbMatch[4]));
+                        return nvgRGBA(std::clamp(std::stoi(rgbMatch[1]), 0, 255), std::clamp(std::stoi(rgbMatch[2]), 0, 255), std::clamp(std::stoi(rgbMatch[3]), 0, 255), std::clamp(std::stoi(rgbMatch[4]), 0, 255));
                     }
                     else
                     {
-                        return nvgRGB(std::stoi(rgbMatch[1]), std::stoi(rgbMatch[2]), std::stoi(rgbMatch[3]));
+                        return nvgRGB(std::clamp(std::stoi(rgbMatch[1]), 0, 255), std::clamp(std::stoi(rgbMatch[2]), 0, 255), std::clamp(std::stoi(rgbMatch[3]), 0, 255));
                     }
                 }
             }