From 221f7ccbedd500fefc43036989b83fd1aa15efb2 Mon Sep 17 00:00:00 2001
From: "Vogel, Rick" <rick.vogel@edelhirsch.io>
Date: Tue, 14 Mar 2023 13:09:17 +0100
Subject: [PATCH] Add RGBA string literal

---
 src/common/QskRgbLiterals.h | 142 ++++++++++++++++++++++++++++++++++++
 src/src.pro                 |   1 +
 2 files changed, 143 insertions(+)
 create mode 100644 src/common/QskRgbLiterals.h

diff --git a/src/common/QskRgbLiterals.h b/src/common/QskRgbLiterals.h
new file mode 100644
index 00000000..e715bd61
--- /dev/null
+++ b/src/common/QskRgbLiterals.h
@@ -0,0 +1,142 @@
+/******************************************************************************
+ * Copyright (C) 2023 Edelhirsch Software GmbH
+ * This file may be used under the terms of the 3-clause BSD License
+ *****************************************************************************/
+
+#ifndef QSK_RGB_LITERALS_H
+#define QSK_RGB_LITERALS_H
+
+namespace QskRgb
+{
+    namespace literals
+    {
+        /// @brief converts HTML #RRGGBB[AA] color hex string to Qt's RGB 0xAARRGGBB integer
+        /// @param str The string literal
+        /// @param len The length of the literal
+        /// @note non-hexadecimal characters are replaced with 0x0 value
+        constexpr unsigned int operator""_rgba( const char* const str, const size_t len )
+        {
+            if ( len != 7 && len != 9 )
+            {
+                return 0;
+            }
+
+            unsigned int rgb = 0x00;
+
+            // skip # character
+            for ( size_t i = 1; i < len; ++i )
+            {
+                switch ( str[ i ] )
+                {
+                    case '0':
+                        rgb = ( rgb << 4 ) | 0x0;
+                        break;
+
+                    case '1':
+                        rgb = ( rgb << 4 ) | 0x1;
+                        break;
+
+                    case '2':
+                        rgb = ( rgb << 4 ) | 0x2;
+                        break;
+
+                    case '3':
+                        rgb = ( rgb << 4 ) | 0x3;
+                        break;
+
+                    case '4':
+                        rgb = ( rgb << 4 ) | 0x4;
+                        break;
+
+                    case '5':
+                        rgb = ( rgb << 4 ) | 0x5;
+                        break;
+
+                    case '6':
+                        rgb = ( rgb << 4 ) | 0x6;
+                        break;
+
+                    case '7':
+                        rgb = ( rgb << 4 ) | 0x7;
+                        break;
+
+                    case '8':
+                        rgb = ( rgb << 4 ) | 0x8;
+                        break;
+
+                    case '9':
+                        rgb = ( rgb << 4 ) | 0x9;
+                        break;
+
+                    case 'A':
+                    case 'a':
+                        rgb = ( rgb << 4 ) | 0xA;
+                        break;
+
+                    case 'B':
+                    case 'b':
+                        rgb = ( rgb << 4 ) | 0xB;
+                        break;
+
+                    case 'C':
+                    case 'c':
+                        rgb = ( rgb << 4 ) | 0xC;
+                        break;
+
+                    case 'D':
+                    case 'd':
+                        rgb = ( rgb << 4 ) | 0xD;
+                        break;
+
+                    case 'E':
+                    case 'e':
+                        rgb = ( rgb << 4 ) | 0xE;
+                        break;
+
+                    case 'F':
+                    case 'f':
+                        rgb = ( rgb << 4 ) | 0xF;
+                        break;
+
+                    default:
+                        rgb = ( rgb << 4 ) | 0x0;
+                        break;
+                }
+            }
+
+            // add default 0xFF for alpha channel
+            if ( len > 1 && len <= 7 )
+            {
+                rgb |= 0xFF000000;
+            }
+
+            // convert rrggbbaa to aarrggbb
+            if ( len > 7 )
+            {
+                rgb = ( 0x000000FF & rgb ) << 24 | ( rgb >> 8 );
+            }
+
+            return rgb;
+        }
+
+        // example for rgb
+        static_assert( "#123456"_rgba == 0xFF123456, "not constexpr" );
+        // example for rgba
+        static_assert( "#112233aa"_rgba == 0xAA112233, "not constexpr" );
+
+        // bad examples
+        static_assert( ""_rgba == 0x0, "not constexpr" );
+        static_assert( "#"_rgba == 0x0, "not constexpr" );
+        static_assert( "#1"_rgba == 0x0, "not constexpr" );
+        static_assert( "#12"_rgba == 0x0, "not constexpr" );
+        static_assert( "#123"_rgba == 0x0, "not constexpr" );
+        static_assert( "#1234"_rgba == 0x0, "not constexpr" );
+        static_assert( "#12345"_rgba == 0x0, "not constexpr" );
+        static_assert( "#112233a"_rgba == 0x0, "not constexpr" );
+        static_assert( "#fffffffff"_rgba == 0x0, "not constexpr" );
+        static_assert( "#WTF01337"_rgba == 0x3700F013, "not constexpr" );
+        static_assert( "#JUSTWHY?"_rgba == 0x0, "not constexpr" );
+    }
+}
+
+#endif
diff --git a/src/src.pro b/src/src.pro
index 6cd9ba77..81df011b 100644
--- a/src/src.pro
+++ b/src/src.pro
@@ -40,6 +40,7 @@ HEADERS += \
     common/QskPlacementPolicy.h \
     common/QskPlatform.h \
     common/QskRgbValue.h \
+    common/QskRgbLiterals.h \
     common/QskScaleEngine.h \
     common/QskScaleTickmarks.h \
     common/QskShadowMetrics.h \