From fb27932e4cf1253c2ba46a4fb5acdc478a10b9d7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Va=CC=81clav=20Slavi=CC=81k?= <vaclav@slavik.io>
Date: Sun, 20 Nov 2016 12:12:38 +0100
Subject: [PATCH] Support #rrggbbaa, #rgb and #rgba colors syntax

Add support for alpha channel in the #rrggbbaa format to
wxColour::GetAsString() and FromString(). This syntax is introduced in
CSS4 spec draft (see https://drafts.csswg.org/css-color/#hex-notation)
and already used by Pango for markup as well.

Also recognize #rgb and #rgba shorter variants in FromString().
---
 src/common/colourcmn.cpp | 52 ++++++++++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 12 deletions(-)

diff --git a/src/common/colourcmn.cpp b/src/common/colourcmn.cpp
index a27e3b56cb..805eb0202d 100644
--- a/src/common/colourcmn.cpp
+++ b/src/common/colourcmn.cpp
@@ -158,16 +158,42 @@ bool wxColourBase::FromString(const wxString& str)
             (unsigned char)wxClip(blue, 0, 255),
             (unsigned char)wxClip(alpha, 0, 255));
     }
-    else if ( str[0] == wxT('#') && wxStrlen(str) == 7 )
+    else if ( str[0] == wxT('#') )
     {
-        // hexadecimal prefixed with # (HTML syntax)
+        // hexadecimal prefixed with # ("HTML syntax")
+        // see https://drafts.csswg.org/css-color/#hex-notation
+        size_t len = wxStrlen(str) - 1;
         unsigned long tmp;
         if (wxSscanf(str.wx_str() + 1, wxT("%lx"), &tmp) != 1)
             return false;
 
-        Set((unsigned char)(tmp >> 16),
-            (unsigned char)(tmp >> 8),
-            (unsigned char)tmp);
+        switch ( len )
+        {
+            case 6: // #rrggbb
+                tmp = (tmp << 8) + wxALPHA_OPAQUE;
+                wxFALLTHROUGH;
+
+            case 8: // #rrggbbaa
+                Set((unsigned char)((tmp >> 24) & 0xFF),
+                    (unsigned char)((tmp >> 16) & 0xFF),
+                    (unsigned char)((tmp >> 8)  & 0xFF),
+                    (unsigned char)( tmp        & 0xFF));
+                break;
+
+            case 3: // #rgb
+                tmp = (tmp << 4) + 0xF;
+                wxFALLTHROUGH;
+
+            case 4: // #rgba
+                Set((unsigned char)(((tmp >> 12) & 0xF) * 0x11),
+                    (unsigned char)(((tmp >> 8)  & 0xF) * 0x11),
+                    (unsigned char)(((tmp >> 4)  & 0xF) * 0x11),
+                    (unsigned char)(( tmp        & 0xF) * 0x11));
+                break;
+
+            default:
+                return false; // unrecognized
+        }
     }
     else if (wxTheColourDatabase) // a colour name ?
     {
@@ -195,7 +221,8 @@ wxString wxColourBase::GetAsString(long flags) const
 {
     wxString colName;
 
-    const bool isOpaque = Alpha() == wxALPHA_OPAQUE;
+    const int alpha = Alpha();
+    const bool isOpaque = alpha == wxALPHA_OPAQUE;
 
     // we can't use the name format if the colour is not opaque as the alpha
     // information would be lost
@@ -208,8 +235,8 @@ wxString wxColourBase::GetAsString(long flags) const
     if ( colName.empty() )
     {
         const int red = Red(),
-                  blue = Blue(),
-                  green = Green();
+                  green = Green(),
+                  blue = Blue();
 
         if ( flags & wxC2S_CSS_SYNTAX )
         {
@@ -222,15 +249,16 @@ wxString wxColourBase::GetAsString(long flags) const
             {
                 colName.Printf(wxT("rgba(%d, %d, %d, %s)"),
                                red, green, blue,
-                               wxString::FromCDouble(Alpha() / 255., 3));
+                               wxString::FromCDouble(alpha / 255., 3));
             }
         }
         else if ( flags & wxC2S_HTML_SYNTAX )
         {
-            wxASSERT_MSG( isOpaque, "alpha is lost in HTML syntax" );
-
             // no name for this colour; return it in HTML syntax
-            colName.Printf(wxT("#%02X%02X%02X"), red, green, blue);
+            if ( isOpaque )
+                colName.Printf(wxT("#%02X%02X%02X"), red, green, blue);
+            else
+                colName.Printf(wxT("#%02X%02X%02X%02X"), red, green, blue, alpha);
         }
     }