[raw_ostream] When printing color on Windows, use correct bg color.

When using SetConsoleTextAttribute() to set the foreground or
background color, if you don't explicitly set both colors, then
a default value of black will be chosen for whichever you don't
specify a value for.

This is annoying when you have a non default console background
color, for example, and you try to set the foreground color.

This patch gets the existing fg/bg color and when you set one
attribute, sets the opposite attribute to its existing color
prior to comitting the update.

Reviewed by: Aaron Ballman
Differential Revision: http://reviews.llvm.org/D7967

llvm-svn: 230859

llvm/lib/Support/Windows/Process.inc

@@ -329,6 +329,16 @@ class DefaultColors
 };
 
 DefaultColors defaultColors;
+
+WORD fg_color(WORD color) {
+  return color & (FOREGROUND_BLUE | FOREGROUND_GREEN |
+                  FOREGROUND_INTENSITY | FOREGROUND_RED);
+}
+
+WORD bg_color(WORD color) {
+  return color & (BACKGROUND_BLUE | BACKGROUND_GREEN |
+                  BACKGROUND_INTENSITY | BACKGROUND_RED);
+}
 }
 
 bool Process::ColorNeedsFlush() {
@@ -350,19 +360,22 @@ const char *Process::OutputBold(bool bg) {
 const char *Process::OutputColor(char code, bool bold, bool bg) {
   if (UseANSI) return colorcodes[bg?1:0][bold?1:0][code&7];
 
+  WORD current = DefaultColors::GetCurrentColor();
   WORD colors;
   if (bg) {
     colors = ((code&1) ? BACKGROUND_RED : 0) |
       ((code&2) ? BACKGROUND_GREEN : 0 ) |
       ((code&4) ? BACKGROUND_BLUE : 0);
     if (bold)
       colors |= BACKGROUND_INTENSITY;
+    colors |= fg_color(current);
   } else {
     colors = ((code&1) ? FOREGROUND_RED : 0) |
       ((code&2) ? FOREGROUND_GREEN : 0 ) |
       ((code&4) ? FOREGROUND_BLUE : 0);
     if (bold)
       colors |= FOREGROUND_INTENSITY;
+    colors |= bg_color(current);
   }
   SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE), colors);
   return 0;