nicko 2005/02/01 12:20:37
Modified: src/Appender ColoredConsoleAppender.cs
Log:
Fixed background color overspill when changing background colors and the
console buffer is scrolled - see comment in code
Revision Changes Path
1.15 +60 -1 logging-log4net/src/Appender/ColoredConsoleAppender.cs
Index: ColoredConsoleAppender.cs
===================================================================
RCS file: /home/cvs/logging-log4net/src/Appender/ColoredConsoleAppender.cs,v
retrieving revision 1.14
retrieving revision 1.15
diff -u -r1.14 -r1.15
--- ColoredConsoleAppender.cs 31 Jan 2005 20:41:28 -0000 1.14
+++ ColoredConsoleAppender.cs 1 Feb 2005 20:20:37 -0000 1.15
@@ -341,14 +341,73 @@
// See the ActivateOptions method below for the
code that
// retrieves and wraps the stream.
+
+ // The windows console uses
ScrollConsoleScreenBuffer internally to
+ // scroll the console buffer when the display
buffer of the console
+ // has been used up. ScrollConsoleScreenBuffer
fills the area uncovered
+ // by moving the current content with the
background color
+ // currently specified on the console. This
means that it fills the
+ // whole line in front of the cursor position
with the current
+ // background color.
+ // This causes an issue when writing out text
with a non default
+ // background color. For example; We write a
message with a Blue
+ // background color and the scrollable area of
the console is full.
+ // When we write the newline at the end of the
message the console
+ // needs to scroll the buffer to make space
available for the new line.
+ // The ScrollConsoleScreenBuffer internals will
fill the newly created
+ // space with the current background color:
Blue.
+ // We then change the console color back to
default (White text on a
+ // Black background). We write some text to the
console, the text is
+ // written correctly in White with a Black
background, however the
+ // remainder of the line still has a Blue
background.
+ //
+ // This causes a disjointed appearance to the
output where the background
+ // colors change.
+ //
+ // This can be remedied by restoring the
console colors before causing
+ // the buffer to scroll, i.e. before writing
the last newline. This does
+ // assume that the rendered message will end
with a newline.
+ //
+ // Therefore we identify a trailing newline in
the message and don't
+ // write this to the output, then we restore
the console color and write
+ // a newline. Note that we must AutoFlush
before we restore the console
+ // color otherwise we will have no effect.
+ //
+ // There will still be a slight artefact for
the last line of the message
+ // will have the background extended to the end
of the line, however this
+ // is unlikely to cause any user issues.
+ //
+ // Note that none of the above is visible while
the console buffer is scrollable
+ // within the console window viewport, the
effects only arise when the actual
+ // buffer is full and needs to be scrolled.
+
+ char[] messageCharArray =
strLoggingMessage.ToCharArray();
+ int arrayLength = messageCharArray.Length;
+ bool appendNewline = false;
+
+ // Trim off last newline, if it exists
+ if (arrayLength > 1 &&
messageCharArray[arrayLength-2] == '\r' && messageCharArray[arrayLength-1] ==
'\n')
+ {
+ arrayLength -= 2;
+ appendNewline = true;
+ }
+
// Write to the output stream
- m_consoleOutputWriter.Write(strLoggingMessage);
+ m_consoleOutputWriter.Write(messageCharArray,
0, arrayLength);
// Restore the console back to its previous
color scheme
SetConsoleTextAttribute(consoleHandle,
bufferInfo.wAttributes);
+
+ if (appendNewline)
+ {
+ // Write the newline, after changing
the color scheme
+
m_consoleOutputWriter.Write(s_windowsNewline, 0, 2);
+ }
}
}
+ private static readonly char[] s_windowsNewline = {'\r', '\n'};
+
/// <summary>
/// This appender requires a <see cref="Layout"/> to be set.
/// </summary>
