Mail: Make quote and unquote work better

Always quote and unquote starting from the beginning of the line
instead of the current cursor position.

src/apps/mail/Content.cpp

@@ -3121,6 +3121,7 @@ TTextView::AddQuote(int32 start, int32 finish)
 	int32 lineStart;
 	GoToLine(CurrentLine());
 	GetSelection(&lineStart, &lineStart);
+	lineStart = LineStart(lineStart);
 
 	// make sure that we're changing the whole last line, too
 	int32 lineEnd = finish > lineStart ? finish - 1 : finish;
@@ -3198,6 +3199,7 @@ TTextView::RemoveQuote(int32 start, int32 finish)
 	GoToLine(CurrentLine());
 	int32 lineStart;
 	GetSelection(&lineStart, &lineStart);
+	lineStart = LineStart(lineStart);
 
 	// make sure that we're changing the whole last line, too
 	int32 lineEnd = finish > lineStart ? finish - 1 : finish;
@@ -3280,6 +3282,39 @@ TTextView::RemoveQuote(int32 start, int32 finish)
 }
 
 
+int32
+TTextView::LineStart(int32 offset)
+{
+	if (offset <= 0)
+		return 0;
+
+	while (offset > 0) {
+		offset = PreviousByte(offset);
+		if (ByteAt(offset) == B_ENTER)
+			return offset + 1;
+	}
+
+	return offset;
+}
+
+
+int32
+TTextView::PreviousByte(int32 offset) const
+{
+	if (offset <= 0)
+		return 0;
+
+	int32 count = 6;
+
+	for (--offset; offset > 0 && count; --offset, --count) {
+		if ((ByteAt(offset) & 0xC0) != 0x80)
+			break;
+	}
+
+	return count ? offset : 0;
+}
+
+
 void
 TTextView::Undo(BClipboard */*clipboard*/)
 {
@@ -3374,4 +3409,3 @@ TTextView::Redo()
 		fUndoBuffer.On();
 	}
 }
-

src/apps/mail/Content.h

@@ -208,6 +208,9 @@ class TTextView : public BTextView {
 
 		void ContentChanged(void);
 
+		int32 LineStart(int32 offset);
+		int32 PreviousByte(int32 offset) const;
+
 		class Reader;
 		friend class TTextView::Reader;