Added a custom widget for tagging dives

A custom tag widget has been added to MainTab.
Tags are seperated by a comma ",". The implementation
supports escaping a comma by using "\,".
While typing, the widget supports the user by suggesting
tags using a QCompleter.

Signed-off-by: Maximilian Güntner <maximilian.guentner@gmail.com>

qt-ui/tagwidget.cpp

@@ -0,0 +1,135 @@
+#include "tagwidget.h"
+#include <QPair>
+#include <QDebug>
+
+TagWidget::TagWidget(QWidget *parent) : GroupedLineEdit(parent), m_completer(NULL)
+{
+	connect(this, SIGNAL(cursorPositionChanged()), this, SLOT(reparse()));
+
+	addColor(QColor(0x00, 0xAE, 0xFF));
+	addColor(QColor(0x00, 0x78, 0xB0));
+}
+
+void TagWidget::setCompleter(QCompleter *completer)
+{
+	m_completer = completer;
+	m_completer->setWidget(this);
+	connect(m_completer, SIGNAL(activated(QString)), this, SLOT(completionSelected(QString)));
+}
+
+QPair<int,int> TagWidget::getCursorTagPosition() {
+	int i = 0, start = 0, end = 0;
+	/* Parse string near cursor */
+	i = cursorPosition();
+	while (--i > 0) {
+		if (text().at(i) == ',') {
+			if (i > 0 && text().at(i-1) != '\\') {
+				i++;
+				break;
+			}
+		}
+	}
+	start = i;
+	while (++i < text().length()) {
+		if (text().at(i) == ',') {
+			if (i > 0 && text().at(i-1) != '\\')
+				break;
+		}
+	}
+	end = i;
+	if (start < 0 || end < 0) {
+		start = 0;
+		end = 0;
+	}
+	return QPair<int,int>(start,end);
+}
+
+enum ParseState {FINDSTART, FINDEND};
+
+void TagWidget::highlight() {
+	int i = 0, start = 0, end = 0;
+	ParseState state = FINDEND;
+	removeAllBlocks();
+
+	while(i < text().length()) {
+		if (text().at(i) == ',') {
+			if (state == FINDSTART) {
+				/* Detect empty tags */
+			} else if (state == FINDEND) {
+				/* Found end of tag */
+				if (i > 1) {
+					if(text().at(i-1) != '\\') {
+						addBlock(start, end);
+						state = FINDSTART;
+					}
+				} else {
+					state = FINDSTART;
+				}
+			}
+		} else if (text().at(i) == ' ') {
+			/* Handled */
+		} else {
+			/* Found start of tag */
+			if (state == FINDSTART) {
+				state = FINDEND;
+				start = i;
+			} else if (state == FINDEND) {
+				end = i;
+			}
+		}
+		i++;
+	}
+	if (state == FINDEND) {
+		if (end < start)
+			end = text().length()-1;
+		if (text().length() > 0)
+			addBlock(start, end);
+	}
+}
+
+void TagWidget::reparse()
+{
+	highlight();
+	QPair<int,int> pos = getCursorTagPosition();
+	QString currentText;
+	if (pos.first >= 0 && pos.second > 0)
+		currentText = text().mid(pos.first, pos.second-pos.first).trimmed();
+	else
+		currentText = "";
+	if (m_completer) {
+		m_completer->setCompletionPrefix(currentText);
+		m_completer->complete();
+	}
+}
+
+void TagWidget::completionSelected(QString completion) {
+	QPair <int,int> pos;
+	pos = getCursorTagPosition();
+	if (pos.first >= 0 && pos.second > 0) {
+		setText(text().remove(pos.first, pos.second-pos.first).insert(pos.first, completion));
+		setCursorPosition(pos.first+completion.length());
+	}
+	else {
+		setText(completion.append(", "));
+		setCursorPosition(text().length());
+	}
+}
+
+void TagWidget::setCursorPosition(int position) {
+	blockSignals(true);
+	GroupedLineEdit::setCursorPosition(position);
+	blockSignals(false);
+}
+
+void TagWidget::setText(QString text) {
+	blockSignals(true);
+	GroupedLineEdit::setText(text);
+	blockSignals(false);
+	highlight();
+}
+
+void TagWidget::clear() {
+	blockSignals(true);
+	GroupedLineEdit::clear();
+	blockSignals(false);
+}