SCM Plugin: Option to merge constellation lines into polylines (Stellarium#4563)

* implement mergeLinesIntoPolylines function

* do not create working copy

* [skip ci] update changelog

* increase code readability

Author: xLPMG

plugins/SkyCultureMaker/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Version 1.0.1
 
+* New Feature: Option to automatically merge lines into polylines on export
 * Fix: Drawn constellations are not reset after "Export and Exit"
 * Fix: "Export and Exit" exits even when export failed, deleting all unsaved progress
 * Fix: Stop drawing line key (Double Right Click) only works when Star/DSO is selected

plugins/SkyCultureMaker/src/ScmConstellation.cpp

@@ -188,7 +188,7 @@ void scm::ScmConstellation::drawNames(StelCore *core, StelPainter &sPainter) con
 	drawNames(core, sPainter, defaultConstellationNameColor);
 }
 
-QJsonObject scm::ScmConstellation::toJson(const QString &skyCultureId) const
+QJsonObject scm::ScmConstellation::toJson(const QString &skyCultureId, const bool mergeLines) const
 {
 	QJsonObject json;
 
@@ -212,6 +212,11 @@ QJsonObject scm::ScmConstellation::toJson(const QString &skyCultureId) const
 		}
 	}
 
+	if (mergeLines)
+	{
+		mergeLinesIntoPolylines(linesArray);
+	}
+
 	json["id"]    = "CON " + skyCultureId + " " + id;
 	json["lines"] = linesArray;
 	if (artwork.getHasArt() && !artworkPath.isEmpty())
@@ -284,3 +289,82 @@ void scm::ScmConstellation::show()
 {
 	isHidden = false;
 }
+
+void scm::ScmConstellation::mergeLinesIntoPolylines(QJsonArray &lines) const
+{
+	if (lines.size() < 2)
+	{
+		// Nothing to merge
+		return;
+	}
+
+	// Step 1: merge line ends with other line starts
+	for (int growableLineIdx = 0; growableLineIdx < lines.size(); ++growableLineIdx)
+	{
+		QJsonArray growableLine = lines.at(growableLineIdx).toArray();
+
+		// Look for a line that starts where the growableLine ends
+		for (int attachableLineIdx = growableLineIdx + 1; attachableLineIdx < lines.size(); ++attachableLineIdx)
+		{
+			QJsonArray attachableLine = lines.at(attachableLineIdx).toArray();
+
+			// Merge attachableLine into growableLine
+			if (growableLine.last() == attachableLine.first())
+			{
+				// Append all points from attachableLine except the first (which is duplicate)
+				attachableLine.removeFirst();
+				for (QJsonValue attachableLinePoint : attachableLine)
+				{
+					growableLine.append(attachableLinePoint);
+				}
+				
+				// Update the merged lines array
+				lines[growableLineIdx] = growableLine;
+				lines.removeAt(attachableLineIdx);
+
+				// Recheck the merged line
+				--growableLineIdx;
+				// Reset j to growableLineIdx + 1 to continue merging
+				attachableLineIdx = growableLineIdx + 1;
+				break;
+			}
+		}
+	}
+
+	// Step 2: merge line starts with other line ends
+	for (int growableLineIdx = 0; growableLineIdx < lines.size(); ++growableLineIdx)
+	{
+		QJsonArray growableLine = lines.at(growableLineIdx).toArray();
+
+		// Look for a line that ends where the growableLine starts
+		for (int attachableLineIdx = growableLineIdx + 1; attachableLineIdx < lines.size(); ++attachableLineIdx)
+		{
+			QJsonArray attachableLine = lines.at(attachableLineIdx).toArray();
+
+			if (growableLine.first() == attachableLine.last())
+			{
+				QJsonArray newGrowableLine;
+				// Prepend all points from attachableLine except the last (which is duplicate)
+				attachableLine.removeLast();
+				for (QJsonValue attachableLinePoint : attachableLine)
+				{
+					newGrowableLine.append(attachableLinePoint);
+				}
+				for (QJsonValue growableLinePoint : growableLine)
+				{
+					newGrowableLine.append(growableLinePoint);
+				}
+				growableLine = newGrowableLine;
+
+				lines[growableLineIdx] = growableLine;
+				lines.removeAt(attachableLineIdx);
+
+				// Recheck the merged line
+				--growableLineIdx;
+				// Reset j to growableLineIdx + 1 to continue merging
+				attachableLineIdx = growableLineIdx + 1;
+				break;
+			}
+		}
+	}
+}

plugins/SkyCultureMaker/src/ScmConstellation.hpp

@@ -183,9 +183,10 @@ class ScmConstellation
 	  * @brief Returns the constellation data as a JSON object.
 	  * 
 	  * @param skyCultureId The ID of the sky culture to which this constellation belongs.
+	  * @param mergeLines Whether to merge lines into polylines where possible.
 	  * @return QJsonObject 
 	  */
-	QJsonObject toJson(const QString &skyCultureId) const;
+	QJsonObject toJson(const QString &skyCultureId, const bool mergeLines) const;
 
 	/**
 	 * @brief Saves the artwork of this constellation, if art is attached, to the give filepath.
@@ -266,6 +267,28 @@ class ScmConstellation
 	 * @brief Updates the XYZname that is used for the text position.
 	 */
 	void updateTextPosition();
+
+	/**
+	 * @brief Merges individual star lines into polylines where possible.
+	 *
+	 * Merging is done in a two step process, where first the ends of lines are merged
+	 * with the starts of other lines if they match, and secondly the starts of lines are
+	 * merged with the ends of other lines if they match. The lines are processed in the order
+	 * they have been drawn. However, lines which point to opposite directions are not merged.
+	 * 
+	 * Example:
+	 * 
+	 * Input 1: [[1,2], [2,3], [0,1]]
+	 * 
+	 * Output 1: [[0,1,2,3]]
+	 * 
+	 * Input 2: [[1,2], [2,3], [1,0]]
+	 * 
+	 * Output 2: [[1,2,3], [1,0]]
+	 *
+	 * @param lines The individual star lines to merge.
+	 */
+	void mergeLinesIntoPolylines(QJsonArray &lines) const;
 };
 
 } // namespace scm

plugins/SkyCultureMaker/src/ScmSkyCulture.cpp

@@ -67,7 +67,7 @@ std::vector<scm::ScmConstellation> *scm::ScmSkyCulture::getConstellations()
 	return &constellations;
 }
 
-QJsonObject scm::ScmSkyCulture::toJson() const
+QJsonObject scm::ScmSkyCulture::toJson(const bool mergeLines) const
 {
 	QJsonObject scJsonObj;
 	scJsonObj["id"] = id;
@@ -79,7 +79,7 @@ QJsonObject scm::ScmSkyCulture::toJson() const
 	QJsonArray constellationsArray;
 	for (const auto &constellation : constellations)
 	{
-		constellationsArray.append(constellation.toJson(id));
+		constellationsArray.append(constellation.toJson(id, mergeLines));
 	}
 	scJsonObj["constellations"] = constellationsArray;
 

plugins/SkyCultureMaker/src/ScmSkyCulture.hpp

@@ -69,8 +69,10 @@ class ScmSkyCulture
 
 	/**
 	* @brief Returns the sky culture as a JSON object
+	*
+	* @param mergeLines Whether to merge the lines of the constellations into polylines where possible.
 	*/
-	QJsonObject toJson() const;
+	QJsonObject toJson(const bool mergeLines) const;
 
 	/**
 	* @brief Draws the sky culture.

plugins/SkyCultureMaker/src/SkyCultureMaker.cpp

@@ -94,6 +94,7 @@ SkyCultureMaker::SkyCultureMaker()
 	initSetting(conf, "floatingLineColor", "1.0,0.7,0.7");
 	initSetting(conf, "floatingLineAlpha", 0.5);
 	initSetting(conf, "maxSnapRadiusInPixels", 25);
+	initSetting(conf, "mergeLinesOnExport", true);
 
 	conf->endGroup();
 }

plugins/SkyCultureMaker/src/gui/ScmSkyCultureExportDialog.cpp

@@ -69,6 +69,12 @@ void ScmSkyCultureExportDialog::createDialogContent()
 	connect(&StelApp::getInstance(), SIGNAL(languageChanged()), this, SLOT(retranslate()));
 	connect(ui->titleBar, SIGNAL(movedTo(QPoint)), this, SLOT(handleMovedTo(QPoint)));
 	connect(ui->titleBar, &TitleBar::closeClicked, this, &ScmSkyCultureExportDialog::close);
+
+	ui->mergeLinesCB->setChecked(
+		StelApp::getInstance().getSettings()->value("SkyCultureMaker/mergeLinesOnExport", true).toBool());
+	connect(ui->mergeLinesCB, &QCheckBox::toggled, this, [](bool checked)
+	        { StelApp::getInstance().getSettings()->setValue("SkyCultureMaker/mergeLinesOnExport", checked); });
+
 	connect(ui->exportBtn, &QPushButton::clicked, this, &ScmSkyCultureExportDialog::exportSkyCulture);
 	connect(ui->exportAndExitBtn, &QPushButton::clicked, this, &ScmSkyCultureExportDialog::exportAndExitSkyCulture);
 	connect(ui->cancelBtn, &QPushButton::clicked, this, &ScmSkyCultureExportDialog::close);
@@ -146,8 +152,10 @@ bool ScmSkyCultureExportDialog::exportSkyCulture()
 	}
 
 	// Export the sky culture to the index.json file
-	qDebug() << "SkyCultureMaker: Exporting sky culture...";
-	QJsonObject scJsonObject = currentSkyCulture->toJson();
+	bool mergeLinesOnExport =
+		StelApp::getInstance().getSettings()->value("SkyCultureMaker/mergeLinesOnExport", true).toBool();
+	qDebug() << "SkyCultureMaker: Exporting sky culture. Merge lines on export:" << mergeLinesOnExport;
+	QJsonObject scJsonObject = currentSkyCulture->toJson(mergeLinesOnExport);
 	QJsonDocument scJsonDoc(scJsonObject);
 	if (scJsonDoc.isNull() || scJsonDoc.isEmpty())
 	{

plugins/SkyCultureMaker/src/gui/scmSkyCultureExportDialog.ui

@@ -121,6 +121,13 @@
         </property>
        </widget>
       </item>
+      <item>
+       <widget class="QCheckBox" name="mergeLinesCB">
+        <property name="text">
+         <string>Merge constellation lines into polylines on export</string>
+        </property>
+       </widget>
+      </item>
      </layout>
     </widget>
    </item>