ModelEditor: Do not query all files in the project for their mime type

Consulting the mime type database is much too expensive to do it for all
files in a project, so take a shortcut.
Example benchmark: When loading the Qt Creator super project (with all
the commercial plugins) on my Linux machine, with this patch the time
spent in ModelIndexer::scanProject() goes down from ~8 seconds to under
300 milliseconds. Note that the UI is frozen during that period.

Task-number: QTCREATORBUG-18533
Change-Id: Id75d6bbcf37b4f4e41383a089e9e0dc5262cfbae
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Jochen Becher <jochen_becher@gmx.de>

2 files changed, 21 insertions, 13 deletions

diff --git a/src/plugins/modeleditor/modelindexer.cpp b/src/plugins/modeleditor/modelindexer.cpp
index c5a4437508..5186a269f3 100644
--- a/src/plugins/modeleditor/modelindexer.cpp
+++ b/src/plugins/modeleditor/modelindexer.cpp
@@ -399,17 +399,20 @@ void ModelIndexer::scanProject(ProjectExplorer::Project *project)
     QQueue<QueuedFile> filesQueue;
     QSet<QueuedFile> filesSet;
 
-    for (const Utils::FilePath &file : files) {
-        QFileInfo fileInfo = file.toFileInfo();
-        Utils::MimeType mimeType = Utils::mimeTypeForFile(fileInfo);
-        if (mimeType.name() == QLatin1String(Constants::MIME_TYPE_MODEL)) {
-            QueuedFile queuedFile(file.toString(), project, fileInfo.lastModified());
-            filesQueue.append(queuedFile);
-            filesSet.insert(queuedFile);
+    const Utils::MimeType modelMimeType = Utils::mimeTypeForName(Constants::MIME_TYPE_MODEL);
+    if (modelMimeType.isValid()) {
+        for (const Utils::FilePath &file : files) {
+            const QFileInfo fileInfo = file.toFileInfo();
+            if (modelMimeType.suffixes().contains(fileInfo.completeSuffix())) {
+                QueuedFile queuedFile(file.toString(), project, fileInfo.lastModified());
+                filesQueue.append(queuedFile);
+                filesSet.insert(queuedFile);
+            }
         }
     }
 
-    QString defaultModelFile = findFirstModel(project->rootProjectNode());
+    // FIXME: This potentially iterates over all files again.
+    QString defaultModelFile = findFirstModel(project->rootProjectNode(), modelMimeType);
 
     bool filesAreQueued = false;
     {
@@ -460,15 +463,17 @@ void ModelIndexer::scanProject(ProjectExplorer::Project *project)
         emit filesQueued();
 }
 
-QString ModelIndexer::findFirstModel(ProjectExplorer::FolderNode *folderNode)
+QString ModelIndexer::findFirstModel(ProjectExplorer::FolderNode *folderNode,
+                                     const Utils::MimeType &mimeType)
 {
+    if (!mimeType.isValid())
+        return QString();
     foreach (ProjectExplorer::FileNode *fileNode, folderNode->fileNodes()) {
-        Utils::MimeType mimeType = Utils::mimeTypeForFile(fileNode->filePath().toFileInfo());
-        if (mimeType.name() == QLatin1String(Constants::MIME_TYPE_MODEL))
+        if (mimeType.suffixes().contains(fileNode->filePath().toFileInfo().completeSuffix()))
             return fileNode->filePath().toString();
     }
     foreach (ProjectExplorer::FolderNode *subFolderNode, folderNode->folderNodes()) {
-        QString modelFileName = findFirstModel(subFolderNode);
+        QString modelFileName = findFirstModel(subFolderNode, mimeType);
         if (!modelFileName.isEmpty())
             return modelFileName;
     }
diff --git a/src/plugins/modeleditor/modelindexer.h b/src/plugins/modeleditor/modelindexer.h
index da925977b6..708ec26e9b 100644
--- a/src/plugins/modeleditor/modelindexer.h
+++ b/src/plugins/modeleditor/modelindexer.h
@@ -34,6 +34,8 @@ class Project;
 class FolderNode;
 }
 
+namespace Utils { class MimeType; }
+
 namespace ModelEditor {
 namespace Internal {
 
@@ -72,7 +74,8 @@ private:
 
 private:
     void scanProject(ProjectExplorer::Project *project);
-    QString findFirstModel(ProjectExplorer::FolderNode *folderNode);
+    QString findFirstModel(ProjectExplorer::FolderNode *folderNode,
+                           const Utils::MimeType &mimeType);
     void forgetProject(ProjectExplorer::Project *project);
     void removeModelFile(const QString &file, ProjectExplorer::Project *project);
     void removeDiagramReferenceFile(const QString &file, ProjectExplorer::Project *project);