Clang: Fix delayed reparse of dirty and visible but not current documents

1. Open document foo.h
2. Create a split and open foo.cpp (#including "foo.h")
3. Edit foo.h (e.g. by introducing a syntax error, so that foo.cpp will
   indicate header errors in the toolbar or as info bar)
=> Actual: foo.cpp will be reparsed immediately.
 Expected: foo.cpp should be reparsed after a delay.

This saves resources (cpu time) and minimizes poping up of the header
info bar while editing header files in splits.

Regression introduced by

    commit 380d756a03
    Clang: Hook up supportive translation unit on first edit

Change-Id: Ib5fd90e49415dfc3aefacab7cd627b0e1937f5fc
Reviewed-by: David Schulz <david.schulz@qt.io>

src/tools/clangbackend/ipcsource/clangcodemodelserver.cpp

@@ -50,6 +50,8 @@
 #include <updatetranslationunitsforeditormessage.h>
 #include <updatevisibletranslationunitsmessage.h>
 
+#include <utils/qtcassert.h>
+
 #include <QCoreApplication>
 #include <QDebug>
 
@@ -57,16 +59,21 @@ namespace ClangBackEnd {
 
 ClangCodeModelServer::ClangCodeModelServer()
     : documents(projects, unsavedFiles)
-    , updateDocumentAnnotationsTimeOutInMs(1500)
 {
     updateDocumentAnnotationsTimer.setSingleShot(true);
-
     QObject::connect(&updateDocumentAnnotationsTimer,
                      &QTimer::timeout,
                      [this]() {
         processJobsForDirtyAndVisibleDocuments();
     });
 
+    updateVisibleButNotCurrentDocumentsTimer.setSingleShot(true);
+    QObject::connect(&updateVisibleButNotCurrentDocumentsTimer,
+                     &QTimer::timeout,
+                     [this]() {
+        processJobsForDirtyAndVisibleButNotCurrentDocuments();
+    });
+
     QObject::connect(documents.clangFileSystemWatcher(),
                      &ClangFileSystemWatcher::fileChanged,
                      [this](const Utf8String &filePath) {
@@ -265,16 +272,44 @@ bool ClangCodeModelServer::isTimerRunningForTestOnly() const
 
 void ClangCodeModelServer::processJobsForDirtyAndVisibleDocuments()
 {
-    for (const auto &document : documents.documents()) {
-        if (document.isNeedingReparse() && document.isVisibleInEditor()) {
-            DocumentProcessor processor = documentProcessors().processor(document);
-            processor.addJob(createJobRequest(document,
-                                              JobRequest::Type::UpdateDocumentAnnotations,
-                                              PreferredTranslationUnit::PreviouslyParsed));
-        }
-    }
+    processJobsForDirtyCurrentDocument();
+    processTimerForVisibleButNotCurrentDocuments();
+}
 
-    documentProcessors().process();
+void ClangCodeModelServer::processJobsForDirtyCurrentDocument()
+{
+    const auto currentDirtyDocuments = documents.filtered([](const Document &document) {
+        return document.isNeedingReparse() && document.isUsedByCurrentEditor();
+    });
+    QTC_CHECK(currentDirtyDocuments.size() <= 1);
+
+    addAndRunUpdateJobs(currentDirtyDocuments);
+}
+
+void ClangCodeModelServer::addAndRunUpdateJobs(const std::vector<Document> &documents)
+{
+    for (const auto &document : documents) {
+        DocumentProcessor processor = documentProcessors().processor(document);
+        processor.addJob(createJobRequest(document,
+                                          JobRequest::Type::UpdateDocumentAnnotations,
+                                          PreferredTranslationUnit::PreviouslyParsed));
+        processor.process();
+    }
+}
+
+void ClangCodeModelServer::processTimerForVisibleButNotCurrentDocuments()
+{
+    if (documents.dirtyAndVisibleButNotCurrentDocuments().empty()) {
+        updateVisibleButNotCurrentDocumentsTimer.stop();
+    } else {
+        updateVisibleButNotCurrentDocumentsTimer.start(
+                    updateVisibleButNotCurrentDocumentsTimeOutInMs);
+    }
+}
+
+void ClangCodeModelServer::processJobsForDirtyAndVisibleButNotCurrentDocuments()
+{
+    addAndRunUpdateJobs(documents.dirtyAndVisibleButNotCurrentDocuments());
 }
 
 void ClangCodeModelServer::processInitialJobsForDocuments(const std::vector<Document> &documents)
@@ -332,6 +367,11 @@ void ClangCodeModelServer::setUpdateDocumentAnnotationsTimeOutInMsForTestsOnly(i
     updateDocumentAnnotationsTimeOutInMs = value;
 }
 
+void ClangCodeModelServer::setUpdateVisibleButNotCurrentDocumentsTimeOutInMsForTestsOnly(int value)
+{
+    updateVisibleButNotCurrentDocumentsTimeOutInMs = value;
+}
+
 DocumentProcessors &ClangCodeModelServer::documentProcessors()
 {
     if (!documentProcessors_) {