SyntaxHighlighter: Move SyntaxHighlighter to separate thread

This change involves the relocation of SyntaxHighlighter processing
to another thread. The core idea is to create a duplicate of the
original TextDocument using SyntaxHighlighterRunnerPrivate::cloneDocument.
A new SyntaxHighlighter is then instantiated by SyntaxHighLighterCreator
for the cloned document. The entire SyntaxHighLighterCreator class is
moved to a new thread, where it performs highlighting on the cloned
document. Upon completion of the highlighting process, the resultsReady
signal is emitted, and the updated highlighting data is applied to the
original document.

This shift of SyntaxHighlighter to another thread enhances the user
experience by preventing UI slowdowns during the highlighting process.

- Introduction of BaseSyntaxHighlighterRunner as an interface class for
future *SyntaxHighlighterRunner.
- Inclusion of DirectSyntaxHighlighterRunner class for performing
highlighting in the main thread, suitable for syntax highlighters
that cannot be moved to another thread.
- Introduction of ThreadedSyntaxHighlighterRunner class for highlighting
in a separate thread, preventing UI blocking during the process.
- Addition of Result data to the SyntaxHighlighter class to facilitate
data exchange between threads.

Task-number: QTCREATORBUG-28727
Change-Id: I4b6a38d15f5ec9b8828055d38d2a0c6f21a657b4
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
Reviewed-by: David Schulz <david.schulz@qt.io>

1 files changed, 52 insertions, 26 deletions

diff --git a/src/plugins/texteditor/syntaxhighlighter.cpp b/src/plugins/texteditor/syntaxhighlighter.cpp
index 36c4549487..0d7b4d2ede 100644
--- a/src/plugins/texteditor/syntaxhighlighter.cpp
+++ b/src/plugins/texteditor/syntaxhighlighter.cpp
@@ -2,7 +2,6 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
 
 #include "syntaxhighlighter.h"
-#include "textdocument.h"
 #include "textdocumentlayout.h"
 #include "texteditorsettings.h"
 #include "fontsettings.h"
@@ -54,13 +53,13 @@ public:
     void updateFormats(const FontSettings &fontSettings);
 
     FontSettings fontSettings;
-    QVector<QTextCharFormat> formatChanges;
+    QList<QTextCharFormat> formatChanges;
     QTextBlock currentBlock;
     bool rehighlightPending = false;
     bool inReformatBlocks = false;
     TextDocumentLayout::FoldValidator foldValidator;
-    QVector<QTextCharFormat> formats;
-    QVector<std::pair<int,TextStyle>> formatCategories;
+    QList<QTextCharFormat> formats;
+    QList<std::pair<int,TextStyle>> formatCategories;
     QTextCharFormat whitespaceFormat;
     bool noAutomaticHighlighting = false;
 };
@@ -102,8 +101,8 @@ void SyntaxHighlighterPrivate::applyFormatChanges(int from, int charsRemoved, in
 
     QTextLayout *layout = currentBlock.layout();
 
-    QVector<QTextLayout::FormatRange> ranges;
-    QVector<QTextLayout::FormatRange> oldRanges;
+    QList<QTextLayout::FormatRange> ranges;
+    QList<QTextLayout::FormatRange> oldRanges;
     std::tie(oldRanges, ranges)
         = Utils::partition(layout->formats(), [](const QTextLayout::FormatRange &range) {
               return range.format.property(SyntaxHighlight).toBool();
@@ -119,7 +118,7 @@ void SyntaxHighlighterPrivate::applyFormatChanges(int from, int charsRemoved, in
 
     QTextLayout::FormatRange r;
 
-    QVector<QTextLayout::FormatRange> newRanges;
+    QList<QTextLayout::FormatRange> newRanges;
     int i = 0;
     while (i < formatChanges.count()) {
 
@@ -179,6 +178,7 @@ void SyntaxHighlighter::reformatBlocks(int from, int charsRemoved, int charsAdde
 
 void SyntaxHighlighterPrivate::reformatBlocks(int from, int charsRemoved, int charsAdded)
 {
+    Q_Q(SyntaxHighlighter);
     foldValidator.reset();
 
     rehighlightPending = false;
@@ -192,10 +192,12 @@ void SyntaxHighlighterPrivate::reformatBlocks(int from, int charsRemoved, int ch
     if (lastBlock.isValid())
         endPosition = lastBlock.position() + lastBlock.length();
     else
-        endPosition =  doc->lastBlock().position() + doc->lastBlock().length(); //doc->docHandle()->length();
+        endPosition = doc->lastBlock().position() + doc->lastBlock().length();
 
     bool forceHighlightOfNextBlock = false;
 
+    QList<SyntaxHighlighter::Result> vecRes;
+
     while (block.isValid() && (block.position() < endPosition || forceHighlightOfNextBlock)) {
         const int stateBeforeHighlight = block.userState();
 
@@ -203,12 +205,25 @@ void SyntaxHighlighterPrivate::reformatBlocks(int from, int charsRemoved, int ch
 
         forceHighlightOfNextBlock = (block.userState() != stateBeforeHighlight);
 
+        SyntaxHighlighter::Result res;
+        res.m_formatRanges = block.layout()->formats();
+        res.fillByBlock(block);
+        vecRes << res;
+
+        // Sending data to the text editor in chunks of 200 blocks is a sensible approach.
+        // This helps avoid UI slowdowns when applying formatting to the text.
+        if (vecRes.size() >= 200) {
+            emit q->resultsReady(vecRes);
+            vecRes.clear();
+        }
+
         block = block.next();
     }
 
     formatChanges.clear();
 
     foldValidator.finalize();
+    emit q->resultsReady(vecRes);
 }
 
 void SyntaxHighlighterPrivate::reformatBlock(const QTextBlock &block, int from, int charsRemoved, int charsAdded)
@@ -670,22 +685,22 @@ static bool byStartOfRange(const QTextLayout::FormatRange &range, const QTextLay
     return range.start < other.start;
 }
 
-// The formats is passed in by rvalue reference in order to prevent unnecessary copying of its items.
-// After this function returns, the list is modified, and should be considered invalidated!
 void SyntaxHighlighter::setExtraFormats(const QTextBlock &block,
-                                        QVector<QTextLayout::FormatRange> &&formats)
+                                        const QList<QTextLayout::FormatRange> &formats)
 {
     Q_D(SyntaxHighlighter);
 
+    QList<QTextLayout::FormatRange> formatsCopy = formats;
+
     const int blockLength = block.length();
     if (block.layout() == nullptr || blockLength == 0)
         return;
 
     const QString preeditText = block.layout()->preeditAreaText();
     if (!preeditText.isEmpty()) {
-        QVector<QTextLayout::FormatRange> additionalRanges;
+        QList<QTextLayout::FormatRange> additionalRanges;
         const int preeditPosition = block.layout()->preeditAreaPosition();
-        for (QTextLayout::FormatRange &r : formats) {
+        for (QTextLayout::FormatRange &r : formatsCopy) {
             if (r.start >= preeditPosition) {
                 r.start += preeditText.length();
             } else if (r.start + r.length > preeditPosition) {
@@ -696,33 +711,39 @@ void SyntaxHighlighter::setExtraFormats(const QTextBlock &block,
                 r.length = preeditPosition - r.start;
             }
         }
-        formats << additionalRanges;
+        formatsCopy << additionalRanges;
     }
 
-    Utils::sort(formats, byStartOfRange);
+    Utils::sort(formatsCopy, byStartOfRange);
 
-    const QVector<QTextLayout::FormatRange> all = block.layout()->formats();
-    QVector<QTextLayout::FormatRange> previousSemanticFormats;
-    QVector<QTextLayout::FormatRange> formatsToApply;
+    const QList<QTextLayout::FormatRange> all = block.layout()->formats();
+    QList<QTextLayout::FormatRange> previousSemanticFormats;
+    QList<QTextLayout::FormatRange> formatsToApply;
     std::tie(previousSemanticFormats, formatsToApply)
         = Utils::partition(all, [](const QTextLayout::FormatRange &r) {
               return r.format.property(SemanticHighlight).toBool();
           });
 
-    for (auto &format : formats)
+    for (auto &format : formatsCopy)
         format.format.setProperty(SemanticHighlight, true);
 
-    if (formats.size() == previousSemanticFormats.size()) {
+    if (formatsCopy.size() == previousSemanticFormats.size()) {
         Utils::sort(previousSemanticFormats, byStartOfRange);
         if (formats == previousSemanticFormats)
             return;
     }
 
-    formatsToApply += formats;
+    formatsToApply += formatsCopy;
 
     bool wasInReformatBlocks = d->inReformatBlocks;
     d->inReformatBlocks = true;
     block.layout()->setFormats(formatsToApply);
+
+    SyntaxHighlighter::Result res;
+    res.m_formatRanges = block.layout()->formats();
+    res.fillByBlock(block);
+    emit resultsReady({res});
+
     document()->markContentsDirty(block.position(), blockLength - 1);
     d->inReformatBlocks = wasInReformatBlocks;
 }
@@ -735,7 +756,7 @@ void SyntaxHighlighter::clearExtraFormats(const QTextBlock &block)
     if (block.layout() == nullptr || blockLength == 0)
         return;
 
-    const QVector<QTextLayout::FormatRange> formatsToApply
+    const QList<QTextLayout::FormatRange> formatsToApply
         = Utils::filtered(block.layout()->formats(), [](const QTextLayout::FormatRange &r) {
               return !r.format.property(SemanticHighlight).toBool();
           });
@@ -743,6 +764,12 @@ void SyntaxHighlighter::clearExtraFormats(const QTextBlock &block)
     bool wasInReformatBlocks = d->inReformatBlocks;
     d->inReformatBlocks = true;
     block.layout()->setFormats(formatsToApply);
+
+    SyntaxHighlighter::Result res;
+    res.m_formatRanges = block.layout()->formats();
+    res.fillByBlock(block);
+    emit resultsReady({res});
+
     document()->markContentsDirty(block.position(), blockLength - 1);
     d->inReformatBlocks = wasInReformatBlocks;
 }
@@ -832,7 +859,7 @@ void SyntaxHighlighter::setDefaultTextFormatCategories()
 void SyntaxHighlighter::setTextFormatCategories(int count,
                                                 std::function<TextStyle(int)> formatMapping)
 {
-    QVector<std::pair<int, TextStyle>> categories;
+    QList<std::pair<int, TextStyle>> categories;
     categories.reserve(count);
     for (int i = 0; i < count; ++i)
         categories.append({i, formatMapping(i)});
@@ -848,12 +875,12 @@ void SyntaxHighlighter::setTextFormatCategories(int count,
 
     \sa setDefaultTextFormatCategories()
 */
-void SyntaxHighlighter::setTextFormatCategories(const QVector<std::pair<int, TextStyle>> &categories)
+void SyntaxHighlighter::setTextFormatCategories(const QList<std::pair<int, TextStyle>> &categories)
 {
     Q_D(SyntaxHighlighter);
     d->formatCategories = categories;
     const int maxCategory = Utils::maxElementOr(categories, {-1, C_TEXT}).first;
-    d->formats = QVector<QTextCharFormat>(maxCategory + 1);
+    d->formats = QList<QTextCharFormat>(maxCategory + 1);
     d->updateFormats(TextEditorSettings::fontSettings());
 }
 
@@ -899,4 +926,3 @@ void SyntaxHighlighterPrivate::updateFormats(const FontSettings &fontSettings)
 
 } // namespace TextEditor
 
-#include "moc_syntaxhighlighter.cpp"