From 2650a5e6b02f9524e9c17c77fe7d7832f5acbb21 Mon Sep 17 00:00:00 2001
From: Yuri Timenkov <s.kde@timenkov.pro>
Date: Sat, 5 Jul 2025 08:21:13 +0000
Subject: [PATCH] Automatically highlight symbol under cursor

Instead of explicit command to get all highlights of the symbol under
the cursor this send these requests to LSP automatically in background.

Added Next/Previous actions simplify researching the code by allowing
quickly jump around symbol usages.

BUG: 503414
---
 addons/lspclient/CMakeLists.txt               |   1 +
 addons/lspclient/lspclientconfigpage.cpp      |   3 +
 addons/lspclient/lspclientplugin.cpp          |   3 +
 addons/lspclient/lspclientplugin.h            |   1 +
 addons/lspclient/lspclientpluginview.cpp      |  10 +-
 .../lspclient/lspclientsymbolhighlighter.cpp  | 157 ++++++++++++++++++
 addons/lspclient/lspclientsymbolhighlighter.h |  60 +++++++
 addons/lspclient/lspconfigwidget.ui           |  53 +++---
 8 files changed, 264 insertions(+), 24 deletions(-)
 create mode 100644 addons/lspclient/lspclientsymbolhighlighter.cpp
 create mode 100644 addons/lspclient/lspclientsymbolhighlighter.h

diff --git a/addons/lspclient/CMakeLists.txt b/addons/lspclient/CMakeLists.txt
index fcb26731fd..98ad02db99 100644
--- a/addons/lspclient/CMakeLists.txt
+++ b/addons/lspclient/CMakeLists.txt
@@ -27,6 +27,7 @@ target_sources(
     lspclientpluginview.cpp
     lspclientserver.cpp
     lspclientservermanager.cpp
+    lspclientsymbolhighlighter.cpp
     lspclientsymbolview.cpp
     lspclientutils.cpp
     lspsemantichighlighting.cpp
diff --git a/addons/lspclient/lspclientconfigpage.cpp b/addons/lspclient/lspclientconfigpage.cpp
index 83fa669dd3..6f90c5ebae 100644
--- a/addons/lspclient/lspclientconfigpage.cpp
+++ b/addons/lspclient/lspclientconfigpage.cpp
@@ -68,6 +68,7 @@ LSPClientConfigPage::LSPClientConfigPage(QWidget *parent, LSPClientPlugin *plugi
              ui->chkFmtOnSave,
              ui->chkInlayHint,
              ui->chkShowCompl,
+             ui->chkHighlightSymbol,
          }) {
         connect(cb, &QCheckBox::toggled, this, &LSPClientConfigPage::changed);
     }
@@ -133,6 +134,7 @@ void LSPClientConfigPage::apply()
     m_plugin->m_autoImport = ui->chkAutoImport->isChecked();
     m_plugin->m_fmtOnSave = ui->chkFmtOnSave->isChecked();
     m_plugin->m_inlayHints = ui->chkInlayHint->isChecked();
+    m_plugin->m_highLightSymbol = ui->chkHighlightSymbol->isChecked();
 
     m_plugin->m_diagnostics = ui->chkDiagnostics->isChecked();
     m_plugin->m_messages = ui->chkMessages->isChecked();
@@ -178,6 +180,7 @@ void LSPClientConfigPage::resetUiTo(const LSPClientPluginOptions &options)
     ui->chkAutoImport->setChecked(options.m_autoImport);
     ui->chkFmtOnSave->setChecked(options.m_fmtOnSave);
     ui->chkInlayHint->setChecked(options.m_inlayHints);
+    ui->chkHighlightSymbol->setChecked(options.m_highLightSymbol);
 
     ui->chkDiagnostics->setChecked(options.m_diagnostics);
     ui->chkMessages->setChecked(options.m_messages);
diff --git a/addons/lspclient/lspclientplugin.cpp b/addons/lspclient/lspclientplugin.cpp
index d1becb8dc1..3d608a569c 100644
--- a/addons/lspclient/lspclientplugin.cpp
+++ b/addons/lspclient/lspclientplugin.cpp
@@ -45,6 +45,7 @@ static constexpr char CONFIG_BLOCKED_COMMANDS[] = "BlockedServerCommandLines";
 static constexpr char CONFIG_FORMAT_ON_SAVE[] = "FormatOnSave";
 static constexpr char CONFIG_INLAY_HINT[] = "InlayHints";
 static constexpr char CONFIG_SHOW_COMPL[] = "ShowCompletions";
+static constexpr char CONFIG_HIGHLIGHT_SYMBOL[] = "HighlightSymbol";
 
 K_PLUGIN_FACTORY_WITH_JSON(LSPClientPluginFactory, "lspclientplugin.json", registerPlugin<LSPClientPlugin>();)
 
@@ -135,6 +136,7 @@ void LSPClientPlugin::readConfig()
     m_autoImport = config.readEntry(CONFIG_AUTO_IMPORT, defaults.m_autoImport);
     m_fmtOnSave = config.readEntry(CONFIG_FORMAT_ON_SAVE, defaults.m_fmtOnSave);
     m_inlayHints = config.readEntry(CONFIG_INLAY_HINT, defaults.m_inlayHints);
+    m_highLightSymbol = config.readEntry(CONFIG_HIGHLIGHT_SYMBOL, true);
 
     m_diagnostics = config.readEntry(CONFIG_DIAGNOSTICS, defaults.m_diagnostics);
     m_messages = config.readEntry(CONFIG_MESSAGES, defaults.m_messages);
@@ -178,6 +180,7 @@ void LSPClientPlugin::writeConfig() const
     config.writeEntry(CONFIG_FORMAT_ON_SAVE, m_fmtOnSave);
     config.writeEntry(CONFIG_INLAY_HINT, m_inlayHints);
     config.writeEntry(CONFIG_SHOW_COMPL, m_showCompl);
+    config.writeEntry(CONFIG_HIGHLIGHT_SYMBOL, m_highLightSymbol);
 
     // write allow + block lists as two separate keys
     QStringList allowed, blocked;
diff --git a/addons/lspclient/lspclientplugin.h b/addons/lspclient/lspclientplugin.h
index 8ede057f1f..6240bf2572 100644
--- a/addons/lspclient/lspclientplugin.h
+++ b/addons/lspclient/lspclientplugin.h
@@ -43,6 +43,7 @@ struct LSPClientPluginOptions {
     bool m_autoImport = true;
     bool m_fmtOnSave = false;
     bool m_inlayHints = false;
+    bool m_highLightSymbol = true;
 
     bool m_diagnostics = true;
     bool m_messages = true;
diff --git a/addons/lspclient/lspclientpluginview.cpp b/addons/lspclient/lspclientpluginview.cpp
index 72186e981a..0418559b70 100644
--- a/addons/lspclient/lspclientpluginview.cpp
+++ b/addons/lspclient/lspclientpluginview.cpp
@@ -12,6 +12,7 @@
 #include "lspclienthover.h"
 #include "lspclientplugin.h"
 #include "lspclientservermanager.h"
+#include "lspclientsymbolhighlighter.h"
 #include "lspclientsymbolview.h"
 #include "lspclientutils.h"
 #include "texthint/KateTextHintManager.h"
@@ -454,6 +455,7 @@ class LSPClientPluginViewImpl : public QObject, public KXMLGUIClient
     };
 
     LSPDiagnosticProvider m_diagnosticProvider;
+    LSPClientSymbolHighlighter m_symbolHighlighter;
 
 public:
     LSPClientPluginViewImpl(LSPClientPlugin *plugin, KTextEditor::MainWindow *mainWin, std::shared_ptr<LSPClientServerManager> serverManager)
@@ -468,6 +470,7 @@ public:
         , m_semHighlightingManager(m_serverManager)
         , m_inlayHintsHandler(m_serverManager, this)
         , m_diagnosticProvider(mainWin, this)
+        , m_symbolHighlighter(actionCollection())
     {
         KXMLGUIClient::setComponentName(QStringLiteral("lspclient"), i18n("LSP Client"));
         setXMLFile(QStringLiteral("ui.rc"));
@@ -661,7 +664,6 @@ public:
         connect(this, &self_type::ctrlClickDefRecieved, this, &self_type::onCtrlMouseMove);
 
         configUpdated();
-        updateState();
 
         m_mainWindow->guiFactory()->addClient(this);
     }
@@ -2297,6 +2299,12 @@ public:
         actionCollection()->action(QStringLiteral("lspclient_rename"))->setVisible(server != nullptr);
         actionCollection()->action(QStringLiteral("lspclient_other_menu"))->setVisible(server != nullptr);
 
+        if (m_plugin->m_highLightSymbol) {
+            m_symbolHighlighter.attach(activeView, server);
+        } else {
+            m_symbolHighlighter.attach(nullptr, nullptr);
+        }
+
         if (m_findDef) {
             m_findDef->setEnabled(defEnabled);
         }
diff --git a/addons/lspclient/lspclientsymbolhighlighter.cpp b/addons/lspclient/lspclientsymbolhighlighter.cpp
new file mode 100644
index 0000000000..0176675b68
--- /dev/null
+++ b/addons/lspclient/lspclientsymbolhighlighter.cpp
@@ -0,0 +1,157 @@
+/*
+ *    SPDX-FileCopyrightText: 2025 Yuri Timenkov <yuri@timenkov.pro>
+ *
+ *    SPDX-License-Identifier: MIT
+ */
+
+#include "lspclientsymbolhighlighter.h"
+
+#include "lspclientservermanager.h"
+
+#include <KActionCollection>
+#include <KLocalizedString>
+#include <KTextEditor/Document>
+#include <KTextEditor/Editor>
+#include <KTextEditor/MainWindow>
+#include <KTextEditor/View>
+
+LSPClientSymbolHighlighter::LSPClientSymbolHighlighter(KActionCollection *actions)
+    : m_highlightAttribute(new KTextEditor::Attribute())
+{
+    m_highlightDelayTimer.setSingleShot(true);
+    m_highlightDelayTimer.setInterval(100);
+    connect(&m_highlightDelayTimer, &QTimer::timeout, this, &LSPClientSymbolHighlighter::highlight);
+
+    m_requestTimeout.setSingleShot(true);
+    m_requestTimeout.setInterval(1000);
+    connect(&m_requestTimeout, &QTimer::timeout, this, &LSPClientSymbolHighlighter::cancelRequest);
+
+    m_nextSymbolHighlight = actions->addAction(QStringLiteral("lspclient_next_symbol_highlight"), this, &LSPClientSymbolHighlighter::gotoNextHighlight);
+    m_nextSymbolHighlight->setText(i18n("Go to next symbol highlight"));
+    m_prevSymbolHighlight = actions->addAction(QStringLiteral("lspclient_prev_symbol_highlight"), this, &LSPClientSymbolHighlighter::gotoPrevHighlight);
+    m_prevSymbolHighlight->setText(i18n("Go to previous symbol highlight"));
+
+    connect(KTextEditor::Editor::instance(), &KTextEditor::Editor::configChanged, this, &LSPClientSymbolHighlighter::themeChange);
+    themeChange(KTextEditor::Editor::instance());
+}
+
+void LSPClientSymbolHighlighter::attach(KTextEditor::View *view, std::shared_ptr<LSPClientServer> server)
+{
+    bool actionsEnabled;
+    if (!view || !server) {
+        m_currentView = nullptr;
+        m_currentServer = nullptr;
+        actionsEnabled = false;
+    } else {
+        m_currentView = view;
+        m_currentServer = std::move(server);
+        actionsEnabled = true;
+        connect(view, &KTextEditor::View::cursorPositionChanged, this, &LSPClientSymbolHighlighter::cursorPositionChanged, Qt::UniqueConnection);
+        connect(view, &KTextEditor::View::selectionChanged, this, &LSPClientSymbolHighlighter::rangesInvalidated, Qt::UniqueConnection);
+    }
+    m_nextSymbolHighlight->setEnabled(actionsEnabled);
+    m_prevSymbolHighlight->setEnabled(actionsEnabled);
+
+    rangesInvalidated();
+}
+
+void LSPClientSymbolHighlighter::cursorPositionChanged(KTextEditor::View *, const KTextEditor::Cursor &newPosition)
+{
+    if (!m_currentWord.contains(newPosition)) {
+        rangesInvalidated();
+    }
+}
+
+void LSPClientSymbolHighlighter::rangesInvalidated()
+{
+    m_ranges.clear();
+    m_currentWord = KTextEditor::Range::invalid();
+    cancelRequest();
+
+    if (m_currentView && !m_currentView->selection())
+        m_highlightDelayTimer.start();
+    else
+        m_highlightDelayTimer.stop();
+}
+
+void LSPClientSymbolHighlighter::themeChange(KTextEditor::Editor *e)
+{
+    const auto theme = e->theme();
+    m_highlightAttribute->setBackground(QBrush(theme.editorColor(KSyntaxHighlighting::Theme::SearchHighlight)));
+}
+
+void LSPClientSymbolHighlighter::cancelRequest()
+{
+    m_requestHandle.cancel() = {};
+}
+
+void LSPClientSymbolHighlighter::highlight()
+{
+    if (!m_currentView || !m_currentServer)
+        return;
+
+    m_requestTimeout.start();
+    m_requestHandle.cancel() = m_currentServer->documentHighlight(
+        m_currentView->document()->url(),
+        m_currentView->cursorPosition(),
+        this,
+        [this](const QList<LSPDocumentHighlight> &locations) {
+            // By the time we get response view may change.
+            if (!m_currentView)
+                return;
+
+            m_ranges.resize(locations.length());
+
+            std::ranges::transform(locations, m_ranges.begin(), [attr = m_highlightAttribute, document = m_currentView->document()](auto &loc) {
+                auto mr = std::unique_ptr<KTextEditor::MovingRange>(document->newMovingRange(loc.range));
+                mr->setZDepth(-90000.0); // Set the z-depth to slightly worse than the selection
+                mr->setAttribute(attr);
+                mr->setAttributeOnlyForViews(true);
+                return mr;
+            });
+
+            if (auto it = findRange(m_currentView->cursorPosition()); it != m_ranges.end()) {
+                m_currentWord = **it;
+            }
+        });
+}
+
+LSPClientSymbolHighlighter::MovingRangeList::iterator LSPClientSymbolHighlighter::findRange(const KTextEditor::Cursor &position)
+{
+    return std::find_if(m_ranges.begin(), m_ranges.end(), [&position](auto &range) {
+        return range->contains(position);
+    });
+}
+
+void LSPClientSymbolHighlighter::gotoNextHighlight()
+{
+    if (auto it = findRange(m_currentWord.start()); it != m_ranges.end()) {
+        if (++it == m_ranges.end()) {
+            it = m_ranges.begin();
+        }
+        goToRange(**it);
+    }
+}
+
+void LSPClientSymbolHighlighter::gotoPrevHighlight()
+{
+    if (auto it = findRange(m_currentWord.start()); it != m_ranges.end()) {
+        if (it == m_ranges.begin()) {
+            it = m_ranges.end();
+        }
+        --it;
+
+        goToRange(**it);
+    }
+}
+
+void LSPClientSymbolHighlighter::goToRange(const KTextEditor::MovingRange &range)
+{
+    if (!m_currentView)
+        return;
+
+    // Update the current word position to skip new query to LSP
+    // when signal is received.
+    m_currentWord = range;
+    m_currentView->setCursorPosition(range.start().toCursor());
+}
diff --git a/addons/lspclient/lspclientsymbolhighlighter.h b/addons/lspclient/lspclientsymbolhighlighter.h
new file mode 100644
index 0000000000..b426daefe8
--- /dev/null
+++ b/addons/lspclient/lspclientsymbolhighlighter.h
@@ -0,0 +1,60 @@
+/*
+ *    SPDX-FileCopyrightText: 2025 Yuri Timenkov <yuri@timenkov.pro>
+ *
+ *    SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include "lspclientserver.h"
+
+#include <KTextEditor/Attribute>
+
+namespace KTextEditor
+{
+class Cursor;
+class Editor;
+class MovingRange;
+class View;
+}
+class KActionCollection;
+
+// Highlights all occurrences of symbol under the cursor
+class LSPClientSymbolHighlighter : public QObject
+{
+public:
+    explicit LSPClientSymbolHighlighter(KActionCollection *actions);
+
+    void attach(KTextEditor::View *view, std::shared_ptr<LSPClientServer> server);
+
+private:
+    using MovingRangeList = std::vector<std::unique_ptr<KTextEditor::MovingRange>>;
+
+    void cursorPositionChanged(KTextEditor::View *view, const KTextEditor::Cursor &newPosition);
+    void themeChange(KTextEditor::Editor *e);
+
+    void highlight();
+    void rangesInvalidated();
+    void cancelRequest();
+
+    void gotoNextHighlight();
+    void gotoPrevHighlight();
+
+    MovingRangeList::iterator findRange(const KTextEditor::Cursor &position);
+    void goToRange(const KTextEditor::MovingRange &range);
+
+private:
+    KTextEditor::Attribute::Ptr m_highlightAttribute;
+    QAction *m_nextSymbolHighlight;
+    QAction *m_prevSymbolHighlight;
+
+    QPointer<KTextEditor::View> m_currentView;
+    std::shared_ptr<LSPClientServer> m_currentServer;
+
+    KTextEditor::Range m_currentWord;
+    MovingRangeList m_ranges;
+
+    QTimer m_highlightDelayTimer;
+    QTimer m_requestTimeout;
+    LSPClientServer::RequestHandle m_requestHandle;
+};
diff --git a/addons/lspclient/lspconfigwidget.ui b/addons/lspclient/lspconfigwidget.ui
index 12f0a3a05c..ea5fa54917 100644
--- a/addons/lspclient/lspconfigwidget.ui
+++ b/addons/lspclient/lspconfigwidget.ui
@@ -36,7 +36,7 @@
        <item>
         <layout class="QFormLayout" name="formLayout">
          <property name="formAlignment">
-          <set>Qt::AlignHCenter|Qt::AlignTop</set>
+          <set>Qt::AlignmentFlag::AlignHCenter|Qt::AlignmentFlag::AlignTop</set>
          </property>
          <property name="bottomMargin">
           <number>0</number>
@@ -69,133 +69,133 @@
            </property>
           </widget>
          </item>
-         <item row="4" column="0">
+         <item row="5" column="0">
           <widget class="QLabel" name="label_2">
            <property name="text">
             <string>Completions:</string>
            </property>
           </widget>
          </item>
-         <item row="4" column="1">
+         <item row="5" column="1">
           <widget class="QCheckBox" name="chkShowCompl">
            <property name="text">
             <string>Show completions</string>
            </property>
           </widget>
          </item>
-         <item row="5" column="1">
+         <item row="6" column="1">
           <widget class="QCheckBox" name="chkComplDoc">
            <property name="text">
             <string>Show inline docs for selected completion</string>
            </property>
           </widget>
          </item>
-         <item row="6" column="1">
+         <item row="7" column="1">
           <widget class="QCheckBox" name="chkSignatureHelp">
            <property name="text">
             <string>Show function signature when typing a function call</string>
            </property>
           </widget>
          </item>
-         <item row="7" column="1">
+         <item row="8" column="1">
           <widget class="QCheckBox" name="chkComplParens">
            <property name="text">
             <string>Add parentheses upon function completion</string>
            </property>
           </widget>
          </item>
-         <item row="8" column="1">
+         <item row="9" column="1">
           <widget class="QCheckBox" name="chkAutoImport">
            <property name="text">
             <string>Add imports automatically if needed upon completion</string>
            </property>
           </widget>
          </item>
-         <item row="9" column="0">
+         <item row="10" column="0">
           <widget class="QLabel" name="label_5">
            <property name="text">
             <string>Navigation:</string>
            </property>
           </widget>
          </item>
-         <item row="9" column="1">
+         <item row="10" column="1">
           <widget class="QCheckBox" name="chkRefDeclaration">
            <property name="text">
             <string>Count declarations when searching for references to a symbol</string>
            </property>
           </widget>
          </item>
-         <item row="10" column="1">
+         <item row="11" column="1">
           <widget class="QCheckBox" name="chkAutoHover">
            <property name="text">
             <string>Show information about currently hovered symbol</string>
            </property>
           </widget>
          </item>
-         <item row="11" column="1">
+         <item row="12" column="1">
           <widget class="QCheckBox" name="chkHighlightGoto">
            <property name="text">
             <string>Highlight target line when hopping to it</string>
            </property>
           </widget>
          </item>
-         <item row="12" column="0">
+         <item row="14" column="0">
           <widget class="QLabel" name="label_3">
            <property name="text">
             <string>Server:</string>
            </property>
           </widget>
          </item>
-         <item row="12" column="1">
+         <item row="14" column="1">
           <widget class="QCheckBox" name="chkDiagnostics">
            <property name="text">
             <string>Show program diagnostics</string>
            </property>
           </widget>
          </item>
-         <item row="13" column="1">
+         <item row="15" column="1">
           <widget class="QCheckBox" name="chkMessages">
            <property name="text">
             <string>Show notifications from the LSP server</string>
            </property>
           </widget>
          </item>
-         <item row="14" column="1">
+         <item row="16" column="1">
           <widget class="QCheckBox" name="chkIncrementalSync">
            <property name="text">
             <string>Incrementally synchronize documents with the LSP server</string>
            </property>
           </widget>
          </item>
-         <item row="15" column="0">
+         <item row="17" column="0">
           <widget class="QLabel" name="label_6">
            <property name="text">
             <string>Document outline:</string>
            </property>
           </widget>
          </item>
-         <item row="15" column="1">
+         <item row="17" column="1">
           <widget class="QCheckBox" name="chkSymbolSort">
            <property name="text">
             <string>Sort symbols alphabetically</string>
            </property>
           </widget>
          </item>
-         <item row="16" column="1">
+         <item row="18" column="1">
           <widget class="QCheckBox" name="chkSymbolDetails">
            <property name="text">
             <string>Display additional details for symbols</string>
            </property>
           </widget>
          </item>
-         <item row="17" column="1">
+         <item row="19" column="1">
           <widget class="QCheckBox" name="chkSymbolTree">
            <property name="text">
             <string>Present symbols in a hierarchy instead of a flat list</string>
            </property>
           </widget>
          </item>
-         <item row="18" column="1">
+         <item row="20" column="1">
           <layout class="QHBoxLayout" name="horizontalLayout_4">
            <property name="leftMargin">
             <number>20</number>
@@ -212,12 +212,19 @@
            </item>
           </layout>
          </item>
+         <item row="13" column="1">
+          <widget class="QCheckBox" name="chkHighlightSymbol">
+           <property name="text">
+            <string>Highlight symbol under cursor</string>
+           </property>
+          </widget>
+         </item>
         </layout>
        </item>
        <item>
         <spacer name="verticalSpacer">
          <property name="orientation">
-          <enum>Qt::Vertical</enum>
+          <enum>Qt::Orientation::Vertical</enum>
          </property>
          <property name="sizeHint" stdset="0">
           <size>
@@ -254,8 +261,8 @@
           </widget>
          </item>
          <item>
-          <widget class="KUrlRequester" name="edtConfigPath">
-           <property name="text">
+          <widget class="KUrlRequester" name="edtConfigPath" native="true">
+           <property name="text" stdset="0">
             <string/>
            </property>
           </widget>
-- 
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