CppEditor: Tell users about clangd configuration files

It's not feasible to map every possible setting into our UI, so instead
teach people how to use the clangd configuration mechanism.

Change-Id: Id11e81e25b687a4f49af4e090203faca3a75722d
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangdclient.cpp

@@ -88,7 +88,6 @@
 #include <QPair>
 #include <QPointer>
 #include <QRegularExpression>
-#include <QStandardPaths>
 #include <QVBoxLayout>
 #include <QWidget>
 #include <QtConcurrent>
@@ -603,10 +602,9 @@ public:
 
 void setupClangdConfigFile()
 {
-    const Utils::FilePath baseDir = Utils::FilePath::fromString(
-                QStandardPaths::writableLocation(QStandardPaths::GenericConfigLocation)) / "clangd";
+    const Utils::FilePath targetConfigFile = CppEditor::ClangdSettings::clangdUserConfigFilePath();
+    const Utils::FilePath baseDir = targetConfigFile.parentDir();
     baseDir.ensureWritableDir();
-    const Utils::FilePath targetConfigFile = baseDir / "config.yaml";
     Utils::FileReader configReader;
     const QByteArray firstLine = "# This file was generated by Qt Creator and will be overwritten "
                                  "unless you remove this line.";

src/plugins/cppeditor/cppcodemodelsettings.cpp

@@ -42,6 +42,7 @@
 #include <QHash>
 #include <QPair>
 #include <QSettings>
+#include <QStandardPaths>
 
 using namespace Utils;
 
@@ -418,6 +419,13 @@ FilePath ClangdSettings::clangdIncludePath() const
     return includePath;
 }
 
+FilePath ClangdSettings::clangdUserConfigFilePath()
+{
+    return FilePath::fromString(
+                QStandardPaths::writableLocation(QStandardPaths::GenericConfigLocation))
+            / "clangd/config.yaml";
+}
+
 void ClangdSettings::loadSettings()
 {
     Utils::fromSettings(clangdSettingsKey(), {}, Core::ICore::settings(), &m_data);

src/plugins/cppeditor/cppcodemodelsettings.h

@@ -156,6 +156,7 @@ public:
     static QVersionNumber clangdVersion(const Utils::FilePath &clangdFilePath);
     QVersionNumber clangdVersion() const { return clangdVersion(clangdFilePath()); }
     Utils::FilePath clangdIncludePath() const;
+    static Utils::FilePath clangdUserConfigFilePath();
 
 #ifdef WITH_TESTS
     static void setUseClangd(bool use);

src/plugins/cppeditor/cppcodemodelsettingspage.cpp

@@ -39,6 +39,7 @@
 #include <utils/pathchooser.h>
 #include <utils/qtcassert.h>
 
+#include <QDesktopServices>
 #include <QFormLayout>
 #include <QGroupBox>
 #include <QHBoxLayout>
@@ -341,6 +342,26 @@ ClangdSettingsWidget::ClangdSettingsWidget(const ClangdSettings::Data &settingsD
         // TODO: Remove once the concept is functional.
         d->sessionsGroupBox->hide();
     }
+
+    const auto configFilesHelpLabel = new QLabel;
+    configFilesHelpLabel->setText(tr("Additional settings are available via "
+            "<a href=\"https://clangd.llvm.org/config\"> clangd configuration files</a>.<br>"
+            "General settings go <a href=\"%1\">here</a> "
+            "and can be overridden per project by putting a .clangd file into "
+            "the project source tree.")
+                .arg(ClangdSettings::clangdUserConfigFilePath().toUserOutput()));
+    connect(configFilesHelpLabel, &QLabel::linkHovered, configFilesHelpLabel, &QLabel::setToolTip);
+    connect(configFilesHelpLabel, &QLabel::linkActivated, [](const QString &link) {
+        if (link.startsWith("https"))
+            QDesktopServices::openUrl(link);
+        else
+            Core::EditorManager::openEditor(Utils::FilePath::fromString(link));
+    });
+    const auto separator = new QFrame;
+    separator->setFrameShape(QFrame::HLine);
+    layout->addWidget(separator);
+    layout->addWidget(configFilesHelpLabel);
+
     layout->addStretch(1);
 
     static const auto setWidgetsEnabled = [](QLayout *layout, bool enabled, const auto &f) -> void {