Clang: Provide tooltips

This includes also the query data for the help system (F1) for an
identifier under cursor.

Regressions (libclang changes necessary):
 - Function signatures do not contain default values.
 - Aliases are not resolved for/at:
   - template types
   - qualified name of a type

Fixes/Improvements:
 - Resolve "auto"
 - On a template type, show also the template parameter.
 - For a typedef like
     typedef long long superlong;
   the tooltip was "long long superlong", which was confusing.
   Now, "long long" is shown.

New:
 - Show first or \brief paragraph of a documentation comment.
 - Show size of a class at definition.
 - Show size of a field member in class definition.

Task-number: QTCREATORBUG-11259
Change-Id: Ie1a07930d0e882015d07dc43e35bb81a685cdeb8
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/cpptools/baseeditordocumentprocessor.h

@@ -32,6 +32,7 @@
 #include "cpptools_global.h"
 
 #include <texteditor/codeassist/assistinterface.h>
+#include <texteditor/helpitem.h>
 #include <texteditor/quickfix.h>
 #include <texteditor/texteditor.h>
 #include <texteditor/textdocument.h>
@@ -48,6 +49,18 @@ class TextDocument;
 
 namespace CppTools {
 
+// For clang code model only, move?
+struct CPPTOOLS_EXPORT ToolTipInfo {
+    QString text;
+    QString briefComment;
+
+    QStringList qDocIdCandidates;
+    QString qDocMark;
+    TextEditor::HelpItem::Category qDocCategory;
+
+    QString sizeInBytes;
+};
+
 class CPPTOOLS_EXPORT BaseEditorDocumentProcessor : public QObject
 {
     Q_OBJECT
@@ -78,6 +91,7 @@ public:
     virtual QFuture<CursorInfo> cursorInfo(const CursorInfoParams &params) = 0;
     virtual QFuture<CursorInfo> requestLocalReferences(const QTextCursor &cursor) = 0;
     virtual QFuture<SymbolInfo> requestFollowSymbol(int line, int column) = 0;
+    virtual QFuture<ToolTipInfo> toolTipInfo(const QByteArray &codecName, int line, int column);
 
 public:
     using HeaderErrorDiagnosticWidgetCreator = std::function<QWidget*()>;