TextEditor: Fix is visible check of function hint

Since the FunctionHintProposalWidget is just a proxy witget that uses a
FakeToolTip it is not shown directly so we cannot check the visibility
with isVisible.

Fixes: QTCREATORBUG-25664
Change-Id: I6888e373afcfc79565ce8e3dad1bb05501d58200
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/texteditor/codeassist/codeassistant.cpp

@@ -407,7 +407,7 @@ void CodeAssistantPrivate::finalizeProposal()
 
 bool CodeAssistantPrivate::isDisplayingProposal() const
 {
-    return m_proposalWidget != nullptr && m_proposalWidget->isVisible();
+    return m_proposalWidget != nullptr && m_proposalWidget->proposalIsVisible();
 }
 
 bool CodeAssistantPrivate::isWaitingForProposal() const

src/plugins/texteditor/codeassist/functionhintproposalwidget.cpp

@@ -219,10 +219,15 @@ void FunctionHintProposalWidget::closeProposal()
     abort();
 }
 
+bool FunctionHintProposalWidget::proposalIsVisible() const
+{
+    return d->m_popupFrame->isVisible();
+}
+
 void FunctionHintProposalWidget::abort()
 {
     qApp->removeEventFilter(this);
-    if (d->m_popupFrame->isVisible())
+    if (proposalIsVisible())
         d->m_popupFrame->close();
     deleteLater();
 }

src/plugins/texteditor/codeassist/functionhintproposalwidget.h

@@ -52,6 +52,8 @@ public:
     void updateProposal(const QString &prefix) override;
     void closeProposal() override;
 
+    bool proposalIsVisible() const override;
+
 protected:
     bool eventFilter(QObject *o, QEvent *e) override;
 

src/plugins/texteditor/codeassist/iassistproposalwidget.h

@@ -57,6 +57,8 @@ public:
     virtual void updateProposal(const QString &prefix) = 0;
     virtual void closeProposal() = 0;
 
+    virtual bool proposalIsVisible() const { return isVisible(); }
+
     int basePosition() const;
     void setBasePosition(int basePosition);