Don't call wxTextMeasure::BeginMeasuring() when using non-native wxDC.

This is useless as we don't use wxTextMeasure in this case but just forward to
the wxDC itself, and also results in an assert in wxMSW wxTextMeasure
implementation.

Closes #14916.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73292 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/include/wx/private/textmeasure.h b/include/wx/private/textmeasure.h
index 4788c992eda29c2ca3a55bb7356065538519396e..393946e7bf476453e280045f234321f409853c5c 100644 (file)
--- a/include/wx/private/textmeasure.h
+++ b/include/wx/private/textmeasure.h
@@ -75,6 +75,9 @@ public:
     virtual void BeginMeasuring() { }
     virtual void EndMeasuring() { }
 
+    // This is another method which is only used by MeasuringGuard.
+    bool IsUsingDCImpl() const { return m_useDCImpl; }
+
 protected:
     // RAII wrapper for the two methods above.
     class MeasuringGuard
@@ -82,12 +85,16 @@ protected:
     public:
         MeasuringGuard(wxTextMeasureBase& tm) : m_tm(tm)
         {
-            m_tm.BeginMeasuring();
+            // BeginMeasuring() should only be called if we have a native DC,
+            // so don't call it if we delegate to a DC of unknown type.
+            if ( !m_tm.IsUsingDCImpl() )
+                m_tm.BeginMeasuring();
         }
 
         ~MeasuringGuard()
         {
-            m_tm.EndMeasuring();
+            if ( !m_tm.IsUsingDCImpl() )
+                m_tm.EndMeasuring();
         }
 
     private: