Add wxTextCtrl::PositionToCoords() functions for wxMSW and wxGTK.

The new method allows to find the coordinates in pixels of the given character
in a text control.

Closes #13221.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68450 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/textctrl.h

@@ -574,6 +574,11 @@ public:
     virtual long XYToPosition(long x, long y) const = 0;
     virtual bool PositionToXY(long pos, long *x, long *y) const = 0;
 
+    // translate the given position (which is just an index in the text control)
+    // to client coordinates
+    wxPoint PositionToCoords(long pos) const;
+
+
     virtual void ShowPosition(long pos) = 0;
 
     // find the character at position given in pixels
@@ -592,6 +597,13 @@ protected:
     virtual bool DoLoadFile(const wxString& file, int fileType);
     virtual bool DoSaveFile(const wxString& file, int fileType);
 
+    // Return true if the given position is valid, i.e. positive and less than
+    // the last position.
+    virtual bool IsValidPosition(long pos) const = 0;
+
+    // Default stub implementation of PositionToCoords() always returns
+    // wxDefaultPosition.
+    virtual wxPoint DoPositionToCoords(long pos) const;
 
     // the name of the last file loaded with LoadFile() which will be used by
     // SaveFile() by default
@@ -625,6 +637,12 @@ public:
        wxTextEntryBase::SetValue(value);
     }
 
+protected:
+    virtual bool IsValidPosition(long pos) const
+    {
+        return pos >= 0 && pos <= GetLastPosition();
+    }
+
 private:
     wxDECLARE_NO_COPY_CLASS(wxTextCtrlIface);
 };
@@ -723,6 +741,12 @@ protected:
     virtual bool DoLoadFile(const wxString& file, int fileType);
     virtual bool DoSaveFile(const wxString& file, int fileType);
 
+    // Another wxTextAreaBase override.
+    virtual bool IsValidPosition(long pos) const
+    {
+        return pos >= 0 && pos <= GetLastPosition();
+    }
+
     // implement the wxTextEntry pure virtual method
     virtual wxWindow *GetEditableWindow() { return this; }