Add std::string_view constructors to wxString

include/wx/string.h

@@ -44,6 +44,17 @@
 #include "wx/beforestd.h"
 #include <string>
 #include <utility>
+
+// Check if C++17 <string_view> is available
+#ifdef __has_include
+    #if __has_include(<string_view>)
+        #include <string_view>
+        #ifdef __cpp_lib_string_view
+            #define wxHAS_STD_STRING_VIEW
+        #endif
+    #endif
+#endif
+
 #include "wx/afterstd.h"
 
 // by default we cache the mapping of the positions in UTF-8 string to the byte
@@ -1253,9 +1264,19 @@ public:
         { assign(str.c_str(), str.length()); }
   #endif
 
+#ifdef wxHAS_STD_STRING_VIEW
+    wxString(std::wstring_view view)
+        { assign(view.data(), view.length()); }
+#endif  // wxHAS_STD_STRING_VIEW
+
 #ifndef wxNO_IMPLICIT_WXSTRING_ENCODING
   wxString(const std::string& str)
       { assign(str.c_str(), str.length()); }
+
+    #ifdef wxHAS_STD_STRING_VIEW
+        wxString(std::string_view view)
+            { assign(view.data(), view.length()); }
+    #endif  // wxHAS_STD_STRING_VIEW
 #endif // wxNO_IMPLICIT_WXSTRING_ENCODING
 
   // Also always provide explicit conversions to std::[w]string in any case,
@@ -1700,6 +1721,14 @@ public:
     const wxScopedCharBuffer utf8_str() const { return mb_str(wxMBConvUTF8()); }
 #endif // wxUSE_UNICODE_UTF8/wxUSE_UNICODE_WCHAR
 
+// Conversion from std::string_view is the same for both of the two cases above
+#ifdef wxHAS_STD_STRING_VIEW
+    static wxString FromUTF8Unchecked(std::string_view view)
+      { return FromUTF8Unchecked(view.data(), view.length()); }
+    static wxString FromUTF8(std::string_view view)
+      { return FromUTF8(view.data(), view.length()); }
+#endif // wxHAS_STD_STRING_VIEW
+
     const wxScopedCharBuffer ToUTF8() const { return utf8_str(); }
 
     // functions for storing binary data in wxString:

interface/wx/string.h

@@ -68,10 +68,17 @@
         Notice that this constructor supposes that the string contains data in
         the current locale encoding, use FromUTF8() if the string contains
         UTF-8-encoded data instead.
+        - Standard @c std::string_view using implicit wxString::wxString(std::string_view)
+        constructor.
+        Notice that this constructor supposes that the string contains data in
+        the current locale encoding, use FromUTF8() if the string contains
+        UTF-8-encoded data instead.
         - Wide @c wchar_t* string using implicit
         wxString::wxString(const wchar_t*) constructor.
         - Standard @c std::wstring using implicit
         wxString::wxString(const std::wstring&) constructor.
+        - Standard @c std::wstring_view using implicit
+        wxString::wxString(std::wstring_view) constructor.
 
     Notice that many of the constructors are implicit, meaning that you don't
     even need to write them at all to pass the existing string to some
@@ -477,6 +484,16 @@ public:
     */
     wxString(const std::string& str);
 
+    /**
+       Constructs a string from @a str using the using the current locale encoding
+       to convert it to Unicode (wxConvLibc).
+
+       @note Requires the application to be compiled with C++17
+
+       @since 3.3.0
+    */
+    wxString(std::string_view str);
+
     /**
        Constructs a string from @a str.
 
@@ -484,6 +501,15 @@ public:
     */
     wxString(const std::wstring& str);
 
+    /**
+       Constructs a string from @a str.
+
+       @note Requires the application to be compiled with C++17
+
+       @since 3.3.0
+    */
+    wxString(std::wstring_view str);
+
     /**
         String destructor.
 
@@ -1931,11 +1957,15 @@ public:
         The overload taking @c std::string is only available starting with
         wxWidgets 3.1.1.
 
+        The overload taking @c std::string_view is only available starting with
+        wxWidgets 3.3.0 and requires the consumer application to use C++17.
+
         @since 2.8.4
     */
     static wxString FromUTF8(const char* s);
     static wxString FromUTF8(const char* s, size_t len);
     static wxString FromUTF8(const std::string& s);
+    static wxString FromUTF8(std::string_view s);
     ///@}
 
     ///@{
@@ -1955,11 +1985,15 @@ public:
         The overload taking @c std::string is only available starting with
         wxWidgets 3.1.1.
 
+        The overload taking @c std::string_view is only available starting with
+        wxWidgets 3.3.0 and requires the consumer application to use C++17.
+
         @since 2.8.9
     */
     static wxString FromUTF8Unchecked(const char* s);
     static wxString FromUTF8Unchecked(const char* s, size_t len);
     static wxString FromUTF8Unchecked(const std::string& s);
+    static wxString FromUTF8Unchecked(std::string_view s);
     ///@}
 };
 

tests/strings/stdstrings.cpp

@@ -657,3 +657,38 @@ TEST_CASE("StdString::Algo", "[stdstring]")
     std::reverse(s.begin(), s.end());
     CHECK( s == "BA" );
 }
+
+#ifdef wxHAS_STD_STRING_VIEW
+TEST_CASE("StdString::View", "[stdstring]")
+{
+    std::string strStd("std::string value");
+    std::wstring strStdWide(L"std::wstring value");
+
+    std::string_view strStdView(strStd);
+    std::wstring_view strStdWideView(strStdWide);
+
+    wxString s1(strStdView);
+    CHECK( s1 == "std::string value" );
+
+    wxString s2(strStdWideView);
+    CHECK( s2 == "std::wstring value" );
+
+    wxString s3;
+    s3 = strStdView;
+    CHECK( s3 == "std::string value" );
+    s3 = strStdWideView;
+    CHECK( s3 == "std::wstring value" );
+
+    std::string strUTF("\xF0\x9F\x90\xB1\0\xE7\x8C\xAB", 9); /* U+1F431 U+0000 U+732B */
+    std::string_view strViewUTF(strUTF);
+
+    wxString wxstrUTF = wxString::FromUTF8(strViewUTF);
+    CHECK( wxstrUTF.ToStdString(wxConvUTF8) == strUTF );
+    CHECK( wxstrUTF.utf8_string() == strUTF );
+
+    std::string strInvalidUTF("xyz\0\xFF", 5); /* an invalid UTF-8 sequence */
+    std::string_view strViewInvalidUTF(strInvalidUTF);
+
+    CHECK( "" == wxString::FromUTF8(strViewInvalidUTF) );
+}
+#endif