From cb2474f0408bb02cf1905126cd29e730867a187f Mon Sep 17 00:00:00 2001
From: Vadim Zeitlin <vadim@zeitlins.org>
Date: Thu, 24 Nov 2016 02:12:08 +0100
Subject: [PATCH] Use wxDC::GetPartialTextExtents() in wxStaticText::Wrap()

This is more efficient than calling GetTextExtent() with a growing string in a
loop as we used to do (with ~60 character string wrapped on 2 lines it brings
wrapping time down from 4ms to 600us).

It is also slightly more accurate under macOS, even though it's still off and
some text may be truncated when wrapping.
---
 src/common/stattextcmn.cpp | 70 ++++++++++++++++++++------------------
 1 file changed, 36 insertions(+), 34 deletions(-)

diff --git a/src/common/stattextcmn.cpp b/src/common/stattextcmn.cpp
index f2960c928b..eb8f05bf3c 100644
--- a/src/common/stattextcmn.cpp
+++ b/src/common/stattextcmn.cpp
@@ -40,6 +40,8 @@
 
 #include "wx/private/markupparser.h"
 
+#include <algorithm>
+
 extern WXDLLEXPORT_DATA(const char) wxStaticTextNameStr[] = "staticText";
 
 // ----------------------------------------------------------------------------
@@ -103,52 +105,52 @@ wxCONSTRUCTOR_6( wxStaticText, wxWindow*, Parent, wxWindowID, Id, \
 
 void wxTextWrapper::Wrap(wxWindow *win, const wxString& text, int widthMax)
 {
-    wxString line;
+    const wxClientDC dc(win);
 
-    wxString::const_iterator lastSpace = text.end();
-    wxString::const_iterator lineStart = text.begin();
-    for ( wxString::const_iterator p = lineStart; ; ++p )
+    const wxArrayString ls = wxSplit(text, '\n', '\0');
+    for ( wxArrayString::const_iterator i = ls.begin(); i != ls.end(); ++i )
     {
-        if ( IsStartOfNewLine() )
+        wxString line = *i;
+
+        if ( i != ls.begin() )
         {
+            // Do this even if the line is empty, except if it's the first one.
             OnNewLine();
-
-            lastSpace = text.end();
-            line.clear();
-            lineStart = p;
         }
 
-        if ( p == text.end() || *p == wxT('\n') )
+        for ( bool newLine = false; !line.empty(); newLine = true )
         {
-            DoOutputLine(line);
+            if ( newLine )
+                OnNewLine();
 
-            if ( p == text.end() )
-                break;
-        }
-        else // not EOL
-        {
-            if ( *p == wxT(' ') )
-                lastSpace = p;
+            wxArrayInt widths;
+            dc.GetPartialTextExtents(line, widths);
 
-            line += *p;
+            const size_t posEnd = std::lower_bound(widths.begin(),
+                                                   widths.end(),
+                                                   widthMax) - widths.begin();
 
-            if ( widthMax >= 0 && lastSpace != text.end() )
+            // Does the entire remaining line fit?
+            if ( posEnd == line.length() )
             {
-                int width;
-                win->GetTextExtent(line, &width, NULL);
-
-                if ( width > widthMax )
-                {
-                    // remove the last word from this line
-                    line.erase(lastSpace - lineStart, p + 1 - lineStart);
-                    DoOutputLine(line);
-
-                    // go back to the last word of this line which we didn't
-                    // output yet
-                    p = lastSpace;
-                }
+                DoOutputLine(line);
+                break;
             }
-            //else: no wrapping at all or impossible to wrap
+
+            // Find the last word to chop off.
+            const size_t lastSpace = line.rfind(' ', posEnd);
+            if ( lastSpace == wxString::npos )
+            {
+                // No spaces, so can't wrap.
+                DoOutputLine(line);
+                break;
+            }
+
+            // Output the part that fits.
+            DoOutputLine(line.substr(0, lastSpace));
+
+            // And redo the layout with the rest.
+            line = line.substr(lastSpace + 1);
         }
     }
 }