Remove extraneous instances of .c_str().

Most of these were just converting char* into std::string back and
forth; some more used ReadUTF8, which was converted to use nicer
STL-style iterators over UTF-8 text.

The remaining ones are:
  * arguments to Expr::From, which we'll change when refactoring
    the expression lexer;
  * arguments to varargs functions, which we'll change when adding
    localization (that requires custom printf-style functions to
    allow for changing argument order);
  * arguments where only string literals are ever passed, which
    are OK;
  * in platform-specific code, which is OK.

src/describescreen.cpp

@@ -14,7 +14,7 @@ void TextWindow::ScreenEditTtfText(int link, uint32_t v) {
     hRequest hr = { v };
     Request *r = SK.GetRequest(hr);
 
-    SS.TW.ShowEditControl(10, r->str.c_str());
+    SS.TW.ShowEditControl(10, r->str);
     SS.TW.edit.meaning = EDIT_TTF_TEXT;
     SS.TW.edit.request = hr;
 }

src/drawconstraint.cpp

@@ -124,7 +124,7 @@ void Constraint::DoLabel(Vector ref, Vector *labelPos, Vector gr, Vector gu) {
 
 
     if(dogd.drawing) {
-        ssglWriteTextRefCenter(s.c_str(), th, ref, gr, gu, LineCallback, this);
+        ssglWriteTextRefCenter(s, th, ref, gr, gu, LineCallback, this);
     } else {
         double l = swidth/2 - sheight/2;
         l = max(l, 5/SS.GW.scale);

src/drawentity.cpp

@@ -447,7 +447,7 @@ void Entity::GenerateBezierCurves(SBezierList *sbl) {
             Vector v = topLeft.Minus(botLeft);
             Vector u = (v.Cross(n)).WithMagnitude(v.Magnitude());
 
-            SS.fonts.PlotString(font.c_str(), str.c_str(), sbl, botLeft, u, v);
+            SS.fonts.PlotString(font, str, sbl, botLeft, u, v);
             break;
         }
 
@@ -610,7 +610,7 @@ void Entity::DrawOrGetDistance(void) {
             std::string str = DescriptionString().substr(5);
             double th = DEFAULT_TEXT_HEIGHT;
             if(dogd.drawing) {
-                ssglWriteText(str.c_str(), th, mm2, u, v, NULL, NULL);
+                ssglWriteText(str, th, mm2, u, v, NULL, NULL);
             } else {
                 Vector pos = mm2.Plus(u.ScaledBy(ssglStrWidth(str, th)/2)).Plus(
                                       v.ScaledBy(ssglStrHeight(th)/2));

src/generate.cpp

@@ -242,7 +242,7 @@ void SolveSpaceUI::GenerateAll(int first, int last, bool andFindFree, bool genFo
             glPushMatrix();
                 glTranslated(left+8, top-20, 0);
                 glScaled(1, -1, 1);
-                ssglBitmapText(msg.c_str(), Vector::From(0, 0, 0));
+                ssglBitmapText(msg, Vector::From(0, 0, 0));
             glPopMatrix();
             glFlush();
             glDrawBuffer(GL_BACK);

src/glhelper.cpp

@@ -40,11 +40,7 @@ static const VectorGlyph &GetVectorGlyph(char32_t chr) {
 double ssglStrWidth(const std::string &str, double h)
 {
     int width = 0;
-    const char *iter = str.c_str();
+    for(char32_t chr : ReadUTF8(str)) {
-    while(*iter) {
-        char32_t chr;
-        iter = ReadUTF8(iter, &chr);
-
         const VectorGlyph &glyph = GetVectorGlyph(chr);
         if(glyph.baseCharacter != 0) {
             const VectorGlyph &baseGlyph = GetVectorGlyph(glyph.baseCharacter);
@@ -149,11 +145,7 @@ void ssglWriteText(const std::string &str, double h, Vector t, Vector u, Vector
 
     double scale = FONT_SCALE(h) / SS.GW.scale;
     Vector o = { 5.0, 5.0 };
-    const char *iter = str.c_str();
+    for(char32_t chr : ReadUTF8(str)) {
-    while(*iter) {
-        char32_t chr;
-        iter = ReadUTF8(iter, &chr);
-
         const VectorGlyph &glyph = GetVectorGlyph(chr);
         o.x += ssglDrawCharacter(glyph, t, o, u, v, scale, fn, fndata);
     }
@@ -678,14 +670,11 @@ void ssglBitmapCharQuad(char32_t chr, double x, double y)
     }
 }
 
-void ssglBitmapText(const char *str, Vector p)
+void ssglBitmapText(const std::string &str, Vector p)
 {
     glEnable(GL_TEXTURE_2D);
     glBegin(GL_QUADS);
-    while(*str) {
+    for(char32_t chr : ReadUTF8(str)) {
-        char32_t chr;
-        str = ReadUTF8(str, &chr);
-
         ssglBitmapCharQuad(chr, p.x, p.y);
         p.x += 8 * ssglBitmapCharWidth(chr);
     }

src/solvespace.cpp

@@ -399,7 +399,7 @@ bool SolveSpaceUI::Autosave()
 void SolveSpaceUI::RemoveAutosave()
 {
     std::string autosaveFile = saveFile + AUTOSAVE_SUFFIX;
-    ssremove(autosaveFile.c_str());
+    ssremove(autosaveFile);
 }
 
 bool SolveSpaceUI::OkayToStartNewFile(void) {

src/solvespace.h

@@ -310,6 +310,25 @@ typedef IdList<Param,hParam> ParamList;
 
 
 // Utility functions that are provided in the platform-independent code.
+class utf8_iterator : std::iterator<std::forward_iterator_tag, char32_t> {
+    const char *p, *n;
+public:
+    utf8_iterator(const char *p) : p(p), n(NULL) {}
+    bool           operator==(const utf8_iterator &i) const { return p==i.p; }
+    bool           operator!=(const utf8_iterator &i) const { return p!=i.p; }
+    ptrdiff_t      operator- (const utf8_iterator &i) const { return p -i.p; }
+    utf8_iterator& operator++()    { **this; p=n; n=NULL; return *this; }
+    utf8_iterator  operator++(int) { utf8_iterator t(*this); operator++(); return t; }
+    char32_t       operator*();
+};
+class ReadUTF8 {
+    const std::string &str;
+public:
+    ReadUTF8(const std::string &str) : str(str) {}
+    utf8_iterator begin() const { return utf8_iterator(&str[0]); }
+    utf8_iterator end()   const { return utf8_iterator(&str[str.length()]); }
+};
+
 void ssglLineWidth(GLfloat width);
 void ssglVertex3v(Vector u);
 void ssglAxisAlignedQuad(double l, double r, double t, double b, bool lone = true);
@@ -345,7 +364,7 @@ void ssglDepthRangeOffset(int units);
 void ssglDepthRangeLockToFront(bool yes);
 void ssglDrawPixelsWithTexture(uint8_t *data, int w, int h);
 void ssglInitializeBitmapFont();
-void ssglBitmapText(const char *str, Vector p);
+void ssglBitmapText(const std::string &str, Vector p);
 void ssglBitmapCharQuad(char32_t chr, double x, double y);
 int ssglBitmapCharWidth(char32_t chr);
 #define TEXTURE_BACKGROUND_IMG  10
@@ -362,8 +381,6 @@ void MakeMatrix(double *mat, double a11, double a12, double a13, double a14,
                              double a31, double a32, double a33, double a34,
                              double a41, double a42, double a43, double a44);
 bool MakeAcceleratorLabel(int accel, char *out);
-const char *ReadUTF8(const char *str, char32_t *chr);
-bool StringAllPrintable(const char *str);
 bool FilenameHasExtension(const std::string &str, const char *ext);
 void Message(const char *str, ...);
 void Error(const char *str, ...);

src/style.cpp

@@ -476,7 +476,7 @@ void TextWindow::ShowListOfStyles(void) {
 void TextWindow::ScreenChangeStyleName(int link, uint32_t v) {
     hStyle hs = { v };
     Style *s = Style::Get(hs);
-    SS.TW.ShowEditControl(12, s->name.c_str());
+    SS.TW.ShowEditControl(12, s->name);
     SS.TW.edit.style = hs;
     SS.TW.edit.meaning = EDIT_STYLE_NAME;
 }

src/textwin.cpp

@@ -248,20 +248,15 @@ void TextWindow::Printf(bool halfLine, const char *fmt, ...) {
                     break;
             }
         } else {
-            char32_t chr;
+            utf8_iterator it2(fmt), it1 = it2++;
-            const char *fmtNext = ReadUTF8(fmt, &chr);
+            strncpy(buf, fmt, it2 - it1);
-            strncpy(buf, fmt, fmtNext - fmt);
+            buf[it2 - it1] = '\0';
-            buf[fmtNext - fmt] = '\0';
         }
 
-        const char *bufIter = buf;
+        for(utf8_iterator it(buf); *it; ++it) {
-        while(*bufIter) {
+            for(int i = 0; i < ssglBitmapCharWidth(*it); i++) {
-            char32_t chr;
-            bufIter = ReadUTF8(bufIter, &chr);
-
-            for(int i = 0; i < ssglBitmapCharWidth(chr); i++) {
                 if(c >= MAX_COLS) goto done;
-                text[r][c] = (i == 0) ? chr : ' ';
+                text[r][c] = (i == 0) ? *it : ' ';
                 meta[r][c].fg = fg;
                 meta[r][c].bg = bg;
                 meta[r][c].bgRgb = bgRgb;
@@ -463,7 +458,7 @@ void TextWindow::DrawOrHitTestIcons(int how, double mx, double my)
             ssglAxisAlignedLineLoop(ox, ox+tw, oy, oy+LINE_HEIGHT);
 
             glColor4d(0, 0, 0, 1);
-            ssglBitmapText(str.c_str(), Vector::From(ox+5, oy-3+LINE_HEIGHT, 0));
+            ssglBitmapText(str, Vector::From(ox+5, oy-3+LINE_HEIGHT, 0));
         } else {
             if(!hoveredIcon ||
                 (hoveredIcon != tooltippedIcon))

src/toolbar.cpp

@@ -233,7 +233,7 @@ bool GraphicsWindow::ToolbarDrawOrHitTest(int mx, int my,
             glPushMatrix();
                 glTranslated(ox+5, oy+3, 0);
                 glScaled(1, -1, 1);
-                ssglBitmapText(str.c_str(), Vector::From(0, 0, 0));
+                ssglBitmapText(str, Vector::From(0, 0, 0));
             glPopMatrix();
         }
         ssglDepthRangeLockToFront(false);

src/ttf.cpp

@@ -213,12 +213,8 @@ static const FT_Outline_Funcs outline_funcs = {
 void TtfFont::PlotString(const std::string &str,
                          SBezierList *sbl, Vector origin, Vector u, Vector v)
 {
-    const char *cstr = str.c_str();
     FT_Pos dx = 0;
-    while(*cstr) {
+    for(char32_t chr : ReadUTF8(str)) {
-        char32_t chr;
-        cstr = ReadUTF8(cstr, &chr);
-
         uint32_t gid = FT_Get_Char_Index(fontFace, chr);
         if (gid == 0) {
             dbp("freetype: CID-to-GID mapping for CID 0x%04x failed: %s; using CID as GID",

src/util.cpp

@@ -25,39 +25,26 @@ std::string SolveSpace::ssprintf(const char *fmt, ...)
     return result;
 }
 
-// See https://github.com/GNOME/glibmm/blob/2fbd9f23/glib/glibmm/ustring.cc#L227
+char32_t utf8_iterator::operator*()
-const char *SolveSpace::ReadUTF8(const char *str, char32_t *result)
 {
-    *result = (unsigned char) *str;
+    const uint8_t *it = (const uint8_t*) this->p;
+    char32_t result = *it;
 
-    if((*result & 0x80) != 0)
+    if((result & 0x80) != 0) {
-    {
       unsigned int mask = 0x40;
 
-      do
+      do {
-      {
+        result <<= 6;
-        *result <<= 6;
+        unsigned int c = (*++it);
-        const unsigned int c = (unsigned char) (*++str);
         mask   <<= 5;
-        *result  += c - 0x80;
+        result  += c - 0x80;
-      }
+      } while((result & mask) != 0);
-      while((*result & mask) != 0);
 
-      *result &= mask - 1;
+      result &= mask - 1;
     }
 
-    return str + 1;
+    this->n = (const char*) (it + 1);
-}
+    return result;
-
-bool SolveSpace::StringAllPrintable(const char *str)
-{
-    const char *t;
-    for(t = str; *t; t++) {
-        if(!(isalnum(*t) || *t == '-' || *t == '_')) {
-            return false;
-        }
-    }
-    return true;
 }
 
 bool SolveSpace::FilenameHasExtension(const std::string &str, const char *ext)