我正在使用 NeHe 的关于 FreeType 和 OpenGL 的教程，并且在命名空间 freetype 中定义 struct font_data 的成员时遇到问题。当我在命名空间中定义其成员时，它不会将 font_data 识别为结构。
CE_Text.h：
#ifndef CE_TEXT
#define CE_TEXT
#include <Common/Headers.h>
/////////////////// MAJOR CREDIT TO NeHe FOR HIS TUTORIAL ON FREETPYE ///////////////////
///Wrap everything in a namespace, that we can use common
///function names like "print" without worrying about
///overlapping with anyone else's code.
namespace freetype {
//Inside of this namespace, give ourselves the ability
//to write just "vector" instead of "std::vector"
using std::vector;
//Ditto for string.
using std::string;
//This holds all of the information related to any
//freetype font that we want to create.
struct font_data{
float h; ///< Holds the height of the font.
GLuint * textures; ///< Holds the texture id's
GLuint list_base; ///< Holds the first display list id
//The init function will create a font of
//of the height h from the file fname.
void init(const char * fname, unsigned int h);
//Free all the resources assosiated with the font.
void clean();
};
//The flagship function of the library - this thing will print
//out text at window coordinates x,y, using the font ft_font.
//The current modelview matrix will also be applied to the text.
void print(const font_data &ft_font, float x, float y, const char *fmt) ;
}
#endif
CE_Text.cpp（我的问题是在 void font_data::init）：
#include <Common/Headers.h>
using namespace freetype;
namespace freetype {
///This function gets the first power of 2 >= the
///int that we pass it.
inline int next_p2 ( int a )
{
int rval=1;
while(rval<a) rval<<=1;
return rval;
}
///Create a display list coresponding to the give character.
void make_dlist ( FT_Face face, char ch, GLuint list_base, GLuint * tex_base ) {
//The first thing we do is get FreeType to render our character
//into a bitmap. This actually requires a couple of FreeType commands:
//Load the Glyph for our character.
if(FT_Load_Glyph( face, FT_Get_Char_Index( face, ch ), FT_LOAD_DEFAULT ))
throw std::runtime_error("FT_Load_Glyph failed");
//Move the face's glyph into a Glyph object.
FT_Glyph glyph;
if(FT_Get_Glyph( face->glyph, &glyph ))
throw std::runtime_error("FT_Get_Glyph failed");
//Convert the glyph to a bitmap.
FT_Glyph_To_Bitmap( &glyph, ft_render_mode_normal, 0, 1 );
FT_BitmapGlyph bitmap_glyph = (FT_BitmapGlyph)glyph;
//This reference will make accessing the bitmap easier
FT_Bitmap& bitmap=bitmap_glyph->bitmap;
//Use our helper function to get the widths of
//the bitmap data that we will need in order to create
//our texture.
int width = next_p2( bitmap.width );
int height = next_p2( bitmap.rows );
//Allocate memory for the texture data.
GLubyte* expanded_data = new GLubyte[ 2 * width * height];
//Here we fill in the data for the expanded bitmap.
//Notice that we are using two channel bitmap (one for
//luminocity and one for alpha), but we assign
//both luminocity and alpha to the value that we
//find in the FreeType bitmap.
//We use the ?: operator so that value which we use
//will be 0 if we are in the padding zone, and whatever
//is the the Freetype bitmap otherwise.
for(int j=0; j <height;j++) {
for(int i=0; i < width; i++){
expanded_data[2*(i+j*width)]= expanded_data[2*(i+j*width)+1] =
(i>=bitmap.width || j>=bitmap.rows) ?
0 : bitmap.buffer[i + bitmap.width*j];
}
}
//Now we just setup some texture paramaters.
glBindTexture( GL_TEXTURE_2D, tex_base[ch]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
//Here we actually create the texture itself, notice
//that we are using GL_LUMINANCE_ALPHA to indicate that
//we are using 2 channel data.
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, width, height,
0, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, expanded_data );
//With the texture created, we don't need to expanded data anymore
delete [] expanded_data;
//So now we can create the display list
glNewList(list_base+ch,GL_COMPILE);
glBindTexture(GL_TEXTURE_2D,tex_base[ch]);
glPushMatrix();
//first we need to move over a little so that
//the character has the right amount of space
//between it and the one before it.
glTranslatef(bitmap_glyph->left,0,0);
//Now we move down a little in the case that the
//bitmap extends past the bottom of the line
//(this is only true for characters like 'g' or 'y'.
glTranslatef(0,bitmap_glyph->top-bitmap.rows,0);
//Now we need to account for the fact that many of
//our textures are filled with empty padding space.
//We figure what portion of the texture is used by
//the actual character and store that information in
//the x and y variables, then when we draw the
//quad, we will only reference the parts of the texture
//that we contain the character itself.
float x=(float)bitmap.width / (float)width,
y=(float)bitmap.rows / (float)height;
//Here we draw the texturemaped quads.
//The bitmap that we got from FreeType was not
//oriented quite like we would like it to be,
//so we need to link the texture to the quad
//so that the result will be properly aligned.
glBegin(GL_QUADS);
glTexCoord2d(0,0); glVertex2f(0,bitmap.rows);
glTexCoord2d(0,y); glVertex2f(0,0);
glTexCoord2d(x,y); glVertex2f(bitmap.width,0);
glTexCoord2d(x,0); glVertex2f(bitmap.width,bitmap.rows);
glEnd();
glPopMatrix();
glTranslatef(face->glyph->advance.x >> 6 ,0,0);
//increment the raster position as if we were a bitmap font.
//(only needed if you want to calculate text length)
//glBitmap(0,0,0,0,face->glyph->advance.x >> 6,0,NULL);
//Finnish the display list
glEndList();
}
void font_data::init(const char * fname, unsigned int h) {
//Allocate some memory to store the texture ids.
textures = new GLuint[128];
this->h=h;
//Create and initilize a freetype font library.
FT_Library library;
if (FT_Init_FreeType( &library ))
throw std::runtime_error("FT_Init_FreeType failed");
//The object in which Freetype holds information on a given
//font is called a "face".
FT_Face face;
//This is where we load in the font information from the file.
//Of all the places where the code might die, this is the most likely,
//as FT_New_Face will die if the font file does not exist or is somehow broken.
if (FT_New_Face( library, fname, 0, &face ))
throw std::runtime_error("FT_New_Face failed (there is probably a problem with your font file)");
//For some twisted reason, Freetype measures font size
//in terms of 1/64ths of pixels. Thus, to make a font
//h pixels high, we need to request a size of h*64.
//(h << 6 is just a prettier way of writting h*64)
FT_Set_Char_Size( face, h << 6, h << 6, 96, 96);
//Here we ask opengl to allocate resources for
//all the textures and displays lists which we
//are about to create.
list_base=glGenLists(128);
glGenTextures( 128, textures );
//This is where we actually create each of the fonts display lists.
for(unsigned char i=0;i<128;i++)
make_dlist(face,i,list_base,textures);
//We don't need the face information now that the display
//lists have been created, so we free the assosiated resources.
FT_Done_Face(face);
//Ditto for the library.
FT_Done_FreeType(library);
}
void font_data::clean() {
glDeleteLists(list_base,128);
glDeleteTextures(128,textures);
delete [] textures;
}
/// A fairly straight forward function that pushes
/// a projection matrix that will make object world
/// coordinates identical to window coordinates.
inline void pushScreenCoordinateMatrix() {
glPushAttrib(GL_TRANSFORM_BIT);
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
gluOrtho2D(viewport[0],viewport[2],viewport[1],viewport[3]);
glPopAttrib();
}
/// Pops the projection matrix without changing the current
/// MatrixMode.
inline void pop_projection_matrix() {
glPushAttrib(GL_TRANSFORM_BIT);
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glPopAttrib();
}
///Much like Nehe's glPrint function, but modified to work
///with freetype fonts.
void print(const font_data &ft_font, float x, float y, const char *fmt, ...) {
// We want a coordinate system where things coresponding to window pixels.
pushScreenCoordinateMatrix();
GLuint font=ft_font.list_base;
float h=ft_font.h/.63f; //We make the height about 1.5* that of
char text[256]; // Holds Our String
va_list ap; // Pointer To List Of Arguments
if (fmt == NULL) // If There's No Text
*text=0; // Do Nothing
else {
va_start(ap, fmt); // Parses The String For Variables
vsprintf(text, fmt, ap); // And Converts Symbols To Actual Numbers
va_end(ap); // Results Are Stored In Text
}
//Here is some code to split the text that we have been
//given into a set of lines.
//This could be made much neater by using
//a regular expression library such as the one avliable from
//boost.org (I've only done it out by hand to avoid complicating
//this tutorial with unnecessary library dependencies).
const char *start_line=text;
vector<string> lines;
for(const char *c=text;*c;c++) {
if(*c=='\n') {
string line;
for(const char *n=start_line;n<c;n++) line.append(1,*n);
lines.push_back(line);
start_line=c+1;
}
}
if(start_line) {
string line;
for(const char *n=start_line;n<c;n++) line.append(1,*n);
lines.push_back(line);
}
glPushAttrib(GL_LIST_BIT | GL_CURRENT_BIT | GL_ENABLE_BIT | GL_TRANSFORM_BIT);
glMatrixMode(GL_MODELVIEW);
glDisable(GL_LIGHTING);
glEnable(GL_TEXTURE_2D);
glDisable(GL_DEPTH_TEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glListBase(font);
float modelview_matrix[16];
glGetFloatv(GL_MODELVIEW_MATRIX, modelview_matrix);
//This is where the text display actually happens.
//For each line of text we reset the modelview matrix
//so that the line's text will start in the correct position.
//Notice that we need to reset the matrix, rather than just translating
//down by h. This is because when each character is
//draw it modifies the current matrix so that the next character
//will be drawn immediatly after it.
for(int i=0;i<lines.size();i++) {
glPushMatrix();
glLoadIdentity();
glTranslatef(x,y-h*i,0);
glMultMatrixf(modelview_matrix);
// The commented out raster position stuff can be useful if you need to
// know the length of the text that you are creating.
// If you decide to use it make sure to also uncomment the glBitmap command
// in make_dlist().
// glRasterPos2f(0,0);
glCallLists(lines[i].length(), GL_UNSIGNED_BYTE, lines[i].c_str());
// float rpos[4];
// glGetFloatv(GL_CURRENT_RASTER_POSITION ,rpos);
// float len=x-rpos[0];
glPopMatrix();
}
glPopAttrib();
pop_projection_matrix();
}
}