Problem with Freetype and OpenGL
- by Morgan
Hey, i'm having a weird issue with drawing text in openGL loaded with the Freetype 2 library. Here is a screenshot of what I'm seeing.
http://img203.imageshack.us/img203/3316/freetypeweird.png
Here are my code bits for loading and rendering my text.
class Font
{
Font(const String& filename)
{
if (FT_New_Face(Font::ftLibrary, "arial.ttf", 0, &mFace)) {
cout << "UH OH!" << endl;
}
FT_Set_Char_Size(mFace, 16 * 64, 16 * 64, 72, 72);
}
Glyph* GetGlyph(const unsigned char ch)
{
if(FT_Load_Char(mFace, ch, FT_LOAD_RENDER))
cout << "OUCH" << endl;
FT_Glyph glyph;
if(FT_Get_Glyph( mFace->glyph, &glyph ))
cout << "OUCH" << endl;
FT_BitmapGlyph bitmap_glyph = (FT_BitmapGlyph)glyph;
Glyph* thisGlyph = new Glyph;
thisGlyph->buffer = bitmap_glyph->bitmap.buffer;
thisGlyph->width = bitmap_glyph->bitmap.width;
thisGlyph->height = bitmap_glyph->bitmap.rows;
return thisGlyph;
}
};
The relevant glyph information (width, height, buffer) is stored in the following struct
struct Glyph {
GLubyte* buffer;
Uint width;
Uint height;
};
And finally, to render it, I have this class called RenderFont.
class RenderFont
{
RenderFont(Font* font)
{
mTextureIds = new GLuint[128];
mFirstDisplayListId=glGenLists(128);
glGenTextures( 128, mTextureIds );
for(unsigned char i=0;i<128;i++)
{
MakeDisplayList(font, i);
}
}
void MakeDisplayList(Font* font, unsigned char ch)
{
Glyph* glyph = font->GetGlyph(ch);
glBindTexture( GL_TEXTURE_2D, mTextureIds[ch]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGBA,
glyph->width,
glyph->height,
0,
GL_ALPHA,
GL_UNSIGNED_BYTE,
glyph->buffer);
glNewList(mFirstDisplayListId+ch,GL_COMPILE);
glBindTexture(GL_TEXTURE_2D, mTextureIds[ch]);
glBegin(GL_QUADS);
glTexCoord2d(0,1); glVertex2f(0,glyph->height);
glTexCoord2d(0,0); glVertex2f(0,0);
glTexCoord2d(1,0); glVertex2f(glyph->width,0);
glTexCoord2d(1,1); glVertex2f(glyph->width,glyph->height);
glEnd();
glTranslatef(16, 0, 0);
glEndList();
}
void Draw(const String& text, Uint size, const TransformComponent* transform, const Color32* color)
{
glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glTranslatef(100, 250, 0.0f);
glListBase(mFirstDisplayListId);
glCallLists(text.length(), GL_UNSIGNED_BYTE, text.c_str());
glDisable(GL_TEXTURE_2D);
glDisable(GL_BLEND);
glLoadIdentity();
}
private:
GLuint mFirstDisplayListId;
GLuint* mTextureIds;
};
Can anybody see anything weird going on here that would cause the garbled text? It's strange because if I change the font size, or the DPI, then some of the letters that display correctly become garbled, and other letters that were garbled before then display correctly.
