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deadstar

OpenGL Using SDL_TTF with OpenGL - halves my framerate

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Hi, I'm using a modified version of C-Junkie's code (from here: http://www.gamedev.net/community/forums/topic.asp?topic_id=284259) to render text from SDL_TTF to an OpenGl quad.
void SDL_GL_RenderText(string Text, TTF_Font *Font, SDL_Color Colour, SDL_Rect *Position)
{
	SDL_Surface *Initial;
	SDL_Surface *Intermediary;
	SDL_Rect Rect;
	int Width, Height;
	GLuint Texture;

	//Cast the string as a non-const char*
	char *Text_NonConst = const_cast<char*>(Text.c_str());

	//Enable blending
	glEnable(GL_BLEND);
	
	//Render text to SDL surface
	Initial = TTF_RenderText_Blended(Font, Text_NonConst, Colour);
	
	//Get the width and height of the SDL surface containing the text
	Width = nextpoweroftwo(Initial->w);
	Height = nextpoweroftwo(Initial->h);
	
	//Create a surface with useable format for OpenGL
	Intermediary = SDL_CreateRGBSurface(0, Width, Height, 32, 0x00ff0000, 0x0000ff00, 0x000000ff, 0xff000000);

	//Blit the text surface onto the OpenGL compliant one
	SDL_BlitSurface(Initial, 0, Intermediary, 0);
	
	//Setup the texture
	glGenTextures(1, &Texture);
	glBindTexture(GL_TEXTURE_2D, Texture);

	//Copy SDL surface to the OpenGL texture
	glTexImage2D(GL_TEXTURE_2D, 0, 4, Width, Height, 0, GL_BGRA, GL_UNSIGNED_BYTE, Intermediary->pixels );
	
	//Setup texture filter
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

	//Enable textures
	glEnable(GL_TEXTURE_2D);

	//Set the colour to white (for correct blending)
	glColor3f(1.0f, 1.0f, 1.0f);
	
	//Draw texture using a quad
	glBegin(GL_QUADS);

		glTexCoord2f(0.0f, 0.0f); glVertex2f(Position->x, Position->y);
		glTexCoord2f(1.0f, 0.0f); glVertex2f(Position->x + Width, Position->y);
		glTexCoord2f(1.0f, 1.0f); glVertex2f(Position->x + Width, Position->y + Height);
		glTexCoord2f(0.0f, 1.0f); glVertex2f(Position->x, Position->y + Height);

	glEnd();

	//Disable blending
	glDisable(GL_BLEND);
	
	//Clean up
	SDL_FreeSurface(Initial);
	SDL_FreeSurface(Intermediary);
	glDeleteTextures(1, &Texture);
}



Simply rendering a single word halves my framerate. Is there a way to reduce the amount of code used? Or a simpler way to copy an SDL surface to an OpenGL texture? I don't want to change my font library to something else, I like SDL_TTF for its simplicity and cross-platform capability. Thanks

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When you say it halves your framerate, are you comparing doing nothing at all versus just rendering text? Because if so, that would not be a good comparison.

One big way to speed the code up would be to save the OpenGL textures you create and simply reuse them. This of course would require you to use static text though.

If you want to use dynamic text, you could render the entire alphabet to a texture in the manner you have, and using texture coordinates, write a message one letter at a time. That would be harder to code though.

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As the poster before me pointed out dont compare to rendering nothing at all because that's not a good baseline.

With regards performance .. This is the slowest performing code you could possibly write and I dont mean that in a bad way, just as constructive criticism. It is by understanding why the code is slow that you can speed it up.

#1. You are rendering using immediate mode gl draw calls. Very slow, so read up on how to use vertex arrays or even better vertex buffer objects if you want the ultimate performance.

#2. You are rendering using quads. Although the gl vendor will convert the quads to triangles somewhere down the pipeline, the fastest data to send is indexed triangles to take advantage of the vertex cache on the gpu. Make your quads 2 indexed triangles each (tip: your triangle indices will ALWAYS be the same).

#3. You are generating a fresh texture every single frame. Big nono. Uploading data to the gpu is SLOW, so where possible generate the texture once and reuse. You should pack all your font characters (glyphs) into a single texture and bind it for the draw call, then use texture coordinates to map a characters onto a quad.

#4. Try to avoid memory allocations in your rendering loop. Memory allocation / deallocation is very slow.

Hope these tips help, and good luck with your code!

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Quote:
Original post by Simian Man
When you say it halves your framerate, are you comparing doing nothing at all versus just rendering text? Because if so, that would not be a good comparison.


Well, it's rendering a grid and a few 3D models. Maybe I'm jumping the gun a bit then.

Quote:
Original post by Simian Man
One big way to speed the code up would be to save the OpenGL textures you create and simply reuse them. This of course would require you to use static text though.


I'm using the text to show the FPS and some debug info, as well as putting it into good use on a quake-style console, so I wouldn't find use for static text.

Quote:
Original post by Simian Man
If you want to use dynamic text, you could render the entire alphabet to a texture in the manner you have, and using texture coordinates, write a message one letter at a time. That would be harder to code though.


I can't see much benefits over using bitmapped fonts in this instance.


Thanks for your response, I think I'm rendering too few things on the screen to give an accurate result.

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Quote:
Original post by TheGilb
As the poster before me pointed out dont compare to rendering nothing at all because that's not a good baseline.

With regards performance .. This is the slowest performing code you could possibly write and I dont mean that in a bad way, just as constructive criticism. It is by understanding why the code is slow that you can speed it up.

#1. You are rendering using immediate mode gl draw calls. Very slow, so read up on how to use vertex arrays or even better vertex buffer objects if you want the ultimate performance.

#2. You are rendering using quads. Although the gl vendor will convert the quads to triangles somewhere down the pipeline, the fastest data to send is indexed triangles to take advantage of the vertex cache on the gpu. Make your quads 2 indexed triangles each (tip: your triangle indices will ALWAYS be the same).

#3. You are generating a fresh texture every single frame. Big nono. Uploading data to the gpu is SLOW, so where possible generate the texture once and reuse. You should pack all your font characters (glyphs) into a single texture and bind it for the draw call, then use texture coordinates to map a characters onto a quad.

#4. Try to avoid memory allocations in your rendering loop. Memory allocation / deallocation is very slow.

Hope these tips help, and good luck with your code!


Thanks for the reply.

The code isn't mine, it was taken from the above thread and slightly modified to include STL::String support.

I thought about using a vertex array, but I thought a single quad wouldn't be THAT much of a slow-down, and a vertex array wouldn't be worth the hassle. Am I wrong?

I'll try and remove as much memory allocation I can from the code (maybe make a class, and call glGenTextures once), and use a bitmapped font solution only as a last resort, since I am fond of this method dispite these drawbacks.

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That code is horrible.

Take a good hard look at what it's doing and you'll throw it away without a thought.

For single frame, it takes a font and renders it.
Then it creates a texture. Every frame!
And finally renders the texture to a quad. and deletes the texture.

EVERY FRAME! :)

I'd suggest taking a look at Nehe's font tutorial, it's about 10000 times faster than this. Granted, his example is windows specific, but it's possible to make it multiplatform if you need to.

http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=13
I think it's this one. It actually does load fonts from normal font files, not textures.

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Quote:
Original post by TheGilb
#1. You are rendering using immediate mode gl draw calls. Very slow, so read up on how to use vertex arrays or even better vertex buffer objects if you want the ultimate performance.

#2. You are rendering using quads. Although the gl vendor will convert the quads to triangles somewhere down the pipeline, the fastest data to send is indexed triangles to take advantage of the vertex cache on the gpu. Make your quads 2 indexed triangles each (tip: your triangle indices will ALWAYS be the same).

#4. Try to avoid memory allocations in your rendering loop. Memory allocation / deallocation is very slow.


These three are *nothing* compared with your #3 (sending a new texture the video card each frame). Until that is optimized, using triangles or vertex arrays would be meaningless.

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Quote:
Original post by deadstar
I'm using the text to show the FPS and some debug info, as well as putting it into good use on a quake-style console, so I wouldn't find use for static text.

Well, unless you're updating all of the text every single frame, then you can still take advantage of the static text concept. I started out with similar horribly inefficient code and it would drop my framerate to the teens or lower when I had my console on screen (maybe a dozen or two lines of text). I updated the code to cache text textures that don't change from frame to frame and now it runs much more acceptably.

Here's my new version of the function (there's plenty of room for improvement, but it didn't require any huge changes and it works well enough for me). Note that it's integrated into my GUI class so each widget automatically keeps track of the previous string it rendered and the current string, which are the first two parameters (if they match then it just reuses the texture), and it also requires that you manage the OpenGL texture outside of the function. There's some other classes referenced in there too but you can probably figure out what's going on.

void GUI::RenderText(string str, string oldstr, int x, int y, int justify, TTF_Font *font, GLuint tex, float scale, bool shadow)
{
SDL_Surface *text;

if (str.length() == 0 || !TTF_WasInit())
return;
SDL_Color col;
col.r = 255;
col.g = 255;
col.b = 255;

SDL_Surface *t = TTF_RenderText_Solid(font, str.c_str(), col);
if (!t) // Had some problems with sdl-ttf at one point
{ // At least this way it won't segfault
cout << "Error rendering text: " << str << endl;
exit(-1);
}
int neww = PowerOf2(t->w);
int newh = PowerOf2(t->h);

texman->texhand->BindTexture(tex);

if (oldstr != str)
{
Uint32 rmask, gmask, bmask, amask;
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
rmask = 0xff000000;
gmask = 0x00ff0000;
bmask = 0x0000ff00;
amask = 0x000000ff;
#else
rmask = 0x000000ff;
gmask = 0x0000ff00;
bmask = 0x00ff0000;
amask = 0xff000000;
#endif
text = SDL_CreateRGBSurface(SDL_SWSURFACE, neww, newh, 32,
rmask, gmask, bmask, amask);


SDL_BlitSurface(t, NULL, text, NULL);

SDL_LockSurface(text);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, text->w, text->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, text->pixels);
}

float texwidth = (float)t->w / (float)neww;
float texheight = (float)t->h / (float)newh;

int offset = 2;
int shadowpass = shadow ? 1 : 0;
while (shadowpass >= 0)
{
if (shadow)
{
if (shadowpass)
{
glColor4f(0, 0, 0, 1);
x += offset;
y += offset;
}
else
{
glColor4f(1, 1, 1, 1);
x -= offset;
y -= offset;
}
}
glBegin(GL_TRIANGLE_STRIP);
if (justify == 0)
{
glTexCoord2f(0, 0);
glVertex2f(x, y);
glTexCoord2f(0, texheight);
glVertex2f(x, y + t->h * scale);
glTexCoord2f(texwidth, 0);
glVertex2f(x + t->w * scale, y);
glTexCoord2f(texwidth, texheight);
glVertex2f(x + t->w * scale, y + t->h * scale);
}
else if (justify == 1)
{
glTexCoord2f(0, 0);
glVertex2f(x - t->w, y);
glTexCoord2f(0, texheight);
glVertex2f(x - t->w, y + t->h);
glTexCoord2f(texwidth, 0);
glVertex2f(x, y);
glTexCoord2f(texwidth, texheight);
glVertex2f(x, y + t->h);
}
glEnd();
--shadowpass;
}
glColor4f(1, 1, 1, 1);

SDL_FreeSurface(t);
if (oldstr != str)
SDL_FreeSurface(text);
}

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What I would do if you want to use SDL for font rendering, is use the same method nehe uses. It creates a quad for every character and stores every quad in a display list. It then uses a really clever way of calling these display lists. This way you can have text that updates every frame and still not really affect your framerate. I think it's by far the best solution.

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The easiest way to increase the speed of your code is to:
1. Create the openGL texture just once (pick the maximum size you need/can afford)
2. Use glTexSubImage2D instead of glTexImage2D to update the texture when the text changes

If you have multiple text targets (like a Quake-style console plus a HUD), use multiple target textures.

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Thanks everyone.

The common vote seems to be making use of NeHe's font tutorials.

I'm having trouble finding cross platform alternatives to wglUseFontBitmaps or wglUseFontOutlines. MacOSX seems to have aglUseFontBitmaps with the use of an extra library, and X11's implementation seems completely different.

In the meantime, I've dug into the SDL_TTF headers and found useful functions such as TTF_RenderGlyph, I might sit down and write a custom function to extract each glyph into a texture. I also didn't know you could do a FOR loop using chars:


for ( i = ' '; i <= '~'; i++ )
{

}



Found at www.objectmix.com. Could come in handy unless someone can pick out any disadvantages.

So I have one question remaining - I plan to create a vector of GLuints to hold every glyph, how could I reference those glyphs by char?

Making a struct containing a GLuint and a char, then looping through every glyph until the char is found seems a little expensive, and inconsistent, to me. Quick for a's and b's, slow for Y's and Z's :(

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Quote:
Original post by deadstarSo I have one question remaining - I plan to create a vector of GLuints to hold every glyph, how could I reference those glyphs by char?

If you end up doing this rather than using SiCrane or sigsegv42's links, you can index a vector by the value of the character. Iterate over the characters and insert them into the vector, then when you need to look one up just go to index int(chartofind - 'a') (replace 'a' with whatever the first character you put in the vector was) and that should get you the character you're looking for.

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Quote:
Original post by nemebean
Quote:
Original post by deadstarSo I have one question remaining - I plan to create a vector of GLuints to hold every glyph, how could I reference those glyphs by char?

If you end up doing this rather than using SiCrane or sigsegv42's links, you can index a vector by the value of the character. Iterate over the characters and insert them into the vector, then when you need to look one up just go to index int(chartofind - 'a') (replace 'a' with whatever the first character you put in the vector was) and that should get you the character you're looking for.


Thanks, that makes sense.

The only reason I'm not using the above two methods is that they are purely Bitmap font methods (creating a bitmap font image first using an external tool, then loading into the program).

My implementation needs to directly support TTF, and the interface to be as simple as Font.LoadTTF("arial.ttf") then Font.RenderText("Hello", x, y).

I've got as far as loading the TTF file and creating all the glyphs, I'm just starting work on the rendering now.

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Well I finally got somewhere, and it's given me an UNBELIEVABLE speed increase!

I can't believe rendering "Hello" with my old code was so damn slow.

Problem is, the text looks pretty ugly, and very inconsistent. Here's a screenshot rendering Arial 28pt:



And some source:


namespace SYM
{
SYM_FONT::SYM_FONT()
{
//Set default colour
Colour.r = 255;
Colour.g = 255;
Colour.b = 255;
Colour.unused = 255;
}

bool SYM_FONT::LoadFont(string TTF_Filename, int Size)
{
//Load the font
Font = TTF_OpenFont(TTF_Filename.c_str(), Size);

//Check font loaded
if (Font == NULL)
{
//Return
return false;
}

//Get font attributes
Ascent = TTF_FontAscent(Font);
Descent = TTF_FontDescent(Font);
Height = TTF_FontHeight(Font);
LineSkip = TTF_FontLineSkip(Font);

//Loop through all chars
for (int i = 0; i <= 255; i++)
{
//Clear the surface
TempSurface = NULL;

//Render the glyph onto the SDL surface
TempSurface = TTF_RenderGlyph_Blended(Font, i, Colour);

//Check the glyph rendered
if ( TempSurface == NULL )
{
//Close the font
TTF_CloseFont(Font);

//Return
return false;
}

//New temp glyph
TempGlyph = new SYM_GLYPH;

//Get the glyph attributes
TTF_GlyphMetrics(Font, i, &TempGlyph->MinX, &TempGlyph->MaxX, &TempGlyph->MinY, &TempGlyph->MaxY, &TempGlyph->Advance);

//Convert SDL surface into OpenGL GLuint texture
TempGlyph->Texture = SDL_Surface_To_GL_Tex(TempSurface);

//Push back to glyphs vector
Glyphs.push_back(*TempGlyph);

//Delete temp glyph
delete TempGlyph;

//Free surface
SDL_FreeSurface(TempSurface);
}

//Close the font
TTF_CloseFont(Font);

return true;
}

void SYM_FONT::RenderText(string Text, float x, float y)
{
int TexMinX, TexMaxX, TexMinY, TexMaxY, Width, Height, CharID;

//Enable OpenGL texture mapping
glEnable(GL_TEXTURE_2D);

//Enable blending
glEnable(GL_BLEND);

//Loop through characters
for (int i = 0; i < Text.size(); i++)
{
//Get ID of current char
CharID = (int)Text[i];

Width = Glyphs[CharID].MaxX;
Height = Glyphs[CharID].MaxY;

//Bind the glyph texture
glBindTexture(GL_TEXTURE_2D, Glyphs[CharID].Texture);

//Set the colour to white (for correct blending)
glColor3f(1.0f, 1.0f, 1.0f);

//Draw the glyph
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex2f(x, y );
glTexCoord2f(1, 0); glVertex2f(x + Width, y );
glTexCoord2f(1, 1); glVertex2f(x + Width, y + Height);
glTexCoord2f(0, 1); glVertex2f(x, y + Height);
glEnd();

x += Glyphs[CharID].Advance;
}

//Disable blending
glDisable(GL_BLEND);

//Disable texture mapping
glDisable(GL_TEXTURE_2D);
}

GLuint SDL_Surface_To_GL_Tex(SDL_Surface *Surface)
{
GLuint Texture;
int Width, Height;
SDL_Surface *Image;
SDL_Rect Area;

//Get the dimentions of the surface
Area.x = 0;
Area.y = 0;
Area.w = Surface->w;
Area.h = Surface->h;

//Make sure the width and height are powers of two
Width = NextPowerOfTwo(Surface->w);
Height = NextPowerOfTwo(Surface->h);

//Create an OpenGL compliant surface
Image = SDL_CreateRGBSurface(SDL_SWSURFACE, Width, Height, 32, 0x00ff0000, 0x0000ff00, 0x000000ff, 0xff000000);

//Copy the surface to the OpenGL compatible one
SDL_BlitSurface(Surface, &Area, Image, &Area);

//Generate an OpenGL texture
glGenTextures(1, &Texture);

//Bind the texture ready for use
glBindTexture(GL_TEXTURE_2D, Texture);

//Copy data from the SDL surface to the OpenGL texture
glTexImage2D(GL_TEXTURE_2D, 0, 4, Width, Height, 0, GL_RGBA, GL_UNSIGNED_BYTE, Image->pixels);

//Set texture filtering
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

//Free the SDL surface
SDL_FreeSurface(Image);

//Return the texture
return Texture;
}

} //Namespace



I can't pick out the fault. I've tried other texture filters to take off the slight 'blur' too, but to no avail.

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Glancing over your screenshot and your code, I think your problem is that you're populating the Glyph.MaxX and Y values with TTF_GlyphMetrics and using that for rendering when the texture is actually NextPowerOf2 in size, and you need to render a quad with that power of 2 size in order for the glyph to end up at the right size. I suspect that the reason your characters are different sizes is that some of them fall just to one side of a power of two and others fall just on the other side, so some end up very close to the right size and others end up half height or width.

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I was hoping you hadn't.. but you had... a texture per Glyph is just such a bad bad idea, both speed (texture switching) and resources wise (lots of small textures takes up more space than one larger one).

For the record, I developed a font renderer based on FT2 which used texture updating (instead of destorying and recreating the texture was just updated) and Glyph caching which hardly touched the framerate in the slighest, so it's possible.

That said, currently I'm prefering to use the font generator at Anglecode which SiCrane linked to.

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Quote:
Original post by nemebean
Glancing over your screenshot and your code, I think your problem is that you're populating the Glyph.MaxX and Y values with TTF_GlyphMetrics and using that for rendering when the texture is actually NextPowerOf2 in size, and you need to render a quad with that power of 2 size in order for the glyph to end up at the right size. I suspect that the reason your characters are different sizes is that some of them fall just to one side of a power of two and others fall just on the other side, so some end up very close to the right size and others end up half height or width.


Good call. I've changed it to draw the quad the same size as the SDL surface used after rendering the glyph. Sizes look fine now, but positions are still off.



A related problem?

Quote:
Original post by phantom
I was hoping you hadn't.. but you had... a texture per Glyph is just such a bad bad idea, both speed (texture switching) and resources wise (lots of small textures takes up more space than one larger one).


Yes it had crossed my mind. One step at a time I suppose, once I get the text to render correctly I could modify it have per-string texture capabilities, OR have all the glyphs rendered to a giant sheet and shift around it with texture coords per glyph.

Then again, maybe I won't. The render speed right now is very impressive compared to the first method. Maybe if the game speed starts to become unbearable then I'll give this class a rewrite.



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Right off hand I can't say what's going on now, but I do see another problem that may make you reconsider rendering them all to a single texture. The characters that are supposed to hang below the line are shifted up (and the half-height small characters are the ones that seem to be offset too low, so it might be related). If you rendered them all to a single texture I think SDL_TTF would take care of that for you.

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Quote:
Original post by Blackskyliner
Have you solved the problem??
I need this sort of code too and don't want to begin a second project like yours...

so if you have the problem cleared please post the solution.


Blackskyliner


Hi Blackskyliner, my Uni work held me back for a few weeks and the project was on hold, but I'm now working on it again.

I'll post if I find a solution.

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Ok, I'm altering the code to render all glyphs to one texture, and store the UV coords of each glyph into a tidy vector.

So far, the glyphs correctly render neatly to an SDL surface, I've confirmed this by writing the surface to a file using SDL_SaveBMP().

Although probably not done the best way, I think my code to save the texture coords is fine, and so is the drawing code, but the characters won't render.

To verify the drawing positions, I've filled the SDL surface with a colour.

This is what I get:



And here is the code:


bool SYM_FONT::LoadFont(string TTF_Filename, int Size)
{
//Load the font
Font = TTF_OpenFont(TTF_Filename.c_str(), Size);

//Check font loaded
if (Font == NULL)
{
//Return
return false;
}

//Get font attributes
Ascent = TTF_FontAscent(Font);
Descent = TTF_FontDescent(Font);
Height = TTF_FontHeight(Font);
LineSkip = TTF_FontLineSkip(Font);

//TODO: Pre-calculate the size of the glyph sheet
TempGlyphSheet = SDL_CreateRGBSurface(SDL_SWSURFACE, 1024, 512, 32, 0, 0, 0, 0);

SDL_FillRect(TempGlyphSheet, 0, SDL_MapRGB(TempGlyphSheet->format, 255, 0, 255));

//Loop through all chars
for (int i = 0; i <= 254; i++)
{
//Clear the surface
TempGlyphSurface = NULL;

//Render the glyph onto the SDL surface, in white
SDL_Color GlyphColour = {255, 255, 255, 0};
TempGlyphSurface = TTF_RenderGlyph_Blended(Font, i, GlyphColour);

//New temp glyph
TempGlyph = new SYM_GLYPH;

//Get the glyph attributes
TTF_GlyphMetrics(Font, i, &TempGlyph->MinX, &TempGlyph->MaxX, &TempGlyph->MinY, &TempGlyph->MaxY, &TempGlyph->Advance);

//Set the width and height of the glyph
TempGlyph->Width = TempGlyphSurface->w;
TempGlyph->Height = TempGlyphSurface->h;

TempGlyph->MinX = TempGlyph->MinX;
TempGlyph->MaxX = TempGlyph->MaxX;
TempGlyph->MinY = TempGlyph->MinY;
TempGlyph->MaxY = TempGlyph->MaxY;

//Set the glyph rect size
GlyphRect.w = TempGlyphSurface->w;
GlyphRect.h = TempGlyphSurface->h;

//Advance size of current position rect
CurrentPos.w = CurrentPos.x + GlyphRect.w;
CurrentPos.h = CurrentPos.y + GlyphRect.h;

//Blit the glyph onto the glyph sheet
SDL_BlitSurface(TempGlyphSurface, &GlyphRect, TempGlyphSheet, &CurrentPos);

//Set texture coordinates for the glyph
TempGlyph->TexCoords[0].u = (float)CurrentPos.x / 1024;
TempGlyph->TexCoords[0].v = (float)CurrentPos.y / 512;

TempGlyph->TexCoords[1].u = (float)(CurrentPos.x + CurrentPos.w) / 1024;
TempGlyph->TexCoords[1].v = (float)(CurrentPos.y + CurrentPos.h) / 512;

//Advance position of current position rect
CurrentPos.x += GlyphRect.w;

//Put glyphs into rows
if (Count > 40)
{
CurrentPos.x = 0;
CurrentPos.y += Height;
Count = 0;
}

//Push back to glyphs vector
Glyphs.push_back(*TempGlyph);

//Delete temp glyph
delete TempGlyph;

//Free surface
SDL_FreeSurface(TempGlyphSurface);

Count++;
}

//Close the font
TTF_CloseFont(Font);

//Convert the SDL glyph sheet to an OpenGL compliant texture
GlyphSheet = SDL_Surface_To_GL_Tex(TempGlyphSheet);

//Free the temp glyph sheet surface
SDL_FreeSurface(TempGlyphSheet);

return true;
}

void SYM_FONT::RenderText(string Text, float x, float y)
{
int Width, Height, CharID;

//Enable OpenGL texture mapping
glEnable(GL_TEXTURE_2D);

//Bind the glyph sheet texture
glBindTexture(GL_TEXTURE_2D, GlyphSheet);

//Enable blending
glEnable(GL_BLEND);

//Loop through characters
for (int i = 0; i < Text.size(); i++)
{
//Get ID of current char
CharID = (int)Text[i];

Width = Glyphs[CharID].Width;
Height = Glyphs[CharID].Height;

//Set the colour to white (for correct blending)
glColor3f(1.0f, 1.0f, 1.0f);

//Draw the glyph
glBegin(GL_QUADS);
glTexCoord2f(Glyphs[CharID].TexCoords[0].u, Glyphs[CharID].TexCoords[0].v); glVertex2f(x, y);
glTexCoord2f(Glyphs[CharID].TexCoords[1].u, Glyphs[CharID].TexCoords[0].v); glVertex2f(x + Width, y);
glTexCoord2f(Glyphs[CharID].TexCoords[1].u, Glyphs[CharID].TexCoords[1].v); glVertex2f(x + Width, y + Height);
glTexCoord2f(Glyphs[CharID].TexCoords[0].u, Glyphs[CharID].TexCoords[1].v); glVertex2f(x, y + Height);
glEnd();

x += Glyphs[CharID].Advance;
}

//Disable blending
glDisable(GL_BLEND);

//Disable texture mapping
glDisable(GL_TEXTURE_2D);
}



Any ideas?

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