Text Drawing is SLOWWWW!

[wademcgillis]

Why is it so slow?

Why does drawing the text dynamically slow it down so much?

Code: [Select]


void draw_text(int x, int y, char* text)
    {
    sf::String displayText = sf::String();
    displayText.SetColor(sf::Color(globalsys::current_color->getRed(),globalsys::current_color->getGreen(),
        globalsys::current_color->getBlue(),255*globalsys::current_alpha));
    displayText.SetFont(globalsys::current_font.font);
    displayText.SetSize(globalsys::current_font.size);
    if (view_enabled)
        displayText.Move(x-view_xview,y-view_yview);
    else
        displayText.Move(x,y);
displayText.SetText(text);
    App.Draw(displayText);
    }


[Laurent]

What is "slow" to you? What is your configuration?

How do you use this function? Can you extract a minimal and complete example using this function that is slow?

[wademcgillis]

Slow meaning it drops in frame rate by a lot when I draw large text. Like, drawing 1 piece of text at 12 pt is fine. But when I do 64pt there is a noticeable drop, and when I do 128pt it is awful.

http://www.wademcgillis.com/downloads/fps3D.zip

Right click to draw big text.

[Laurent]

It shouldn't be so slow. I'd like to see your code, if possible.

[Tank]

I really bet you call that "draw_text" function each frame. Please tell me you're not.

[wademcgillis]

I am.

[Laurent]

I really bet you call that "draw_text" function each frame. Please tell me you're not.

What's wrong with that? He's just setting up and drawing a graphical string. It's not as if he was loading the font on each call

[Tank]

I really bet you call that "draw_text" function each frame. Please tell me you're not.

What's wrong with that? He's just setting up and drawing a graphical string. It's not as if he was loading the font on each call

Well, that maybe gives you a hint on how the rest of his program is written. I think it's a total waste of resources and time.

wademcgillis, could you please show us the rest of your (relevant) code?

[Nexus]

Did you profile it and find out what part of code is responsible for the bad frame rate?

And you're not testing in debug mode, are you?

[Laurent]

Well, that maybe gives you a hint on how the rest of his program is written. I think it's a total waste of resources and time.

I agree. But it's perfectly ok to use SFML drawables like this, nothing is wasted.

From the (incomplete) source code I got in PM, I can find only one potential cause for the bad performances. What is the ptototype of the draw_set_font function?
If the font is passed by value rather than by reference, then you're copying the whole font (including its OpenGL texture) everytime you call it.

[Tank]

I agree. But it's perfectly ok to use SFML drawables like this, nothing is wasted.

You must be kidding.

Code: [Select]

sf::String displayText = sf::String();
Standard constructor, assignment. Why not directly assign the text? (this may be optimized by your favorite compiler, but that doesn't mean you shouldn't do it right)

Code: [Select]

displayText.SetColor(sf::Color(globalsys::current_color->getRed(),globalsys::current_color->getGreen(),
        globalsys::current_color->getBlue(),255*globalsys::current_alpha));
Absolute unnecessary sf::Color temporary.

Code: [Select]

displayText.SetFont(globalsys::current_font.font);
displayText.SetSize(globalsys::current_font.size);
Again, this can be done through the constructor, saves calls.

The problem is not within that single function. It's that when it's done everywhere like this (and I think it is), performance will decrease sooner or later.

But okay, it's getting off topic here.

[Laurent]

You must be kidding

Absolutely not

All he does is assigning a few primitive types (either pointer, float or int). Internally, nothing happens until the call to Draw.

I know that this kind of design is globally bad, but some people prefer this C-like approach instead of a clean OO design. And SFML won't be slower for these people.

[wademcgillis]

Oops. I forgot to send the other .h files.

[Laurent]

I was right:

Code: [Select]

void draw_set_font(Font f)
    {
    globalsys::current_font = f;
    }

You're creating / copying / destroying a huge amout of data and resources on every call.

This should be like this:

Code: [Select]

const sf::Font* current_font;

void draw_set_font(const Font& f)
{
    globalsys::current_font = &f;
}

[wademcgillis]

Oh wow... THANK YOU!