Re: Drawing a lot of SVG images is slow

Hi,
Sorry for top-posting, but…

What platform are you on?
What wx version?
Are you working with Debug build?
Choosing wxWidgets for the game is kind of weird - are you sure about that?

Thank you.

On Tue, Apr 1, 2025 at 12:36 PM Quentin Cosendey <
[email protected]> wrote:

> Hello,
>
> I'm developing a game. I'm trying to use SVG images to draw the board
> and all game elements (tokens, dice, etc.).
> I wanted to use SVG because it allows the board to be seen all at once
> and have its size adapted to the size of the window, i.e. fill the
> window as much as possible / make the board as big as possible, without
> pixelization effects. It also allows the user to customize the color of
> some game elements (for example tokens) quite easily, as well as select
> their own colors to make their own dark or high-contrast mode. All this
> is good for visually impaired players.
>
> However, displaying everything (~1000 elements) seems to be quite slow,
> and it makes the interface lagging globally. It takes hundreds of
> milliseconds to update the screen after having pressed a key and/or
> moved the mouse.
> Am I doing something wrong ? Do you have ideas on how I could improve
> performances ?
>
> Drawing code looks as follows, I have tried to simplify it a little:
>
> void GameWindow::OnPaint (wxPaintEvent& e) {
>    wxAutoBufferedPaintDC dc(this);
>    std::unique_ptr<wxGraphicsContext> g(wxGraphicsContext::Create(dc));
>      ...
>    for (auto& square: squares) {
>      wxRect pos = ... ; // boundaries of the square
>      g->ResetClip();
>      g->Clip(pos);
>      for (std::string& image: square.getElements()) {
>        auto bundle = app.getImage(image);
>        wxSize defaultSize = bundle.GetDefaultSize();
>        wxSize finalImageSize =
> calcGreatestPossibleSize(wxSize(pos.width, pos.height), defaultSize);
>        auto bitmap = bundle.GetBitmap(finalImageSize);
>        if (bitmap.IsOk()) {
>          finalImageSize = bitmap.GetSize();
>          g->DrawBitmap(bitmap, pos.x, pos.y, finalImageSize.x,
> finalImageSize.y);
>        }
>      }
>      g->ResetClip();
>    }
> }
>
>
> Loading code: wxImageBundle are stored in a
> std::unordered_map<std::string, wxImageBundle> .
> Using a simple array instead of the map and indexing images by index
> instead of by name doesn't make a lot of difference, I have already tested.
>
> wxBitmapBundle App::getImage (const std::string& name) {
>    auto it = images.find(name);
>    if (it!=images.end()) return it->second;
>    wxString svgfn = "images/" + name + ".svg";
>    if (!svgfn.size()) return wxBitmapBundle(); // not found, return
> empty bundle
>    wxSize imSize = readSVGImageSize(svgfn);
>    auto bundle = wxBitmapBundle::FromSVGFile(svgfn, imSize);
>    images[name] = bundle;
>    return bundle;
> }
>
> The SVG images used are extremely simple for the moment, there are no
> complex things: basic shapes, polygons, polylines, paths; plain fill and
> stroke colors, no gradients or stuff like that.
> Most squares have always the same size if the window isn't resized.
>
> In case it can make a difference, GameWindows extends wxControl,
> wxVarHVScrollHelper, wxAccessible
>
> Where could the problem be ?
>
> As far as I understand, the method wxImageBundle::GetBitmap basically
> renders the SVG in a traditional in-memory bitmap. Is that really
> necessary ? Isn't there a more direct way to draw SVG images ?
> The documentation says that generated bitmaps are cached, so since the
> size don't change unless the window is resized, it shouldn't be a
> problem, right ?
>
> Is SVG support in WX just not made for that kind of thing ?
> In this case do you have an alternate SVG library integrable with WX to
> advise ?
>
> Thank you very much for your answers !
>
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>

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