More FontAwesome options about hello_imgui

[pthom]

More options were added in this PR

[pthom]

Hello,

There are lots of possible customizations that users might desire when it comes to fonts (glyph range, glyph layout options, additional icon fonts other than font awesome, etc).

Thus, at the moment, the user is given the possibility to completely override the font loading function (simply by setting runnerParams.callbacks.LoadAdditionalFonts. I suspect you know this already)). This gives the maximum level of customization, and keeps the API simple.

For example, in src/hello_imgui_demos/hello_imgui_demodocking/hello_imgui_demodocking.main.cpp, we have this:

void MyLoadFonts()
{
    // First, we load the default fonts (the font that was loaded first is the default font)
    HelloImGui::ImGuiDefaultSettings::LoadDefaultFont_WithFontAwesomeIcons();

    // Then we load a second font from
    // Since this font is in a local assets/ folder, it was embedded automatically
    std::string fontFilename = "fonts/Akronim-Regular.ttf";
    gAkronimFont = HelloImGui::LoadFontTTF_WithFontAwesomeIcons(fontFilename, 40.f);
}

...

    // Custom load fonts
    runnerParams.callbacks.LoadAdditionalFonts = MyLoadFonts;

I think it could be possible to update the available functions inside src/hello_imgui/imgui_default_settings.h (these functions enable users to build their own font loading function). You seem to know more than me about font configurations. Would you like to work on a PR related to this?

[codecat]

Sure! After taking a quick look, it seems there might already have been an attempt at adding customization to font configurations in HelloImGui::LoadFontTTF? There's a makeFontConfig lambda which I don't think has to be a lambda right now, so I suspect it was going to be some kind of default for a parameter.

Do you think lambda's for font configurations is a good idea? Perhaps something like this could work:

LoadFontTTF("fonts/DroidSans.ttf", 12.0f, [](ImFontConfig& config) {
  // modify the config here
  config.GlyphMinAdvanceX = 18;
  config.GlyphMaxAdvanceX = 18;
});

And then probably exposing MergeFontAwesomeToLastFont with the same kind of lambda function.

[pthom]

I don't know if a lambda is the most appropriate. The important thing to know is that the ImFontConfig instance has to live during the whole application lifecycle (imgui only takes a pointer to it, which should not be dangling).

This is why I added this static container:

 static std::map<std::string, ImFontConfig> allFontConfigs;
    allFontConfigs[fontFilename] = makeFontConfig();
    auto& fontConfig = allFontConfigs.at(fontFilename);

[codecat]

If you look at the code of AddFontFromMemoryTTF, it doesn't actually keep the pointer around at all:

https://github.com/ocornut/imgui/blob/5f45047fb67c2147c6a1b1798b98d401e7998b51/imgui_draw.cpp#L2133

So it's safe to just keep it on the stack, which will simplify a lot of this code.

I'll do a pull request shortly!