[bug] Custom nerdfont displays as ? for short period before displaying

[damntourists]

What happend?

Hi there, Before I display anything in my app, I load a couple additional fonts that I obtained from https://www.nerdfonts.com/ and set one of them as a default font. This happens in init() so they should be loaded before the main function executes. I noticed that for approximately 1-2 seconds after the window displays, the font doesn't render, so instead it shows as "?" briefly. Have you ever encountered this? Is there a known way to get around this?

Code example

main.go

// put your code here!

To Reproduce

1. Run my demo
2. will see the crash...

Version

master

OS

ubuntu

[gucio321]

sounds strange
It may be because of RebuildFontAtlas needs some time to build fonts so if you're initializing more fonts, it may take a bit longer to build it all
If you want to get rid of this effect, I'd suggest using imgui's font api instead of giu's one

[damntourists]

Okay! I'll take a look and see what I can do. Thanks for your input!

[damntourists]

Actually, not sure if this is intentional or not, but it looks like when the master window renders, it runs:

func (w *MasterWindow) render() {
	if !w.platform.IsVisible() || w.platform.IsMinimized() {
		return
	}

	Context.invalidAllState()
	defer Context.cleanState()

	rebuildFontAtlas()     <========= returns immediately on first run

	p := w.platform
	r := w.renderer

	p.NewFrame()
	r.PreRender(w.clearColor)

	imgui.NewFrame()
	w.updateFunc()
	imgui.Render()

	r.Render(p.DisplaySize(), p.FramebufferSize(), imgui.RenderedDrawData())
	p.PostRender()
}

The part that causes it to return immediately, since rebuildFontAtlas is only defined as a variable at this point, not actually set:

// Rebuild font atlas when necessary.
func rebuildFontAtlas() {
	if !shouldRebuildFontAtlas {
		return
	}

So imgui.Render() executes before the rebuilding of the Font atlas occurs. Eventually it hits the PostRender() function, and the first frame is drawn without ever having rebuilt the font atlas.

// PostRender performs a buffer swap.
func (platform *GLFW) PostRender() {
	platform.window.SwapBuffers()
}

The only way shouldRebuildFontAtlas seems to get set is by running functions SetSize and tStr.

[gucio321]

yes, its intentional. Its because of how FontAtlas works.
it collects data about all characters that needs to be rendered in your app and then includes only these charactes as GlyphRanges argument to imgui.AddFont*
thats why imgui needs to be rendered at least once before fonts are build