internal/ui: a canvas size might not be initialized when ebiten.SetRunnableOnUnfocused(false) in an iframe

[hajimehoshi]

Ebitengine Version

126af14 and v2.7.6

Operating System

• Windows
• macOS
• Linux
• FreeBSD
• OpenBSD
• Android
• iOS
• Nintendo Switch
• PlayStation 5
• Xbox
• Web Browsers

Go Version (go version)

go version go1.22.4 darwin/arm64

What steps will reproduce the problem?

Run an HTML5 game with ebiten.SetRunnableOnUnfocused(false) within an iframe.

The prbably easiest way to reproduce this issue is:

0. Move to the ebitengine directory
1. Create main.html like this

<iframe src="./index.html"></iframe>

2. Run wasmserve ./examples/windowsize -runnableonunfocused=false
3. Open http://localhost:8080/main.html

What is the expected result?

The canvas size is initialized correctly.

What happens instead?

The canvas size is not initialized correctly.

Anything else you feel useful to add?

A game in an iframe doesn't focus the canvas automatically (#1373).

I found this issue on itch.io.

/CC @wasedaigo