Canvas size calculation error

[rpahut]

Tested versions

The issue is discovered in 3.6 .
Possibly was introduced with GodotDisplayScreen class back in 2021.

System information

Does not appear to be system or browser specific

Issue description

GodotDisplayScreen.updateSize() does not handle calculations correctly, resulting in wrong canvas dimensions when browser zoom is applied. Occasionally this leads to scroll bars appearing over a canvas that is expected to fit the window.

Steps to reproduce

1. Export HTML project with Canvas Resize Policy set to Adaptive
2. Run in browser
3. Zoom in using browser controls to 110%, 125%, other values

Minimal reproduction project (MRP)

ZoomRepro.zip

also for example https://html-classic.itch.zone/html/12218877/index.html

[rpahut]

@marcosc90

I think it is worth noting that canvas.width and .height are integer dimensions representing pixels, but canvas.style.width and .height are logical dimensions and accept fractional values. Possibly the correct and sufficient solution is to floor() the pixel dimensions, but keep the fractional part for the logical ones, so that they match the number of pixels scaled by whatever zoom factor is applied.