Text selection is not correct on hdpi

[calixteman]

Attach (recommended) or Link to PDF file here:

Configuration:

• Web browser and its version: Firefox nightly
• Operating system and its version: Windows 11

Steps to reproduce the problem:

1. Open tracemonkey.pdf
2. Zoom at 80%

I get:

My screen resolution is 3840x2160 and the global scale is 150%.

If I change the scale setting in System > Display to 100%, the selection is correct:

The text is measured here:

pdf.js/src/display/text_layer.js

Line 695 in 8ebd2d3

const { width } = this._layoutTextCtx.measureText(textDiv.textContent);

and it returns the same value whatever the screen I use is.

So I think we must take into account the window.devicePixelRatio value when computing the text width.