[Bug]: `use_xft = true` breaks window sizing

[simotek]

What happened?

Window sizing is smaller when use_xft = true is set then when it is not, if a window is a forced size with min_width and max_width being the same then the window size will be slightly smaller then that.

This first image is with use_xft=true the colored temperature shape should be centered

This second shot is showing everything working properly with it disabled

Issue is seen running a few day old version of conky from git on openSUSE Tumbleweed

Version

git

Which OS/distro are you seeing the problem on?

Linux (other)

Conky config

https://github.com/philer/polycore  `/opt/conky/bin/conky -c  conkyrc.lua` I had to comment out line 45 of layout.lua to stop a crash as I don't have gpu support.

Stack trace

No response

Relevant log output

No response

[Caellian]

My guess was that font size (glyph width) gets used for window width calculation somehow, but that's not the case.

Closing for now as I can't reproduce (Openbox) with:

conky.config = {
  own_window = true,
  own_window_type = 'override',
  own_window_hints = 'undecorated,sticky,skip_taskbar,skip_pager',
  minimum_width = 500,
  maximum_width = 500,
  use_xft = true,
  font = 'Ubuntu:pixelsize=200',
}
conky.text = [[
  $conky_version
  $conky_version
  $conky_version
]]

Not sure if I'm missing something, but use_xft doesn't have any interaction with window size (besides making it larger if maximum_width not set).

Reopen the issue if you still have it and add which WM you're using.

[Caellian]

Nvm, reopening the issue, you can close it if it's fixed. Try it with minimal example so we can tell whether something else is at play as well (templates?).

[Caellian]

I believe I found what causes this.

In configure event handler there's this:

int mw = surface->dpi_scale(maximum_width.get(*state));
if (text_width > mw && mw > 0) { text_width = mw; }

I don't think expected width in pixels should be affected by DPI. So even though it doesn't affect min_width, by affecting max_width it shrinks the window.

surface->dpi_scale is defined as:

int display_output_x11::dpi_scale(int value) {
#if defined(BUILD_XFT)
  if (use_xft.get(*state) && xft_dpi > 0) {
    return (value * xft_dpi + (value > 0 ? 48 : -48)) / 96;
  } else {
    return value;
  }
#else  /* defined(BUILD_XFT) */
  return value;
#endif /* defined(BUILD_XFT) */
}

There's a few things that might be improved:

• According to a comment on this SO answer, conky should receive resize or move event if DPI changes while it's running.
  • Maybe conky starts on your system before DPI is set to a correct value.
  • That answer said we'd need to reopen temporary connections to the server in order to get up-to-date Xresources.
• According to this SO answer, Xft dpi is a property that has to be set somewhere correctly so it might be wrong.
  • It also includes a function for computing DPI manually.

... and there I was, eagerly closing issues :fearful:

[Caellian]

Let me know if the issue needs to be reopened. I believe the linked PR fixes it.