Added rounded corners option for progress bar

[ghost]

This PR adds the option progress_bar_corner_radius to enable rounded corners on the progress bar. If its value is non-zero, draw_rounded_rect is used in place of draw_rect to render the bar. Please let me know if anything needs to be changed!

[fwsmit]

Thank you for making this PR. It looks pretty good. I've added a few comments. The main thing is that you need to check if the lines of the progress bar are not blurry. This is because of the way cairo draws lines.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 38.46154% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.25%. Comparing base (53a2ff1) to head (cb8d9a4).
⚠️ Report is 544 commits behind head on master.

Files with missing lines	Patch %	Lines
src/draw.c	33.33%	6 Missing ⚠️
src/settings.c	50.00%	2 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1119      +/-   ##
==========================================
- Coverage   65.26%   65.25%   -0.01%     
==========================================
  Files          46       46              
  Lines        7358     7362       +4     
==========================================
+ Hits         4802     4804       +2     
- Misses       2556     2558       +2     

Flag	Coverage Δ
unittests	65.25% <38.46%> (-0.01%)	⬇️

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[fwsmit]

@vlfldr would you mind finishing this PR?

[ghost]

@fwsmit Sorry for the delay. Just want to clarify, when you say "With whole number scaling it should work like this" in a comment above do you mean it should work as-is with the parameters changed to floats, or it should work by rounding to the nearest .5?

I am going to hold off on passing the frame width to draw_rounded_rect to support fractional scaling for now as it would involved either overloading or touching more of the codebase than this PR intended to.

[fwsmit]

@fwsmit Sorry for the delay. Just want to clarify, when you say "With whole number scaling it should work like this" in a comment above do you mean it should work as-is with the parameters changed to floats, or it should work by rounding to the nearest .5?

It should work as is. You can best check this by setting the progress bar width to 1 and seeing if the progress bar border is a nice 1-pixel line and not a blurry multi-pixel line.

I've tested it and it works great.

I am going to hold off on passing the frame width to draw_rounded_rect to support fractional scaling for now as it would involved either overloading or touching more of the codebase than this PR intended to.

Okay that's fine

[fwsmit]

After you address the open comment it's good

[fwsmit]

Thanks! This is a great addition to dunst. I'll go ahead and merge it