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Plan 9 from User Space
https://9fans.github.io/plan9port/
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acme: have Dump save both low and high DPI fontnames #630

Closed matheuristic closed 10 months ago

matheuristic commented 10 months ago

Instead of only saving a window's currently displayed font's name (t->reffont->f->name) to the dump file (the current implementation), have Acme's Dump command save that window's combined low DPI and high DPI font names (t->reffont->f->lodpi->name and t->reffont->f->hidpi->name) when both are available.

This patch enables Acme dumps to better retain window font state.

In particular, it addresses the following font display quirk when using Dump and Load in Acme on high-DPI screens (200 DPI or more, like macOS Retina screens) without this patch, shown as an example:

  1. Suppose we are using Acme on a high DPI screen, say a Retina MacBook screen.
  2. Open a non-empty text file, say /tmp/abc.txt, in Acme on a high DPI screen type.
  3. Execute Font /mnt/font/AndaleMono/15a/font. This font is treated as the low DPI font and Acme automatically doubles its point size to /mnt/font/AndaleMono/30a/font as the high DPI font. Since we are using a high DPI screen, the high DPI font is displayed.
  4. Execute Dump to save window state to a dump file ~/acme.dump. The saved font for the /tmp/abc.txt window in the dump file is /mnt/font/AndaleMono/30a/font as that's the displayed font.
  5. Close then start a fresh instance of Acme.
  6. Execute Load to restore window state from ~/acme.dump. The saved font name for the /tmp/abc.txt window, /mnt/font/AndaleMono/30a/font, is treated as a low DPI font so it is automatically doubled to in point size (i.e., /mnt/font/AndaleMono/60a/font is used) for use as the high DPI font, and since we are on a high DPI screen that 60pt font is displayed.

In the example, the displayed font in the /tmp/abc.txt window is clearly too large. That is, font display state was restored incorrectly.

With this patch applied, in step 4 of the example, the saved font name for the /tmp/abc.txt window in the dump file is now /mnt/font/AndaleMono/15a/font,/mnt/font/AndaleMono/30a/font. So, on Load in step 6, the high DPI font /mnt/font/AndaleMono/30a/font is used to display text in the file window. That is, display font state was restored correctly.

dancrossnyc commented 10 months ago

This is great! Thank you so much!