bug#72721: 31.0.50; Visual-wrap-prefix-mode breaks Magit log buffers

[Jim Porter <jporterbugs@gmail.com>]

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On 8/20/2024 10:18 PM, Jim Porter wrote:
> On 8/20/2024 8:15 PM, Jim Porter wrote:
>> Hopefully the attached reproducers help make sense of this. I've also 
>> updated my patch to handle 'min-width' in what I think is a simpler 
>> way. This implementation relies on the fact that you can't nest 
>> 'min-width' specs (the iterator struct can only hold one spec at a 
>> time). I'm guessing on some of these parts, so I may be totally 
>> off-base, but the test cases do what I expect anyway...
> 
> Whoops, I'd uploaded the wrong patch. Here's the correct one.

... and here's a new test case (overlay-min-width). This shows that now 
you can apply 'min-width' as an overlay property, which would be great 
for 'visual-wrap-prefix-mode'. I could then convert that code to use 
overlays (at least for 'min-width', maybe for 'wrap-prefix' too), which 
would make it easier to clean up when deactivating the mode.

Of course, if there's a way to write regression tests for this, I'm 
happy to do so, but I've never looked into how (or if) one can write 
regression tests for display engine features.

[-- Attachment #2: test-cases.el --]
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(progn
  ;; Should look like:
  ;; 12345
  ;; 678     90
  (switch-to-buffer "simple")
  (erase-buffer)
  (insert "12345\n67890")
  (redisplay)
  (put-text-property
   7 10 'display '((min-width (8)))))


(progn
  ;; Should look like:
  ;; 12345
  ;; 67  89  0
  (switch-to-buffer "consecutive")
  (erase-buffer)
  (insert "12345\n67890")
  (redisplay)
  (put-text-property
   7 9 'display '((min-width (4))))
  (put-text-property
   9 11 'display '((min-width (4)))))


(progn
  ;; Should look like:
  ;; 12345
  ;; hi  890
  (switch-to-buffer "nested")
  (erase-buffer)
  (insert "12345\n67890")
  (redisplay)
  (put-text-property
   7 9 'display
   (propertize "hi" 'display '((min-width (4))))))


(progn
  ;; Should look like:
  ;; 12345         |
  ;; 678     90    |X
  (switch-to-buffer "overlay")
  (erase-buffer)
  (insert "12345\n67890")
  (set-window-margins (selected-window) 0 1)
  (redisplay)
  (setq o (make-overlay 8 9))
  (overlay-put o 'before-string
               (propertize "o" 'display '((margin right-margin) "X")))
  (put-text-property
   7 10 'display '((min-width (8)))))


(progn
  ;; Should look like:
  ;; 12345
  ;; 678     90
  (switch-to-buffer "overlay-min-width")
  (erase-buffer)
  (insert "12345\n67890")
  (set-window-margins (selected-window) 0 1)
  (redisplay)
  (setq o (make-overlay 7 10))
  (overlay-put o 'display '((min-width (8)))))