Patch Generator erroneously saying that a file has been written

[vlakoff]

Steps to reproduce:

1. Open "Tools > Generate Patch..."
2. Ensure that "Result:" input is blank (which is its initial state)
3. Click on "OK"

Currently, WinMerge shows a "Patch file successfully written" message, although it didn't create any file actually.

Note there is a "Copy to Clipboard" checkbox, that can be used whether writing a file or not.

UI that I may suggest:

☐ Copy to Clipboard
☑ Write to file
    ☐ Append to existing file

• If "Write to file" is unchecked, disable "Append to existing file" checkbox, and maybe also disable "Result:" input.
• If both "Copy to Clipboard" and "Write to file" are unchecked, display error message "No action selected" when clicking OK.
  • Even better, disable the OK button.
• If "Write to file" is checked but no file is provided in "Result:", display error message "No result file selected" when clicking OK.
  • Even better, disable the OK button.

[sdottaka]

Well, actually, WinMerge isn't lying and actually writes to a temporary file %TEMP%\WinMerge_TEMP_xxxx\patxxxx.tmp. This is useful if the "Open to external editor" option is checked, but may not make sense if that option is not used...

[vlakoff]

I had searched for created files, but missed this temp file…

Thus, I could suggest the following:

☐ Copy to Clipboard
☑ Write to file
    ☐ Append to existing file
    ☐ Open IN external editor

With these amendments:

• Allow blank "Result:" input, in which case a temp file is created, as currently (not really a satisfying UX, but we may settle on this for now).
• Show path of the created (or appended) file in the success message. That would help to alleviate the issue.

[vlakoff]

Thinking about adding a "Write to temporary file" checkbox:

☐ Copy to Clipboard
☑ Write to file
    ☐ Append to existing file
    ☐ Open IN external editor
    Result: ________ [Browse...]
    ☐ Write to temporary file

• Unchecking "Write to file" disables all the elements below.
• Important: Checking "Write to temporary file" disables the "Result:" input.
• "Append to existing file" checkbox is useless when outputting to a temp file (as the file is different each time).
  • Disabling this checkbox would let the user understand it's not possible to append when using temp files.
• Using temp file is useless when "Open IN external editor" is unchecked. But that's the issue we already have currently, and I'm afraid that automatically (and forcibly) checking the box wouldn't be great.
  • With my suggestions implemented (mainly, the temp file being explicit), the user would have everything to understand what is done. So he could by himself change the settings (output to a regular file and/or open in external editor) to get an useful behavior.

[vlakoff]

And thinking about an alternative approach (the following represents 3 radio buttons, the first one is toggled on):

⚫ Write to file
    Result: ________ [Browse...]
    ☐ Append to existing file
    ☐ Open IN external editor
⚪ Open in temporary file
⚪ Copy to Clipboard

• It's important that "Write to file" and "Open in temporary file" are exclusive modes. We have to avoid writing 2 files.
  • Hence the radio buttons (BTW, it's 2024 and we still don't have emojis for enabled/disabled radios…)
• We need to keep the possibility to copy to clipboard without writing any file (whether regular or temporary).
  • Because the radios force to choose a mode, in order to be able to unselect both "write to file" modes, I had to make "Copy to Clipboard" a radio as well.
  • Previously, we were able to, at the same time, write to file and copy to clipboard. We are losing this possibility, but I'm not sure it was really useful. And making "Copy to Clipboard" a dedicated mode seems to be great.