Plain text has no formatting. That is fundamental to it's description as "plain"

Not sure I understand the meaning but when I hit RETURN that's formatting and it's what I practice and the quest is about fixed-width font in the composition window. From my perspective the entire question of fonts as well as wrapping are inadequately intuitive in mozilla for some reason. The topic shouldn't even arise in such a a mature suite of apps, my comment not to be confused with antipathy, I use T-Bird, Seamonkey, FF and its torred fork every day :-)

No return is a carriage return, not formatting. It worked just as well on an olivetti typewriter as it does in plain text messages and like plain text you got no control over the formatting before it was indelibly marked on paper.

By definition you can not control the font used to display your message, because you message does not contain any information about fonts. Unlike that Olivetti typewriter you can not even set tabs because the medium is not intended for paper, but on screen display.

As far as setting the fixed width font for the compose window goes you simply turn off the compose in HTML option in Account settings > copies and folders. This is a per account setting. Clearly the font used is irrelevant here are no fond data will be transmitted. Like an IBM 3270 mainframe terminal from the 1970s the text will wrap as 72 characters. However it is my understanding that the font specified in the preferences for monospaced will be used in the display.

Just as this forum is capable of fixed with fonts.

So is Thunderbird, and you can set your compose to use plain text as I mentioned above. Or you can swap from plain text to HTML and vise versa by holding shift when you click on the reply, compose or forward buttons. This will reverse the current option for the current composition. Very handy for newsgroups that only accept text when your preference is HTML. There is a similar option on contacts in the address book so you can choose to send only particular contacts plain text. Finally there is the option to send plain text to certain domains. in send options. So if you are communicating with folks on a domain (the part of the address after the @ in the email address) that uses plain text, not that I am aware of any domain where plain text email is enforced these days, you can set the domain in there to enforce plain text to the domain.

Now if you want your formatting to translate you need to stop using plain text and move the HTML, that is why the vast majority of mail users simple do not even know plain text exists, because they want to include tables and layout data so the recipient sees what they send set out as they intended. This provides a far closer replication of what you see is what you get that plain text can ever offer, but still it is subject to things like screen resolution, size and available fonts on the reading device.

It was with the aim of providing true what you see is what you get that Adobe first came up with the postscript language for printing and then the adobe file format which is mostly postscript codified into a screen display format. So we have the ubiquitous PDF which is about as close to guaranteeing what the reader will see as you can get with electronic transfer of data.

But nothing electronic really replaces the medium of paper. With that you get total control.

Prefs/Composition/ There's HTML style but I want to globally interdict HTML. There is NO other font setting to be seen here

As I said, you do not get to specify the viewing font used. each reader will use what their preferences state.

Thanks for the detailed response, there's stuff in there I didn't know.

I'll field a wild guess that I misunderstand the nature of fixed width fonts. I always presumed that a line typed using fixed width font X using size 16 would show exactly the same new lines and line length when read using any other fixed width font as long as it too used size 16. This may not be the case.

When I send out a message using fixed width font and I read my own message also using fixed width font I don't get the same line length, I'll have to do more tests to pinpoint exactly where I'm screwing it up, this is mainly why I'd like the entire font pref interface to be more intuitive, like any time, in any window, one click and 'I want all this in font so and so', so to speak. I find the font and wrapping parts of prefs a hard act to follow (and I don't think I alone do so).

I know that the reader can chose not to use fixed fonts, that's easily taken care of if necessary in the message, maybe it isn't enough to just say to use fixed font unless the type and size are also specified. Sorry about rambling on, like I said I need to test more :-)

The preference you might be looking for is called mailnews.send_plaintext_flowed. It is set to true by default and it determines whether the sent message is in the flowed format or not. Set it to false so that the reader client doesn't reflow the text to utilize their viewing window's width, but why you would want to control the reader's view baffles me. See https://fastmail.blog/advanced/format-flowed/

I found no file containing "mailnews.send_plaintext_flowed" so I inserted this into prefs.js

user_pref("mailnews.send_plaintext_flowed", false);

One reason I might want the reader to use fixed width is for poems and such, in all such cases I would include a note to use fixed-width font to read it. Some others do the same for ascii sigs, for code, etc.

My posted (perceived) issue has nothing to do with how others reading the message see it, it has to do with how "I" see it in my composition window and in my message body window when reading my own message.

Although the issue has irritated me several times I'm now unable to duplicate it. The only discrepancy I can see is that the font size in the composition window is about half that in the readers message body window.

I might be on to the cause of my displeasure. The supplied image does not make it sufficiently clear but what happens at times is that manual CR insertion results in what appears to be acceptable justification while the same text next viewed in the reader shows line ends jagged by whole words or more making the blurb look like cowpiss.

It looks like the problem arises from the composition window font which I presumed as being also fixed being actually proportional. I have no idea where this composition window font is set, or if it's settable at all. This is what I mean by font handling that is neither intuitive nor clearly methodical and transparent, it is and always has been a hard act to follow @ Mozilla.

Possibly the user trend has been misinterpreted as being free of fixed-width usage or of too much interest in formatting.

The image clearly shows a proportional font being used in the reader. Looks like Arial or one of that sans serif group.

Preferences > Language and appearance > Advanced.

The mono spaced font there will be being used for the display is my understanding of things. Mine is set to Consolas and I do not recall ever changing it.

Having said that if I select the view menu and message body as plain text I appear to be getting monspaced to the point of courier. Might as well be back on my 3270 console.

I have no idea where this composition window font is set, or if it's settable at all. This is what I mean by font handling that is neither intuitive nor clearly methodical and transparent, it is and always has been a hard act to follow @ Mozilla.

It is settable, under Preferences > General > Language & Appearance > Fonts & Colours > Advanced. Choose your prefered font for monospace (fixed-width) and the size. In my case, it's set to Consolas size 13. This is what is displayed in the compose window when I'm writing a plain-text message. If I change the font and size there, it reflects immediately in the compose window. When I open the plain-text message (after sending it to myself), it displays using a monospace font and whichever zoom level I have set.

While composing, the text is wrapped after 72 characters. When opening the received message, it is reflowed to occupy the width of the window, because I have mailnews.send_plaintext_flowed set to true and mailnews.display.disable_format_flowed_support set to false, which are the default values for those preferences. If I toggle mailnews.display.disable_format_flowed_support to true, the message is not reflowed, instead, it is wrapped at 72 characters just like it is in the compose window despite the message being of the flowed format.

k03 said

I have no idea where this composition window font is set, or if it's settable at all. This is what I mean by font handling that is neither intuitive nor clearly methodical and transparent, it is and always has been a hard act to follow @ Mozilla.

It is settable, under Preferences > General > Language & Appearance > Fonts & Colours > Advanced. Choose your prefered font for monospace (fixed-width) and the size. In my case, it's set to Consolas size 13. This is what is displayed in the compose window when I'm writing a plain-text message. If I change the font and size there, it reflects immediately in the compose window. When I open the plain-text message (after sending it to myself), it displays using a monospace font and whichever zoom level I have set.

While composing, the text is wrapped after 72 characters. When opening the received message, it is reflowed to occupy the width of the window, because I have mailnews.send_plaintext_flowed set to true and mailnews.display.disable_format_flowed_support set to false, which are the default values for those preferences. If I toggle mailnews.display.disable_format_flowed_support to true, the message is not reflowed, instead, it is wrapped at 72 characters just like it is in the compose window despite the message being of the flowed format.

Thanks, I think I got a little farther. Note on the snapshot that both the sent message as down-read and the one in the reply show identical line endings. THIS is already progress. But also note that although even the MINIMUM font size is preffed to #20, the size in the composition window (for the reply) is still tiny at the default setting. Where does THIS come from? What "I" would like is the ability to set a mono-spaced fixed-width font of the same size for all text body being read and all text body being composed.

As I said before the prefs GUI for fonts is confusing, it should be either totally intuitive (probably impossible) or totally specific (digital page real-estate costs nothing). There are basically 2 types of windows: listing and header ones, and text-body ones. That's where font prefs should start and without ever requiring the user to become a typsetting guru :-).

I could be wrong but isn't that exactly the way that Mozilla used to do it at one time????

How do I set Default font to Lucida Typerwritter (which I think is fixed-wodth) 20?

If the "Default" is set to 20 what's with the size 6 or whatever "default" in the edit window?

Why do I need to set Prop: Serif and then Serif: some proportional serif font? Shouldn't that be jus a single line like "For proportional font use: 'whatever proportional font like Adobe Times)'? Ditto for monospace.

How do I set Default font to Lucida Typerwritter (which I think is fixed-wodth) 20?

Select Lucida Typerwritter in the field for Monospace. See attached image.

I noticed you're setting fonts for the "Other writing systems" encoding, and yet you are writing using the Latin alphabet. What's up with that? Is this a result of you tinkering with preferences hoping to find a solution?

For plain-text message display when reading a message, you can set a global preferences using css. Create a new folder called chrome inside your Thunderbird profile folder. Inside the chrome folder, create a text file called userContent.css. Make sure the filename extension is .css and NOT .css.txt or it won't work. Inside the file, copy the following css code:

.moz-text-flowed, .moz-text-plain, .moz-text-plain pre {
	font-size: 16px !important;
}  

Save the file, then using the Config Editor, set toolkit.legacyUserProfileCustomizations.stylesheets to true. Restart Thunderbird. When you open a plain-text message either in a new tab or message (reading) pane, it should now appear in the size set in the css code.

Note: make sure the checkbox labelled Use fixed width font for plain text messages is checked. See attached image.