The official Emacs documentation says:
...to change the sizes of the fonts globally, type C-x C-M-+, C-x C-M-=, C-x C-M-- or C-x C-M-0,...1
Unfortunately, when I type
C-x C-M-+ on my laptop's keyboard2, the error message
C-x C-M-+ is undefined appears in the mini-buffer.
Mysteriously enough, I have not been able to find out the command that would have been executed upon typing
C-x C-M-+ if the documentation had been correct.
This is all old-news for me, actually.
In fact, I had already resigned myself to there not being any convenient way to globally modify the font size in Emacs.
But the other day, while I was in the middle of a Zoom meeting for work, sharing my screen, and viewing an Emacs window, I accidentally typed something that caused the font-size of the Emacs buffer to become larger. Further (as I was able to confirm after the meeting ended), this font-size change was global.
Even though this incident did startle me when it happened, I could not investigate it further at the time, because I was in the middle of an important discussion with my team at work.
To make matters worse, this discussion went on for another hour or so, during which I had to run multiple Emacs commands. As a result, by the time I had a chance to run
view-lossage, there was no longer any trace of the mystery shortcut I had stumbled upon.
I have spent a long time since then, trying to replicate this shortcut, in vain.
In fact, I can't swear that what I did to change the font-size was only typing something. I may have been doing something else at the same time, such as moving the cursor, etc.
Be that as it may, the experience convinced me that there is in Emacs, after all, a reasonably convenient way to change the font size globally, and I really would like to find out what it is.
In summary, my question is: what is the mystery shortcut that causes the font size in Emacs to change globally?
I should point out that this thread addresses the same problem, but none of the answers given there answer the question raised above.
1 The documentation continues with "or scroll the mouse wheel with both the Ctrl and Meta modifiers pressed". Unfortunately, with my (extremely "mouseless") MacBook Pro laptop, AFAIK, there is no way to simulate this mouse-wheel-based interaction, so this method, whether it works or not under the right circumstances, is of no use to me.
2 Namely, by first simultaneously pressing controlx, and then simultaneously pressing controloptionshift+