User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:25.0) Gecko/20100101 Firefox/25.0 (Beta/Release) Build ID: 20131025151332 Steps to reproduce: Whenever I'm composing a message in TBird, if I pause during typing even for a fraction of a second, the font size will suddenly get smaller. This isn't even about starting a new paragraph; this will happen in the middle of a word or a sentence. This has been the case for at least a year or two, through many, many versions of TBird, and through my old and new Macs. I'm now on a 21.5" Mac, OS 10.8.5 I'm Actual results: Font size will suddenly get smaller Expected results: I expect that the font size will remain the default throughout the entire message as I compose it.

missmick, thanks for your bug report. 1. Does this happen in *every* composition, or only for some? 2. Did you change your default font size for composition (in the HTML Options)? 3. Did you apply any manual changes to font size in the same composition? 4. Does this also happen for a starting with a blank composition, or only for reply/forward compositions? 5. Can you pls try this: - go to tools > Options > composition > spelling - remove the checkmark for "Enable spell check as you type" - click "OK" to confirm option changes - After that, start another composition, and do the same that would usually cause the bug to occur - does the bug still occur? Does similar bug 925271 describe your issue? Somehow this reminds me of those inline-spell-check related font tag reduplication issues we used to have.

(In reply to Thomas D. from comment #1) > missmick, thanks for your bug report. > > 1. Does this happen in *every* composition, or only for some? > 2. Did you change your default font size for composition (in the HTML > Options)? > 3. Did you apply any manual changes to font size in the same composition? > 4. Does this also happen for a starting with a blank composition, or only > for reply/forward compositions? > 5. Can you pls try this: > - go to tools > Options > composition > spelling > - remove the checkmark for "Enable spell check as you type" > - click "OK" to confirm option changes > - After that, start another composition, and do the same that would usually > cause the bug to occur - does the bug still occur? > > Does similar bug 925271 describe your issue? > > Somehow this reminds me of those inline-spell-check related font tag > reduplication issues we used to have. Thanks, Thomas, for helping me to clarify this bug report. 1. Yes—literally, every single message I compose. 2. Yes—I changed the default size to large. 3. I never make any other font size changes while composing. I do, however, have to manually go back at the end, highlight all of the text, and apply the format change SIZE>LARGER so that all of the text will be the same size. 4. It happens in all cases, whether a blank start or a reply. 5. I've just unchecked "spell check as you type" and will see what that does. I'll report back after a few test messages. 6. Bug 925271 doesn't seem to apply at all——the font changes to a smaller size in the midst of typing; it's there from the beginning. I'm curious, though, and will try a test of this later when I have time.

Followup: I changed the default font and size to "variable width" and "medium." Since I made this set of changes, I have NEVER experienced one single incident of spontaneous change of font size during typing. This leads me to assume that, for unknown reasons, Thunderbird does not like using the large font size as a default. Will be interested in finding out if this bug is looked into and addressed. Using a medium font when typing emails is NOT my preference; it's easier for me to read the text at the large size on screen.

(In reply to missmick from comment #3) > Followup: I changed the default font and size to "variable width" and > "medium." Since I made this set of changes, I have NEVER experienced one > single incident of spontaneous change of font size during typing. missmick, can you (temporarily) switch back default font to "large" in the options, then uncheck (disable!) "spell check as you type" and report back pls if the bug still occurs after that? > This leads me to assume that, for unknown reasons, Thunderbird does not like > using the large font size as a default. Possible, perhaps something like Bug 812638 or its followup bug 917027. > Will be interested in finding out if this bug is looked into and addressed. > Using a medium font when typing emails is NOT my preference; it's easier for > me to read the text at the large size on screen. Missmick, good news for you (you can have what you want without seeing the bug): For your purposes ("to read the text at large size on screen" "when typing"), there is a much better solution which will also avoid your font size problem: You can just change the *zoom* instead of changing the actual default font size. I understand you just want fonts bigger for *your own* reading on screen but if you change the default font size for that purpose, that's the wrong approach because your *recipients* will also get those large font sizes in their message content which is certainly undesired for them. Changing the zoom means that you can *view* it big, but the real font in yr msg is still normal size for recipients. Change zoom as you would in Firefox: Ctrl++ to zoom in (or use Ctrl+mouse wheel) Ctrl+- to zoom out (or use Ctrl+mouse wheel) Ctrl+0 to reset zoom to 100% Zoom commands also found in View > Zoom menu. Does that help?

Thanks, Thomas. A sensible approach I never considered with email——I'll try zooming when I compose messages to see if this is a habit I can live with. I'll also try the additional requested test by going back to the large font for a while, but I've always kept both spell-checking options unchecked (I'm pretty adept at spelling ;-) ). Don't know if this makes a difference for you in your quest to further investigate the bugs mentioned...I'll just continue my "no spell checking" tradition with this additional test. Will report back as soon as I've gone through enough messages for a reasonable test.

I've gone through some test emails with the previously-mentioned change, and the bug has again reappeared; the font will spontaneously switch to the medium size when I pause even momentarily in my typing. Seems to confirm my assumption that TBird gets buggy when using the font size "large."

missmick, do you still see this issue?

Resolved per whiteboard