Font Sizes

In this post I am going to look at two perennial Thunderbird support questions.  Both related to fonts.

Size of fonts in the program it self.

Due to the extremely high resolution many people are running on their graphics cards Thunderbirds internal fonts often appear tiny and difficult to read.  These internal fonts are sized by default based on certain internal operating system fonts,   The oft asked question is how to modify these fonts and the answer traditionally has been to hand craft a UserChrome.CSS file the specifies the fonts you want for the elements you desire to change.   While it is undoubtedly true that this will work, it is well beyond the technical skills of most people. The element names are not well documented and the intricacies of CSS (Cascading Style Sheets) is not something many people are familiar with at all.  Thankfully in the recent past someone has written an add-on, the Theme and Font size changer, to manager the process for us.  This add-on is simple to use and makes Thunderbird so much easier to read for those struggling with what was often refered to as microscopic fonts.

If you have never installed an add-on, my earlier post on that topic might be of some assistance.

Size of Fonts in Messages being displayed

If it is only the display font of your incoming emails that is an issue,  the settings in Tools > Options > Display >Formating and then clicking on the advanced button will allow you to specify font sizes for the display of emails.  These are only display fonts, and have no effect on the fonts used to actually send email.  Note that the font sizes are set in Pixels, not the points that most people are used to from programs like Word.  Pixels are smaller than points so if you would normally set text to 12 points, that will translate to around 18 pixels.


Size and Consistency of Fonts when composing a message

This is a multi pronged issue.  So I will look at the issues on at a time.

1. Thunderbird composes HTML mail by default. This style of mail has variable sized fonts that can be specified at the time the message is written. One of the issues many people complain about is that they can not specify their font in points, it is simply sized in the editor as larger and smaller.  This is based on the HTML standard which uses the <font> tag to specify the size of a font.  The font tag in HTML has only 7 values. (ie in the actual HTML code it looks like this <font size="number">with the default being 3) 
2. HTML font tags are depreciated in HTML 4 and totally absent from HTML 5.  In HTML 5 fonts must be specified in the CSS for the document. So at some point the Editor for Thunderbird is going to need to move forward, not it will not be now.
3. Fonts change in the middle of typing your message.  This will only occur if you change the default font in Thunderbirds Composer.  This is because this bug  reverts to the default font at seemingly random intervals.  The workaround is to install the Quote and Compose manager add-on and turn on the option it contains to stabilize fonts. This bug has been around for some 8 years, and I doubt there will be a resolution until the composer is completely rewritten to support HTML 5
4. Some add-ons, for reasons I don't understand, turn on plain text formatting of email.  This is set from the view menu > messagebody as entry. If your fonts are not working, it is likely that this is not set to 'Original HTML'