Format placeholder text and hide on focus

[sssoleileraaa]

Description

Currently the text Compose a reply to [sourcename] remains in front of the cursor in the ReplyBoxWidget until you start typing. It should be removed as soon as soon as textbox is active. It also needs to be updated so that it is formatted to match the Zeplin screen so that the source name is:

• font and font size: Montserrat-Bold
• size: 18px
• letter spacing: 0.25px
• color: #24276d

and the Compose a reply part is:

• font and font size: Montserrat-Regular
• size: 18px
• color: #404040

[deeplow]

It seems that we are fighting against the nature of Qt. Here are my findings so far:

• QTextEdit.setPlaceholderText() does NOT allow html as input (although this is not documented)
• QTextEdit.setText() allows for html but for some reason it does not work if we wanted to set it as a "placeholder" (meaning that we cannot setText as soon as the text box is created) - again, undocumented behavior.

We need the html in order to format the source name with bold.

Probably just adding a label on top the text box with the formatting is the best we can do to circumvent these limitations