Fix #1124, #1125

[sysint64]

PR fixes #1124 and #1125.

[cmyr]

Thanks! this stuff is definitely going to be in flux for the next little while but good to get this fixed.

[totsteps]

+ self.move_selection(Movement::StartOfDocument, data, false);

I don't think this is what we want. One needs to click twice in order to enter new text. This also results in some weird behavior(happens randomly), where the whole text is selected when the textbox receives focus by the first click(gif below).

The textbox should preserve the selection movement and only draw the selection if it is being focused. As seen in CLion, vscode, JavaFX, etc.

I am not sure what the best solution is, but again not resetting the selection does not resolve #1125. Maybe resetting hscroll_offset when FocusChanged solves this!

[cmyr]

so I think the desired behaviour is platform dependant.

• On all platforms, if a widget does not have focus it should not draw its selection.
• on mac, when a textbox gains focus, it should select all text.
• in windows, a textbox should preserve its previous selection state.

additionally:

• on mac, a textbox should not draw the cursor if the selection is not a caret.

I think it's best to do this work on top of #1274.