Have TextDocument listen for state changes on the internal undo stack,
and forward those to all clients via a new virtual function.
This simplifies updating the can_undo / can_redo states of TextEditor.
This patch removes an incorrect way for TextDocument::text_in_range
to return early when the first line of the selection was empty. This
fixes an issue in TextEditor where the status bar showed that 0
characters are selected when the selection started on an empty line.
Until now, this has been hackishly tracked by the TextEditor app's
main widget. Let's do it in GUI::TextDocument instead, so that anyone
who uses this class can know whether it's modified or not.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
