So I recently migrated to SB from Roam, and I missed the persistent folding of outline blocks. With thanks to inspiration from this topic:
I have written some Lua code to do this.
I was hoping to be able to write an event listener that would activate whenever it detected blocks being folded or unfolded, but no such event seems to be emitted. Therefore I fell back on writing my own “togglePersistentFold” command, and forgetting the existing fold/unfold commands entirely. When you use this command with the cursor in a suitable line, it adds or removes a specific character from the end of the line (a down arrow emoji) and then toggles the fold status of the line.
On page load (when the blocks you previously folded would normally reappear in their unfolded state), an event listener folds up any lines that have that character at the end so that they are in the same state as you left them.
Regex wizards could probably have done this in about two lines, but I’m not one of them! Also my first time writing Lua so this is probably horrible code, but it works.
```space-lua
persFold = persFold or {} -- define namespace for persistent fold supporting functions
persFold.marker = "⬇️"
function persFold.lineStart(pageText, pos)
-- Return the starting position of the line of the current page containing position pos
-- Get the content of the page text up to pos
local pageTextToPos = string.sub(pageText, 1, pos)
-- Reverse it
local pageTextToPosReversed = string.reverse(pageTextToPos)
-- Find the number of characters before the first new line character
local posPositionInLine, _ = string.find(pageTextToPosReversed, "\n") - 2
-- Subtract that number from pos
local startOfLine = pos - posPositionInLine
return startOfLine
end
function persFold.lineLength(pageText, startOfLine)
local pageTextFromStartOfLine = string.sub(pageText, startOfLine)
local lineLength, _ = string.find(pageTextFromStartOfLine, "\n") - 1
return lineLength
end
function persFold.lineText(pageText, pos)
-- Return the text of the line of the current page containing position pos
--local startOfLine = persFold.currentLineStart(pageText, pos)
--local pageTextFromStartOfLine = string.sub(pageText, startOfLine)
-- Find the end of the current line, or the end of the page if it's the last line
local startOfLine = persFold.lineStart(pageText, pos)
local lineLength = persFold.lineLength(pageText, startOfLine)
if lineLength == -1 then
lineLength = string.len(pageText) - startOfLine + 1
end
local lineText = string.sub(pageText, startOfLine, startOfLine + lineLength - 1)
return lineText
end
```
```space-lua
command.define {
name = "togglePersistentFold",
key = "ctrl-alt-q",
run = function()
local pageText = editor.getText()
local cursorPositionInPage = editor.getCursor()
-- Get the text, starting position and length of the current line
local currentLineText = persFold.lineText(pageText, cursorPositionInPage)
local currentLineStart = persFold.lineStart(pageText,cursorPositionInPage)
local currentLineLength = persFold.lineLength(pageText,currentLineStart)
-- Search in current line for the first instance of `* `
local bulletPositionInLine, _ = string.find(currentLineText, "\\* ")
if (bulletPositionInLine != nil) and (currentLineLength != -1) then
-- If there is a bullet point in this line and this is not the last line
-- Find start, length and text of next line
local nextLineStart = currentLineStart + currentLineLength
local nextLineLength = persFold.lineLength(pageText,nextLineStart)
local nextLineText = persFold.lineText(pageText,nextLineStart)
-- Find bullet position in next line
local bulletPositionInNextLine, _ = string.find(nextLineText, "\\* ")
-- Is it indented further than the current line's bullet, if there is a bullet at all? (If there isn't, string.find returns 0, so the same expression tests for both cases.)
if bulletPositionInNextLine > bulletPositionInLine then
-- Now we are sure we are on a line which has a bullet point and has a sub-bullet in the next line.
-- Check if this line has the fold marker at the end
if string.sub(currentLineText,currentLineLength - string.len(persFold.marker) + 1, currentLineLength) == persFold.marker then
-- If yes, remove marker
editor.replaceRange(nextLineStart - 1 - string.len(persFold.marker), nextLineStart - 1, "")
else
-- If no, add marker
editor.insertAtPos(persFold.marker, nextLineStart - 1)
end
editor.toggleFold()
end
end
end
}
-- Event listener to fold up marked bullets on page load
event.listen {
name = "editor:pageLoaded",
run = function()
-- move backward through the page looking for the fold marker at the end of a line, and fold whenever you find it
-- (it might work going forward, but it was easier to write it this way than to test.)
-- repeat until you can't find the fold marker at the end of any more lines
local markerNewline = persFold.marker .. "\n"
local pageText = editor.getText()
pageTextReversed = string.reverse(pageText)
nextFold, _ = string.find(pageTextReversed, string.reverse(markerNewline))
while nextFold > 0 do
editor.moveCursor(string.len(pageText)-nextFold, false)
editor.toggleFold()
nextFold, _ = string.find(pageTextReversed, string.reverse(markerNewline), nextFold + 1)
end
editor.moveCursor(0) -- put the cursor back at the top of the page
end
}
```
As written, it requires nested bullet points to be on strictly successive lines, which is not quite in accordance with SB’s folding logic. Close enough for me, for now…
EDIT: changed a 1 to a 0 in the last line there, 1 caused an out of range error on empty pages.
Edit by @zef: Helped you a bit making it clear you’re using space-lua blocks here
