scenario: position a tall node with its top within the viewport, and extending past bottom of viewport press page-down
Before this commit we were seeing strange patches of empty space above the old top.
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print('modified screen_top to', node.editor.screen_top1.line, 'at', node.editor.top, 'vpx')
else
-- adjust editor to start rendering near top of viewport
--? print(Viewport.y)
node.editor.top = Viewport.y%node.editor.line_height
if node.editor.top > 0 then node.editor.top = node.editor.top - node.editor.line_height end
--? print('top', node.editor.top)