From 72b93116784ec944f49c7f6a335b0aa663f1430e Mon Sep 17 00:00:00 2001 From: Pascal Kuthe Date: Mon, 6 Mar 2023 16:25:41 +0100 Subject: [PATCH] fix view anchors not at start of a visual line The top of a view is marked by a char idx anchor. That char idx is usually the first character of the visual line it's on. We use a char index instead of a line index because the view may start in the middle of a line with soft wrapping. However, it's possible to temporarily endup in a state where this anchor is not the first character of the first visual line. This is pretty rare because edits usually happen inside/after the view. In most cases we handle this case correctly. However, if the cursor is before the anchor (but still in view) there can be crashes or visual artifacts. This is caused by the fact that visual_offset_from_anchor (and the positioning code in view.rs) incorrectly assumed that the (cursor) position is always after the view anchor if the cursor is in view. But if the anchor is not the first character of the first visual line this is not the case anymore. In that case crashes and visual artifacts are possible. This commit fixes that problem by changing `visual_offset_from_anchor` (and callsites) to properly consider that case. --- helix-core/src/lib.rs | 2 +- helix-core/src/position.rs | 40 ++++++++++++++++---- helix-view/src/view.rs | 76 +++++++++++++++++++------------------- 3 files changed, 70 insertions(+), 48 deletions(-) diff --git a/helix-core/src/lib.rs b/helix-core/src/lib.rs index e3f862a60..4d50e48bf 100644 --- a/helix-core/src/lib.rs +++ b/helix-core/src/lib.rs @@ -98,7 +98,7 @@ pub use {regex, tree_sitter}; pub use graphemes::RopeGraphemes; pub use position::{ char_idx_at_visual_offset, coords_at_pos, pos_at_coords, visual_offset_from_anchor, - visual_offset_from_block, Position, + visual_offset_from_block, Position, VisualOffsetError, }; #[allow(deprecated)] pub use position::{pos_at_visual_coords, visual_coords_at_pos}; diff --git a/helix-core/src/position.rs b/helix-core/src/position.rs index 7b8dc326e..c3233a340 100644 --- a/helix-core/src/position.rs +++ b/helix-core/src/position.rs @@ -137,6 +137,12 @@ pub fn visual_offset_from_block( (last_pos, block_start) } +#[derive(Debug, PartialEq, Eq, Clone, Copy)] +pub enum VisualOffsetError { + PosBeforeAnchorRow, + PosAfterMaxRow, +} + /// Returns the visual offset from the start of the visual line /// that contains anchor. pub fn visual_offset_from_anchor( @@ -146,28 +152,46 @@ pub fn visual_offset_from_anchor( text_fmt: &TextFormat, annotations: &TextAnnotations, max_rows: usize, -) -> Option<(Position, usize)> { +) -> Result<(Position, usize), VisualOffsetError> { let (formatter, block_start) = DocumentFormatter::new_at_prev_checkpoint(text, text_fmt, annotations, anchor); let mut char_pos = block_start; let mut anchor_line = None; + let mut found_pos = None; let mut last_pos = Position::default(); + if pos < block_start { + return Err(VisualOffsetError::PosBeforeAnchorRow); + } + for (grapheme, vpos) in formatter { last_pos = vpos; char_pos += grapheme.doc_chars(); - if char_pos > anchor && anchor_line.is_none() { - anchor_line = Some(last_pos.row); - } if char_pos > pos { - last_pos.row -= anchor_line.unwrap(); - return Some((last_pos, block_start)); + if let Some(anchor_line) = anchor_line { + last_pos.row -= anchor_line; + return Ok((last_pos, block_start)); + } else { + found_pos = Some(last_pos); + } + } + if char_pos > anchor && anchor_line.is_none() { + if let Some(mut found_pos) = found_pos { + return if found_pos.row == last_pos.row { + found_pos.row = 0; + Ok((found_pos, block_start)) + } else { + Err(VisualOffsetError::PosBeforeAnchorRow) + }; + } else { + anchor_line = Some(last_pos.row); + } } if let Some(anchor_line) = anchor_line { if vpos.row >= anchor_line + max_rows { - return None; + return Err(VisualOffsetError::PosAfterMaxRow); } } } @@ -175,7 +199,7 @@ pub fn visual_offset_from_anchor( let anchor_line = anchor_line.unwrap_or(last_pos.row); last_pos.row -= anchor_line; - Some((last_pos, block_start)) + Ok((last_pos, block_start)) } /// Convert (line, column) coordinates to a character index. diff --git a/helix-view/src/view.rs b/helix-view/src/view.rs index 0ac7ca3b1..ee6fc1275 100644 --- a/helix-view/src/view.rs +++ b/helix-view/src/view.rs @@ -7,9 +7,13 @@ use crate::{ }; use helix_core::{ - char_idx_at_visual_offset, doc_formatter::TextFormat, syntax::Highlight, - text_annotations::TextAnnotations, visual_offset_from_anchor, visual_offset_from_block, - Position, RopeSlice, Selection, Transaction, + char_idx_at_visual_offset, + doc_formatter::TextFormat, + syntax::Highlight, + text_annotations::TextAnnotations, + visual_offset_from_anchor, visual_offset_from_block, Position, RopeSlice, Selection, + Transaction, + VisualOffsetError::{PosAfterMaxRow, PosBeforeAnchorRow}, }; use std::{ @@ -213,46 +217,38 @@ impl View { // - 1 so we have at least one gap in the middle. // a height of 6 with padding of 3 on each side will keep shifting the view back and forth // as we type - let scrolloff = scrolloff.min(viewport.height.saturating_sub(1) as usize / 2); + let scrolloff = if CENTERING { + 0 + } else { + scrolloff.min(viewport.height.saturating_sub(1) as usize / 2) + }; let cursor = doc.selection(self.id).primary().cursor(doc_text); let mut offset = self.offset; + let off = visual_offset_from_anchor( + doc_text, + offset.anchor, + cursor, + &text_fmt, + &annotations, + vertical_viewport_end, + ); - let (visual_off, mut at_top) = if cursor >= offset.anchor { - let off = visual_offset_from_anchor( - doc_text, - offset.anchor, - cursor, - &text_fmt, - &annotations, - vertical_viewport_end, - ); - (off, false) - } else if CENTERING { - // cursor out of view - return None; - } else { - (None, true) - }; - - let new_anchor = match visual_off { - Some((visual_pos, _)) if visual_pos.row < scrolloff + offset.vertical_offset => { - if CENTERING && visual_pos.row < offset.vertical_offset { + let (new_anchor, at_top) = match off { + Ok((visual_pos, _)) if visual_pos.row < scrolloff + offset.vertical_offset => { + if CENTERING { // cursor out of view return None; } - at_top = true; - true + (true, true) } - Some((visual_pos, _)) if visual_pos.row + scrolloff + 1 >= vertical_viewport_end => { - if CENTERING && visual_pos.row >= vertical_viewport_end { - // cursor out of view - return None; - } - true + Ok((visual_pos, _)) if visual_pos.row + scrolloff >= vertical_viewport_end => { + (true, false) } - Some(_) => false, - None => true, + Ok((_, _)) => (false, false), + Err(_) if CENTERING => return None, + Err(PosBeforeAnchorRow) => (true, true), + Err(PosAfterMaxRow) => (true, false), }; if new_anchor { @@ -269,8 +265,8 @@ impl View { offset.horizontal_offset = 0; } else { // determine the current visual column of the text - let col = visual_off - .unwrap_or_else(|| { + let col = off + .unwrap_or_else(|_| { visual_offset_from_block( doc_text, offset.anchor, @@ -360,8 +356,9 @@ impl View { ); match pos { - Some((Position { row, .. }, _)) => row.saturating_sub(self.offset.vertical_offset), - None => visual_height.saturating_sub(1), + Ok((Position { row, .. }, _)) => row.saturating_sub(self.offset.vertical_offset), + Err(PosAfterMaxRow) => visual_height.saturating_sub(1), + Err(PosBeforeAnchorRow) => 0, } } @@ -390,7 +387,8 @@ impl View { &text_fmt, &annotations, viewport.height as usize, - )? + ) + .ok()? .0; if pos.row < self.offset.vertical_offset { return None;