fix: render IME preedit text inline instead of only in the candidate popup by zhulenghan · Pull Request #1919 · raphamorim/rio

zhulenghan · 2026-09-04T04:19:40Z

Summary

The composing string (e.g. the pinyin typed before a candidate is chosen) never reached the terminal grid — typing was effectively blind aside from the OS candidate popup. This is cross-platform, not Windows-specific: see #1883 (Wayland), which also has a comment confirming the same symptom on macOS.

Three independent things were blocking this, all needed together (verified each is load-bearing by testing with one removed at a time):

Renderer::run only stashed the first preedit char into an unused cursor field; nothing ever painted the actual composing text. Added overlay_preedit_text (mirrors the existing overlay_hint_labels mechanism) to splice the preedit string into the cursor's row, and a HintTag::Preedit that reuses the HyperlinkHover forced-underline treatment so it's visually marked without recoloring the cell.
Ime::Preedit updates never marked the panel dirty, so the render pipeline's per-context damage gate skipped the panel outright on an IME-only frame — same category as command-palette/search-bar input, which already has a documented set_dirty() escape hatch for exactly this. Without this, the overlay only updates on the very first keystroke of a composition and then visibly freezes (confirmed by testing with it removed).
IME composition generates no terminal damage, so even with the panel dirty, the row-rebuild decision (driven by PTY/UI damage) never selected the cursor's row. Track the last row that carried a preedit overlay per route and force it into the rebuild set, both while composing and once more after composing ends without a commit (e.g. Escape), so the overlay is cleaned up correctly.

Test plan

Verified end-to-end on Windows 11 with Microsoft Pinyin (built release binary, drove it with real IME input, screenshotted each state):

Composing text ("ni'hao") now renders live at the cursor, tracking every keystroke, not just the first
Selecting a candidate commits normally, no leftover overlay artifacts
Escape cancels the composition cleanly, overlay is erased and the row reverts to real terminal content
Also checked with cursor blinking disabled, to rule out the blink timer masking a missing redraw
cargo check --workspace, cargo clippy -p rio-grid -p rioterm --release, cargo fmt --check all clean (no new warnings)

🤖 Generated with Claude Code

https://claude.ai/code/session_01KmiYRs6weCxNBesjhEM3QQ

Hosts that paint the cursor themselves had the position but not the shape: DECSCUSR (block / underline / beam) and DECTCEM hidden lived only in the Rust RenderState. rio_render_state_cursor_shape returns them as RIO_CURSOR_*, folding "scrolled into history" into HIDDEN the way cursor_visible() already does. rio_surface_child_pid hands out the spawned program's pid. It is a session leader, so a host can killpg() the whole tree on teardown; dropping the surface only hangs up the pty and SIGHUPs that one pid, which left editors the shell had started running as orphans. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

…popup The composing string (e.g. pinyin typed before a candidate is chosen) never reached the terminal grid, so typing was effectively blind aside from the OS candidate popup - visible cross-platform (issue raphamorim#1883 on Wayland, also reported on macOS in that thread), not Windows-specific. Three things were needed together: - `Renderer::run` only stashed the first preedit char into an unused cursor field; nothing ever painted the actual composing text. Added `overlay_preedit_text` (mirrors the existing `overlay_hint_labels` mechanism) to splice the preedit string into the cursor's row, and a `HintTag::Preedit` that reuses the `HyperlinkHover` forced-underline path so it's visually marked without recoloring the cell. - `Ime::Preedit` updates never marked the panel dirty, so the render pipeline's per-context damage gate skipped the panel outright on an IME-only frame - same category as command-palette/search-bar input, which already has a documented `set_dirty()` escape hatch for exactly this. - IME composition doesn't generate terminal damage, so even with the panel marked dirty, the row-rebuild decision (driven by PTY/UI damage) never selected the cursor's row. Track the last row that carried a preedit overlay per route and force it into the rebuild set, both while composing and once more after composing ends without a commit (e.g. Escape), so the overlay is cleaned up correctly. Verified end-to-end on Windows 11 with Microsoft Pinyin: composing text now renders live, selecting a candidate commits normally, and Escape cancels cleanly with no leftover overlay. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01KmiYRs6weCxNBesjhEM3QQ

Copilot

🟡 Changes recommended

The new preedit overlay logic has correctness issues that can cause unintended recoloring and potential stale overlay artifacts when the cursor row changes during composition.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR fixes IME composition (“preedit”) rendering so that in-progress text is drawn inline in the terminal grid (at the cursor), rather than being visible only via the OS IME candidate popup. It does this by adding a preedit overlay pass in the grid rendering path and ensuring IME-only updates still trigger the render pipeline to rebuild the affected row.

Changes:

Add HintTag::Preedit plus overlay_preedit_text to splice IME preedit text into the cursor row and mark it for forced underline rendering.
Ensure IME preedit updates mark the current context as dirty so IME-only frames don’t get skipped by the panel dirty gate.
Track/force rebuild of the cursor row for preedit frames (and after composition ends) so the overlay appears and is properly cleared.

File summaries

File	Description
rio-grid/src/lib.rs	Adds preedit hint tagging and a new overlay function to render IME preedit text inline with forced underline treatment.
frontends/rioterm/src/screen/mod.rs	Threads preedit text into the per-panel render snapshot and forces the cursor row into the rebuild set for IME-only frames.
frontends/rioterm/src/application.rs	Marks the context dirty on IME preedit updates so the renderer doesn’t skip drawing when only IME state changes.

Review details

Files reviewed: 3/3 changed files
Comments generated: 2
Review effort level: Lite

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zhulenghan · 2026-09-04T04:34:32Z

+                let prev_preedit_row = preedit_rows.get(route_id).copied();
+                let force_preedit_row = if p.preedit_text.is_some() {
+                    preedit_rows.insert(*route_id, p.cursor_row);
+                    Some(p.cursor_row)
+                } else {
+                    preedit_rows.remove(route_id);
+                    prev_preedit_row
+                };
+                let rows_to_rebuild = match (rows_to_rebuild, force_preedit_row) {
+                    (RowsToRebuild::None, Some(row)) => {
+                        if let Some(r) = p.visible_rows.get_mut(row as usize) {
+                            r.dirty = true;
+                        }
+                        RowsToRebuild::Dirty
+                    }
+                    (mode, Some(row)) => {
+                        if let Some(r) = p.visible_rows.get_mut(row as usize) {
+                            r.dirty = true;
+                        }
+                        mode
+                    }
+                    (mode, None) => mode,
+                };


Fixed — now tracking both the current cursor row and the previous overlay row, and forcing whichever ones changed into the rebuild set so a stale overlay from a row the cursor left never lingers. See 619e59a.

zhulenghan · 2026-09-04T04:34:33Z

+    let mut out: Option<(Row<Square>, Vec<Style>)> = None;
+    let start_col = col;
+    for ch in text.chars() {
+        if col >= width {
+            break;
+        }
+        let (target, styles) = out.get_or_insert_with(|| {
+            let mut styles = row_styles.to_vec();
+            styles.resize(width, Style::default());
+            (row.clone(), styles)
+        });
+        let mut sq = Square::from_char(ch);
+        sq.set_style_id(PREEDIT_STYLE_ID);
+        target[Column(col)] = sq;
+        styles[col] = Style::default();
+        col += 1;
+    }


Fixed — the per-cell style is no longer reset; it keeps whatever row_styles already had there, so composing over colored text (e.g. a colored prompt) no longer flashes it to default colors. See 619e59a.

…t row - overlay_preedit_text was resetting each overlaid cell's style to Style::default(), which would recolor the cell (e.g. composing over colored prompt text) even though HintTag::Preedit is meant to be underline-only, same as HyperlinkHover. Leave the cloned row_styles entry untouched instead. - The forced-row-rebuild logic only ever dirtied one row (the current cursor row, or the previous one if composing just ended) - if the cursor moved to a different row while still composing, the now-stale row's overlay was never cleared. Track and force both the current and (if different) the just-vacated row. Verified with a rebuilt binary: composing over colored prompt text no longer flashes it to default colors, and commit/cancel still work correctly end-to-end. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01KmiYRs6weCxNBesjhEM3QQ

zhulenghan · 2026-09-04T04:41:39Z

@raphamorim would appreciate a review when you have a moment. Also FYI: the ubuntu test-native CI failure is pre-existing on main itself (cargo fmt --check fails on librio/src/capi.rs, unrelated to this PR — confirmed by running the check against a clean checkout of main), not something this PR introduced.

raphamorim and others added 2 commits September 3, 2026 14:39

Copilot AI lite review requested due to automatic review settings September 4, 2026 04:19

Copilot started reviewing on behalf of zhulenghan September 4, 2026 04:20 View session

Copilot AI reviewed Sep 4, 2026

View reviewed changes

raphamorim force-pushed the main branch from f2391b6 to f1344df Compare September 5, 2026 07:37

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fix: render IME preedit text inline instead of only in the candidate popup - #1919

fix: render IME preedit text inline instead of only in the candidate popup#1919
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