feat(editor): clip a screenshot region from Select (rect / ellipse / lasso + Snap) by lukejmorrison · Pull Request #111 · omacom/omasnap

lukejmorrison · 2026-08-28T11:05:57Z

Select already grows the canvas when you drag a layer off the screenshot; this lets the screenshot itself be the source of that layer — lock a mask, fill the hole, lift a copy, repeat.

Split (pick what you want)

This PR is clip-out only. Two follow-ups, so each can land on its own:

PR	What
This (#111)	Clip-out: V cycles Rect / Ellipse / Lasso, Snap as a toggle (off here), hole-fill fly-out (transparent default)
#113	Stacked: Snap on + surroundings fill by default + `T` cycles fill while the mask is locked
#114	Independent: Ctrl+Cut inserts a transparent band

Kitchen-sink daily use (all three) stays on lukejmorrison/omasnap main.

Behavior

In Select (V):

V cycles clip shape: rectangle → ellipse → lasso. A chip strip under the toolbar shows those plus a Snap toggle.
A large enough empty drag that hits no layers locks a pixel mask of the current shape. Lasso keeps the traced path even if you close back near the start.
Snap (off in this PR; on in feat(editor): Snap on and surroundings fill by default #113): drag a box around the object, leave a little background in the corners. Snap reads what is connected under the pointer inside that box — 8-connected flood with a 1px close. Rect keeps gray chrome, not just the colourful bits. Ellipse fits a circle that covers protrusions (a pin on a badge). Lasso follows the silhouette. Rect + Snap uses the object's corner radius so the overlay matches a rounded card. Crop handles hide while the mask is locked.
A fly-out picks the hole infill (transparent by default here; match-surroundings swatch; 1–8 / Sample from image I / # while the mask is locked).
Drag inside to lift a layer with alpha outside the path. Release near the hole to snap back; elsewhere to commit. Esc / Ctrl+Z during a lift cancels only the lift. R / E / F still arm the drawing tools.

This is not Cut (X). Cut removes a band and collapses the gap. Clip copies a region, leaves the rest in place, and does not shift other annotations.

Model

One Operation::Type::Clip (shape + radius + fill + clip annotation). Replay walks from pristineSource_, applying cuts and clip punches in order, and copies the tile from the composed image as it existed at that op so later cuts cannot rewrite an already-torn piece. Live drag is editor-only preview; the log is touched only on release.

Engine lives in src/clip.cpp. No new tool, no config key.

Tests

runClipSmoke — copy, punch, hidpi mapping. Fails without clip.cpp.
runClipMappingSmoke — empty marquee, lift, hole alpha, undo, two sequential clips. Fails without the editor glue.

make check is green (build, offscreen smoke, clang-tidy).

Pitch

Select already grows the canvas when you drag a layer off the screenshot; this lets the screenshot itself be the source of that layer. Then you can select any part of the image, pull the clip, copy the clip, repeat.

Select already grows the canvas when you drag a layer off the screenshot; this lets the screenshot itself be the source of that layer. An empty marquee locks a pixel clip; drag it to lift those pixels, punch a hole (backdrop shows through), and commit one Clip operation. Repeat to pull another region. Ctrl+Z undoes the hole and the layer together. Covered by runClipSmoke (copy/punch/mapping) and runClipMappingSmoke (empty marquee, lift, hole, undo, repeat). The suite fails without the change. make check is green.

Copilot

🟡 Changes recommended

There are a couple of correctness issues in the new code paths (JSON parsing symmetry for clip PNG data and cursor state after canceling a clip lift) that should be fixed before approval.

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

Pull request overview

Adds a new “clip-out” interaction to the Select tool, letting users marquee a pixel region of the screenshot, lift it into a new layer, and punch a transparent hole in the source while keeping the operation-log model (undo restores both hole + layer).

Changes:

Introduces a new clip engine (copyRect, punchRect, logical→native mapping, snap threshold) and a new Operation::Type::Clip / Annotation::Kind::Clip.
Wires Select-mode empty-marquee → locked pixel rect → lift preview → commit/undo into CaptureEditor, including replay behavior and persistence.
Adds smoke coverage for both the clip engine and editor mapping, plus documentation/build wiring updates.

File summaries

File	Description
tests/editor-smoke.cpp	Registers the new clip smoke tests in the overall smoke runner.
tests/clip-smoke.hpp	Declares the clip engine smoke test entry point.
tests/clip-smoke.cpp	Adds focused unit-style smoke coverage for clip engine primitives and mapping.
tests/clip-mapping-smoke.hpp	Declares editor-level clip mapping smoke test entry point.
tests/clip-mapping-smoke.cpp	Adds editor-driven smoke coverage for marquee→lift→hole→undo and repeated clips.
src/editor.hpp	Adds clip-related test hooks and new internal helpers/state for pixel clip + lift.
src/editor.cpp	Implements Select-mode pixel clip interaction, commit logic, replay support, and preview drawing.
src/clip.hpp	Defines `ClipOp` and clip engine APIs.
src/clip.cpp	Implements rectangular copy/punch and logical→native mapping + snapping helpers.
src/capture.hpp	Extends `Annotation::Kind` / `Operation::Type` to include clip and stores clip tile pixels on annotations.
src/capture.cpp	Adds drawing + JSON (de)serialization support for clip annotations and clip operations.
README.md	Documents the new clip-out user behavior and keybinding description.
docs/editing-model.md	Updates the editing model doc to describe Clip as an operation-log primitive.
CMakeLists.txt	Adds new source/test files to the build.
AGENTS.md	Updates repository layout docs to include the new clip module.

Review details

Files reviewed: 15/16 changed files
Comments generated: 3
Review effort level: Lite

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+  const QByteArray png = QByteArray::fromBase64(
+      object.value(QStringLiteral("png")).toString().toLatin1());
+  if (!png.isEmpty())
+    annotation.image.loadFromData(png, "PNG");


+  if (clipLiftActive_) {
+    cancelClipLift();
+    dragging_ = false;
+    setStatus(QStringLiteral("Clip cancelled"));
+  }


+      QImage tile = copyRect(composed, op.clip.sourceRect);
+      punchRect(composed, op.clip.sourceRect);
+      Annotation layer;


After an empty Select marquee locks a region, a swatch row appears under the rect: transparent (checkerboard, default), the palette colours, and custom. 1–8 and the eyedropper set the infill while the clip is armed. The fill is stored on Operation::Clip so undo/replay keep the hole.

Ctrl+Z during a lift cancels only the in-progress drag — QTest (and real keyboards) send Control before Z, so a modifier-only press must not drop the lift and then let Z undo the previous op. Empty marquees need a 12px floor, crop chrome stays until lift, and the hole-fill fly-out docks to the side. Replay keeps a present clip tile, PNG loads only on Clip, and live lift paints a downsampled pixmap with snap hysteresis. Co-authored-by: Luke Morrison <lukejmorrison@users.noreply.github.com>

Rectangle, ellipse, and lasso masks with click-to-snap, keyboard hole fill, and drag-to-lift. Spec for the follow-on to rectangular clip-out.

Select cycles clip shape with V and a chip strip. Empty-canvas drags that miss layers still lock a mask; R/E/F keep arming drawing tools. Snap ray-casts to an axis-aligned ellipse. Lifted tiles carry alpha outside the path. Fable and Sol P0s applied to the key layer.

lukejmorrison · 2026-08-28T16:13:06Z

Follow-up on this branch: clip-out now supports rectangle, ellipse, and lasso masks plus click-to-snap (axis-aligned ellipse from a ray-cast), after a Fable + GPT Sol review of the key layer.

V while Select cycles clip shape (strip under the toolbar). R / E / F still arm drawing tools — first-press clip-on-those-keys was rejected as a P0 against daily drawing.
Empty-canvas drag still multi-selects layers first; only a large enough empty marquee locks a pixel mask.
Snap is explicit (Snap chip or Alt+click), not every empty click.
Lifted tile has alpha outside the path. Hole fill: T / 1–8 / I / # while the mask is locked.
Spec: docs/superpowers/specs/2026-08-28-clip-shape-masks-design.md
make check passed locally (offscreen smoke + clang-tidy).

Happy to split this into a stacked PR if you want the rectangular clip-out merged first.

Cycling clip shape now updates the path already on screen (rect to ellipse, and Snap ray-casts from the mask centre). Installed to ~/.local/bin so Print no longer launches last morning's build.

…e hole Snap treats the drag as a search window: 8-connected flood with a 1px close, an enclosing circle for Ellipse (pins stay in), and a rounded rect for Rect when two corners agree on a radius. Crop chrome hides while a mask is locked. The hole-fill fly-out adds match-surroundings and the same Sample from image eyedropper as the toolbar.

Copilot AI lite review requested due to automatic review settings August 28, 2026 11:05

Copilot started reviewing on behalf of lukejmorrison August 28, 2026 11:06 View session

Copilot AI reviewed Aug 28, 2026

View reviewed changes

lukejmorrison and others added 4 commits August 28, 2026 07:53

docs: clip-out shape mask design

e131cd1

Rectangle, ellipse, and lasso masks with click-to-snap, keyboard hole fill, and drag-to-lift. Spec for the follow-on to rectangular clip-out.

lukejmorrison added 2 commits August 28, 2026 12:44

fix(editor): V converts a locked clip mask and install the new binary

2d1eaee

Cycling clip shape now updates the path already on screen (rect to ellipse, and Snap ray-casts from the mask centre). Installed to ~/.local/bin so Print no longer launches last morning's build.

lukejmorrison force-pushed the feat/select-clip-out branch from 0842f55 to 5e51400 Compare August 29, 2026 15:10

This was referenced Aug 29, 2026

feat(editor): Snap on and surroundings fill by default #113

Open

feat(editor): Ctrl+Cut inserts a transparent band #114

Open

lukejmorrison changed the title ~~feat(editor): clip a screenshot region by dragging the select marquee~~ feat(editor): clip a screenshot region from Select (rect / ellipse / lasso + Snap) Aug 29, 2026

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feat(editor): clip a screenshot region from Select (rect / ellipse / lasso + Snap) - #111

feat(editor): clip a screenshot region from Select (rect / ellipse / lasso + Snap)#111
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lukejmorrison commented Aug 28, 2026 •

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