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Add flip selection with H/V keyboard shortcuts #51

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49 changes: 49 additions & 0 deletions celstomp/js/ui/interaction-shortcuts.js
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Original file line number Diff line number Diff line change
Expand Up @@ -580,6 +580,47 @@ function _wireExtraKeyboardShortcuts() {
}, true);
}
}

function flipSelection(horizontal) {
if (!rectSelection.active) return;
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@hingler hingler Feb 17, 2026

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Would we be OK throwing an error in this case? IDK what the defacto standard is for error handling on the web but I figure we should handle this more gracefully, as flipSelection should only be called when the rectSelection is already active.

const c = getFrameCanvas(rectSelection.L, rectSelection.F, rectSelection.key);
if (!c) return;
const ctx = c.getContext("2d", { willReadFrequently: true });
if (!ctx) return;
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@hingler hingler Feb 17, 2026

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Same here— not sure what would be best but i figure if c or ctx are null then we're encountering anomalous behavior which we want to log instead of returning silently to avoid a crash.


const selSnap = ctx.getImageData(rectSelection.x, rectSelection.y, rectSelection.w, rectSelection.h);
const fullSnap = ctx.getImageData(0, 0, contentW, contentH);

beginGlobalHistoryStep(rectSelection.L, rectSelection.F, rectSelection.key);

ctx.clearRect(rectSelection.x, rectSelection.y, rectSelection.w, rectSelection.h);

const flipped = ctx.createImageData(rectSelection.w, rectSelection.h);
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@hingler hingler Feb 17, 2026

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not "mission critical" but at a glance it seems like there should be some more optimal way to snapshot a region of the canvas, flip it, and write it back. Some combination of transformation operations on the dest canvas should work to accomplish the same, I think?

const src = selSnap.data;
const dst = flipped.data;

for (let y = 0; y < rectSelection.h; y++) {
for (let x = 0; x < rectSelection.w; x++) {
const srcIdx = (y * rectSelection.w + x) * 4;
const dstY = horizontal ? y : (rectSelection.h - 1 - y);
const dstX = horizontal ? (rectSelection.w - 1 - x) : x;
const dstIdx = (dstY * rectSelection.w + dstX) * 4;
dst[dstIdx] = src[srcIdx];
dst[dstIdx + 1] = src[srcIdx + 1];
dst[dstIdx + 2] = src[srcIdx + 2];
dst[dstIdx + 3] = src[srcIdx + 3];
}
}

ctx.putImageData(flipped, rectSelection.x, rectSelection.y);

markGlobalHistoryDirty();
commitGlobalHistoryStep();
recomputeHasContent(rectSelection.L, rectSelection.F, rectSelection.key);
queueRenderAll();
updateTimelineHasContent(rectSelection.F);
}

function wireKeyboardShortcuts() {
if (document._celstompKeysWired) return;
document._celstompKeysWired = true;
Expand Down Expand Up @@ -749,6 +790,14 @@ function onWindowKeyDown(e) {
return;
}
}
if (rectSelection.active && (e.key.toLowerCase() === "h" || e.key.toLowerCase() === "v")) {
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@hingler hingler Feb 17, 2026

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also not "mission-critical" but in the future we should maybe be factoring this "event handler" code into a different function.

const tag = e.target && e.target.tagName ? e.target.tagName.toUpperCase() : "";
if (tag !== "INPUT" && tag !== "TEXTAREA" && tag !== "SELECT") {
e.preventDefault();
flipSelection(e.key.toLowerCase() === "h");
return;
}
}
if ((e.key === "Delete" || e.key === "Backspace") && rectSelection.active) {
const tag = e.target && e.target.tagName ? e.target.tagName.toUpperCase() : "";
if (tag !== "INPUT" && tag !== "TEXTAREA" && tag !== "SELECT") {
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7 changes: 6 additions & 1 deletion celstomp/parts/modals.js
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Expand Up @@ -70,13 +70,18 @@ document.getElementById('part-modals').innerHTML = `
<div class="shortcutRow"><kbd>E</kbd><span>Prev Frame</span></div>
<div class="shortcutRow"><kbd>R</kbd><span>Next Frame</span></div>
</div>
<div class="shortcutSection">
<h4>Selection</h4>
<div class="shortcutRow"><kbd>H</kbd><span>Flip Horizontal</span></div>
<div class="shortcutRow"><kbd>V</kbd><span>Flip Vertical</span></div>
<div class="shortcutRow"><kbd>Del</kbd><span>Delete Selection</span></div>
</div>
<div class="shortcutSection">
<h4>Actions</h4>
<div class="shortcutRow"><kbd>Space</kbd><span>Play/Pause</span></div>
<div class="shortcutRow"><kbd>Ctrl+Z</kbd><span>Undo</span></div>
<div class="shortcutRow"><kbd>Ctrl+Y</kbd><span>Redo</span></div>
<div class="shortcutRow"><kbd>Ctrl+Shift+Z</kbd><span>Redo</span></div>
<div class="shortcutRow"><kbd>Del</kbd><span>Delete Selection/Color</span></div>
<div class="shortcutRow"><kbd>F</kbd><span>Fill Current Frame</span></div>
<div class="shortcutRow"><kbd>O</kbd><span>Toggle Onion</span></div>
</div>
Expand Down