fix(mcp): refuse a camera crop and pan that place the framing in two spots

Part of #1180

Author: EtienneLescot

electron/ai-edition/editor-settings-tool.test.ts

@@ -184,6 +184,19 @@ describe("setEditorSettings", () => {
 		expect(set(document, { webcamCropRegion: { x: 0, y: 0, width: 0.5, height: 0.6 } }).ok).toBe(
 			false,
 		);
+		// A rect and a pan that disagree are refused; at full size any pan agrees.
+		expect(
+			set(framed, {
+				webcamCropRegion: { x: 0, y: 0, width: 0.5, height: 0.5 },
+				webcamCropPan: { x: 1, y: 0 },
+			}).ok,
+		).toBe(false);
+		expect(
+			set(framed, {
+				webcamCropRegion: { x: 0, y: 0, width: 1, height: 1 },
+				webcamCropPan: { x: 1, y: 0 },
+			}).ok,
+		).toBe(true);
 	});
 
 	it("says which of the settings it wrote change nothing in the current state", () => {

electron/ai-edition/editor-settings-tool.ts

@@ -388,6 +388,18 @@ function editorPatch(document: AxcutDocument, args: SetEditorSettingsArgs): Edit
 	return patch;
 }
 
+/** A rect and a pan sent together that place the window in two different spots. At full size
+ *  there is no room to place it in, so any pan agrees with the rect there. */
+function cropFramingConflict(args: SetEditorSettingsArgs): string | null {
+	const { webcamCropRegion: region, webcamCropPan: pan } = args;
+	if (!region || !pan) return null;
+	const agrees = (offset: number, size: number, share: number) =>
+		Math.abs(offset - share * (1 - size)) < 1e-6;
+	return agrees(region.x, region.width, pan.x) && agrees(region.y, region.height, pan.y)
+		? null
+		: "webcamCropRegion and webcamCropPan place the framing in two different spots: send one of them, or both as getCurrentDocument returns them.";
+}
+
 /** Every key a patch sets, `cursor.*` for the cursor's: what the result reports as applied. */
 function patchKeys(patch: EditorSettingsPatch): string[] {
 	const { cursor, ...rest } = patch;
@@ -406,6 +418,8 @@ export function executeSetEditorSettings(
 	if (!parsed.success) {
 		return { ok: false, resultJson: JSON.stringify({ error: parsed.error.message }) };
 	}
+	const conflict = cropFramingConflict(parsed.data);
+	if (conflict) return { ok: false, resultJson: JSON.stringify({ error: conflict }) };
 	const patch = editorPatch(document, parsed.data);
 	const keys = patchKeys(patch);
 	if (keys.length === 0) {