perf(web): dedupe terminal mouse motion reports

apps/web/src/terminal/ghostty/surface.test.ts

@@ -16,6 +16,7 @@ import {
   isTerminalPasteShortcut,
   loadTerminalFontFamily,
   primeTerminalCopyInput,
+  resolveTerminalMouseData,
   shouldBlinkTerminalCursor,
   shouldReportTerminalMouse,
   shouldShowTerminalLinkHover,
@@ -402,6 +403,22 @@ describe("application mouse reporting", () => {
     expect([0, 1, 2, 3, 4, 5].map(ghosttyMouseButton)).toEqual([1, 3, 2, 4, 5, null]);
   });
 
+  it("drops repeated motion reports until another mouse action resets the cell", () => {
+    const first = resolveTerminalMouseData("motion", "\u001b[<35;8;4M", "");
+    expect(first).toEqual({ send: true, nextMotionData: "\u001b[<35;8;4M" });
+
+    const duplicate = resolveTerminalMouseData("motion", "\u001b[<35;8;4M", first.nextMotionData);
+    expect(duplicate).toEqual({ send: false, nextMotionData: "\u001b[<35;8;4M" });
+
+    const press = resolveTerminalMouseData("press", "\u001b[<0;8;4M", duplicate.nextMotionData);
+    expect(press).toEqual({ send: true, nextMotionData: "" });
+
+    expect(resolveTerminalMouseData("motion", "\u001b[<35;8;4M", press.nextMotionData)).toEqual({
+      send: true,
+      nextMotionData: "\u001b[<35;8;4M",
+    });
+  });
+
   it("only shows link hover during mouse tracking when the link modifier is held", () => {
     expect(shouldShowTerminalLinkHover(false, false)).toBe(true);
     expect(shouldShowTerminalLinkHover(false, true)).toBe(true);

apps/web/src/terminal/ghostty/surface.ts

@@ -418,6 +418,20 @@ export function shouldReportTerminalMouse(
   return tracking && !event.shiftKey && !event.ctrlKey && !event.metaKey;
 }
 
+type TerminalMouseAction = "press" | "release" | "motion";
+
+export function resolveTerminalMouseData(
+  action: TerminalMouseAction,
+  data: string,
+  previousMotionData: string,
+): { readonly send: boolean; readonly nextMotionData: string } {
+  const nextMotionData = action === "motion" ? data : "";
+  return {
+    send: data.length > 0 && (action !== "motion" || data !== previousMotionData),
+    nextMotionData,
+  };
+}
+
 export function terminalWheelDeltaRows(
   event: Pick<WheelEvent, "deltaY" | "deltaMode">,
   cellHeight: number,
@@ -593,6 +607,7 @@ export class GhosttyTerminalSurface {
   private clearSelectionAfterCopy = false;
   private primedCopySelection = "";
   private wheelRemainder = 0;
+  private lastMouseMotionData = "";
   private dprMedia: MediaQueryList | null = null;
   // Read live on every blink decision, and watched so that dropping the
   // preference restarts a blink cycle that has no timer left to notice it.
@@ -1364,6 +1379,7 @@ export class GhosttyTerminalSurface {
   }
 
   private readonly onPointerLeave = () => {
+    this.lastMouseMotionData = "";
     this.clearHoveredLink();
   };
 
@@ -1822,11 +1838,7 @@ export class GhosttyTerminalSurface {
     return terminalLinkAtPositionWithRange(this.snapshot.rowData, cell.y, cell.x);
   }
 
-  private sendMouse(
-    action: "press" | "release" | "motion",
-    button: number | null,
-    event: MouseEvent,
-  ): void {
+  private sendMouse(action: TerminalMouseAction, button: number | null, event: MouseEvent): void {
     const bounds = this.canvas.getBoundingClientRect();
     const data = this.core.encodeMouse({
       action,
@@ -1848,7 +1860,9 @@ export class GhosttyTerminalSurface {
       paddingBottom: Math.max(0, bounds.height - this.originY - this.rows * this.metrics.height),
       anyButtonPressed: event.buttons !== 0,
     });
-    if (data.length > 0) this.options.onData(data);
+    const resolution = resolveTerminalMouseData(action, data, this.lastMouseMotionData);
+    this.lastMouseMotionData = resolution.nextMotionData;
+    if (resolution.send) this.options.onData(data);
   }
 
   private buttonFromButtons(buttons: number): number | null {