feat(cdp): support mouse button and clickCount in Input.dispatchMouseEvent

Input.dispatchMouseEvent ignored the button and clickCount params, and
mousePressed only fired a click event (never mousedown). Add them:

- mousePressed now fires mousedown carrying the pressed button.
- mouseReleased fires mouseup, then the button-appropriate activation
  event: click for the main button, auxclick for the auxiliary button,
  and contextmenu for the secondary (right) button.
- a clickCount of 2 additionally fires dblclick.

This unblocks right-click, middle-click and double-click interactions
for Playwright/Puppeteer scripts. Follows the mouse event work in
#2636, #2640 and #2641.

src/browser/Frame.zig

@@ -3902,25 +3902,35 @@ fn findFrameByName(frame: *Frame, name: []const u8) ?*Frame {
     return null;
 }
 
-pub fn triggerMouseClick(self: *Frame, x: f64, y: f64) !void {
-    const target = (try self.window._document.elementFromPoint(x, y, self)) orelse return;
-    if (comptime IS_DEBUG) {
-        log.debug(.frame, "frame mouse click", .{
-            .url = self.url,
-            .node = target,
-            .x = x,
-            .y = y,
-            .type = self._type,
-        });
-    }
-    const mouse_event: *MouseEvent = try .initTrusted(comptime .wrap("click"), .{
+// Dispatch a single trusted mouse event of the given type on `target`, carrying
+// the pressed button and pointer position. `detail` is the click count (used for
+// click/dblclick); 0 for events where it does not apply.
+fn dispatchMouseEventOn(self: *Frame, target: *Element, comptime typ: []const u8, x: f64, y: f64, button: i32, detail: u32) !void {
+    const event: *MouseEvent = try .initTrusted(comptime .wrap(typ), .{
         .bubbles = true,
         .cancelable = true,
         .composed = true,
         .clientX = x,
         .clientY = y,
+        .button = button,
+        .detail = detail,
     }, self);
-    try self._event_manager.dispatch(target.asEventTarget(), mouse_event.asEvent());
+    try self._event_manager.dispatch(target.asEventTarget(), event.asEvent());
+}
+
+pub fn triggerMousePress(self: *Frame, x: f64, y: f64, button: i32) !void {
+    const target = (try self.window._document.elementFromPoint(x, y, self)) orelse return;
+    if (comptime IS_DEBUG) {
+        log.debug(.frame, "frame mouse press", .{
+            .url = self.url,
+            .node = target,
+            .x = x,
+            .y = y,
+            .button = button,
+            .type = self._type,
+        });
+    }
+    try self.dispatchMouseEventOn(target, "mousedown", x, y, button, 0);
 }
 
 pub fn triggerMouseMove(self: *Frame, x: f64, y: f64) !void {
@@ -3961,7 +3971,7 @@ pub fn triggerMouseMove(self: *Frame, x: f64, y: f64) !void {
     try self._event_manager.dispatch(target.asEventTarget(), enter_event.asEvent());
 }
 
-pub fn triggerMouseRelease(self: *Frame, x: f64, y: f64) !void {
+pub fn triggerMouseRelease(self: *Frame, x: f64, y: f64, button: i32, click_count: i32) !void {
     const target = (try self.window._document.elementFromPoint(x, y, self)) orelse return;
     if (comptime IS_DEBUG) {
         log.debug(.frame, "frame mouse release", .{
@@ -3969,17 +3979,31 @@ pub fn triggerMouseRelease(self: *Frame, x: f64, y: f64) !void {
             .node = target,
             .x = x,
             .y = y,
+            .button = button,
             .type = self._type,
         });
     }
-    const up_event: *MouseEvent = try .initTrusted(comptime .wrap("mouseup"), .{
-        .bubbles = true,
-        .cancelable = true,
-        .composed = true,
-        .clientX = x,
-        .clientY = y,
-    }, self);
-    try self._event_manager.dispatch(target.asEventTarget(), up_event.asEvent());
+
+    const detail: u32 = if (click_count > 0) @intCast(click_count) else 1;
+
+    try self.dispatchMouseEventOn(target, "mouseup", x, y, button, detail);
+
+    // After mouseup, the activation event depends on the button:
+    //   main (0)      -> click
+    //   auxiliary (1) -> auxclick
+    //   secondary (2) -> contextmenu
+    switch (button) {
+        0 => {
+            try self.dispatchMouseEventOn(target, "click", x, y, button, detail);
+            // A second click in quick succession also fires dblclick.
+            if (click_count == 2) {
+                try self.dispatchMouseEventOn(target, "dblclick", x, y, button, detail);
+            }
+        },
+        1 => try self.dispatchMouseEventOn(target, "auxclick", x, y, button, detail),
+        2 => try self.dispatchMouseEventOn(target, "contextmenu", x, y, button, detail),
+        else => {},
+    }
 }
 
 pub fn triggerMouseWheel(self: *Frame, x: f64, y: f64, delta_x: f64, delta_y: f64) !void {

src/cdp/domains/input.zig

@@ -82,6 +82,8 @@ fn dispatchMouseEvent(cmd: *CDP.Command) !void {
         x: f64,
         y: f64,
         type: Type,
+        button: Button = .none,
+        clickCount: i32 = 0,
         deltaX: f64 = 0,
         deltaY: f64 = 0,
         // Many optional parameters are not implemented yet, see documentation url.
@@ -92,15 +94,36 @@ fn dispatchMouseEvent(cmd: *CDP.Command) !void {
             mouseMoved,
             mouseWheel,
         };
+
+        // https://chromedevtools.github.io/devtools-protocol/tot/Input/#type-MouseButton
+        const Button = enum {
+            none,
+            left,
+            middle,
+            right,
+            back,
+            forward,
+        };
     })) orelse return error.InvalidParams;
 
     try cmd.sendResult(null, .{});
 
     const bc = cmd.browser_context orelse return;
     const frame = bc.session.currentFrame() orelse return;
+
+    // Map the CDP button name to the DOM MouseEvent.button numbering
+    // (left/main = 0, middle/auxiliary = 1, right/secondary = 2, ...).
+    const button: i32 = switch (params.button) {
+        .none, .left => 0,
+        .middle => 1,
+        .right => 2,
+        .back => 3,
+        .forward => 4,
+    };
+
     switch (params.type) {
-        .mousePressed => try frame.triggerMouseClick(params.x, params.y),
-        .mouseReleased => try frame.triggerMouseRelease(params.x, params.y),
+        .mousePressed => try frame.triggerMousePress(params.x, params.y, button),
+        .mouseReleased => try frame.triggerMouseRelease(params.x, params.y, button, params.clickCount),
         .mouseMoved => try frame.triggerMouseMove(params.x, params.y),
         .mouseWheel => try frame.triggerMouseWheel(params.x, params.y, params.deltaX, params.deltaY),
     }
@@ -237,3 +260,55 @@ test "cdp.input: dispatchMouseEvent mouseWheel fires wheel event" {
     const result = try ls.local.compileAndRun("window.wheelDeltaY === 40", null);
     try testing.expect(result.isTrue());
 }
+
+test "cdp.input: dispatchMouseEvent right button fires contextmenu, double-click fires dblclick" {
+    var ctx = try testing.context();
+    defer ctx.deinit();
+
+    const bc = try ctx.loadBrowserContext(.{});
+    const frame = try bc.session.createPage();
+    const url = "http://localhost:9582/src/browser/tests/mcp_actions.html";
+    try frame.navigate(url, .{ .reason = .address_bar, .kind = .{ .push = null } });
+    var runner = try bc.session.runner(.{});
+    try runner.wait(.{ .ms = 2000 });
+
+    var ls: lp.js.Local.Scope = undefined;
+    frame.js.localScope(&ls);
+    defer ls.deinit();
+
+    var try_catch: lp.js.TryCatch = undefined;
+    try_catch.init(&ls.local);
+    defer try_catch.deinit();
+
+    _ = try ls.local.compileAndRun(
+        \\const t = document.getElementById('hoverTarget');
+        \\t.addEventListener('mousedown', (e) => { window.downButton = e.button; });
+        \\t.addEventListener('contextmenu', (e) => { window.ctxButton = e.button; });
+        \\t.addEventListener('dblclick', () => { window.dbl = true; });
+    , null);
+
+    const rect_x = try (try ls.local.compileAndRun("document.getElementById('hoverTarget').getBoundingClientRect().x", null)).toF64();
+    const rect_y = try (try ls.local.compileAndRun("document.getElementById('hoverTarget').getBoundingClientRect().y", null)).toF64();
+
+    // Right button: press carries button=2, release fires contextmenu (not click).
+    try ctx.processMessage(.{
+        .id = 1,
+        .method = "Input.dispatchMouseEvent",
+        .params = .{ .type = "mousePressed", .x = rect_x, .y = rect_y, .button = "right" },
+    });
+    try ctx.processMessage(.{
+        .id = 2,
+        .method = "Input.dispatchMouseEvent",
+        .params = .{ .type = "mouseReleased", .x = rect_x, .y = rect_y, .button = "right" },
+    });
+
+    // Left button with clickCount 2 fires dblclick.
+    try ctx.processMessage(.{
+        .id = 3,
+        .method = "Input.dispatchMouseEvent",
+        .params = .{ .type = "mouseReleased", .x = rect_x, .y = rect_y, .button = "left", .clickCount = 2 },
+    });
+
+    const result = try ls.local.compileAndRun("window.downButton === 2 && window.ctxButton === 2 && window.dbl === true", null);
+    try testing.expect(result.isTrue());
+}