This change affects developers who need to synthesize **native** mouse
events in mochitest of any flavor.
Currently, these APIs take raw native event message as their param.
I.e., they require helper functions returning different value for each
platform. This causes some tests messy because of copying them from
Additionally these API don't take mouse button ID nor modifiers. The
former is caused by `nsIDOMWindowUtils::SendNativeMouseEvent` was
designed assuming that any platforms having native mouse press/release
message for each button, but it's not true on Linux, macOS and Android.
The latter is caused by that the APIs do not have an argument to specify it.
Bug 1691622  will make them easier to use, and align the API style to
`synthesizeNativeMouseClickAtCenter` and `synthesizeMouseMove` will be
merged to `synthesizeNativeMouseEvent*`. Then it'll take an `Object`
param which contains a `type` member to specify which mouse event should
be synthesized. It takes "mousemove", "click", "mousedown" and "mouseup".
Next, the `Object` param will contain `modifiers` member which is an
`Object` containing `shitKey`, `ctrlKey`, `altKey`, `metaKey`,
`capsLockKey`, `numLockKey`, `accelKey`, etc.
Next, the `Object` param contains `target` element. It's must not be
`null` if you use APZ-aware version. `offsetX` and `offsetY` are
relative to it, setting `atCenter` to `true` means to synthesize the
native mouse event(s) at center of `target`.
Next, the `Object` param can contain `screenX` and `screenY`. When the
caller knows screen pixels, these members are useful.
Next, you can specify in which unit `clientX`, `clientY`, `screenX` and
`screenY` are only for `EventUtils` version. "inScreenPixels" means that
they are in device pixels, "screenPixelPerCSSPixels" (this is default
value) means that they are in CSS pixels with current zoom level.
"screenPixelPerCSSPixelsNoOverride" means that they are in CSS pixels
but ignoring zoom state (IIUC for the latter 2).
Finally, there will be `promiseNativeMouseEvent`,
Note that unfortunately, modifiers are not available on Windows and
Android for now, and X1 and X2 button events can be synthesized only on
Windows, but they may not be caused mouse events since they are
typically converted to `WM_APPCOMMAND` message for "back" and "forward"
I hope this change will help you to write chrome and content
collaborating test like related to xorigin event delivering and
If you have some additional suggestions, let me know.
Masayuki Nakano <masay...@d-toybox.com>
Working on DOM, Events, editor and IME handling for Gecko
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