Mouse click in an entry updates cursor position twice, with a noticeable delay

[nullst]

Describe the bug:

Suppose an entry widget has some text in it. User does a mouse click somewhere in the text and immediately starts typing "qwerty". When I do that, I usually get "ertyqw" because after I type one or two symbols (in this case, "qw") the cursor resets back to the position where I clicked, and the remaining symbols (in this case, "erty") are inserted before "qw".

This behavior is easily visible in a multiline entry: click at the end of some line and quickly press Enter to start a new line. Soon the cursor will return back to the end of the line you clicked. This does not require extreme speed, I can easily trigger this behavior even using the same hand to click the mouse first and press Enter afterwards.

Bug location

In widget/entry.go both callbacks Tapped() and MouseDown() call e.updateMousePointer. For some reason Tapped() is invoked after a delay, allowing user to type some text in between these two callbacks. I'm not sure how input handling works in fyne, but maybe on a desktop machine it is enough to update the cursor only in MouseDown()? For example, by modifying Tapped() as follows:

func (e *Entry) Tapped(ev *fyne.PointEvent) {
	if !e.Disabled() {
		e.requestFocus()
	}
	if fyne.CurrentDevice().IsMobile() && e.selecting {
		e.selecting = false
	}
	if fyne.CurrentDevice().IsMobile() { // Added this line
		e.updateMousePointer(ev.Position, false)
	} // Added this line
}

This fixes the problem on my machine.

To Reproduce:

Steps to reproduce the behaviour:

1. Open fyne_demo and navigate to "Widget/Entry" page.
2. Type something in the entry.
3. Click in the middle of the text you typed and start typing "qwerty".
4. You will probably see "ertyqw" or something like that instead of the intended result.

Device (please complete the following information):

• OS: MacOS
• Version: 10.12 Sierra
• Go version: go1.15.3 darwin/amd64
• Fyne version: 6e90820

[andydotxyz]

Good call.
Tapped has a delay because we first need to check it was not a DoubleTap, hence the short delay.
Your proposed fix is a good one, however it could leave the delay on Mobile.
Instead we could move it to only move cursor on MouseDown and TouchDown (that should catch both specific platforms, removing the need for Tapped).

[nullst]

Apparently, this modification would break TestEntry_Tapped in widget/entry_test.go since that test uses TapCanvas() to simulate mouse clicks. In fact, the fyne/v2/test package can only call Tapped() on a widget, not device-specific mouse or touch events. I don't know what the proper fix would do: maybe switch the test package to MouseDown()/MouseUp() pairs when on desktop?

UPD: in the file widget/entry_internal_test.go the callbacks Tapped(), DoubleTapped() are also invoked a lot. Should the tests there be rewritten in some way?

[andydotxyz]

DoubleTapped is separate and shouldn't be touched.
I don't think we should change how the test package works, but it would be reasonable to add a test helper for the entry test that uses MouseDown/Up on desktop and TouchDown/Up when running in mobile mode.

[andydotxyz]

on release/v2.1.x