app/internal/window: [wasm] report key modifiers for pointer events

Signed-off-by: Elias Naur <mail@eliasnaur.com>
cmd,example: bump gio version

Signed-off-by: Elias Naur <mail@eliasnaur.com>
app/internal/window: [X11] report key modifiers for pointer events

Fixes #120

Signed-off-by: Elias Naur <mail@eliasnaur.com>
app/internal/window,app/internal/xkb: [Wayland] report modifiers for pointer events

Updates #120

Signed-off-by: Elias Naur <mail@eliasnaur.com>
cmd,example: bump gio version

Signed-off-by: Elias Naur <mail@eliasnaur.com>
app/internal/window: [macOS] avoid racy access to window width, height, scale

The macOS redraw callback is not invoked on the main thread, so its
access to window fields must be synchronized.

An alternative would be to schedule the asynchronous redraws on the main
thread, but I believe frame callbacks are performance-sensitive enough
to warrant the extra locking complexity.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
app/internal/window: [macOS] don't call Cococa from non-main thread

Only the synchronous draws from the main thread may involve changing
width, height and scale. Introduce cached window.width and window.height
fields and limits updates to main-thread draws.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
widget: redefine Enum.Changed and Bool.Changed to consider only user interaction

Ignore programmatic value changes to avoid feedback loops.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
widget: change Enum.Layout to follow layout protocol

Respect constraints and return dimensions.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
widget: change Bool.Layout to follow layout protocol

Just like Clickable, Bool.Layout should respect constraints and
return its dimensions.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
example,cmd: bump gio version

Signed-off-by: Elias Naur <mail@eliasnaur.com>
widget: add Button.Clicks for retrieving clicks

An earlier change unexported the Button.Update method that exposed raw pointer
input not available from the boolean Button.Clicked method. Introduce Click
and Button.Clicks to replace it, and implement Clicked in terms of it.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
widget,widget/material: rename widget.Click to widget.Press

Press tracks pointer presses, not clicks, and we're about to add a Click
type that does.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
widget,widget/material: only process events in Layout methods

Before this change, events were typically processed twice or more per
widget: once in the Layout method for refreshing the visual state, and
once per method that queries for state changes.

One example is widget.Clickable that processed events in both its Layout
and Clicked method.

This change establishes the convention that events are processed once, in
the Layout method. There are several advantages to that approach:

- Query methods such as Clickable.Clicked no longer need a layout.Context.
- State updates from events only occur in Layout.
- Widgets are simplified because they won't need a separate processEvents
(or similar) method and won't forget to call it from methods other than Layout.
- Useless calls to gtx.Events are avoided (gtx.Events only returns events
for the first call each frame for a given event.Tag).

The disadvantage is that state updates from input events will not appear
before Layout. For example, in the call sequence

	var btn *widget.Clickable

	if btn.Clicked() {...}

the Clicked call will not detect an incoming click until the frame after it

This is ok because

- The Gio event router automatically dispatches an extra frame after events
arrive, bounding the latency from events to queries such as Clicked to
at most one frame (~17 ms).
- The potential extra frame of latency does not apply to Layout methods as long
as they process events before drawing. In other words, the visual feedback
from input events are not delayed because of this change.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
widget: simplify Editor event flushing

Signed-off-by: Elias Naur <mail@eliasnaur.com>
example,cmd: bump gio version

Signed-off-by: Elias Naur <mail@eliasnaur.com>
widget/material: move widget state object from Layout methods to constructors

Instead of, say,

	var th *material.Theme
	var btn *widget.Clickable

	material.Button(th, "Click me").Layout(gtx, btn)

move the widget state objects to the constructor:

	material.Button(th, btn, "Click me").Layout(gtx)

The advatage is that several widgets can now be used without
wrapping them in function literals. For example,

	layout.Inset{}.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
		material.Button(th, "Click me").Layout(gtx, btn)

collapses to just

	layout.Inset{}.Layout(gtx, material.Button(th, btn, "Click me").Layout)

Signed-off-by: Elias Naur <mail@eliasnaur.com>
layout: change Widget to take explicit Context and return explicit Dimensions

Change the definition of Widget from the implicit

        type Widget func()

to the explicit functional

        type Widget func(gtx layout.Context) layout.Dimensions

The advantages are numerous:

- Clearer connection between the incoming context and the output dimensions.
- Returning the Dimensions are impossible to omit.
- Contexts passed by value, so its fields can be exported
and freely mutated by the program.

The only disadvantage is the longer function literals and the many "returns".
What tipped the scales in favour of the explicit Widget variant is that type
aliases can dramatically shorten the literals:

	type (
		C = layout.Context
		D = layout.Dimensions

	widget := func(gtx C) D {

Note that the aliases are not part of the Gio API and it is up to each user
whether they want to use them.

Finally the Go proposal for lightweight function literals,
https://github.com/golang/go/issues/21498, may remove the disadvantage
completely in future.

Context becomes a plain struct with only public fields, and its Reset is
replaced by a NewContext convenience constructor.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
widget/material: drop Padding from IconButtonStyle

Use Inset instead, matching the other buttons.

Redefine Size to apply to the icon size, without padding.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
cmd/gogio: use URL query for passing arguments to wasm programs

The location.hash method doesn't work correctly with multiple
iframes and Safari.

Signed-off-by: Elias Naur <mail@eliasnaur.com>