backend/internal/system/event.go

package system

import "image"
import "git.tebibyte.media/tomo/tomo/input"

// TODO: once go v1.23 comes out, replace the explicit iterator calls here with
// range loops

// HandleFocusChange sets whether or not the window containing this Hierarchy
// has input focus.
func (this *Hierarchy) HandleFocusChange (focused bool) {
	if this.windowFocused == focused { return }
	this.windowFocused = focused
}

// HandleModifiers sets the modifier keys that are currently being pressed.
func (this *Hierarchy) HandleModifiers (modifiers input.Modifiers) {
	if this.modifiers == modifiers { return }
	this.modifiers = modifiers
}

// HandleKeyDown sends a key down event to the currently focused Box. If the
// event which triggers this comes with modifier key information,
// HandleModifiers must be called *before* HandleKeyDown.
func (this *Hierarchy) HandleKeyDown (key input.Key, numberPad bool) {
	caught := false
	if this.anyFocused() {
		this.keyboardTargets(func (target anyBox) bool {
			if target.handleKeyDown(key, numberPad) {
				caught = true
				return false
			}
			return true
		})
	} else {
		if this.root != nil {
			caught = this.root.handleKeyDown(key, numberPad)
		}
	}
	if caught { return }

	switch key {
	case input.KeyTab:
		if this.modifiers.Shift {
			this.focusPrevious()
		} else {
			this.focusNext()
		}
	case input.KeyUp:   this.focusPrevious()
	case input.KeyDown: this.focusNext()
	}
}

// HandleKeyUp sends a key up event to the currently focused Box. If the event
// which triggers this comes with modifier key information, HandleModifiers must
// be called *before* HandleKeyUp.
func (this *Hierarchy) HandleKeyUp (key input.Key, numberPad bool) {
	if this.anyFocused() {
		this.keyboardTargets(func (target anyBox) bool {
			if target.handleKeyUp(key, numberPad) {
				return false
			}
			return true
		})
	} else {
		if this.root != nil {
			this.root.handleKeyUp(key, numberPad)
		}
	}
}

// HandleMouseDown sends a mouse down event to the Boxes positioned underneath
// the mouse cursor and marks them as being "dragged" by that mouse button,
// starting at the first Box to mask events and ending at the first box to
// catch the event. If the event which triggers this comes with mouse position
// information, HandleMouseMove must be called *before* HandleMouseDown.
func (this *Hierarchy) HandleMouseDown (button input.Button) {
	boxes := []anyBox { }
	first := true
	this.boxesUnder(this.mousePosition)(func (box anyBox) bool {
		if first {
			if box.canBeFocused() {
				this.focus(box)
			} else {
				this.focus(nil)
			}
			first = false
		}
		boxes = append(boxes, box)
		return !box.handleMouseDown(button)
	})
	this.drags[button] = boxes
}

// HandleMouseUp sends a mouse up event to the Boxes currently being "dragged"
// by the specified mouse button, and marks them as being "not dragged" by that
// mouse button. If the event which triggers this comes with mouse position
// information, HandleMouseMove must be caleld *before* HandleMouseUp
func (this *Hierarchy) HandleMouseUp (button input.Button) {
	for _, box := range this.drags[button] {
		box.handleMouseUp(button)
	}
	this.drags[button] = nil
}

// HandleMouseMove sends a mouse move event to any Boxes currently being
// "dragged" by a mouse button. If none are, it sends the event to the Boxes
// which are underneath the mouse pointer, starting at the first Box to mask
// events and ending at the first box to catch the event.
func (this *Hierarchy) HandleMouseMove (position image.Point) {
	if this.mousePosition == position { return }
	this.mousePosition = position

	dragged := false
	for _, dragSet := range this.drags {
		for _, box := range dragSet {
			if box.handleMouseMove() { break }
			dragged = true
		}
	}
	if dragged { return }

	// TODO we can hover over multiple boxes at once. however, any way of
	// detecting this involves several slice allocations every time we
	// process a MouseMove event. perhaps we just ought to suck it up and do
	// it. or perhaps doing *this* is the better way? we may never know.
	box := this.boxUnder(position)
	if box != nil {
		box := this.considerMaskingParents(box)
		this.hover(box)
		box.handleMouseMove()
	}
}

// HandleScroll sends a scroll event to the Box currently underneath the mouse
// cursor. If the event which triggers this comes with mouse position
// information, HandleMouseMove must be called *before* HandleScroll.
func (this *Hierarchy) HandleScroll (x, y float64) {
	this.boxesUnder(this.mousePosition)(func (box anyBox) bool {
		return !box.handleScroll(x, y)
	})
}