322 lines
8.7 KiB
Go
322 lines
8.7 KiB
Go
package elements
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import "image"
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import "tomo"
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import "tomo/input"
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import "art"
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// ScrollBar is an element similar to Slider, but it has special behavior that
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// makes it well suited for controlling the viewport position on one axis of a
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// scrollable element. Instead of having a value from zero to one, it stores
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// viewport and content boundaries. When the user drags the scroll bar handle,
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// the scroll bar calls the OnScroll callback assigned to it with the position
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// the user is trying to move the handle to. A program can check to see if this
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// value is valid, move the viewport, and give the scroll bar the new viewport
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// bounds (which will then cause it to move the handle).
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//
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// Typically, you wont't want to use a ScrollBar by itself. A ScrollContainer is
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// better for most cases.
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type ScrollBar struct {
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entity tomo.Entity
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c tomo.Case
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vertical bool
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enabled bool
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dragging bool
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dragOffset image.Point
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track image.Rectangle
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bar image.Rectangle
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contentBounds image.Rectangle
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viewportBounds image.Rectangle
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onScroll func (viewport image.Point)
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}
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// NewVScrollBar creates a new vertical scroll bar.
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func NewVScrollBar () (element *ScrollBar) {
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element = &ScrollBar {
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vertical: true,
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enabled: true,
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}
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element.c = tomo.C("tomo", "scrollBarVertical")
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element.entity = tomo.GetBackend().NewEntity(element)
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element.updateMinimumSize()
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return
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}
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// NewHScrollBar creates a new horizontal scroll bar.
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func NewHScrollBar () (element *ScrollBar) {
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element = &ScrollBar {
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enabled: true,
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}
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element.c = tomo.C("tomo", "scrollBarHorizontal")
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element.entity = tomo.GetBackend().NewEntity(element)
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element.updateMinimumSize()
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return
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}
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// Entity returns this element's entity.
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func (element *ScrollBar) Entity () tomo.Entity {
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return element.entity
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}
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// Draw causes the element to draw to the specified destination canvas.
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func (element *ScrollBar) Draw (destination art.Canvas) {
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element.recalculate()
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bounds := element.entity.Bounds()
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state := tomo.State {
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Disabled: !element.Enabled(),
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Pressed: element.dragging,
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}
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element.entity.Theme().Pattern(tomo.PatternGutter, state, element.c).Draw (
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destination,
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bounds)
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element.entity.Theme().Pattern(tomo.PatternHandle, state, element.c).Draw (
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destination,
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element.bar)
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}
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func (element *ScrollBar) HandleMouseDown (
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position image.Point,
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button input.Button,
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modifiers input.Modifiers,
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) {
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velocity := element.entity.Config().ScrollVelocity()
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if position.In(element.bar) {
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// the mouse is pressed down within the bar's handle
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element.dragging = true
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element.entity.Invalidate()
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element.dragOffset =
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position.Sub(element.bar.Min).
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Add(element.entity.Bounds().Min)
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element.dragTo(position)
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} else {
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// the mouse is pressed down within the bar's gutter
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switch button {
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case input.ButtonLeft:
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// start scrolling at this point, but set the offset to
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// the middle of the handle
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element.dragging = true
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element.dragOffset = element.fallbackDragOffset()
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element.dragTo(position)
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case input.ButtonMiddle:
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// page up/down on middle click
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viewport := 0
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if element.vertical {
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viewport = element.viewportBounds.Dy()
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} else {
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viewport = element.viewportBounds.Dx()
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}
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if element.isAfterHandle(position) {
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element.scrollBy(viewport)
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} else {
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element.scrollBy(-viewport)
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}
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case input.ButtonRight:
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// inch up/down on right click
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if element.isAfterHandle(position) {
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element.scrollBy(velocity)
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} else {
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element.scrollBy(-velocity)
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}
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}
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}
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}
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func (element *ScrollBar) HandleMouseUp (
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position image.Point,
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button input.Button,
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modifiers input.Modifiers,
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) {
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if element.dragging {
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element.dragging = false
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element.entity.Invalidate()
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}
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}
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func (element *ScrollBar) HandleMotion (position image.Point) {
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if element.dragging {
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element.dragTo(position)
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}
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}
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func (element *ScrollBar) HandleScroll (
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position image.Point,
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deltaX, deltaY float64,
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modifiers input.Modifiers,
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) {
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if element.vertical {
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element.scrollBy(int(deltaY))
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} else {
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element.scrollBy(int(deltaX))
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}
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}
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// SetEnabled sets whether or not the scroll bar can be interacted with.
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func (element *ScrollBar) SetEnabled (enabled bool) {
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if element.enabled == enabled { return }
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element.enabled = enabled
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element.entity.Invalidate()
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}
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// Enabled returns whether or not the element is enabled.
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func (element *ScrollBar) Enabled () (enabled bool) {
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return element.enabled
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}
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// SetBounds sets the content and viewport bounds of the scroll bar.
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func (element *ScrollBar) SetBounds (content, viewport image.Rectangle) {
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element.contentBounds = content
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element.viewportBounds = viewport
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element.entity.Invalidate()
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}
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// OnScroll sets a function to be called when the user tries to move the scroll
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// bar's handle. The callback is passed a point representing the new viewport
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// position. For the scroll bar's position to visually update, the callback must
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// check if the position is valid and call ScrollBar.SetBounds with the new
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// viewport bounds.
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func (element *ScrollBar) OnScroll (callback func (viewport image.Point)) {
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element.onScroll = callback
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}
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func (element *ScrollBar) HandleThemeChange () {
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element.updateMinimumSize()
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element.entity.Invalidate()
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}
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func (element *ScrollBar) isAfterHandle (point image.Point) bool {
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if element.vertical {
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return point.Y > element.bar.Min.Y
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} else {
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return point.X > element.bar.Min.X
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}
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}
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func (element *ScrollBar) fallbackDragOffset () image.Point {
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if element.vertical {
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return element.entity.Bounds().Min.
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Add(image.Pt(0, element.bar.Dy() / 2))
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} else {
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return element.entity.Bounds().Min.
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Add(image.Pt(element.bar.Dx() / 2, 0))
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}
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}
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func (element *ScrollBar) scrollBy (delta int) {
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deltaPoint := image.Point { }
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if element.vertical {
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deltaPoint.Y = delta
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} else {
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deltaPoint.X = delta
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}
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if element.onScroll != nil {
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element.onScroll(element.viewportBounds.Min.Add(deltaPoint))
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}
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}
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func (element *ScrollBar) dragTo (point image.Point) {
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point = point.Sub(element.dragOffset)
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var scrollX, scrollY float64
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if element.vertical {
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ratio :=
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float64(element.contentBounds.Dy()) /
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float64(element.track.Dy())
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scrollX = float64(element.viewportBounds.Min.X)
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scrollY = float64(point.Y) * ratio
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} else {
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ratio :=
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float64(element.contentBounds.Dx()) /
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float64(element.track.Dx())
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scrollX = float64(point.X) * ratio
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scrollY = float64(element.viewportBounds.Min.Y)
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}
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if element.onScroll != nil {
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element.onScroll(image.Pt(int(scrollX), int(scrollY)))
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}
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}
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func (element *ScrollBar) recalculate () {
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if element.vertical {
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element.recalculateVertical()
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} else {
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element.recalculateHorizontal()
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}
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}
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func (element *ScrollBar) recalculateVertical () {
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bounds := element.entity.Bounds()
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padding := element.entity.Theme().Padding(tomo.PatternGutter, element.c)
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element.track = padding.Apply(bounds)
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contentBounds := element.contentBounds
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viewportBounds := element.viewportBounds
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if element.Enabled() {
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element.bar.Min.X = element.track.Min.X
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element.bar.Max.X = element.track.Max.X
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ratio :=
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float64(element.track.Dy()) /
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float64(contentBounds.Dy())
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element.bar.Min.Y = int(float64(viewportBounds.Min.Y) * ratio)
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element.bar.Max.Y = int(float64(viewportBounds.Max.Y) * ratio)
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element.bar.Min.Y += element.track.Min.Y
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element.bar.Max.Y += element.track.Min.Y
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}
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// if the handle is out of bounds, don't display it
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if element.bar.Dy() >= element.track.Dy() {
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element.bar = image.Rectangle { }
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}
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}
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func (element *ScrollBar) recalculateHorizontal () {
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bounds := element.entity.Bounds()
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padding := element.entity.Theme().Padding(tomo.PatternGutter, element.c)
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element.track = padding.Apply(bounds)
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contentBounds := element.contentBounds
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viewportBounds := element.viewportBounds
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if element.Enabled() {
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element.bar.Min.Y = element.track.Min.Y
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element.bar.Max.Y = element.track.Max.Y
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ratio :=
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float64(element.track.Dx()) /
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float64(contentBounds.Dx())
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element.bar.Min.X = int(float64(viewportBounds.Min.X) * ratio)
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element.bar.Max.X = int(float64(viewportBounds.Max.X) * ratio)
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element.bar.Min.X += element.track.Min.X
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element.bar.Max.X += element.track.Min.X
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}
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// if the handle is out of bounds, don't display it
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if element.bar.Dx() >= element.track.Dx() {
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element.bar = image.Rectangle { }
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}
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}
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func (element *ScrollBar) updateMinimumSize () {
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gutterPadding := element.entity.Theme().Padding(tomo.PatternGutter, element.c)
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handlePadding := element.entity.Theme().Padding(tomo.PatternHandle, element.c)
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if element.vertical {
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element.entity.SetMinimumSize (
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gutterPadding.Horizontal() + handlePadding.Horizontal(),
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gutterPadding.Vertical() + handlePadding.Vertical() * 2)
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} else {
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element.entity.SetMinimumSize (
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gutterPadding.Horizontal() + handlePadding.Horizontal() * 2,
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gutterPadding.Vertical() + handlePadding.Vertical())
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}
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}
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