136 lines
4.9 KiB
Go
136 lines
4.9 KiB
Go
// 14 march 2014
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package ui
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import (
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"sync"
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"image"
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)
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// Area represents a blank canvas upon which programs may draw anything and receive arbitrary events from the user.
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// An Area has an explicit size, represented in pixels, that may be different from the size shown in its Window; scrollbars are placed automatically should they be needed.
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// The coordinate system of an Area always has an origin of (0,0) which maps to the top-left corner; all image.Points and image.Rectangles sent across Area's channels conform to this.
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// To facilitate development and debugging, for the time being, Areas have a fixed size of 320x240 and only work on GTK+.
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type Area struct {
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// Paint is signaled when the Area needs to be redrawn.
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// You MUST handle Paint signals; failure to do so will result in the UI task hanging.
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// See the documentation of PaintRequest for details.
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Paint chan PaintRequest
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// Mouse is signaled when the Area receives a mouse event.
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// See MouseEvent for details.
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Mouse chan MouseEvent
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lock sync.Mutex
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created bool
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sysData *sysData
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}
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// PaintRequest contains the information needed to redraw an Area.
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// On each Paint event, an Area will receive a full request on its Paint channel.
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// It must send something back on Out in order to complete the painting.
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// Example:
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// imgFromFile, _, err := image.Decode(file)
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// if err != nil { panic(err) }
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// img := image.NewNRGBA(imgFromFile.Rect)
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// draw.Draw(img, img.Rect, imgFromFile, image.ZP, draw.Over)
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// for req := range area.Paint {
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// req.Out <- img.SubImage(req.Rect).(*image.NRGBA)
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// }
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type PaintRequest struct {
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// Rect is the clip rectangle of the whole Area that needs to be redrawn.
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// The image sent on Out must have the same size as Rect (but does not have to have the same Rect.Min/Rect.Max points).
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Rect image.Rectangle
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// Out is where you send the image to draw.
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// Only one image per PaintRequest may be sent; you must send an image.
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// Do not close Out; the package will do this itself.
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Out chan<- *image.NRGBA
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}
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// MouseEvent contains all the information for a mous event sent by Area.Mouse.
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// Mouse button IDs start at 1, with 1 being the left mouse button, 2 being the middle mouse button, and 3 being the right mouse button.
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// (TODO "If additional buttons are supported, they will be returned with 4 being the first additional button (XBUTTON1 on Windows), 5 being the second (XBUTTON2 on Windows), and so on."?) (TODO get the user-facing name for XBUTTON1/2; find out if there's a way to query available button count)
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type MouseEvent struct {
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// Pos is the position of the mouse in the Area at the time of the event.
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// TODO rename to Pt or Point?
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Pos image.Point
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// If the event was generated by a mouse button being pressed, Down contains the ID of that button.
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// Otherwise, Down contains 0.
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Down uint
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// If the event was generated by a mouse button being released, Up contains the ID of that button.
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// Otherwise, Up contains 0.
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// If both Down and Up are 0, the event represents mouse movement (with optional held buttons; see below).
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Up uint
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// If Down is nonzero, Count indicates the number of clicks: 1 for single-click, 2 for double-click.
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// If Count == 2, AT LEAST one event with Count == 1 will have been sent prior.
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// (This is a platform-specific issue: some platforms send one, some send two.)
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Count uint
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// Modifiers is a bit mask indicating the modifier keys being held during the event.
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Modifiers Modifiers
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// Held is a slice of button IDs that indicate which mouse buttons are being held during the event.
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// (TODO "There is no guarantee that Held is sorted."?)
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// (TODO will this include or exclude Down and Up?)
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Held []uint
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}
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// HeldBits returns Held as a bit mask.
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// Bit 0 maps to button 1, bit 1 maps to button 2, etc.
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func (e MouseEvent) HeldBits() (h uintptr) {
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for _, x := range e.Held {
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h |= uintptr(1) << (x - 1)
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}
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return h
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}
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// Modifiers indicates modifier keys being held during a mouse event.
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// There is no way to differentiate between left and right modifier keys.
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type Modifiers uintptr
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const (
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Ctrl Modifiers = 1 << iota // the canonical Ctrl keys ([TODO] on Mac OS X, Control on others)
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Alt // the canonical Alt keys ([TODO] on Mac OS X, Meta on Unix systems, Alt on others)
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Shift // the Shift keys
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)
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// NewArea creates a new Area.
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func NewArea() *Area {
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return &Area{
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sysData: mksysdata(c_area),
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Paint: make(chan PaintRequest),
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Mouse: make(chan MouseEvent),
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}
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}
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func (a *Area) make(window *sysData) error {
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a.lock.Lock()
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defer a.lock.Unlock()
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a.sysData.paint = a.Paint
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a.sysData.mouse = a.Mouse
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err := a.sysData.make("", window)
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if err != nil {
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return err
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}
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a.created = true
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return nil
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}
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func (a *Area) setRect(x int, y int, width int, height int, winheight int) error {
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a.lock.Lock()
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defer a.lock.Unlock()
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return a.sysData.setRect(x, y, width, height, winheight)
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}
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func (a *Area) preferredSize() (width int, height int) {
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a.lock.Lock()
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defer a.lock.Unlock()
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return a.sysData.preferredSize()
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}
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