81 lines
2.5 KiB
Go
81 lines
2.5 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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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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// 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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}
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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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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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