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// 14 march 2014
package ui
import (
"sync"
"image"
)
// Area represents a blank canvas upon which programs may draw anything and receive arbitrary events from the user.
// 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.
// To facilitate development and debugging, for the time being, Areas have a fixed size of 320x240 and only work on GTK+.
type Area struct {
// Paint is signaled when the Area needs to be redrawn.
// You MUST handle Paint signals; failure to do so will result in the UI task hanging.
// See the documentation of PaintRequest for details.
Paint chan PaintRequest
lock sync.Mutex
created bool
sysData *sysData
}
// PaintRequest contains the information needed to redraw an Area.
// On each Paint event, an Area will receive a full request on its Paint channel.
// It must send something back on Out in order to complete the painting.
// Example:
// imgFromFile, _, err := image.Decode(file)
// if err != nil { panic(err) }
// img := image.NewNRGBA(imgFromFile.Rect)
// draw.Draw(img, img.Rect, imgFromFile, image.ZP, draw.Over)
// for req := range area.Paint {
// req.Out <- img.SubImage(req.Rect).(*image.NRGBA)
// }
type PaintRequest struct {
// Rect is the clip rectangle of the whole Area that needs to be redrawn.
// 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).
Rect image.Rectangle
// Out is where you send the image to draw.
// Only one image per PaintRequest may be sent; you must send an image.
// Do not close Out; the package will do this itself.
Out chan<- *image.NRGBA
}
// NewArea creates a new Area.
func NewArea() *Area {
return &Area{
sysData: mksysdata(c_area),
Paint: make(chan PaintRequest),
}
}
func (a *Area) make(window *sysData) error {
a.lock.Lock()
defer a.lock.Unlock()
a.sysData.paint = a.Paint
err := a.sysData.make("", window)
if err != nil {
return err
}
a.created = true
return nil
}
func (a *Area) setRect(x int, y int, width int, height int, winheight int) error {
a.lock.Lock()
defer a.lock.Unlock()
return a.sysData.setRect(x, y, width, height, winheight)
}
func (a *Area) preferredSize() (width int, height int) {
a.lock.Lock()
defer a.lock.Unlock()
return a.sysData.preferredSize()
}
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