Added the portable code for Area.

area.go

@@ -0,0 +1,79 @@
+// 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()
+}