Moved element core to new package

elements/core/core.go

@@ -0,0 +1,135 @@
+package core
+
+import "image"
+import "image/color"
+import "git.tebibyte.media/sashakoshka/tomo"
+
+// Core is a struct that implements some core functionality common to most
+// widgets. It is meant to be embedded directly into a struct.
+type Core struct {
+	canvas *image.RGBA
+	parent tomo.Element
+
+	metrics struct {
+		minimumWidth  int
+		minimumHeight int
+	}
+
+	hooks tomo.ParentHooks
+}
+
+// NewCore creates a new element core and its corresponding control.
+func NewCore (parent tomo.Element) (core *Core, control CoreControl) {
+	core    = &Core { parent: parent }
+	control = CoreControl { core: core }
+	return
+}
+
+func (core Core) ColorModel () (model color.Model) {
+	return color.RGBAModel
+}
+
+func (core Core) At (x, y int) (pixel color.Color) {
+	if core.canvas == nil { return color.RGBA { } }
+	pixel = core.canvas.At(x, y)
+	return
+}
+
+func (core Core) RGBAAt (x, y int) (pixel color.RGBA) {
+	if core.canvas == nil { return color.RGBA { } }
+	pixel = core.canvas.RGBAAt(x, y)
+	return
+}
+
+func (core Core) Bounds () (bounds image.Rectangle) {
+	if core.canvas != nil { bounds = core.canvas.Bounds() }
+	return
+}
+
+func (core *Core) SetParentHooks (hooks tomo.ParentHooks) {
+	core.hooks = hooks
+}
+
+func (core Core) MinimumSize () (width, height int) {
+	return core.metrics.minimumWidth, core.metrics.minimumHeight
+}
+
+// CoreControl is a struct that can exert control over a control struct. It can
+// be used as a canvas. It must not be directly embedded into an element, but
+// instead kept as a private member.
+type CoreControl struct {
+	*image.RGBA
+	core *Core
+}
+
+func (control CoreControl) HasImage () (has bool) {
+	has = control.RGBA != nil
+	return
+}
+
+func (control CoreControl) Select () {
+	control.core.hooks.RunSelectionRequest()
+}
+
+func (control CoreControl) PushRegion (bounds image.Rectangle) {
+	control.core.hooks.RunDraw(control.SubImage(bounds).(*image.RGBA))
+}
+
+func (control CoreControl) PushAll () {
+	control.PushRegion(control.Bounds())
+}
+
+func (control *CoreControl) AllocateCanvas (width, height int) {
+	core := control.core
+	width, height, _ = control.ConstrainSize(width, height)
+	core.canvas  = image.NewRGBA(image.Rect (0, 0, width, height))
+	control.RGBA = core.canvas
+}
+
+func (control CoreControl) SetMinimumSize (width, height int) {
+	core := control.core
+	if width != core.metrics.minimumWidth ||
+		height != core.metrics.minimumHeight {
+
+		core.metrics.minimumWidth  = width
+		core.metrics.minimumHeight = height
+		core.hooks.RunMinimumSizeChange(width, height)
+
+		// if there is an image buffer, and the current size is less
+		// than this new minimum size, send core.parent a resize event.
+		if control.HasImage() {
+			bounds := control.Bounds()
+			imageWidth,
+			imageHeight,
+			constrained := control.ConstrainSize (
+				bounds.Dx(),
+				bounds.Dy())
+			if constrained {
+				core.parent.Handle (tomo.EventResize {
+					Width:  imageWidth,
+					Height: imageHeight,
+				})
+			}
+		}
+	}
+}
+
+func (control CoreControl) ConstrainSize (
+	inWidth, inHeight int,
+) (
+	outWidth, outHeight int,
+	constrained bool,
+) {
+	core := control.core
+	outWidth  = inWidth
+	outHeight = inHeight
+	if outWidth < core.metrics.minimumWidth {
+		outWidth = core.metrics.minimumWidth
+		constrained = true
+	}
+	if outHeight < core.metrics.minimumHeight {
+		outHeight = core.metrics.minimumHeight
+		constrained = true
+	}
+	return
+}