ted/ui/drawable.go

// Provides access to the drawable primitives.

package ui

// A drawable context.  Each context is allocated part of the screen and provides methods for
// drawing within it's context.
type DrawContext struct {

	// The left and top position of the context.
	X, Y int

	// The width and height position of the context.
	W, H int

	// The current driver
	driver Driver

	// The current foregound and background attributes
	fa, ba Attribute
}

// Returns a new subcontext.  The sub-context must be an area within the current context.
func (dc *DrawContext) NewSubContext(offsetX, offsetY, width, height int) *DrawContext {
	return &DrawContext{
		X: intMax(dc.X+offsetX, dc.X),
		Y: intMax(dc.Y+offsetY, dc.Y),
		W: intMax(width, 0),
		H: intMax(height, 0),

		driver: dc.driver,
	}
}

// Sets the foreground attribute
func (dc *DrawContext) SetFgAttr(attr Attribute) {
	dc.fa = attr
}

// Sets the background attribute
func (dc *DrawContext) SetBgAttr(attr Attribute) {
	dc.ba = attr
}

// Draws a horizontal rule with a specific rune.
func (dc *DrawContext) HorizRule(y int, ch rune) {
	for x := 0; x < dc.W; x++ {
		dc.DrawRune(x, y, ch)
	}
}

// Prints a string at a specific offset.  This will be bounded by the size of the drawing context.
func (dc *DrawContext) Print(x, y int, str string) {
	for _, ch := range str {
		dc.DrawRune(x, y, ch)
		x++
	}
}

// Prints a right-justified string at a specific offset.  This will be bounded by the size of the drawing context.
func (dc *DrawContext) PrintRight(x, y int, str string) {
	l := len(str)
	dc.Print(x-l, y, str)
}

// Draws a rune at a local point X, Y with the current foreground and background attributes
func (dc *DrawContext) DrawRune(x, y int, ch rune) {
	if rx, ry, isWithinContext := dc.localPointToRealPoint(x, y); isWithinContext {
		dc.driver.SetCell(rx, ry, ch, dc.fa, dc.ba)
	}
}

// Draws a rune at a local point X, Y with specific foreground and background attributes
func (dc *DrawContext) DrawRuneWithAttrs(x, y int, ch rune, fa, ba Attribute) {
	if rx, ry, isWithinContext := dc.localPointToRealPoint(x, y); isWithinContext {
		dc.driver.SetCell(rx, ry, ch, fa, ba)
	}
}

// Set the position of the cursor
func (dc *DrawContext) SetCursorPosition(x, y int) {
	if rx, ry, isWithinContext := dc.localPointToRealPoint(x, y); isWithinContext {
		dc.driver.SetCursor(rx, ry)
	}
}

// HideCursor hides the cursor
func (dc *DrawContext) HideCursor() {
	dc.driver.HideCursor()
}

// Converts a local point to a real point.  If the point is within the context, also returns true
func (dc *DrawContext) localPointToRealPoint(x, y int) (int, int, bool) {
	rx, ry := x+dc.X, y+dc.Y
	return rx, ry, (rx >= dc.X) && (ry >= dc.Y) && (rx < dc.X+dc.W) && (ry < dc.Y+dc.H)
}