Merge pull request #120 from mum4k/draw-vertical-text

Function that draws text in vertical columns.

draw/vertical_text.go

@@ -0,0 +1,120 @@
+// Copyright 2019 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package draw
+
+// vertical_text.go contains code that prints UTF-8 encoded strings on the
+// canvas in vertical columns instead of lines.
+
+import (
+	"fmt"
+	"image"
+
+	"github.com/mum4k/termdash/canvas"
+	"github.com/mum4k/termdash/cell"
+)
+
+// VerticalTextOption is used to provide options to Text().
+type VerticalTextOption interface {
+	// set sets the provided option.
+	set(*verticalTextOptions)
+}
+
+// verticalTextOptions stores the provided options.
+type verticalTextOptions struct {
+	cellOpts    []cell.Option
+	maxY        int
+	overrunMode OverrunMode
+}
+
+// verticalTextOption implements VerticalTextOption.
+type verticalTextOption func(*verticalTextOptions)
+
+// set implements VerticalTextOption.set.
+func (vto verticalTextOption) set(vtOpts *verticalTextOptions) {
+	vto(vtOpts)
+}
+
+// VerticalTextCellOpts sets options on the cells that contain the text.
+func VerticalTextCellOpts(opts ...cell.Option) VerticalTextOption {
+	return verticalTextOption(func(vtOpts *verticalTextOptions) {
+		vtOpts.cellOpts = opts
+	})
+}
+
+// VerticalTextMaxY sets a limit on the Y coordinate (row) of the drawn text.
+// The Y coordinate of all cells used by the vertical text must be within
+// start.Y <= Y < VerticalTextMaxY.
+// If not provided, the height of the canvas is used as VerticalTextMaxY.
+func VerticalTextMaxY(y int) VerticalTextOption {
+	return verticalTextOption(func(vtOpts *verticalTextOptions) {
+		vtOpts.maxY = y
+	})
+}
+
+// VerticalTextOverrunMode indicates what to do with text that overruns the
+// VerticalTextMaxY() or the width of the canvas if VerticalTextMaxY() isn't
+// specified.
+// Defaults to OverrunModeStrict.
+func VerticalTextOverrunMode(om OverrunMode) VerticalTextOption {
+	return verticalTextOption(func(vtOpts *verticalTextOptions) {
+		vtOpts.overrunMode = om
+	})
+}
+
+// VerticalText prints the provided text on the canvas starting at the provided point.
+// The text is printed in a vertical orientation, i.e:
+//   H
+//   e
+//   l
+//   l
+//   o
+func VerticalText(c *canvas.Canvas, text string, start image.Point, opts ...VerticalTextOption) error {
+	ar := c.Area()
+	if !start.In(ar) {
+		return fmt.Errorf("the requested start point %v falls outside of the provided canvas %v", start, ar)
+	}
+
+	opt := &verticalTextOptions{}
+	for _, o := range opts {
+		o.set(opt)
+	}
+
+	if opt.maxY < 0 || opt.maxY > ar.Max.Y {
+		return fmt.Errorf("invalid VerticalTextMaxY(%v), must be a positive number that is <= canvas.width %v", opt.maxY, ar.Dy())
+	}
+
+	var wantMaxY int
+	if opt.maxY == 0 {
+		wantMaxY = ar.Max.Y
+	} else {
+		wantMaxY = opt.maxY
+	}
+
+	maxCells := wantMaxY - start.Y
+	trimmed, err := TrimText(text, maxCells, opt.overrunMode)
+	if err != nil {
+		return err
+	}
+
+	cur := start
+	for _, r := range trimmed {
+		cells, err := c.SetCell(cur, r, opt.cellOpts...)
+		if err != nil {
+			return err
+		}
+		cur = image.Point{cur.X, cur.Y + cells}
+	}
+	return nil
+}