POC code that determines column widths.

internal/canvas/buffer/buffer.go

@@ -33,6 +33,16 @@ func NewCells(text string, opts ...cell.Option) []*Cell {
 	return res
 }
 
+// CellsWidth returns the width the cells will use on a terminal if printed out.
+// This takes into account if some of the runes are full-width runes.
+func CellsWidth(cells []*Cell) int {
+	width := 0
+	for _, c := range cells {
+		width += runewidth.RuneWidth(c.Rune)
+	}
+	return width
+}
+
 // Cell represents a single cell on the terminal.
 type Cell struct {
 	// Rune is the rune stored in the cell.

internal/canvas/buffer/buffer_test.go

@@ -625,3 +625,35 @@ func TestRemWidth(t *testing.T) {
 		})
 	}
 }
+
+func TestCellsWidth(t *testing.T) {
+	tests := []struct {
+		desc  string
+		cells []*Cell
+		want  int
+	}{
+		{
+			desc:  "ascii characters",
+			cells: NewCells("hello"),
+			want:  5,
+		},
+		{
+			desc:  "string from mattn/runewidth/runewidth_test",
+			cells: NewCells("■㈱の世界①"),
+			want:  10,
+		},
+		{
+			desc:  "string using termdash characters",
+			cells: NewCells("⇄…⇧⇩"),
+			want:  4,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.desc, func(t *testing.T) {
+			if got := CellsWidth(tc.cells); got != tc.want {
+				t.Errorf("CellsWidth => %v, want %v", got, tc.want)
+			}
+		})
+	}
+}

widgets/table/content.go

@@ -19,6 +19,7 @@ package table
 
 import (
 	"fmt"
+	"sync"
 
 	"github.com/mum4k/termdash/align"
 	"github.com/mum4k/termdash/cell"
@@ -143,6 +144,8 @@ func ContentCellOpts(cellOpts ...cell.Option) ContentOption {
 
 // ContentRowHeight sets the height of rows to the provided number of cells.
 // The number must be a non-zero positive integer.
+// Rows still use larger than provided height if wrapping is enabled and the
+// content doesn't fit.
 // Defaults to row height automatically adjusted to the content.
 // This is a hierarchical option and can be overridden when provided at Row
 // level.
@@ -229,8 +232,14 @@ type Content struct {
 	// rows are the rows in the table.
 	rows []*Row
 
+	// layout describes the layout of this table on a canvas.
+	layout *contentLayout
+
 	// opts are the options provided to NewContent.
 	opts *contentOptions
+
+	// mu protects the Content
+	mu sync.Mutex
 }
 
 // NewContent returns a new Content instance.
@@ -240,8 +249,9 @@ type Content struct {
 // allowing for the CellColSpan option.
 func NewContent(cols Columns, rows []*Row, opts ...ContentOption) (*Content, error) {
 	c := &Content{
-		cols: cols,
-		opts: newContentOptions(opts...),
+		cols:   cols,
+		layout: &contentLayout{},
+		opts:   newContentOptions(opts...),
 	}
 	for _, r := range rows {
 		if err := c.addRow(r); err != nil {
@@ -296,6 +306,9 @@ func (c *Content) addRow(row *Row) error {
 
 // AddRowWithOpts adds a row to the content and applies the options.
 func (c *Content) AddRowWithOpts(cells []*Cell, opts ...RowOption) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
 	if err := c.addRow(NewRowWithOpts(cells, opts...)); err != nil {
 		return err
 	}

widgets/table/content_cell.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/mum4k/termdash/align"
 	"github.com/mum4k/termdash/cell"
+	"github.com/mum4k/termdash/internal/canvas/buffer"
 	"github.com/mum4k/termdash/internal/wrap"
 )
 
@@ -69,6 +70,8 @@ func CellOpts(cellOpts ...cell.Option) CellOption {
 
 // CellHeight sets the height of cells to the provided number of cells.
 // The number must be a non-zero positive integer.
+// Rows still use larger than provided height if wrapping is enabled and the
+// content doesn't fit.
 // Defaults to cell height automatically adjusted to the content.
 // This is a hierarchical option, it overrides the one provided at Content or
 // Row level.
@@ -156,6 +159,16 @@ func (c *Cell) String() string {
 	return fmt.Sprintf("| %v ", b.String())
 }
 
+// width returns the width of all the runes in this cell when they are printed
+// on the terminal.
+func (c *Cell) width() int {
+	res := 0
+	for _, d := range c.data {
+		res += buffer.CellsWidth(d.cells)
+	}
+	return res
+}
+
 // NewCell returns a new Cell with the provided text.
 // If you need to apply options at the Cell or Data level use NewCellWithOpts.
 // The text contain cannot control characters (unicode.IsControl) or space

widgets/table/content_layout.go

@@ -0,0 +1,156 @@
+// 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 table
+
+// content_layout.go stores layout calculated for a canvas size.
+
+import (
+	"errors"
+	"image"
+	"log"
+	"math"
+
+	"github.com/mum4k/termdash/internal/wrap"
+)
+
+// columnWidth is the width of a column in cells.
+// This excludes any border, padding or spacing, i.e. this is the data portion
+// only.
+type columnWidth int
+
+// contentLayout determines how the content gets placed onto the canvas.
+type contentLayout struct {
+	// lastCvsAr is the are of the last canvas the content was drawn on.
+	// This is image.ZR if the content hasn't been drawn yet.
+	lastCvsAr image.Rectangle
+
+	// columnWidths are the widths of individual columns in the table.
+	columnWidths []columnWidth
+
+	// Details about HV lines that are the borders.
+}
+
+// newContentLayout calculates new layout for the content when drawn on a
+// canvas represented with the provided area.
+func newContentLayout(content *Content, cvsAr image.Rectangle) (*contentLayout, error) {
+	return nil, errors.New("unimplemented")
+}
+
+// columnWidths given the content and the available canvas width returns the
+// widths of individual columns.
+// The argument cvsWidth is assumed to exclude space required for any border,
+// padding or spacing.
+func columnWidths(content *Content, cvsWidth int) []columnWidth {
+	// This is similar to the rod-cutting problem, except instead of maximizing
+	// the price, we're minimizing the number of rows that would have their
+	// content trimmed.
+
+	idxColumnCosts := columnCosts(content, cvsWidth)
+	log.Printf("idxColumnCosts: %v", idxColumnCosts)
+	minCost, minCuts := cutCanvas(idxColumnCosts, cvsWidth, cvsWidth, int(content.cols), 0, nil)
+	log.Printf("minCost: %v", minCost)
+	log.Printf("minCuts: %v", minCuts)
+
+	var res []columnWidth
+	last := 0
+	for _, cut := range minCuts {
+		res = append(res, columnWidth(cut-last))
+		last = cut
+	}
+	res = append(res, columnWidth(cvsWidth-last))
+	return res
+}
+
+func cutCanvas(idxColumnCosts map[int]widthCost, cvsWidth, remWidth, columns, colIdx int, cuts []int) (int, []int) {
+	log.Printf("cutCanvas remWidth:%d, columns:%d, colIdx:%d, cuts:%v", remWidth, columns, colIdx, cuts)
+	if remWidth <= 0 {
+		log.Printf("  -> 0")
+		return 0, cuts
+	}
+
+	minCost := math.MaxInt32
+	var minCuts []int
+
+	widthCosts := idxColumnCosts[colIdx]
+	nextColIdx := colIdx + 1
+	if nextColIdx > columns-1 {
+		log.Printf("  -> no more cuts remWidth:%d cost:%d", remWidth, widthCosts[remWidth])
+		return widthCosts[remWidth], cuts
+	}
+
+	for colWidth := 1; colWidth < remWidth; colWidth++ {
+		diff := cvsWidth - remWidth
+		idxThisCut := diff + colWidth
+		costThisCut := widthCosts[colWidth]
+		nextCost, nextCuts := cutCanvas(
+			idxColumnCosts,
+			cvsWidth,
+			remWidth-colWidth,
+			columns,
+			nextColIdx,
+			//append(cuts, colWidth+colIdx),
+			append(cuts, idxThisCut),
+		)
+
+		if newMinCost := costThisCut + nextCost; newMinCost < minCost {
+			log.Printf("at cuts %v, costThisCut from widthCosts:%v, at width %d:%d, nextCost:%d, minCost:%d", cuts, widthCosts, colWidth, costThisCut, nextCost, minCost)
+			minCost = newMinCost
+			minCuts = nextCuts
+			log.Printf("new minCost:%d minCuts:%v", minCost, minCuts)
+		}
+	}
+	log.Printf("cutCanvas remWidth:%d, columns:%d, colIdx:%d, cuts:%v -> minCost:%d, minCuts:%d", remWidth, columns, colIdx, cuts, minCost, minCuts)
+	return minCost, minCuts
+}
+
+// widthCost maps column widths to the number of rows that would be trimmed on
+// that width because data in the column are longer than the width.
+type widthCost map[int]int
+
+// columnCosts calculates the costs of cutting the columns to various widths.
+// Returns a map of column indexes to their cut costs.
+func columnCosts(content *Content, cvsWidth int) map[int]widthCost {
+	idxColumnCosts := map[int]widthCost{}
+	maxColWidth := cvsWidth - (int(content.cols) - 1)
+	for colIdx := 0; colIdx < int(content.cols); colIdx++ {
+		for colWidth := 1; colWidth <= maxColWidth; colWidth++ {
+			wc, ok := idxColumnCosts[colIdx]
+			if !ok {
+				wc = widthCost{}
+				idxColumnCosts[colIdx] = wc
+			}
+			wc[colWidth] = trimmedRows(content, colIdx, colWidth)
+		}
+	}
+	return idxColumnCosts
+}
+
+// trimmedRows returns the number of rows that will have data cells with
+// trimmed content in column of the specified index if the assigned width of
+// the column is colWidth.
+func trimmedRows(content *Content, colIdx int, colWidth int) int {
+	trimmed := 0
+	for _, row := range content.rows {
+		tgtCell := row.cells[colIdx]
+		if tgtCell.hierarchical.getWrapMode() != wrap.Never {
+			// Cells that have wrapping enabled are never trimmed.
+			continue
+		}
+		if tgtCell.width() > colWidth {
+			trimmed++
+		}
+	}
+	return trimmed
+}

widgets/table/content_layout_test.go

@@ -0,0 +1,181 @@
+// 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 table
+
+import (
+	"testing"
+
+	"github.com/kylelemons/godebug/pretty"
+)
+
+func TestColumnWidths(t *testing.T) {
+	tests := []struct {
+		desc     string
+		columns  Columns
+		rows     []*Row
+		opts     []ContentOption
+		cvsWidth int
+		want     []columnWidth
+	}{
+		{
+			desc:    "single column, wide enough",
+			columns: Columns(1),
+			rows: []*Row{
+				NewRow(
+					NewCell("ab"),
+				),
+				NewRow(
+					NewCell(""),
+				),
+			},
+			cvsWidth: 2,
+			want:     []columnWidth{2},
+		},
+		{
+			desc:    "single column, not wide enough",
+			columns: Columns(1),
+			rows: []*Row{
+				NewRow(
+					NewCell("ab"),
+				),
+				NewRow(
+					NewCell(""),
+				),
+			},
+			cvsWidth: 1,
+			want:     []columnWidth{1},
+		},
+		{
+			desc:    "two columns, canvas wide enough, no trimming",
+			columns: Columns(2),
+			rows: []*Row{
+				NewRow(
+					NewCell("ab"),
+					NewCell("cde"),
+				),
+				NewRow(
+					NewCell("a"),
+					NewCell("cde"),
+				),
+				NewRow(
+					NewCell(""),
+					NewCell("cde"),
+				),
+			},
+			cvsWidth: 5,
+			want:     []columnWidth{2, 3},
+		},
+		{
+			desc:    "two columns, canvas not wide enough, optimal to trim first",
+			columns: Columns(2),
+			rows: []*Row{
+				NewRow(
+					NewCell("ab"),
+					NewCell("cde"),
+				),
+				NewRow(
+					NewCell("a"),
+					NewCell("cde"),
+				),
+				NewRow(
+					NewCell(""),
+					NewCell("cde"),
+				),
+			},
+			cvsWidth: 4,
+			want:     []columnWidth{1, 3},
+		},
+		{
+			desc:    "two columns, canvas not wide enough, optimal to trim second",
+			columns: Columns(2),
+			rows: []*Row{
+				NewRow(
+					NewCell("ab"),
+					NewCell("c"),
+				),
+				NewRow(
+					NewCell("ab"),
+					NewCell("c"),
+				),
+				NewRow(
+					NewCell(""),
+					NewCell("cde"),
+				),
+			},
+			cvsWidth: 4,
+			want:     []columnWidth{2, 2},
+		},
+		{
+			desc:    "three columns, canvas wide enough, no trimming",
+			columns: Columns(3),
+			rows: []*Row{
+				NewRow(
+					NewCell("ab"),
+					NewCell("cde"),
+					NewCell("fg"),
+				),
+				NewRow(
+					NewCell("a"),
+					NewCell("c"),
+					NewCell("f"),
+				),
+				NewRow(
+					NewCell("ab"),
+					NewCell("cde"),
+					NewCell("fg"),
+				),
+			},
+			cvsWidth: 7,
+			want:     []columnWidth{2, 3, 2},
+		},
+		{
+			desc:    "three columns, canvas not wide enough, one very long cell",
+			columns: Columns(3),
+			rows: []*Row{
+				NewRow(
+					NewCell("00"),
+					NewCell("11111111"),
+					NewCell("22"),
+				),
+				NewRow(
+					NewCell("00"),
+					NewCell("11"),
+					NewCell("22"),
+				),
+				NewRow(
+					NewCell("00"),
+					NewCell("111"),
+					NewCell("22"),
+				),
+			},
+			cvsWidth: 6,
+			want:     []columnWidth{2, 2, 2},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.desc, func(t *testing.T) {
+			content, err := NewContent(tc.columns, tc.rows, tc.opts...)
+			if err != nil {
+				t.Fatalf("NewContent => unexpected error: %v", err)
+			}
+
+			got := columnWidths(content, tc.cvsWidth)
+			if diff := pretty.Compare(tc.want, got); diff != "" {
+				t.Errorf("columnWidths => unexpected diff (-want, +got):\n%s", diff)
+			}
+		})
+	}
+}

widgets/table/content_row.go

@@ -81,6 +81,8 @@ func RowCellOpts(cellOpts ...cell.Option) RowOption {
 
 // RowHeight sets the height of rows to the provided number of cells.
 // The number must be a non-zero positive integer.
+// Rows still use larger than provided height if wrapping is enabled and the
+// content doesn't fit.
 // Defaults to row height automatically adjusted to the content.
 // This is a hierarchical option, it overrides the one provided at Content
 // level and can be overridden when provided at the Cell level.

widgets/table/content_validate.go

@@ -61,6 +61,9 @@ func validateContent(content *Content) error {
 				return err
 			}
 			for _, d := range c.data {
+				if len(d.cells) == 0 {
+					continue
+				}
 				if err := wrap.ValidCells(d.cells); err != nil {
 					return fmt.Errorf("invalid data: %v", err)
 				}