Split*FromEnd functions

container/container.go

@@ -180,14 +180,26 @@ func (c *Container) split() (image.Rectangle, image.Rectangle, error) {
 	}
 	if c.opts.splitFixed > DefaultSplitFixed {
 		if c.opts.split == splitTypeVertical {
+			if c.opts.splitReversed {
+				return area.VSplitCellsReversed(ar, c.opts.splitFixed)
+			}
 			return area.VSplitCells(ar, c.opts.splitFixed)
 		}
+		if c.opts.splitReversed {
+			return area.HSplitCellsReversed(ar, c.opts.splitFixed)
+		}
 		return area.HSplitCells(ar, c.opts.splitFixed)
 	}
 
 	if c.opts.split == splitTypeVertical {
+		if c.opts.splitReversed {
+			return area.VSplitReversed(ar, c.opts.splitPercent)
+		}
 		return area.VSplit(ar, c.opts.splitPercent)
 	}
+	if c.opts.splitReversed {
+		return area.HSplitReversed(ar, c.opts.splitPercent)
+	}
 	return area.HSplit(ar, c.opts.splitPercent)
 }
 

container/container_test.go

@@ -864,6 +864,32 @@ func TestNew(t *testing.T) {
 				return ft
 			},
 		},
+		{
+			desc:     "vertical, reversed unequal split",
+			termSize: image.Point{20, 10},
+			container: func(ft *faketerm.Terminal) (*Container, error) {
+				return New(
+					ft,
+					SplitVertical(
+						Left(
+							Border(linestyle.Light),
+						),
+						Right(
+							Border(linestyle.Light),
+						),
+						SplitPercentFromEnd(20),
+					),
+				)
+			},
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				cvs := testcanvas.MustNew(ft.Area())
+				testdraw.MustBorder(cvs, image.Rect(0, 0, 16, 10))
+				testdraw.MustBorder(cvs, image.Rect(16, 0, 20, 10))
+				testcanvas.MustApply(cvs, ft)
+				return ft
+			},
+		},
 		{
 			desc:     "vertical fixed splits",
 			termSize: image.Point{20, 10},
@@ -890,6 +916,32 @@ func TestNew(t *testing.T) {
 				return ft
 			},
 		},
+		{
+			desc:     "vertical, reversed fixed splits",
+			termSize: image.Point{20, 10},
+			container: func(ft *faketerm.Terminal) (*Container, error) {
+				return New(
+					ft,
+					SplitVertical(
+						Left(
+							Border(linestyle.Light),
+						),
+						Right(
+							Border(linestyle.Light),
+						),
+						SplitFixedFromEnd(4),
+					),
+				)
+			},
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				cvs := testcanvas.MustNew(ft.Area())
+				testdraw.MustBorder(cvs, image.Rect(0, 0, 16, 10))
+				testdraw.MustBorder(cvs, image.Rect(16, 0, 20, 10))
+				testcanvas.MustApply(cvs, ft)
+				return ft
+			},
+		},
 		{
 			desc:     "vertical split, parent and children have borders",
 			termSize: image.Point{10, 10},

container/options.go

@@ -109,6 +109,7 @@ type options struct {
 
 	// split identifies how is this container split.
 	split         splitType
+	splitReversed bool
 	splitPercent  int
 	splitFixed    int
 
@@ -249,6 +250,7 @@ func newOptions(parent *options) *options {
 		},
 		hAlign:        align.HorizontalCenter,
 		vAlign:        align.VerticalMiddle,
+		splitReversed: DefaultSplitReversed,
 		splitPercent:  DefaultSplitPercent,
 		splitFixed:    DefaultSplitFixed,
 	}
@@ -281,13 +283,17 @@ func (so splitOption) setSplit(opts *options) error {
 	return so(opts)
 }
 
+// DefaultSplitReversed is the default value for the SplitReversed option.
+const DefaultSplitReversed = false
+
 // DefaultSplitPercent is the default value for the SplitPercent option.
 const DefaultSplitPercent = 50
 
 // DefaultSplitFixed is the default value for the SplitFixed option.
 const DefaultSplitFixed = -1
 
-// SplitPercent sets the relative size of the split as percentage of the available space.
+// SplitPercent sets the relative size of the split as percentage of the
+// available space.
 // When using SplitVertical, the provided size is applied to the new left
 // container, the new right container gets the reminder of the size.
 // When using SplitHorizontal, the provided size is applied to the new top
@@ -304,6 +310,25 @@ func SplitPercent(p int) SplitOption {
 	})
 }
 
+// SplitPercentFromEnd sets the relative size of the split as percentage of the
+// available space.
+// When using SplitVertical, the provided size is applied to the new right
+// container, the new leftcontainer gets the reminder of the size.
+// When using SplitHorizontal, the provided size is applied to the new bottom
+// container, the new top container gets the reminder of the size.
+// The provided value must be a positive number in the range 0 < p < 100.
+// If not provided, defaults to using SplitPercent with DefaultSplitPercent.
+func SplitPercentFromEnd(p int) SplitOption {
+	return splitOption(func(opts *options) error {
+		if min, max := 0, 100; p <= min || p >= max {
+			return fmt.Errorf("invalid split percentage %d, must be in range %d < p < %d", p, min, max)
+		}
+		opts.splitReversed = true
+		opts.splitPercent = p
+		return nil
+	})
+}
+
 // SplitFixed sets the size of the first container to be a fixed value
 // and makes the second container take up the remaining space.
 // When using SplitVertical, the provided size is applied to the new left
@@ -311,8 +336,9 @@ func SplitPercent(p int) SplitOption {
 // When using SplitHorizontal, the provided size is applied to the new top
 // container, the new bottom container gets the reminder of the size.
 // The provided value must be a positive number in the range 0 <= cells.
-// If SplitFixed() is not specified, it defaults to SplitPercent() and its given value.
-// Only one of SplitFixed() and SplitPercent() can be specified per container.
+// If SplitFixed* or SplitPercent* is not specified, it defaults to
+// SplitPercent() and its given value.
+// Only one SplitFixed* or SplitPercent* may be specified per container.
 func SplitFixed(cells int) SplitOption {
 	return splitOption(func(opts *options) error {
 		if cells < 0 {
@@ -323,6 +349,27 @@ func SplitFixed(cells int) SplitOption {
 	})
 }
 
+// SplitFixedFromEnd sets the size of the second container to be a fixed value
+// and makes the first container take up the remaining space.
+// When using SplitVertical, the provided size is applied to the new right
+// container, the new left container gets the reminder of the size.
+// When using SplitHorizontal, the provided size is applied to the new bottom
+// container, the new top container gets the reminder of the size.
+// The provided value must be a positive number in the range 0 <= cells.
+// If SplitFixed* or SplitPercent* is not specified, it defaults to
+// SplitPercent() and its given value.
+// Only one SplitFixed* or SplitPercent* may be specified per container.
+func SplitFixedFromEnd(cells int) SplitOption {
+	return splitOption(func(opts *options) error {
+		if cells < 0 {
+			return fmt.Errorf("invalid fixed value %d, must be in range %d <= cells", cells, 0)
+		}
+		opts.splitFixed = cells
+		opts.splitReversed = true
+		return nil
+	})
+}
+
 // SplitVertical splits the container along the vertical axis into two sub
 // containers. The use of this option removes any widget placed at this
 // container, containers with sub containers cannot contain widgets.