The LineChart widget now supports zooming the content

CHANGELOG.md

@@ -18,6 +18,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   "roll" through the linechart.
 - The LineChart widget now has a method that returns the observed capacity of
   the LineChart the last time Draw was called.
+- The LineChart widget now supports zoom of the content triggered by mouse
+  events.
 - The Text widget now has a Write option that atomically replaces the entire
   text content.
 

README.md

@@ -119,7 +119,8 @@ go run github.com/mum4k/termdash/widgets/barchart/barchartdemo/barchartdemo.go
 
 ### The LineChart
 
-Displays series of values on a line chart. Run the
+Displays series of values on a line chart, supports zoom triggered by mouse
+events. Run the
 [linechartdemo](widgets/linechart/linechartdemo/linechartdemo.go).
 
 ```go

area/area.go

@@ -96,42 +96,11 @@ func ExcludeBorder(area image.Rectangle) image.Rectangle {
 	)
 }
 
-// findGCF finds the greatest common factor of two integers.
-func findGCF(a, b int) int {
-	if a == 0 || b == 0 {
-		return 0
-	}
-
-	// https://en.wikipedia.org/wiki/Euclidean_algorithm
-	for {
-		rem := a % b
-		a = b
-		b = rem
-
-		if b == 0 {
-			break
-		}
-	}
-	return a
-}
-
-// simplifyRatio simplifies the given ratio.
-func simplifyRatio(ratio image.Point) image.Point {
-	gcf := findGCF(ratio.X, ratio.Y)
-	if gcf == 0 {
-		return image.ZP
-	}
-	return image.Point{
-		X: ratio.X / gcf,
-		Y: ratio.Y / gcf,
-	}
-}
-
 // WithRatio returns the largest area that has the requested ratio but is
 // either equal or smaller than the provided area. Returns zero area if the
 // area or the ratio are zero, or if there is no such area.
 func WithRatio(area image.Rectangle, ratio image.Point) image.Rectangle {
-	ratio = simplifyRatio(ratio)
+	ratio = numbers.SimplifyRatio(ratio)
 	if area == image.ZR || ratio == image.ZP {
 		return image.ZR
 	}

area/area_test.go

@@ -15,7 +15,6 @@
 package area
 
 import (
-	"fmt"
 	"image"
 	"testing"
 
@@ -321,30 +320,6 @@ func TestExcludeBorder(t *testing.T) {
 	}
 }
 
-func TestFindGCF(t *testing.T) {
-	tests := []struct {
-		a    int
-		b    int
-		want int
-	}{
-		{0, 0, 0},
-		{0, 1, 0},
-		{1, 0, 0},
-		{1, 1, 1},
-		{2, 2, 2},
-		{50, 35, 5},
-		{16, 88, 8},
-	}
-
-	for _, tc := range tests {
-		t.Run(fmt.Sprintf("findGCF(%d,%d)", tc.a, tc.b), func(t *testing.T) {
-			if got := findGCF(tc.a, tc.b); got != tc.want {
-				t.Errorf("findGCF(%d,%d) => got %v, want %v", tc.a, tc.b, got, tc.want)
-			}
-		})
-	}
-}
-
 func TestWithRatio(t *testing.T) {
 	tests := []struct {
 		desc  string

canvas/braille/braille.go

@@ -110,6 +110,11 @@ func (c *Canvas) Size() image.Point {
 	return image.Point{s.X * ColMult, s.Y * RowMult}
 }
 
+// CellArea returns the area of the underlying cell canvas in cells.
+func (c *Canvas) CellArea() image.Rectangle {
+	return c.regular.Area()
+}
+
 // Area returns the area of the braille canvas in pixels.
 // This will be zero-based area that is two times wider and four times taller
 // than the area used to create the braille canvas.
@@ -186,17 +191,57 @@ func (c *Canvas) TogglePixel(p image.Point, opts ...cell.Option) error {
 	if err != nil {
 		return err
 	}
-	cell, err := c.regular.Cell(cp)
+	curCell, err := c.regular.Cell(cp)
 	if err != nil {
 		return err
 	}
 
-	if isBraille(cell.Rune) && pixelSet(cell.Rune, p) {
+	if isBraille(curCell.Rune) && pixelSet(curCell.Rune, p) {
 		return c.ClearPixel(p, opts...)
 	}
 	return c.SetPixel(p, opts...)
 }
 
+// SetCellOpts sets options on the specified cell of the braille canvas without
+// modifying the content of the cell.
+// Sets the default cell options if no options are provided.
+// This method is idempotent.
+func (c *Canvas) SetCellOpts(cellPoint image.Point, opts ...cell.Option) error {
+	curCell, err := c.regular.Cell(cellPoint)
+	if err != nil {
+		return err
+	}
+
+	if len(opts) == 0 {
+		// Set the default options.
+		opts = []cell.Option{
+			cell.FgColor(cell.ColorDefault),
+			cell.BgColor(cell.ColorDefault),
+		}
+	}
+	if _, err := c.regular.SetCell(cellPoint, curCell.Rune, opts...); err != nil {
+		return err
+	}
+	return nil
+}
+
+// SetAreaCellOpts is like SetCellOpts, but sets the specified options on all
+// the cells within the provided area.
+func (c *Canvas) SetAreaCellOpts(cellArea image.Rectangle, opts ...cell.Option) error {
+	haveArea := c.regular.Area()
+	if !cellArea.In(haveArea) {
+		return fmt.Errorf("unable to set cell options in area %v, it must fit inside the available cell area is %v", cellArea, haveArea)
+	}
+	for col := cellArea.Min.X; col < cellArea.Max.X; col++ {
+		for row := cellArea.Min.Y; row < cellArea.Max.Y; row++ {
+			if err := c.SetCellOpts(image.Point{col, row}, opts...); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
 // Apply applies the canvas to the corresponding area of the terminal.
 // Guarantees to stay within limits of the area the canvas was created with.
 func (c *Canvas) Apply(t terminalapi.Terminal) error {