adding tracklist widget and columns layout

ui/layout/columnslayout.go

@@ -0,0 +1,66 @@
+package layout
+
+import "fyne.io/fyne/v2"
+
+type ColumnsLayout struct {
+	ColumnWidths []float32
+}
+
+func NewColumnsLayout(widths []float32) *ColumnsLayout {
+	return &ColumnsLayout{ColumnWidths: widths}
+}
+
+func (c *ColumnsLayout) MinSize(objects []fyne.CanvasObject) fyne.Size {
+	var width float32
+	var height float32
+	for i := 0; i < len(objects); i++ {
+		if !objects[i].Visible() {
+			continue
+		}
+		height = fyne.Max(height, objects[i].MinSize().Height)
+		w := objects[i].MinSize().Width
+		if i < len(c.ColumnWidths) && c.ColumnWidths[i] > w {
+			w = c.ColumnWidths[i]
+		}
+		width += w
+	}
+	return fyne.NewSize(width, height)
+}
+
+func (c *ColumnsLayout) Layout(objects []fyne.CanvasObject, size fyne.Size) {
+	var fixedW float32
+	var expandObjCount int
+	for i := 0; i < min(len(objects), len(c.ColumnWidths)); i++ {
+		if !objects[i].Visible() {
+			continue
+		}
+		if c.ColumnWidths[i] < 0 {
+			expandObjCount++
+		} else {
+			itemW := objects[i].MinSize().Width
+			fixedW += fyne.Max(itemW, c.ColumnWidths[i])
+		}
+	}
+	extraW := size.Width - fixedW
+	expandObjW := extraW / float32(expandObjCount)
+
+	var x float32
+	for i := 0; i < len(objects); i++ {
+		w := objects[i].MinSize().Width
+		if i < len(c.ColumnWidths) && c.ColumnWidths[i] > w {
+			w = c.ColumnWidths[i]
+		} else if c.ColumnWidths[i] < 0 && expandObjW > w {
+			w = expandObjW
+		}
+		objects[i].Resize(fyne.NewSize(w, size.Height))
+		objects[i].Move(fyne.NewPos(x, 0))
+		x += w
+	}
+}
+
+func min(x, y int) int {
+	if x < y {
+		return x
+	}
+	return y
+}