add genres page, and extract bottomPanelLayout for reuse in navigation bar

ui/layouts/leftmiddlerightlayout.go

@@ -0,0 +1,40 @@
+package layouts
+
+import (
+	"fyne.io/fyne/v2"
+	"fyne.io/fyne/v2/layout"
+	"fyne.io/fyne/v2/theme"
+)
+
+type LeftMiddleRightLayout struct {
+	middleWidth float32
+	hbox        fyne.Layout
+}
+
+func NewLeftMiddleRightLayout(middleWidth float32) *LeftMiddleRightLayout {
+	return &LeftMiddleRightLayout{
+		middleWidth: middleWidth,
+		hbox:        layout.NewHBoxLayout(),
+	}
+}
+
+func (b *LeftMiddleRightLayout) MinSize(objects []fyne.CanvasObject) fyne.Size {
+	hboxSize := b.hbox.MinSize(objects)
+	return fyne.Size{
+		Height: hboxSize.Height,
+		Width:  hboxSize.Width + fyne.Max(0, b.middleWidth-objects[1].MinSize().Width),
+	}
+}
+
+func (b *LeftMiddleRightLayout) Layout(objects []fyne.CanvasObject, size fyne.Size) {
+	midW := fyne.Max(b.middleWidth, objects[1].MinSize().Width)
+	lrW := (size.Width - midW - theme.Padding()*4) / 2
+	objects[0].Resize(fyne.NewSize(lrW, size.Height))
+	objects[0].Move(fyne.NewPos(theme.Padding(), 0))
+	objects[1].Resize(fyne.NewSize(midW, size.Height))
+	objects[1].Move(fyne.NewPos(lrW+theme.Padding()*2, 0))
+	if objects[2] != nil {
+		objects[2].Resize(fyne.NewSize(lrW, size.Height))
+		objects[2].Move(fyne.NewPos(lrW+midW+theme.Padding()*3, 0))
+	}
+}