d2ui: Add WidgetGroup

this allows us to groups screens together, such that they can be
de-/activated by de-/activating the group instead of every ui element by
hand.

Before we were deactivating buttons and stopped rendering to deactivate ui
elements. This tied the renderer to these elements.

d2core/d2ui/drawable.go

@@ -14,4 +14,6 @@ type Drawable interface {
 	OffsetPosition(xo, yo int)
 	GetVisible() bool
 	SetVisible(visible bool)
+	SetRenderPriority(priority RenderPriority)
+	GetRenderPriority() (priority RenderPriority)
 }

d2core/d2ui/ui_manager.go

@@ -2,6 +2,7 @@ package d2ui
 
 import (
 	"log"
+	"sort"
 
 	"github.com/OpenDiablo2/OpenDiablo2/d2core/d2asset"
 
@@ -17,6 +18,7 @@ type UIManager struct {
 	inputManager     d2interface.InputManager
 	audio            d2interface.AudioProvider
 	widgets          []Widget
+	widgetsGroups    []*WidgetGroup
 	clickableWidgets []ClickableWidget
 	cursorButtons    CursorButton
 	CursorX          int
@@ -49,6 +51,14 @@ func (ui *UIManager) Reset() {
 	ui.pressedWidget = nil
 }
 
+// addWidgetGroup adds a widgetGroup to the UI manager and sorts by priority
+func (ui *UIManager) addWidgetGroup(group *WidgetGroup) {
+	ui.widgetsGroups = append(ui.widgetsGroups, group)
+	sort.SliceStable(ui.widgetsGroups, func(i, j int) bool {
+		return ui.widgetsGroups[i].priority < ui.widgetsGroups[j].priority
+	})
+}
+
 // addWidget adds a widget to the UI manager
 func (ui *UIManager) addWidget(widget Widget) {
 	err := ui.inputManager.BindHandler(widget)
@@ -120,6 +130,15 @@ func (ui *UIManager) Render(target d2interface.Surface) {
 			}
 		}
 	}
+
+	for _, widgetGroup := range ui.widgetsGroups {
+		if widgetGroup.GetVisible() {
+			err := widgetGroup.Render(target)
+			if err != nil {
+				log.Print(err)
+			}
+		}
+	}
 }
 
 // contains determines whether a given x,y coordinate lands within a Widget

d2core/d2ui/widget.go

@@ -1,5 +1,16 @@
 package d2ui
 
+// RenderPriority determines in which order ui elements are drawn.
+// The higher the number the later an element is drawn.
+type RenderPriority int
+
+const (
+	// RenderPriorityBackground is the first element drawn
+	RenderPriorityBackground RenderPriority = iota
+	// RenderPriorityForeground is the last element drawn
+	RenderPriorityForeground
+)
+
 // Widget defines an object that is a UI widget
 type Widget interface {
 	Drawable
@@ -24,6 +35,7 @@ type BaseWidget struct {
 	y              int
 	width          int
 	height         int
+	renderPriority RenderPriority
 	visible        bool
 }
 
@@ -36,6 +48,7 @@ func NewBaseWidget(manager *UIManager) *BaseWidget {
 		width:          0,
 		height:         0,
 		visible:        true,
+		renderPriority: RenderPriorityBackground,
 	}
 }
 
@@ -73,3 +86,13 @@ func (b *BaseWidget) GetVisible() (visible bool) {
 func (b *BaseWidget) SetVisible(visible bool) {
 	b.visible = visible
 }
+
+// GetRenderPriority returns the order in which this widget is rendered
+func (b *BaseWidget) GetRenderPriority() (prio RenderPriority) {
+	return b.renderPriority
+}
+
+// SetRenderPriority sets the order in which this widget is rendered
+func (b *BaseWidget) SetRenderPriority(prio RenderPriority) {
+	b.renderPriority = prio
+}

d2core/d2ui/widget_group.go

@@ -0,0 +1,92 @@
+package d2ui
+
+import (
+	"sort"
+
+	"github.com/OpenDiablo2/OpenDiablo2/d2common/d2interface"
+)
+
+// static check that WidgetGroup implements widget
+var _ Widget = &WidgetGroup{}
+
+// WidgetGroup allows the grouping of widgets to apply actions to all
+// widgets at once.
+type WidgetGroup struct {
+	*BaseWidget
+	entries  []Widget
+	priority RenderPriority
+}
+
+// NewWidgetGroup creates a new widget group
+func (ui *UIManager) NewWidgetGroup(priority RenderPriority) *WidgetGroup {
+	base := NewBaseWidget(ui)
+	base.SetRenderPriority(priority)
+
+	group := &WidgetGroup{
+		BaseWidget: base,
+	}
+
+	ui.addWidgetGroup(group)
+
+	return group
+}
+
+// AddWidget adds a widget to the group
+func (wg *WidgetGroup) AddWidget(w Widget) {
+	wg.adjustSize(w)
+	wg.entries = append(wg.entries, w)
+	sort.SliceStable(wg.entries, func(i, j int) bool {
+		return wg.entries[i].GetRenderPriority() < wg.entries[j].GetRenderPriority()
+	})
+}
+
+// adjustSize recalculates the bounding box if a new widget is added
+func (wg *WidgetGroup) adjustSize(w Widget) {
+	x, y := w.GetPosition()
+	width, height := w.GetSize()
+
+	if x+width > wg.width {
+		wg.width = x + width
+	}
+
+	if wg.x > x {
+		wg.width += wg.x - x
+		wg.x = x
+	}
+
+	if y+height > wg.height {
+		wg.height = x + height
+	}
+
+	if wg.y > y {
+		wg.height += wg.y - y
+		wg.y = y
+	}
+}
+
+// Advance is a no-op here
+func (wg *WidgetGroup) Advance(elapsed float64) error {
+	// No-op
+	return nil
+}
+
+// Render draw the widgets to the screen
+func (wg *WidgetGroup) Render(target d2interface.Surface) error {
+	for _, entry := range wg.entries {
+		if entry.GetVisible() {
+			err := entry.Render(target)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+// SetVisible sets the visibility of all widgets in the group
+func (wg *WidgetGroup) SetVisible(visible bool) {
+	for _, entry := range wg.entries {
+		entry.SetVisible(visible)
+	}
+}