begin work on panel separators

src/dlib

@@ -1 +1 @@
-Subproject commit 421f903cffaa22c7d7f9115ae49daa45576adfa8
+Subproject commit b2b6fef26c0b0e15575ee431eea60235d4565c34

src/editor/editor.d

@@ -180,7 +180,7 @@ Cycle(Editor* ed, Inputs* inputs)
 {
 	Reset(&ed.temp_arena);
 
-	BeginBuild();
+	BeginBuild(inputs);
 
 	Panel("##panel_1", 1.0, 0.3, A2D.X, Vec4(0.2, 0.5, 0.8, 1.0));
 	{

src/editor/ui.d

@@ -1,4 +1,5 @@
 import dlib.aliases;
+import dlib.platform;
 import dlib.math;
 import dlib.util;
 import dlib.alloc;
@@ -14,6 +15,9 @@ UIContext g_ui_ctx;
 const UIItem g_ui_nil_item;
 UIItem* g_UI_NIL;
 
+const UIItemNode g_ui_nil_item_node;
+UIItemNode* g_UI_NIL_NODE;
+
 enum Axis2D
 {
 	X,
@@ -51,7 +55,11 @@ struct UIContext
 	UIBuffer                    buffer;
 
 	UIItem*                     root;
-	UIItem*                     top_parent;
+	UIItemNode*                 top_parent;
+	UIItemNode*                 prev_sibling;
+	u32                         panel_level;
+
+	UIItemStackList             stack_free_list;
 
 	FontAtlas                   atlas;
 	Vec4[4]                     color;
@@ -60,6 +68,18 @@ struct UIContext
 	Axis2D                      layout_axis;
 }
 
+struct UIItemStackList
+{
+	UIItemNode* first;
+	UIItemNode* last;
+}
+
+struct UIItemNode
+{
+	UIItem*      item;
+	UIItemNode*  next;
+}
+
 struct UIItem
 {
 	UIFlags         flags;
@@ -71,7 +91,7 @@ struct UIItem
 	UIItem*         last; // last child
 	UIItem*         parent;
 
-	UIItem*         stack_next;
+	u32             level;
 
 	// Build Parameters
 	Axis2D          layout_axis;
@@ -129,6 +149,7 @@ void
 InitUICtx(Renderer* rd, FontAtlas atlas)
 {
 	g_UI_NIL = cast(UIItem*)&g_ui_nil_item;
+	g_UI_NIL_NODE = cast(UIItemNode*)&g_ui_nil_item_node;
 
 	Arena arena = CreateArena(MB(4));
 
@@ -141,7 +162,8 @@ InitUICtx(Renderer* rd, FontAtlas atlas)
 		arena: CreateArena(MB(4)),
 		atlas: atlas,
 		root: g_UI_NIL,
-		top_parent: g_UI_NIL,
+		top_parent: g_UI_NIL_NODE,
+		prev_sibling: g_UI_NIL_NODE,
 		buffer: {
 			mapped_vtx: m_vtx,
 			mapped_idx: m_idx,
@@ -153,21 +175,138 @@ InitUICtx(Renderer* rd, FontAtlas atlas)
 	g_ui_ctx = ctx;
 }
 
+UIItemNode*
+PopItemNode()
+{
+	UIContext* ctx = GetCtx();
+
+	UIItemNode* node;
+	if (!CheckNil(g_UI_NIL_NODE, ctx.stack_free_list.first))
+	{
+		node = SLLPop(&ctx.stack_free_list, g_UI_NIL_NODE);
+	}
+	else
+	{
+		node = Alloc!(UIItemNode)(&ctx.arena);
+	}
+
+	node.item = g_UI_NIL;
+	node.next = g_UI_NIL_NODE;
+
+	return node;
+}
+
+void
+PushItemNode(UIItemNode* node)
+{
+	UIContext* ctx = GetCtx();
+	SLLPushFront(&ctx.stack_free_list, node, g_UI_NIL_NODE);
+}
+
+void
+PushSiblingPanel(UIItem* panel)
+{
+	UIContext* ctx = GetCtx();
+	UIItemNode* node = PopItemNode();
+
+	node.item = panel;
+	node.next = ctx.prev_sibling;
+	ctx.prev_sibling = node;
+}
+
+UIItem*
+PopSiblingPanel()
+{
+	UIContext* ctx = GetCtx();
+	UIItem* panel = g_UI_NIL;
+	UIItemNode* node = ctx.prev_sibling;
+
+	if (node != g_UI_NIL_NODE)
+	{
+		panel = node.item;
+		ctx.prev_sibling = node.next;
+		PushItemNode(node);
+	}
+
+	return panel;
+}
+
+void
+PopSiblingPanels()
+{
+	UIItem* sibling = PeekSiblingPanel();
+	while(!Nil(sibling))
+	{
+		sibling = PopSiblingPanel();
+	}
+}
+
+UIItem*
+PeekSiblingPanel()
+{
+	return g_ui_ctx.prev_sibling == g_UI_NIL_NODE ? g_UI_NIL : g_ui_ctx.prev_sibling.item;
+}
+
+UIItem*
+PrevSiblingPanel(UIItem* panel)
+{
+	UIContext* ctx = GetCtx();
+	UIItem* result = g_UI_NIL;
+	UIItemNode* prev = ctx.prev_sibling;
+	for(;;)
+	{
+		if (panel == prev.item)
+		{
+			prev = prev.next;
+		}
+
+		if (prev == g_UI_NIL_NODE)
+		{
+			break;
+		}
+
+		if (prev.item.level < panel.level)
+		{
+			break;
+		}
+
+		if (prev.item.level == panel.level)
+		{
+			result = prev.item;
+			break;
+		}
+
+		prev = prev.next;
+	}
+
+	return result;
+}
+
 UIItem*
 PopParent()
 {
 	UIContext* ctx = GetCtx();
-	UIItem* parent = ctx.top_parent;
+	UIItemNode* node = ctx.top_parent;
-	ctx.top_parent = ctx.top_parent.stack_next;
+	UIItem* item = node.item;
-	return parent;
+
+	assert(!Nil(item));
+	ctx.top_parent = node.next;
+	PushItemNode(node);
+	ctx.panel_level -= 1;
+
+	return item;
 }
 
 void
 PushParent(UIItem* parent)
 {
 	UIContext* ctx = GetCtx();
-	parent.stack_next = ctx.top_parent;
+	UIItemNode* node = PopItemNode();
-	ctx.top_parent = parent;
+
+	node.item = parent;
+	node.next = ctx.top_parent;
+	ctx.top_parent = node;
+	ctx.panel_level += 1;
 }
 
 void
@@ -200,6 +339,7 @@ BeginBuild(Inputs* inputs)
 
 	ctx.inputs = inputs;
 	ctx.buffer.count = 0;
+	ctx.panel_level = 0;
 
 	ctx.root = Root();
 	PushParent(ctx.root);
@@ -211,8 +351,10 @@ EndBuild()
 	UIContext* ctx = GetCtx();
 
 	PopParent();
+	PopSiblingPanels();
 
-	assert(Nil(ctx.top_parent));
+	assert(ctx.prev_sibling == g_UI_NIL_NODE);
+	assert(ctx.top_parent == g_UI_NIL_NODE);
 
 	CalcFixedSizes(ctx.root);
 	CalcPercentageSizes(ctx.root);
@@ -312,8 +454,9 @@ BuildItem(u8[] id, UISize size_x, UISize size_y, UIFlags properties)
 	item.size_info[A2D.Y] = size_y;
 	item.color = ctx.color;
 	item.layout_axis = ctx.layout_axis;
+	item.level = ctx.panel_level;
 
-	item.parent = ctx.top_parent;
+	item.parent = ctx.top_parent == g_UI_NIL_NODE ? g_UI_NIL : ctx.top_parent.item;
 	if (!Nil(item.parent))
 	{
 		DLLPush(item.parent, item, g_UI_NIL);

src/editor/widgets.d

@@ -19,6 +19,11 @@ Panel(string id, f32 x_pct, f32 y_pct, Axis2D layout_axis, Vec4 color)
 	SetLayoutAxis(layout_axis);
 	UIItem* item = BuildItem(id, UISize(ST.Percentage, x_pct), UISize(ST.Percentage, y_pct), UIF.DrawBackground);
 
+	UIItem* prev_panel = PrevSiblingPanel(item);
+
+	Logf("%s %s", id, !Nil(prev_panel));
+
+	PushSiblingPanel(item);
 	PushParent(item);
 
 	return item;