vaev-layout+paint: Fix some positioned box related issues.

src/vaev-layout/base.h

@@ -42,15 +42,10 @@ struct Input {
 
 struct Output {
     Vec2Px size;
-    InsetsPx margins = {};
 
     static Output fromSize(Vec2Px size) {
         return Output{size};
     }
-
-    static Output fromSizeAndMargin(Vec2Px size, InsetsPx margins) {
-        return Output{size, margins};
-    }
 };
 
 /// Computed layout values.

src/vaev-layout/block.cpp

@@ -39,20 +39,29 @@ Output blockLayout(Tree &t, Frag &f, Input input) {
         if (c.style->sizing->width == Size::AUTO)
             childInlineSize = inlineSize;
 
+        Input childInput = {
+            .commit = input.commit,
+            .availableSpace = {inlineSize, Px{0}},
+            .containingBlock = {inlineSize, Px{0}},
+        };
+
+        auto margin = computeMargins(t, c, childInput);
+
+        if (c.style->position != Position::ABSOLUTE) {
+            blockSize += margin.top;
+        }
+
+        childInput.position = input.position + Vec2Px{Px{0}, blockSize} + margin.topStart();
+        childInput.knownSize = {childInlineSize, NONE};
+
         auto ouput = layout(
             t,
             c,
-            {
-                .commit = input.commit,
-                .knownSize = {childInlineSize, NONE},
-                .position = input.position + Vec2Px{Px{0}, blockSize},
-                .availableSpace = {inlineSize, Px{0}},
-                .containingBlock = {inlineSize, Px{0}},
-            }
+            childInput
         );
 
         if (c.style->position != Position::ABSOLUTE) {
-            blockSize += ouput.size.y;
+            blockSize += ouput.size.y + margin.bottom + margin.top;
         }
     }
 

src/vaev-layout/frag.cpp

@@ -152,7 +152,7 @@ Output _contentLayout(Tree &t, Frag &f, Input input) {
     }
 }
 
-static InsetsPx _computeMargins(Tree &t, Frag &f, Input input) {
+InsetsPx computeMargins(Tree &t, Frag &f, Input input) {
     InsetsPx res;
     auto margin = f.style->margin;
 
@@ -229,7 +229,6 @@ static Cons<Opt<Px>, IntrinsicSize> _computeSpecifiedSize(Tree &t, Frag &f, Inpu
 }
 
 Output layout(Tree &t, Frag &f, Input input) {
-    auto margin = _computeMargins(t, f, input);
     auto borders = _computeBorders(t, f);
     auto padding = _computePaddings(t, f, input);
     auto sizing = f.style->sizing;
@@ -257,7 +256,7 @@ Output layout(Tree &t, Frag &f, Input input) {
 
     input.position = input.position + borders.topStart() + padding.topStart();
 
-    auto [size, _] = _contentLayout(t, f, input);
+    auto [size] = _contentLayout(t, f, input);
 
     size.width = input.knownSize.width.unwrapOr(size.width);
     size.height = input.knownSize.height.unwrapOr(size.height);
@@ -269,11 +268,10 @@ Output layout(Tree &t, Frag &f, Input input) {
         f.layout.borderSize = size;
         f.layout.padding = padding;
         f.layout.borders = borders;
-        f.layout.margin = margin;
         f.layout.radii = _computeRadii(t, f, size);
     }
 
-    return Output::fromSizeAndMargin(size, margin);
+    return Output::fromSize(size);
 }
 
 void wireframe(Frag &frag, Gfx::Canvas &g) {

src/vaev-layout/frag.h

@@ -49,6 +49,8 @@ Frag build(Style::Computer &c, Markup::Document const &doc);
 
 // MARK: Layout ----------------------------------------------------------------
 
+InsetsPx computeMargins(Tree &t, Frag &f, Input input);
+
 Output layout(Tree &t, Frag &f, Input input);
 
 Px measure(Tree &t, Frag &f, Axis axis, IntrinsicSize intrinsic, Px availableSpace);

src/vaev-paint/base.h

@@ -22,7 +22,7 @@ struct Node {
     virtual void print(Print::Printer &) {}
 
     virtual void repr(Io::Emit &e) const {
-        e("(node)");
+        e("(node z:{})", zIndex);
     }
 };
 

src/vaev-paint/borders.h

@@ -71,7 +71,7 @@ struct Borders : public Node {
     }
 
     void repr(Io::Emit &e) const override {
-        e("(borders {} {} {}", bound, radii, collapse);
+        e("(borders z:{} {} {} {}", zIndex, bound, radii, collapse);
     }
 
     void paint(Gfx::Canvas &ctx) override {

src/vaev-paint/box.h

@@ -18,7 +18,7 @@ struct Box : public Node {
     }
 
     void repr(Io::Emit &e) const override {
-        e("(box {} {} {})", bound, radii, backgrounds);
+        e("(box z:{} {} {} {})", zIndex, bound, radii, backgrounds);
     }
 };
 

src/vaev-paint/image.h

@@ -6,7 +6,7 @@ namespace Vaev::Paint {
 
 struct Image : public Node {
     void repr(Io::Emit &e) const override {
-        e("(image)");
+        e("(image z:{})", zIndex);
     }
 };
 

src/vaev-paint/stack.h

@@ -13,7 +13,7 @@ struct Stack : public Node {
 
     void prepare() override {
         stableSort(_children, [](auto &a, auto &b) {
-            return a->zIndex < b->zIndex;
+            return a->zIndex <=> b->zIndex;
         });
 
         for (auto &child : _children)
@@ -38,7 +38,7 @@ struct Stack : public Node {
     }
 
     void repr(Io::Emit &e) const override {
-        e("(stack");
+        e("(stack z:{}", zIndex);
         if (_children) {
             e.indentNewline();
             for (auto &child : _children) {

src/vaev-paint/text.h

@@ -29,7 +29,7 @@ struct Text : public Node {
     }
 
     void repr(Io::Emit &e) const override {
-        e("(text {})", baseline);
+        e("(text z:{} {})", zIndex, baseline);
     }
 };