fix: overflows with absolutely positioned content

src/css/property-descriptors/overflow.ts

@@ -5,7 +5,8 @@ export enum OVERFLOW {
     VISIBLE = 0,
     HIDDEN = 1,
     SCROLL = 2,
-    AUTO = 3
+    CLIP = 3,
+    AUTO = 4
 }
 
 export const overflow: IPropertyListDescriptor<OVERFLOW[]> = {
@@ -20,6 +21,8 @@ export const overflow: IPropertyListDescriptor<OVERFLOW[]> = {
                     return OVERFLOW.HIDDEN;
                 case 'scroll':
                     return OVERFLOW.SCROLL;
+                case 'clip':
+                    return OVERFLOW.CLIP;
                 case 'auto':
                     return OVERFLOW.AUTO;
                 case 'visible':

src/render/canvas/canvas-renderer.ts

@@ -87,12 +87,12 @@ export class CanvasRenderer extends Renderer {
         );
     }
 
-    applyEffects(effects: IElementEffect[], target: EffectTarget): void {
+    applyEffects(effects: IElementEffect[]): void {
         while (this._activeEffects.length) {
             this.popEffect();
         }
 
-        effects.filter((effect) => contains(effect.target, target)).forEach((effect) => this.applyEffect(effect));
+        effects.forEach((effect) => this.applyEffect(effect));
     }
 
     applyEffect(effect: IElementEffect): void {
@@ -293,7 +293,7 @@ export class CanvasRenderer extends Renderer {
     }
 
     async renderNodeContent(paint: ElementPaint): Promise<void> {
-        this.applyEffects(paint.effects, EffectTarget.CONTENT);
+        this.applyEffects(paint.getEffects(EffectTarget.CONTENT));
         const container = paint.container;
         const curves = paint.curves;
         const styles = container.styles;
@@ -692,7 +692,7 @@ export class CanvasRenderer extends Renderer {
     }
 
     async renderNodeBackgroundAndBorders(paint: ElementPaint): Promise<void> {
-        this.applyEffects(paint.effects, EffectTarget.BACKGROUND_BORDERS);
+        this.applyEffects(paint.getEffects(EffectTarget.BACKGROUND_BORDERS));
         const styles = paint.container.styles;
         const hasBackground = !isTransparent(styles.backgroundColor) || styles.backgroundImage.length;
 
@@ -906,7 +906,7 @@ export class CanvasRenderer extends Renderer {
         const stack = parseStackingContexts(element);
 
         await this.renderStack(stack);
-        this.applyEffects([], EffectTarget.BACKGROUND_BORDERS);
+        this.applyEffects([]);
         return this.canvas;
     }
 }

src/render/effects.ts

@@ -20,36 +20,21 @@ export interface IElementEffect {
 export class TransformEffect implements IElementEffect {
     readonly type: EffectType = EffectType.TRANSFORM;
     readonly target: number = EffectTarget.BACKGROUND_BORDERS | EffectTarget.CONTENT;
-    readonly offsetX: number;
-    readonly offsetY: number;
-    readonly matrix: Matrix;
-
-    constructor(offsetX: number, offsetY: number, matrix: Matrix) {
-        this.offsetX = offsetX;
-        this.offsetY = offsetY;
-        this.matrix = matrix;
-    }
+
+    constructor(readonly offsetX: number, readonly offsetY: number, readonly matrix: Matrix) {}
 }
 
 export class ClipEffect implements IElementEffect {
     readonly type: EffectType = EffectType.CLIP;
-    readonly target: number;
-    readonly path: Path[];
 
-    constructor(path: Path[], target: EffectTarget) {
-        this.target = target;
-        this.path = path;
-    }
+    constructor(readonly path: Path[], readonly target: EffectTarget) {}
 }
 
 export class OpacityEffect implements IElementEffect {
     readonly type: EffectType = EffectType.OPACITY;
     readonly target: number = EffectTarget.BACKGROUND_BORDERS | EffectTarget.CONTENT;
-    readonly opacity: number;
 
-    constructor(opacity: number) {
-        this.opacity = opacity;
-    }
+    constructor(readonly opacity: number) {}
 }
 
 export const isTransformEffect = (effect: IElementEffect): effect is TransformEffect =>

src/render/stacking-context.ts

@@ -1,13 +1,14 @@
 import {ElementContainer, FLAGS} from '../dom/element-container';
 import {contains} from '../core/bitwise';
 import {BoundCurves, calculateBorderBoxPath, calculatePaddingBoxPath} from './bound-curves';
-import {ClipEffect, EffectTarget, IElementEffect, OpacityEffect, TransformEffect} from './effects';
+import {ClipEffect, EffectTarget, IElementEffect, isClipEffect, OpacityEffect, TransformEffect} from './effects';
 import {OVERFLOW} from '../css/property-descriptors/overflow';
 import {equalPath} from './path';
 import {DISPLAY} from '../css/property-descriptors/display';
 import {OLElementContainer} from '../dom/elements/ol-element-container';
 import {LIElementContainer} from '../dom/elements/li-element-container';
 import {createCounterText} from '../css/types/functions/counter';
+import {POSITION} from '../css/property-descriptors/position';
 
 export class StackingContext {
     element: ElementPaint;
@@ -32,27 +33,24 @@ export class StackingContext {
 }
 
 export class ElementPaint {
-    container: ElementContainer;
-    effects: IElementEffect[];
-    curves: BoundCurves;
+    readonly effects: IElementEffect[] = [];
+    readonly curves: BoundCurves;
     listValue?: string;
 
-    constructor(element: ElementContainer, parentStack: IElementEffect[]) {
-        this.container = element;
-        this.effects = parentStack.slice(0);
-        this.curves = new BoundCurves(element);
-        if (element.styles.opacity < 1) {
-            this.effects.push(new OpacityEffect(element.styles.opacity));
+    constructor(readonly container: ElementContainer, readonly parent: ElementPaint | null) {
+        this.curves = new BoundCurves(this.container);
+        if (this.container.styles.opacity < 1) {
+            this.effects.push(new OpacityEffect(this.container.styles.opacity));
         }
 
-        if (element.styles.transform !== null) {
-            const offsetX = element.bounds.left + element.styles.transformOrigin[0].number;
-            const offsetY = element.bounds.top + element.styles.transformOrigin[1].number;
-            const matrix = element.styles.transform;
+        if (this.container.styles.transform !== null) {
+            const offsetX = this.container.bounds.left + this.container.styles.transformOrigin[0].number;
+            const offsetY = this.container.bounds.top + this.container.styles.transformOrigin[1].number;
+            const matrix = this.container.styles.transform;
             this.effects.push(new TransformEffect(offsetX, offsetY, matrix));
         }
 
-        if (element.styles.overflowX !== OVERFLOW.VISIBLE) {
+        if (this.container.styles.overflowX !== OVERFLOW.VISIBLE) {
             const borderBox = calculateBorderBoxPath(this.curves);
             const paddingBox = calculatePaddingBoxPath(this.curves);
 
@@ -65,16 +63,32 @@ export class ElementPaint {
         }
     }
 
-    getParentEffects(): IElementEffect[] {
+    getEffects(target: EffectTarget): IElementEffect[] {
+        let inFlow = [POSITION.ABSOLUTE, POSITION.FIXED].indexOf(this.container.styles.position) === -1;
+        let parent = this.parent;
         const effects = this.effects.slice(0);
-        if (this.container.styles.overflowX !== OVERFLOW.VISIBLE) {
-            const borderBox = calculateBorderBoxPath(this.curves);
-            const paddingBox = calculatePaddingBoxPath(this.curves);
-            if (!equalPath(borderBox, paddingBox)) {
-                effects.push(new ClipEffect(paddingBox, EffectTarget.BACKGROUND_BORDERS | EffectTarget.CONTENT));
+        while (parent) {
+            const croplessEffects = parent.effects.filter((effect) => !isClipEffect(effect));
+            if (inFlow || parent.container.styles.position !== POSITION.STATIC || !parent.parent) {
+                effects.unshift(...croplessEffects);
+                inFlow = [POSITION.ABSOLUTE, POSITION.FIXED].indexOf(parent.container.styles.position) === -1;
+                if (parent.container.styles.overflowX !== OVERFLOW.VISIBLE) {
+                    const borderBox = calculateBorderBoxPath(parent.curves);
+                    const paddingBox = calculatePaddingBoxPath(parent.curves);
+                    if (!equalPath(borderBox, paddingBox)) {
+                        effects.unshift(
+                            new ClipEffect(paddingBox, EffectTarget.BACKGROUND_BORDERS | EffectTarget.CONTENT)
+                        );
+                    }
+                }
+            } else {
+                effects.unshift(...croplessEffects);
             }
+
+            parent = parent.parent;
         }
-        return effects;
+
+        return effects.filter((effect) => contains(effect.target, target));
     }
 }
 
@@ -87,7 +101,7 @@ const parseStackTree = (
     parent.container.elements.forEach((child) => {
         const treatAsRealStackingContext = contains(child.flags, FLAGS.CREATES_REAL_STACKING_CONTEXT);
         const createsStackingContext = contains(child.flags, FLAGS.CREATES_STACKING_CONTEXT);
-        const paintContainer = new ElementPaint(child, parent.getParentEffects());
+        const paintContainer = new ElementPaint(child, parent);
         if (contains(child.styles.display, DISPLAY.LIST_ITEM)) {
             listItems.push(paintContainer);
         }
@@ -182,7 +196,7 @@ const processListItems = (owner: ElementContainer, elements: ElementPaint[]) =>
 };
 
 export const parseStackingContexts = (container: ElementContainer): StackingContext => {
-    const paintContainer = new ElementPaint(container, []);
+    const paintContainer = new ElementPaint(container, null);
     const root = new StackingContext(paintContainer);
     const listItems: ElementPaint[] = [];
     parseStackTree(paintContainer, root, root, listItems);

tests/reftests/overflow/overflow.html

@@ -51,6 +51,9 @@
         .scroll {
             overflow: scroll;
         }
+        .clip {
+            overflow: clip;
+        }
         .auto {
             overflow: auto;
         }
@@ -70,6 +73,10 @@
     scroll
     <p class="scroll">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec luctus pretium facilisis. Praesent rutrum eget nisl in tristique. Sed tincidunt nisl et tellus vulputate, nec rhoncus orci pretium.</p>
 </div>
+<div class="cell">
+    clip
+    <p class="clip">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec luctus pretium facilisis. Praesent rutrum eget nisl in tristique. Sed tincidunt nisl et tellus vulputate, nec rhoncus orci pretium.</p>
+</div>
 <div class="cell">
     auto
     <p class="auto">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec luctus pretium facilisis. Praesent rutrum eget nisl in tristique. Sed tincidunt nisl et tellus vulputate, nec rhoncus orci pretium.</p>
@@ -129,5 +136,17 @@ <h1>Overflow: hidden</h1>
     </script>
 </div>
 <div class="hidden">Hidden<div style="opacity: 0.5">With opacity</div></div>
+<div class="hidden" style="height: 0px; width: 50px;">
+    <div style="position: absolute; width: 50px; height: 50px; left:400px;">absolute on static parent</div>
+</div>
+<div class="hidden" style="height: 0px; width: 50px;">
+    <div style="position: relative; width: 10px; height: 10px; left:400px;">relative on static parent</div>
+</div>
+<div class="hidden" style="height: 0px; width: 50px;">
+    <div style="position: fixed; width: 50px; height: 50px; left:400px; top:0;">fixed on static parent</div>
+</div>
+<div class="hidden" style="height: 0px; width: 50px;position: relative;">
+    <div style="position: absolute; width: 10px; height: 10px; left:400px;">absolute on relative parent</div>
+</div>
 </body>
 </html>