Merge pull request #13 from alfattack/absolute-positioning

Support absolute positioning
mstancombe · Jul 24, 2024 · d936de6 · d936de6
2 parents e2fd2d2 + 71e21af
commit d936de6
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Showing 4 changed files with 60 additions and 9 deletions.
diff --git a/Source/Demos/HtmlRenderer.Demo.Common/TestSamples/37.Absolute position.htm b/Source/Demos/HtmlRenderer.Demo.Common/TestSamples/37.Absolute position.htm
@@ -0,0 +1,17 @@
+<html>
+<body>
+    <div style="position: absolute; top: 700px; left: 90px; width: 75px; height: 75px; background-color: black;"></div>
+
+    <div style="position: relative;">
+        <div style="width: 200px; height: 200px; background-color: green;"></div>
+        <div style="width: 50px; height: 50px; background-color: red; position: absolute; top: 30px; left: 400px;"></div>
+    </div>
+
+    <div style="width: 400px; height: 200px; margin-left: 80px; background-color: purple"></div>
+
+    <div style="width: 600px; height: 300px; background-color: white; position: relative;">
+        <div style="width: 50px; height: 50px; background-color: brown; top: 50px; left: 25px; position: absolute; "></div>
+    </div>
+
+</body>
+</html>
diff --git a/Source/Demos/HtmlRenderer.Demo.Console/Program.cs b/Source/Demos/HtmlRenderer.Demo.Console/Program.cs
@@ -24,11 +24,11 @@
 foreach (var htmlSample in samples)
 {
     ////Just doing one test here.  Comment this for all of them.
-    if (!htmlSample.FullName.Contains("16", StringComparison.OrdinalIgnoreCase)) continue;
+    if (!htmlSample.FullName.Contains("37", StringComparison.OrdinalIgnoreCase)) continue;
 
-    await skia.GenerateSampleAsync(htmlSample);
-    await svgSkia.GenerateSampleAsync(htmlSample);
-    //await pdfSharp.GenerateSampleAsync(htmlSample);
+    //await skia.GenerateSampleAsync(htmlSample);
+    //await svgSkia.GenerateSampleAsync(htmlSample);
+    await pdfSharp.GenerateSampleAsync(htmlSample);
 }
 
 

diff --git a/Source/HtmlRenderer/Core/Dom/CssBox.cs b/Source/HtmlRenderer/Core/Dom/CssBox.cs
@@ -201,6 +201,17 @@ public virtual bool IsFixed
             }
         }
 
+        /// <summary>
+        ///  Gets a value indicating whether this instance has Position = absolute.
+        /// </summary>
+        /// <value>
+        ///   <c>true</c> if this instance is fixed; otherwise, <c>false</c>.
+        /// </value>
+        public virtual bool IsAbsolute
+        {
+            get => Position == CssConstants.Absolute;
+        }
+
         /// <summary>
         /// Get the href link of the box (by default get "href" attribute)
         /// </summary>
@@ -650,6 +661,26 @@ protected virtual async Task PerformLayoutImpAsync(RGraphics g)
                         left = 0;
                         top = 0;
                     }
+                    else if (Position == CssConstants.Absolute)
+                    {
+                        // find the first positioned parent.
+                        CssBox currentParent = ParentBox;
+                        CssBox positionedAncestor = null;
+                        while(currentParent != null && string.IsNullOrEmpty(currentParent.Position))
+                        {
+                            currentParent = currentParent.ParentBox;
+                        }
+                        positionedAncestor = currentParent;
+
+                        if (positionedAncestor != null)
+                        {
+                            var location = GetActualLocation(this.Left, this.Top);
+                            left = positionedAncestor.Location.X + location.X;
+                            top = positionedAncestor.Location.Y + location.Y;
+
+                            Location = new RPoint(left, top);
+                        }
+                    }
                     else
                     {
                         left = ContainingBlock.Location.X + ContainingBlock.ActualPaddingLeft + ActualMarginLeft + ContainingBlock.ActualBorderLeftWidth;
@@ -709,11 +740,11 @@ protected virtual async Task PerformLayoutImpAsync(RGraphics g)
                     ActualBottom = prevSibling.ActualBottom;
                 }
             }
-            ActualBottom = Math.Max(ActualBottom, Location.Y + ActualHeight);
 
+            ActualBottom = Math.Max(ActualBottom, Location.Y + ActualHeight);
             await CreateListItemBoxAsync(g);
 
-            if (!IsFixed)
+            if (!IsFixed && !IsAbsolute)
             {
                 var actualWidth = Math.Max(GetMinimumWidth() + GetWidthMarginDeep(this), Size.Width < 90999 ? ActualRight - HtmlContainer.Root.Location.X : 0);
                 HtmlContainer.ActualSize = CommonUtils.Max(HtmlContainer.ActualSize, new RSize(actualWidth, ActualBottom - HtmlContainer.Root.Location.Y));
@@ -1192,12 +1223,15 @@ private double CalculateActualRight()
         private double MarginBottomCollapse()
         {
             double margin = 0;
+
+            // Get the last child box that doesn't have absolute or fixed positioning.
+            var lastChildBox = _boxes.Where(b => b.Position != CssConstants.Fixed && b.Position != CssConstants.Absolute).LastOrDefault();
             if (ParentBox != null && ParentBox.Boxes.IndexOf(this) == ParentBox.Boxes.Count - 1 && _parentBox.ActualMarginBottom < 0.1)
             {
-                var lastChildBottomMargin = _boxes[_boxes.Count - 1].ActualMarginBottom;
+                var lastChildBottomMargin = lastChildBox?.ActualMarginBottom ?? 0;
                 margin = Height == "auto" ? Math.Max(ActualMarginBottom, lastChildBottomMargin) : lastChildBottomMargin;
             }
-            return Math.Max(ActualBottom, _boxes[_boxes.Count - 1].ActualBottom + margin + ActualPaddingBottom + ActualBorderBottomWidth);
+            return Math.Max(ActualBottom, (lastChildBox?.ActualBottom ?? 0) + margin + ActualPaddingBottom + ActualBorderBottomWidth);
         }
 
         /// <summary>

diff --git a/Source/HtmlRenderer/Core/Utils/DomUtils.cs b/Source/HtmlRenderer/Core/Utils/DomUtils.cs
@@ -106,7 +106,7 @@ public static CssBox GetPreviousSibling(CssBox b)
                         sib = b.ParentBox.Boxes[index - ++diff];
                     }
 
-                    return (sib.Display == CssConstants.None || sib.Position == CssConstants.Fixed) ? null : sib;
+                    return (sib.Display == CssConstants.None || sib.Position == CssConstants.Absolute || sib.Position == CssConstants.Fixed) ? null : sib;
                 }
             }
             return null;