Improve appearance of lists when converting from HTML

Closes #434

Tusker/HTMLConverter.swift

@@ -37,7 +37,12 @@ struct HTMLConverter {
             mutAttrString.trimTrailingCharactersInSet(.whitespacesAndNewlines)
             mutAttrString.collapseWhitespace()
             
-            mutAttrString.addAttribute(.paragraphStyle, value: paragraphStyle, range: mutAttrString.fullRange)
+            // Wait until the end and then fill in the unset paragraph styles, to avoid clobbering the list style.
+            mutAttrString.enumerateAttribute(.paragraphStyle, in: mutAttrString.fullRange, options: .longestEffectiveRangeNotRequired) { value, range, stop in
+                if value == nil {
+                    mutAttrString.addAttribute(.paragraphStyle, value: paragraphStyle, range: range)
+                }
+            }
             
             return mutAttrString
         } else {
@@ -56,6 +61,10 @@ struct HTMLConverter {
             }
             return NSAttributedString(string: text, attributes: [.font: font, .foregroundColor: color])
         case let node as Element:
+            if node.tagName() == "ol" || node.tagName() == "ul" {
+                return attributedTextForList(node, usePreformattedText: usePreformattedText)
+            }
+            
             let attributed = NSMutableAttributedString(string: "", attributes: [.font: font, .foregroundColor: color])
             for child in node.getChildNodes() {
                 var appendEllipsis = false
@@ -115,25 +124,6 @@ struct HTMLConverter {
             case "pre":
                 attributed.append(NSAttributedString(string: "\n\n"))
                 attributed.addAttribute(.font, value: monospaceFont, range: attributed.fullRange)
-            case "ol", "ul":
-                attributed.append(NSAttributedString(string: "\n\n"))
-                attributed.trimLeadingCharactersInSet(.whitespacesAndNewlines)
-            case "li":
-                let parentEl = node.parent()!
-                let parentTag = parentEl.tagName()
-                let bullet: NSAttributedString
-                if parentTag == "ol" {
-                    let index = (try? node.elementSiblingIndex()) ?? 0
-                    // we use the monospace digit font so that the periods of all the list items line up
-                    // TODO: this probably breaks with dynamic type
-                    bullet = NSAttributedString(string: "\(index + 1).\t", attributes: [.font: monospaceFont, .foregroundColor: color])
-                } else if parentTag == "ul" {
-                    bullet = NSAttributedString(string: "\u{2022}\t", attributes: [.font: font, .foregroundColor: color])
-                } else {
-                    bullet = NSAttributedString()
-                }
-                attributed.insert(bullet, at: 0)
-                attributed.append(NSAttributedString(string: "\n", attributes: [.font: font]))
             default:
                 break
             }
@@ -144,5 +134,37 @@ struct HTMLConverter {
         }
     }
     
+    private func attributedTextForList(_ element: Element, usePreformattedText: Bool) -> NSAttributedString {
+        let list = element.tagName() == "ol" ? OrderedNumberTextList(markerFormat: .decimal, options: 0) : NSTextList(markerFormat: .disc, options: 0)
+        let paragraphStyle = paragraphStyle.mutableCopy() as! NSMutableParagraphStyle
+        // I don't like that I can't just use paragraphStyle.textLists, because it makes the list markers
+        // not use the monospace digit font (it seems to just use whatever font attribute is set for the whole thing),
+        // and it doesn't right align the list markers.
+        // Unfortunately, doing it manually means the list markers are incldued in the selectable text.
+        paragraphStyle.headIndent = 32
+        paragraphStyle.firstLineHeadIndent = 0
+        // Use 2 tab stops, one for the list marker, the second for the content.
+        paragraphStyle.tabStops = [NSTextTab(textAlignment: .right, location: 28), NSTextTab(textAlignment: .natural, location: 32)]
+        let str = NSMutableAttributedString(string: "")
+        var item = 1
+        for child in element.children() where child.tagName() == "li" {
+            if let childStr = attributedTextForHTMLNode(child, usePreformattedText: usePreformattedText) {
+                str.append(NSAttributedString(string: "\t\(list.marker(forItemNumber: item))\t", attributes: [
+                    .font: UIFontMetrics(forTextStyle: .body).scaledFont(for: .monospacedDigitSystemFont(ofSize: 17, weight: .regular)),
+                ]))
+                str.append(childStr)
+                str.append(NSAttributedString(string: "\n"))
+                item += 1
+            }
+        }
+        str.addAttribute(.paragraphStyle, value: paragraphStyle, range: str.fullRange)
+        return str
+    }
     
 }
+
+private class OrderedNumberTextList: NSTextList {
+    override func marker(forItemNumber itemNumber: Int) -> String {
+        "\(super.marker(forItemNumber: itemNumber))."
+    }
+}