Fix Theme creation

@@ -3,6 +3,7 @@
 ## 1.3.22
 
 - Fix Text alignment
+- Fix Theme creation
 
 ## 1.3.21
 

@@ -111,7 +111,10 @@ class TextStyle {
     this.decorationStyle,
     this.decorationThickness,
   })  : assert(inherit || color != null),
-        assert(inherit || font != null),
+        assert(inherit || fontNormal != null),
+        assert(inherit || fontBold != null),
+        assert(inherit || fontItalic != null),
+        assert(inherit || fontBoldItalic != null),
         assert(inherit || fontSize != null),
         assert(inherit || fontWeight != null),
         assert(inherit || fontStyle != null),
@@ -120,7 +123,6 @@ class TextStyle {
         assert(inherit || lineSpacing != null),
         assert(inherit || height != null),
         assert(inherit || decoration != null),
-        assert(inherit || decorationColor != null),
         assert(inherit || decorationStyle != null),
         assert(inherit || decorationThickness != null),
         fontNormal = fontNormal ??
@@ -142,6 +144,7 @@ class TextStyle {
 
   factory TextStyle.defaultStyle() {
     return TextStyle(
+      inherit: false,
       color: PdfColors.black,
       fontNormal: Font.helvetica(),
       fontBold: Font.helveticaBold(),

@@ -18,7 +18,36 @@ part of widget;
 
 @immutable
 class Theme extends Inherited {
-  const Theme({
+  factory Theme({
+    TextStyle defaultTextStyle,
+    TextStyle paragraphStyle,
+    TextStyle header0,
+    TextStyle header1,
+    TextStyle header2,
+    TextStyle header3,
+    TextStyle header4,
+    TextStyle header5,
+    TextStyle bulletStyle,
+    TextStyle tableHeader,
+    TextStyle tableCell,
+  }) {
+    final Theme base = Theme.base();
+    return base.copyWith(
+      defaultTextStyle: defaultTextStyle,
+      paragraphStyle: paragraphStyle,
+      bulletStyle: bulletStyle,
+      header0: header0,
+      header1: header1,
+      header2: header2,
+      header3: header3,
+      header4: header4,
+      header5: header5,
+      tableHeader: tableHeader,
+      tableCell: tableCell,
+    );
+  }
+
+  Theme._({
     @required this.defaultTextStyle,
     @required this.paragraphStyle,
     @required this.header0,
@@ -30,7 +59,17 @@ class Theme extends Inherited {
     @required this.bulletStyle,
     @required this.tableHeader,
     @required this.tableCell,
-  });
+  })  : assert(defaultTextStyle.inherit == false),
+        assert(paragraphStyle.inherit == false),
+        assert(header0.inherit == false),
+        assert(header1.inherit == false),
+        assert(header2.inherit == false),
+        assert(header3.inherit == false),
+        assert(header4.inherit == false),
+        assert(header5.inherit == false),
+        assert(bulletStyle.inherit == false),
+        assert(tableHeader.inherit == false),
+        assert(tableCell.inherit == false);
 
   factory Theme.withFont({Font base, Font bold, Font italic, Font boldItalic}) {
     final TextStyle defaultStyle = TextStyle.defaultStyle().copyWith(
@@ -41,19 +80,20 @@ class Theme extends Inherited {
         fontBoldItalic: boldItalic);
     final double fontSize = defaultStyle.fontSize;
 
-    return Theme(
-        defaultTextStyle: defaultStyle,
-        paragraphStyle: defaultStyle.copyWith(lineSpacing: 5),
-        bulletStyle: defaultStyle.copyWith(lineSpacing: 5),
-        header0: defaultStyle.copyWith(fontSize: fontSize * 2.0),
-        header1: defaultStyle.copyWith(fontSize: fontSize * 1.5),
-        header2: defaultStyle.copyWith(fontSize: fontSize * 1.4),
-        header3: defaultStyle.copyWith(fontSize: fontSize * 1.3),
-        header4: defaultStyle.copyWith(fontSize: fontSize * 1.2),
-        header5: defaultStyle.copyWith(fontSize: fontSize * 1.1),
-        tableHeader: defaultStyle.copyWith(
-            fontSize: fontSize * 0.8, fontWeight: FontWeight.bold),
-        tableCell: defaultStyle.copyWith(fontSize: fontSize * 0.8));
+    return Theme._(
+      defaultTextStyle: defaultStyle,
+      paragraphStyle: defaultStyle.copyWith(lineSpacing: 5),
+      bulletStyle: defaultStyle.copyWith(lineSpacing: 5),
+      header0: defaultStyle.copyWith(fontSize: fontSize * 2.0),
+      header1: defaultStyle.copyWith(fontSize: fontSize * 1.5),
+      header2: defaultStyle.copyWith(fontSize: fontSize * 1.4),
+      header3: defaultStyle.copyWith(fontSize: fontSize * 1.3),
+      header4: defaultStyle.copyWith(fontSize: fontSize * 1.2),
+      header5: defaultStyle.copyWith(fontSize: fontSize * 1.1),
+      tableHeader: defaultStyle.copyWith(
+          fontSize: fontSize * 0.8, fontWeight: FontWeight.bold),
+      tableCell: defaultStyle.copyWith(fontSize: fontSize * 0.8),
+    );
   }
 
   factory Theme.base() => Theme.withFont();
@@ -71,18 +111,19 @@ class Theme extends Inherited {
     TextStyle tableHeader,
     TextStyle tableCell,
   }) =>
-      Theme(
-          defaultTextStyle: defaultTextStyle ?? this.defaultTextStyle,
-          paragraphStyle: paragraphStyle ?? this.paragraphStyle,
-          bulletStyle: bulletStyle ?? this.bulletStyle,
-          header0: header0 ?? this.header0,
-          header1: header1 ?? this.header1,
-          header2: header2 ?? this.header2,
-          header3: header3 ?? this.header3,
-          header4: header4 ?? this.header4,
-          header5: header5 ?? this.header5,
-          tableHeader: tableHeader ?? this.tableHeader,
-          tableCell: tableCell ?? this.tableCell);
+      Theme._(
+        defaultTextStyle: this.defaultTextStyle.merge(defaultTextStyle),
+        paragraphStyle: this.paragraphStyle.merge(paragraphStyle),
+        bulletStyle: this.bulletStyle.merge(bulletStyle),
+        header0: this.header0.merge(header0),
+        header1: this.header1.merge(header1),
+        header2: this.header2.merge(header2),
+        header3: this.header3.merge(header3),
+        header4: this.header4.merge(header4),
+        header5: this.header5.merge(header5),
+        tableHeader: this.tableHeader.merge(tableHeader),
+        tableCell: this.tableCell.merge(tableCell),
+      );
 
   static Theme of(Context context) {
     return context.inherited[Theme];

@@ -117,6 +117,19 @@ void main() {
     ));
   });
 
+  test('Theme Page 4', () {
+    pdf.addPage(Page(
+        pageFormat: PdfPageFormat.a4,
+        orientation: PageOrientation.portrait,
+        margin: EdgeInsets.all(8.0),
+        theme: Theme(
+          defaultTextStyle: TextStyle(font: Font.courier(), fontSize: 10.0),
+        ),
+        build: (Context context) {
+          return Center(child: Text('Text'));
+        }));
+  });
+
   tearDownAll(() {
     final File file = File('widgets-theme.pdf');
     file.writeAsBytesSync(pdf.save());