Rework constructors

@@ -27,48 +27,78 @@ class PdfAnnot extends PdfObject {
       this.border,
       this.url,
       this.name})
-      : super(pdfPage.pdfDocument, type ?? '/Annot') {
+      : assert(subtype != null),
+        super(pdfPage.pdfDocument, type ?? '/Annot') {
     pdfPage.annotations.add(this);
   }
 
   /// Creates a text annotation
   /// @param rect coordinates
   /// @param s Text for this annotation
-  factory PdfAnnot.text(PdfPage pdfPage,
-          {@required PdfRect rect,
+  factory PdfAnnot.text(
+    PdfPage pdfPage, {
+    @required PdfRect rect,
     @required String content,
-          PdfBorder border}) =>
-      PdfAnnot._create(pdfPage,
-          subtype: '/Text', srcRect: rect, content: content, border: border);
+    PdfBorder border,
+  }) =>
+      PdfAnnot._create(
+        pdfPage,
+        subtype: '/Text',
+        srcRect: rect,
+        content: content,
+        border: border,
+      );
 
   /// Creates a link annotation
   /// @param srcRect coordinates
   /// @param dest Destination for this link. The page will fit the display.
   /// @param destRect Rectangle describing what part of the page to be displayed
   /// (must be in User Coordinates)
-  factory PdfAnnot.link(PdfPage pdfPage,
-          {@required PdfRect srcRect,
+  factory PdfAnnot.link(
+    PdfPage pdfPage, {
+    @required PdfRect srcRect,
     @required PdfPage dest,
     PdfRect destRect,
-          PdfBorder border}) =>
-      PdfAnnot._create(pdfPage,
+    PdfBorder border,
+  }) =>
+      PdfAnnot._create(
+        pdfPage,
         subtype: '/Link',
         srcRect: srcRect,
         dest: dest,
         destRect: destRect,
-          border: border);
+        border: border,
+      );
 
   /// Creates an external link annotation
-  factory PdfAnnot.urlLink(PdfPage pdfPage,
-          {@required PdfRect rect, @required String dest, PdfBorder border}) =>
-      PdfAnnot._create(pdfPage,
-          subtype: '/Link', srcRect: rect, url: dest, border: border);
+  factory PdfAnnot.urlLink(
+    PdfPage pdfPage, {
+    @required PdfRect rect,
+    @required String dest,
+    PdfBorder border,
+  }) =>
+      PdfAnnot._create(
+        pdfPage,
+        subtype: '/Link',
+        srcRect: rect,
+        url: dest,
+        border: border,
+      );
 
   /// Creates a link annotation to a named destination
-  factory PdfAnnot.namedLink(PdfPage pdfPage,
-          {@required PdfRect rect, @required String dest, PdfBorder border}) =>
-      PdfAnnot._create(pdfPage,
-          subtype: '/Link', srcRect: rect, name: dest, border: border);
+  factory PdfAnnot.namedLink(
+    PdfPage pdfPage, {
+    @required PdfRect rect,
+    @required String dest,
+    PdfBorder border,
+  }) =>
+      PdfAnnot._create(
+        pdfPage,
+        subtype: '/Link',
+        srcRect: rect,
+        name: dest,
+        border: border,
+      );
 
   /// The subtype of the outline, ie text, note, etc
   final String subtype;

@@ -17,7 +17,11 @@
 part of pdf;
 
 class PdfArrayObject extends PdfObject {
-  PdfArrayObject(PdfDocument pdfDocument, this.values) : super(pdfDocument);
+  PdfArrayObject(
+    PdfDocument pdfDocument,
+    this.values,
+  )   : assert(values != null),
+        super(pdfDocument);
 
   final List<String> values;
 

@@ -44,9 +44,14 @@ class PdfBorder extends PdfObject {
   /// @param style The style of the border
   /// @param dash The line pattern definition
   /// @see [PdfAnnot]
-  PdfBorder(PdfDocument pdfDocument, this.width,
-      {this.style = PdfBorderStyle.solid, this.dash})
-      : super(pdfDocument);
+  PdfBorder(
+    PdfDocument pdfDocument,
+    this.width, {
+    this.style = PdfBorderStyle.solid,
+    this.dash,
+  })  : assert(width != null),
+        assert(style != null),
+        super(pdfDocument);
 
   /// The style of the border
   final PdfBorderStyle style;

@@ -23,8 +23,14 @@ class PdfCatalog extends PdfObject {
   /// @param pagemode How the document should appear when opened.
   /// Allowed values are usenone, useoutlines, usethumbs or fullscreen.
   PdfCatalog(
-      PdfDocument pdfDocument, this.pdfPageList, this.pageMode, this.names)
-      : super(pdfDocument, '/Catalog');
+    PdfDocument pdfDocument,
+    this.pdfPageList,
+    this.pageMode,
+    this.names,
+  )   : assert(pdfPageList != null),
+        assert(pageMode != null),
+        assert(names != null),
+        super(pdfDocument, '/Catalog');
 
   /// The pages of the document
   final PdfPageList pdfPageList;

@@ -122,14 +122,12 @@ abstract class PdfFont extends PdfObject {
     params['/Encoding'] = PdfStream.string('/WinAnsiEncoding');
   }
 
-  // Use glyphMetrics instead
-  @deprecated
+  @Deprecated('Use `glyphMetrics` instead')
   double glyphAdvance(int charCode) => glyphMetrics(charCode).advanceWidth;
 
   PdfFontMetrics glyphMetrics(int charCode);
 
-  // Use glyphMetrics instead
-  @deprecated
+  @Deprecated('Use `glyphMetrics` instead')
   PdfRect glyphBounds(int charCode) => glyphMetrics(charCode).toPdfRect();
 
   PdfFontMetrics stringMetrics(String s) {
@@ -152,8 +150,7 @@ See https://github.com/DavBfr/dart_pdf/issues/76
     }
   }
 
-  // Use stringMetrics instead
-  @deprecated
+  @Deprecated('Use `stringMetrics` instead')
   PdfRect stringBounds(String s) => stringMetrics(s).toPdfRect();
 
   PdfPoint stringSize(String s) {

@@ -17,8 +17,12 @@
 part of pdf;
 
 class PdfFontDescriptor extends PdfObject {
-  PdfFontDescriptor(this.ttfFont, this.file)
-      : super(ttfFont.pdfDocument, '/FontDescriptor');
+  PdfFontDescriptor(
+    this.ttfFont,
+    this.file,
+  )   : assert(ttfFont != null),
+        assert(file != null),
+        super(ttfFont.pdfDocument, '/FontDescriptor');
 
   final PdfObjectStream file;
 

@@ -21,7 +21,8 @@ class PdfObject {
   /// Pdf Object Type
   /// @param type the Pdf Object Type
   PdfObject(this.pdfDocument, [String type])
-      : objser = pdfDocument._genSerial() {
+      : assert(pdfDocument != null),
+        objser = pdfDocument._genSerial() {
     if (type != null) {
       params['/Type'] = PdfStream.string(type);
     }

@@ -22,10 +22,10 @@ class PdfPoint {
 
   final double x, y;
 
-  @deprecated
+  @Deprecated('Use `x` instead')
   double get w => x;
 
-  @deprecated
+  @Deprecated('Use `y` instead')
   double get h => y;
 
   static const PdfPoint zero = PdfPoint(0.0, 0.0);

@@ -41,17 +41,22 @@ class PdfRect {
   double get horizondalCenter => x + width / 2;
   double get verticalCenter => y + height / 2;
 
-  @deprecated
+  @Deprecated('Use `left` instead')
   double get l => left;
-  @deprecated
+
+  @Deprecated('Use `bottom` instead')
   double get b => bottom;
-  @deprecated
+
+  @Deprecated('Use `right` instead')
   double get r => right;
-  @deprecated
+
+  @Deprecated('Use `top` instead')
   double get t => top;
-  @deprecated
+
+  @Deprecated('Use `width` instead')
   double get w => width;
-  @deprecated
+
+  @Deprecated('Use `height` instead')
   double get h => height;
 
   @override

@@ -343,7 +343,7 @@ class TextStyle {
     );
   }
 
-  @Deprecated('use font instead')
+  @Deprecated('use `font` instead')
   Font get paintFont => font;
 
   Font get font {

@@ -16,7 +16,7 @@
 
 part of printing;
 
-@deprecated
+@Deprecated('Use `Document` instead')
 class PdfDoc extends Document {
   /// Wrapper for a [Document] with zlib compression enabled by default
   PdfDoc(