Tables in Grail 0.3

Grail now supports Tables based on the HTML3 Table Model draft. Most of the simple tables encountered on the Web are rendered fairly well in Grail, but there are several issues that still need to be addressed. Some will not be fixed until Tk itself supports the necessary functionality (see the Special Interest Group on Tk based Web Browsers). Others will be fixed in a future release of Grail.

General

• Table rendering is too slow, however, approximately 90% of the time building a table is spent simply in creating new Viewer objects for the caption and cells. It would be much better to recycle Viewers where possible. This may be remedied in Grail 0.4.
• Table rendering is synchronous, such that Grail is unresponsive while the actual table layout calculations are being made.
• The fixed layout algorithm is not implemented. Fixed layout tables (e.g. those with an explicit COLS attribute on the TABLE tag), are rendered using the autolayout algorithm.

Adherence to the Specification

• The table parser should be more robust in the face of unbalanced or broken HTML.
• The common attributes (ID, CLASS, STYLE, LANG, DIR), are not honored.
• Of the standard units for widths, only screen pixels (either denoted as a unmodified number, or with the px suffix), and percentage widths (% suffix) are honored. All other width specification is ignored.
• The <TABLE> tag:
  • COLS is ignored.
  • Due to limitations in Tk, FRAME=VOID is rendered with no border, but any other value is rendered as if FRAME=BOX.
  • Similarly, RULES=NONE is rendered with no internal rules, however any other value is rendered as if RULES=ALL.
• The <CAPTION> tag:
  • ALIGN=TOP and ALIGN=BOTTOM are honored, but all other values are rendered as if ALIGN=TOP.
• The <COLGROUP> tag is ignored.
• The <COL> tag is ignored.
• The <TD> and <TH> tags:
  • AXIS and AXES are ignored.
  • NOWRAP is ignored.

Rendering

• Really tall tables aren't scrolled gracefully. This is due to Tk limitation that treats all embedded windows as a single character. Grail can optionally employ a smooth scrolling hack that ought help, but its interaction with tables is currently pretty bad.
• When a table contains cells that are not initially visible, cells can temporarily show up at the upper right corner of the canvas. This seems to be caused by a Tk canvas bug. Fortunately, scrolling around a little bit pops the offending cell into its rightful place within the table.
• When the content of a cell doesn't fill all of its available vertical space, it should be centered within the cell.
• When an applets inside a table resizes its topmost frame, the table will not automatically recalculate its layout.