【 轉 】

Text Model 存儲文本以及相應屬性的模型，主要有兩種不同的實現策略：樹形結構和平面結構。樹形結構類似 Dom，可以很好的表現結構化文檔，但是比較復雜。平面結構相對簡單的多，大多數的編輯器（e.g. Emacs），字處理器（e.g. AbiWord, OpenOffice）都用的是平面結構。

Text Model Coords 用來在 Text Model 中定位的坐標系。對于樹形結構的 Text Model 其定位方式為節點鏈接（或指向節點的路徑 e.g. XPath）以及節點內偏移值。對于平面結構則僅僅是一個索引值。

Text Presentation 展示文本的模型，一般分別為 Block, Line, Run …

Text Presentation Coords 用來在 Text Presentation 中定位的坐標系，其值通常為 (x,y)。Text Editor 必須能夠在 Text Model Coords 和 Text Presentation Coords 之間變換。例如將鼠標點擊（x,y）對應到 Text Model 中的某個字符/元素。由 fp_Page::mapXYToPosition成員函數實現

FL_DocLayout 類：

page fmt_overview Formatter

??? FL_DocLayout is a formatted representation of a specific PD_Document,?
??? formatted for a specific GR_Graphics context.?

??? A %FL_DocLayout encapsulates two related hierarchies of objects.?

??? The? logical ?(or content) hierarchy corresponds
??? to the logical structure of the document.

??????? - each FL_DocLayout contains a list of fl_SectionLayout objects
??????? - each fl_SectionLayout are composed of fl_BlockLayout objects

??? Where each fl_BlockLayout corresponds to a logical element in
??? the PD_Document (i.e., usually a paragraph of text).

??? The? physical ?(or layout) hierarchy, by contrast,
??? encapsulates the subdivision of physical space into objects of
??? successively finer granularity.

??????? - each FL_DocLayout contains a list of fp_Page objects, each
????????? of which was constructed during the process of formatting
????????? the document
??????? - each fp_Page is a list of fp_Columns (fp_Column)
??????? - each fp_Column is a list of fp_Lines (fp_Line)
??????? - each fp_Line is a list of fp_Runs (fp_Run)

??? Where each fp_Run contains some fragment of content from the original?
??? document, usually text.?

Abiword的頁面展示模型