【 轉(zhuǎn) 】

Text Model 存儲(chǔ)文本以及相應(yīng)屬性的模型，主要有兩種不同的實(shí)現(xiàn)策略：樹形結(jié)構(gòu)和平面結(jié)構(gòu)。樹形結(jié)構(gòu)類似 Dom，可以很好的表現(xiàn)結(jié)構(gòu)化文檔，但是比較復(fù)雜。平面結(jié)構(gòu)相對(duì)簡(jiǎn)單的多，大多數(shù)的編輯器（e.g. Emacs），字處理器（e.g. AbiWord, OpenOffice）都用的是平面結(jié)構(gòu)。

Text Model Coords 用來(lái)在 Text Model 中定位的坐標(biāo)系。對(duì)于樹形結(jié)構(gòu)的 Text Model 其定位方式為節(jié)點(diǎn)鏈接（或指向節(jié)點(diǎn)的路徑 e.g. XPath）以及節(jié)點(diǎn)內(nèi)偏移值。對(duì)于平面結(jié)構(gòu)則僅僅是一個(gè)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(lái)在 Text Presentation 中定位的坐標(biāo)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(biāo)點(diǎn)擊（x,y）對(duì)應(yīng)到 Text Model 中的某個(gè)字符/元素。由 fp_Page::mapXYToPosition成員函數(shù)實(shí)現(xiàn)

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(yè)面展示模型