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| author | William Victor Mote <vmote@apache.org> | 2003-04-22 02:44:57 +0000 |
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| committer | William Victor Mote <vmote@apache.org> | 2003-04-22 02:44:57 +0000 |
| commit | 29edecf3ac1a7f53e8ae09586b2e6d637988f664 (patch) | |
| tree | 5e3ec08b9aa7ecaf2bc6ea0b3b7d23d836cb74df | |
| parent | f3c1ad2abe0d5f61d4306537631c47174a037a0d (diff) | |
| download | xmlgraphics-fop-29edecf3ac1a7f53e8ae09586b2e6d637988f664.tar.gz xmlgraphics-fop-29edecf3ac1a7f53e8ae09586b2e6d637988f664.zip | |
Pretty-print & white-space changes only.
git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@196304 13f79535-47bb-0310-9956-ffa450edef68
| -rw-r--r-- | src/documentation/content/xdocs/design/areas.xml | 350 |
1 files changed, 140 insertions, 210 deletions
diff --git a/src/documentation/content/xdocs/design/areas.xml b/src/documentation/content/xdocs/design/areas.xml index 2a6b26c3b..162659cac 100644 --- a/src/documentation/content/xdocs/design/areas.xml +++ b/src/documentation/content/xdocs/design/areas.xml @@ -1,7 +1,6 @@ <?xml version="1.0" standalone="no"?> <!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.1//EN" "http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd"> - <document> <header> <title>Area Tree</title> @@ -10,217 +9,148 @@ <person name="Keiron Liddle" email="keiron@aftexsw.com"/> </authors> </header> - <body> -<p>The Area Tree is an internal representation of the result document, representing pages and their contents. -To make the concepts clearer and easier to understand, the code to implement the area tree matches the areas defined in the XSL-FO specification. - </p> - <p> -The area tree is created by the layout managers once the layout is decided -for a page. Once a completed page is finished it can then be added to the -area tree. From that point forward, the area tree model can then handle the new page. The data in -the area tree must be minimal and independant. This means that the data -uses less memory and can be serialized to an output stream if needed. - </p> -<p>The Area Tree consists of a set of pages, which the actual implemenation places in a set of page sequences.</p> -<section> - <title>Structure</title> -<p> -The area tree is a root element that has a list of page-viewport-areas. -Each page viewport has a page-reference-area which holds the contents of -the page. To handle the processing better FOP does not maintain a list -at the root level but lets the area tree model handle each page as it is added. - </p> - </section> -<section> - <title>Page</title> -<p>A page consists of a page+viewport pair.</p> -<p>The PageViewPort and Page with the regions is created by the -LayoutMasterSet. The contents are then placed by the layout managers. Once -the layout of a page is complete then it is added to the Area Tree.</p> -<p>Inside the page is a set of RegionViewport+Region pairs for each region on -the page.</p><p> -A page is made up of five area regions. These are before, start, body, -end and after. Each region has a viewport and contains the areas -produced from the children in the FO object heirarchy. - </p> - <p> -For the body area there are more subdivisions for before floats, -footnotes and the main reference area. The main reference area is -made from span areas which have normal flow reference areas as -children. The flow areas are then created inside these normal flow -reference areas. - </p> - <p> -Since the layout is done inside a page, the page is created from the -pagemaster with all the appropriate areas. The layout manager then -uses the page to add areas into the normal flow reference areas -and floats and footnotes. After adding the areas for the body region -then the other regions can be done layed out and added. - </p> - </section> -<section> - <title>Block Areas</title> -<p>Block level areas contain either other blocks or line areas (which is a -special block area).</p><p> -A block is either positoned or stacked with other block areas.</p> -<p> -Block areas are created and/or returned by all top level elements -in the flow. The spacing between block areas is handled by an -empty block area. A block area is stacked with other block -areas in a particular direction, it has a size and it contains -line areas made from a group of inline areas and/or block areas. - </p> - </section> -<section> - <title>Line Areas</title> -<p> -A line areas is simply a collection of inline areas that are stacked -in the inline progression direction. A line area has a height and -a start position. The line area is rendered by handling each inline -area. - </p> - <p> -A line area gets a set of inline areas added until complete then -it is justified and vertically alignedi when adding the areas. -If the line area contains unresolved areas then there will -be a line resolver that retains the justification information until -all areas in the line are resolved. - </p> - </section> -<section> - <title>Inline Areas</title> -<p> -There are a few different types of inline areas. All inline areas -have a height and width. - </p> - <p> -Unresolved areas can reserve some space to allow for possible -sizes once it is resolved. Then the line can be re-justified -and finalised. - </p> -<p>Inline areas are stacked in a line area. Inline areas are objects such as -character, viewport, inline-container, leader and space. A special inline -area Word is also used for a group of consecutive characters.</p> -<p>The image and instream foreign object areas are placed inside a viewport. -The leader (with use content) and unresolved page number areas are -resolved to other inline areas.</p> -<p>Once a LineArea is filled with inline areas then the inline areas need to -be aligned and adjusted to fill the line properly.</p> - </section> -<section> - <title>Repeated Areas</title> -<p> -There are cases where the same subtree could be repeated in the area -tree. These areas will be returned by the same layout managers. -So it is possible to put a flag on the created areas so that -the subtree data can be cached in the output. Examples of this are: -static areas, table header/footer, svg. - </p> - </section> -<section> - <title>Traits</title> - -<p>A trait is information associated with an area. This could be information -such as text colour or is-first.</p> -<p>Traits provide information about an area. The traits are derived from -properties on the formatting object or are generated during the layout -process. Many of the layout traits do not have actual values but can be -derived from the Area Tree. Other traits that apply when rendering the -areas are set on the area. Since setting the same value on every area -would use a lot of memory then the traits are derived from default or -parent values.</p> -<p>A dominant trait on a block area is set, for example font colour, so that -every line area with the same dominant value can derive it. The text -inline areas then get the font colour set on the inline area or from the -line area or from the block area.</p> -</section> -<section> - <title>Classes</title> -<p> -The following class structure will be used to represent the area -tree. - </p> -<section> - <title>Page Area Classes</title> -<p> -The page area classes hold the top level layout of a page. The -areas are created by the page master and should be ready to have -flow areas added. - </p> - </section> -<section> - <title>Block Area Classes</title> -<p> -The block areas hold other block areas and/or line areas. The -child areas are stacked in a particular direction. - </p> - <p> -Areas for tables, lists and block container have their child -block areas stacked in different ways. These areas a placed -with an absolute positioning. The absolute positioning is where -the blocks are placed with an offset from the parent reference area. - </p> - </section> -<section> - <title>Inline Area Classes</title> -<p> -The inline areas are used to make up a line area. An inline area -typically has a height, width and some content. The inline area -is offset from the baseline of the current line area. The content -of the inline area can be other inline areas or a simple atomic -object. - </p> - </section> - </section> - -<section> - <title>Forward References</title> -<p>The Area Tree maintains a set of mappings from the reference to pages.</p> -<p>The PageViewPort holds the list of forward references that need resolving -so that if a references is resolved during layout the page can be easily -found and then fixed. Once all the forward references are resolved then -the page is ready to be rendered.</p> -<p>To layout a page any areas that cannot be resolved need to reserve space. -Once the inline area is resolved then the complete line should be adjusted -to accomodate any change in space used by the area.</p> -</section> - -<section> - <title>Caching</title> -<p>We may need to cache pages due to forward references or when keeping all + <p>The Area Tree is an internal representation of the result document, representing pages and their contents. +To make the concepts clearer and easier to understand, the code to implement the area tree matches the areas defined in the XSL-FO specification.</p> + <p>The area tree is created by the layout managers once the layout is decided for a page. +Once a completed page is finished it can then be added to the area tree. +From that point forward, the area tree model can then handle the new page. +The data in the area tree must be minimal and independant. +This means that the data uses less memory and can be serialized to an output stream if needed.</p> + <p>The Area Tree consists of a set of pages, which the actual implemenation places in a set of page sequences.</p> + <section> + <title>Structure</title> + <p>The area tree is a root element that has a list of page-viewport-areas. +Each page viewport has a page-reference-area which holds the contents of the page. +To handle the processing better FOP does not maintain a list at the root level but lets the area tree model handle each page as it is added.</p> + </section> + <section> + <title>Page</title> + <p>A page consists of a page+viewport pair.</p> + <p>The PageViewPort and Page with the regions is created by the +LayoutMasterSet. +The contents are then placed by the layout managers. +Once the layout of a page is complete then it is added to the Area Tree.</p> + <p>Inside the page is a set of RegionViewport+Region pairs for each region on +the page.</p> + <p>A page is made up of five area regions. +These are before, start, body, end and after. +Each region has a viewport and contains the areas produced from the children in the FO object heirarchy.</p> + <p>For the body area there are more subdivisions for before floats, footnotes and the main reference area. +The main reference area is made from span areas which have normal flow reference areas as children. +The flow areas are then created inside these normal flow reference areas.</p> + <p>Since the layout is done inside a page, the page is created from the pagemaster with all the appropriate areas. +The layout manager then uses the page to add areas into the normal flow reference areas and floats and footnotes. +After adding the areas for the body region then the other regions can be done layed out and added.</p> + </section> + <section> + <title>Block Areas</title> + <p>Block level areas contain either other blocks or line areas (which is a +special block area).</p> + <p>A block is either positoned or stacked with other block areas.</p> + <p>Block areas are created and/or returned by all top level elements in the flow. +The spacing between block areas is handled by an empty block area. +A block area is stacked with other block areas in a particular direction, it has a size and it contains line areas made from a group of inline areas and/or block areas.</p> + </section> + <section> + <title>Line Areas</title> + <p>A line areas is simply a collection of inline areas that are stacked in the inline progression direction. +A line area has a height and a start position. +The line area is rendered by handling each inline area.</p> + <p>A line area gets a set of inline areas added until complete then it is justified and vertically alignedi when adding the areas. +If the line area contains unresolved areas then there will be a line resolver that retains the justification information until all areas in the line are resolved.</p> + </section> + <section> + <title>Inline Areas</title> + <p>There are a few different types of inline areas. +All inline areas have a height and width.</p> + <p>Unresolved areas can reserve some space to allow for possible sizes once it is resolved. +Then the line can be re-justified and finalised.</p> + <p>Inline areas are stacked in a line area. +Inline areas are objects such as character, viewport, inline-container, leader and space. +A special inline area Word is also used for a group of consecutive characters.</p> + <p>The image and instream foreign object areas are placed inside a viewport. +The leader (with use content) and unresolved page number areas are resolved to other inline areas.</p> + <p>Once a LineArea is filled with inline areas then the inline areas need to be aligned and adjusted to fill the line properly.</p> + </section> + <section> + <title>Repeated Areas</title> + <p>There are cases where the same subtree could be repeated in the area tree. +These areas will be returned by the same layout managers. +So it is possible to put a flag on the created areas so that the subtree data can be cached in the output. +Examples of this are: static areas, table header/footer, svg.</p> + </section> + <section> + <title>Traits</title> + <p>A trait is information associated with an area. +This could be information such as text colour or is-first.</p> + <p>Traits provide information about an area. +The traits are derived from properties on the formatting object or are generated during the layout +process. +Many of the layout traits do not have actual values but can be derived from the Area Tree. +Other traits that apply when rendering the areas are set on the area. +Since setting the same value on every area would use a lot of memory then the traits are derived from default or parent values.</p> + <p>A dominant trait on a block area is set, for example font colour, so that +every line area with the same dominant value can derive it. +The text inline areas then get the font colour set on the inline area or from the line area or from the block area.</p> + </section> + <section> + <title>Classes</title> + <p>The following class structure will be used to represent the area tree.</p> + <section> + <title>Page Area Classes</title> + <p>The page area classes hold the top level layout of a page. +The areas are created by the page master and should be ready to have flow areas added.</p> + </section> + <section> + <title>Block Area Classes</title> + <p>The block areas hold other block areas and/or line areas. +The child areas are stacked in a particular direction.</p> + <p>Areas for tables, lists and block container have their child block areas stacked in different ways. +These areas a placed with an absolute positioning. +The absolute positioning is where the blocks are placed with an offset from the parent reference area.</p> + </section> + <section> + <title>Inline Area Classes</title> + <p>The inline areas are used to make up a line area. +An inline area typically has a height, width and some content. +The inline area is offset from the baseline of the current line area. +The content of the inline area can be other inline areas or a simple atomic object.</p> + </section> + </section> + <section> + <title>Forward References</title> + <p>The Area Tree maintains a set of mappings from the reference to pages.</p> + <p>The PageViewPort holds the list of forward references that need resolving so that if a references is resolved during layout the page can be easily found and then fixed. +Once all the forward references are resolved then the page is ready to be rendered.</p> + <p>To layout a page any areas that cannot be resolved need to reserve space. +Once the inline area is resolved then the complete line should be adjusted to accomodate any change in space used by the area.</p> + </section> + <section> + <title>Caching</title> + <p>We may need to cache pages due to forward references or when keeping all pages.</p> -<p>This is done by serializing the Page. The PageViewport is retained to be -used as a key for page references and backward references. -The Page is serialized to an object stream and then all of the page -contents are released. The Page is then recoved by reading from the object -stream.</p> -<p>The PageViewport retains information about id areas for easy access.</p> -</section> - -<section> - <title>Extensions</title> -<p>The Area Tree holds the Output Document extensions. This is information -such as pdf bookmarks or other output document specific information that + <p>This is done by serializing the Page. +The PageViewport is retained to be used as a key for page references and backward references. +The Page is serialized to an object stream and then all of the page contents are released. +The Page is then recoved by reading from the object stream.</p> + <p>The PageViewport retains information about id areas for easy access.</p> + </section> + <section> + <title>Extensions</title> + <p>The Area Tree holds the Output Document extensions. +This is information such as pdf bookmarks or other output document specific information that is not handled by XSL:FO.</p> -<p>It is also possible to create custom areas that extend a normal area. The -actual data that is rendered could be set in a different way or depend on -resolving a forward reference.</p> -</section> - -<section> - <title>Area Tree Handlers</title> -<p>To handle different situations the handler for the Area Tree handles each -page as it is added.</p><p> -The RenderPagesModel sends the page directly to the renderer if the page -is ready to be rendered. Once a page is rendered it is discarded. -The StorePagesModel stores all the pages so that any page can be later -accessed.</p> -<p>The Area Tree retains the concept of page sequences (this is not in the -area tree in the spec) so that this information can be passed to the -renderer. This is useful for setting the title and organising the groups -of page sequences.</p> -</section> + <p>It is also possible to create custom areas that extend a normal area. +The actual data that is rendered could be set in a different way or depend on resolving a forward reference.</p> + </section> + <section> + <title>Area Tree Handlers</title> + <p>To handle different situations the handler for the Area Tree handles each +page as it is added.</p> + <p>The RenderPagesModel sends the page directly to the renderer if the page is ready to be rendered. Once a page is rendered it is discarded. The StorePagesModel stores all the pages so that any page can be later accessed.</p> + <p>The Area Tree retains the concept of page sequences (this is not in the area tree in the spec) so that this information can be passed to the renderer. +This is useful for setting the title and organising the groups of page sequences.</p> + </section> </body> </document> - |