cortav  Check-in [5a78370f0f]

* [*subtitle/caption] (["--]): attaches a subtitle to the previous header, or caption to the previous object
* [*embed] ([`&]): embeds a referenced object. can be used to show images or repeat previously defined objects like lists or tables, optionally with a caption. an embed line can be followed immediately by a sequence of [*definitions] in the same way that resource definitions can, to override resource properties on a per-instance basis. note that only presentation-related properties like [$desc] can be meaningful overridden, as embed does not trigger a re-render of the parse tree; if you want to override e.g. context variables, use a multiline macro invocation instead.
** [`&[$image]] embeds an image or other block-level object. [!image] can be a reference with a url or file path, or it can be an embed section (e.g. for SVG files)
***[`&myimg All that remained of the unfortunate blood magic pageant contestants and audience (police photo)]
** [`&-[$ident] [$styled-text]] embeds a closed disclosure element containing the text of the named object (a nonprinting section or cortav resource should usually be used to store the content; it can also name an image or video, of course). in interactive outputs, this will display as a block which can be clicked on to view the full contents of the referenced object [$ident]; if [$styled-text] is present, it overrides the title of the section you are embedding (if any). in static outputs, the disclosure object will display as an enclosed box with [$styled-text] as the title text
*** [`&-ex-a Prosecution Exhibit A (GRAPHIC CONTENT)]
** [`&+[$section] [$styled-text]] is like the above, but the disclosure element is open by default
* [`$[$macro] [$arg1]|[$arg2]|[$argn]…] invokes a block-level macro with the supplied arguments, and can be followed by a property override definition list the same way embed and resource lines can. note that while both [`$[$id]] and [`&[$id]] can be used to instantiate resources of type [`text/x.cortav], there is a critical difference: [`$[$id]] renders out the sub-document separately each time it is named, allowing for parameter expansion and for context variables to be overridden for each invocation. by contrast, [`&[$id]] can only insert copies of the same render; no parameters can be passed and context variables will be expanded to their value at the time the resource was defined.
** [`$mymacro arg 1|arg 2|arg 3]
* [*horizontal rule] (["---]): inserts a horizontal rule or other context break; does not end the section. must be followed by newline. underlines can also be used in place of dashes ([`___], [`-_-], [`__-__-__] etc), as can horizontal unicode box drawing characters ([`─ ━ ┈] etc).
* [*page break] (["^^]): for formats that support pagination, like EPUB or HTML (when printed), indicates that the rest of the current page should be blank. for formats that do not, extra margins will be inserted. does not create a new section
* [*page rule] (["^-^]): inserts a page break for formats that support them, and a horizontal rule for formats that do not. does not create a new section. comprised of any number of horizontal rule characters surrounded by a pair of carets (e.g. [`^-^] [`^_^] [`^----^] [`^__--^] [`^┈┈┈┈┈^])
* [*table cells] ([`+ |]): see [>ex.tab table examples].
* [*equations] ([`=]): block-level equations can be inserted with the [`=] sequence
* [*cross-references] ([`=>] [`⇒]): inserts a block-level link. has two forms for the sake of gemtext compatibility. [$styled-text] is a descriptive text of the destination. especially useful for menus and gemtext output.
** the cortav syntax is [`=>[$ident] [$styled-text]], where [$ident] is an identifier; links to the same destination as [`\[>[$ident] [$styled-text]\]] would

* [*subtitle/caption] (["--]): attaches a subtitle to the previous header, or caption to the previous object
* [*embed] ([`&]): embeds a referenced object. can be used to show images or repeat previously defined objects like lists or tables, optionally with a caption. an embed line can be followed immediately by a sequence of [*definitions] in the same way that resource definitions can, to override resource properties on a per-instance basis. note that only presentation-related properties like [$desc] can be meaningful overridden, as embed does not trigger a re-render of the parse tree; if you want to override e.g. context variables, use a multiline macro invocation instead.
** [`&[$image]] embeds an image or other block-level object. [!image] can be a reference with a url or file path, or it can be an embed section (e.g. for SVG files)
***[`&myimg All that remained of the unfortunate blood magic pageant contestants and audience (police photo)]
** [`&-[$ident] [$styled-text]] embeds a closed disclosure element containing the text of the named object (a nonprinting section or cortav resource should usually be used to store the content; it can also name an image or video, of course). in interactive outputs, this will display as a block which can be clicked on to view the full contents of the referenced object [$ident]; if [$styled-text] is present, it overrides the title of the section you are embedding (if any). in static outputs, the disclosure object will display as an enclosed box with [$styled-text] as the title text
*** [`&-ex-a Prosecution Exhibit A (GRAPHIC CONTENT)]
** [`&+[$section] [$styled-text]] is like the above, but the disclosure element is open by default
* [`$[$macro] [$arg1]|[$arg2]|[$argn]…] invokes a block-level macro with the supplied arguments, and can be followed by a property override definition list the same way embed and resource lines can. note that while both [`$[$id]] and [`&[$id]] can be used to instantiate resources of type [`text/x.cortav], there is a critical difference: [`$[$id]] renders out the sub-document separately each time it is named, allowing for parameter expansion and for context variables to be overridden for each invocation. by contrast, [`&[$id]] can only insert copies of the same render; no parameters can be passed and context variables will be expanded to their value at the time the resource was defined. only [`&[$id]] can instantiate resources of types other than [`text/x.cortav]. there is also a semantic distinction: resources interpreted as macros are inserted "in-band", on an equal basis with nearby elements; resources interpreted as embeds are set off to clearly indicate that they are a sub-document, and on interactive outputs may have their own independently-scrolling viewport.

* [*horizontal rule] (["---]): inserts a horizontal rule or other context break; does not end the section. must be followed by newline. underlines can also be used in place of dashes ([`___], [`-_-], [`__-__-__] etc), as can horizontal unicode box drawing characters ([`─ ━ ┈] etc).
* [*page break] (["^^]): for formats that support pagination, like EPUB or HTML (when printed), indicates that the rest of the current page should be blank. for formats that do not, extra margins will be inserted. does not create a new section
* [*page rule] (["^-^]): inserts a page break for formats that support them, and a horizontal rule for formats that do not. does not create a new section. comprised of any number of horizontal rule characters surrounded by a pair of carets (e.g. [`^-^] [`^_^] [`^----^] [`^__--^] [`^┈┈┈┈┈^])
* [*table cells] ([`+ |]): see [>ex.tab table examples].
* [*equations] ([`=]): block-level equations can be inserted with the [`=] sequence
* [*cross-references] ([`=>] [`⇒]): inserts a block-level link. has two forms for the sake of gemtext compatibility. [$styled-text] is a descriptive text of the destination. especially useful for menus and gemtext output.
** the cortav syntax is [`=>[$ident] [$styled-text]], where [$ident] is an identifier; links to the same destination as [`\[>[$ident] [$styled-text]\]] would