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This property specifies the HTML engine to use when importing HTML pages.
The EngineType enumeration can take any of the
following values:
- MSHtml. Characteristics:
- The Screen style sheets are used during the rendering process.
- Page heights can vary across different pages. Segments of the
HTML document are composed dynamically to fit the target rectangle
as accurately as possible during each call to Doc.AddImageToChain.
This means the target rectangle will be filled with more contents
for larger target rectangles instead of scaled to fit.
- For definite control of HTTP requests, you should set TransferModule to a non-default
value.
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Internet Explorer 9 support
ABCpdf automatically detects and accommodates the
architectural changes introduced in Microsoft Internet
Explorer 9. For many server applications, this is transparent
and and requires no code change.
The Fusion Log Viewer is known to interfere with the
initialization of the MSHtml engine. If any problem arises,
try disabling it or specify a local custom log path.
Currently, there are some limitations when using the MSHtml
engine hosted out-of-process (See
MSHtmlBootstrap):
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- Gecko. Characteristics:
- The Gecko engine is a component independent of other parts of
the Operating System. It will not be affected even if you
upgrade your Internet Explorer or another local Firefox
installation.
- It supports a wide range of the HTML5 and CSS3 standards.
- It supports the majority of the SVG Full profile. SVG graphics
embedded inside Web pages convert natively to PDF primitives.
Alternatively, you can specify the a SVG file's location
in Doc.AddImageUrl or
provide a string of SVG contents to Doc.AddImageHtml
to have it converted to PDF using the Gecko engine.
- It supports XML pages with XSLT and MathML.
- You can specify which set of style sheets to use
(Print/Screen) through the use of the Media property.
- In large tables that span across pages, thead and tfoot elements are repeated
across different pages properly.
- The rendered HTML will always fill the entire current
rectangle. After the initial call to Doc.AddImageUrl or
Doc.AddImageHtml,
the page height will be fixed at that point. Subsequent pages
rendered using Doc.AddImageToChain
will be automatically scaled (instead of having the contents reflowed) to fit in the
current rectangle as much as possible.
- ActiveX components are not supported.
- The Paged property is always assumed
to be true.
- The Gecko engine does not use Page caching. This means that
your rendered PDF is never stored in a memory cache.
- On the other hand, Web caching is used to store contents
downloaded over the Internet and is configurable using with
the UseNoCache property.
- JavaScript in OnLoadScript
cannot directly modify the document object. For example, document.write("hello
world"); would not work. Most of the time, you can work
around to get your desired effect by indirectly modifying elements
on the page, such as document.body.innerHTML
= "hello world";
- The use of OnLoadScript does
not require UseScript. You are free to
use JavaScript to customize the page without allowing JavaScript
execution in the HTML.
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Gecko configuration
The Gecko engine contains a number of preferences that can be
configured. There are a set of .js files in the "XULRunner??_?\defaults\pref"
folder that are loaded in alphabetical order when it starts. Each
file contains a set of preferences. So by adding your own .js file
to this folder, you can add in your own settings.
If you are not familiar with the format of these files, you
may find it easier to copy a configuration file from Firefox:
- View the URI "about:config" in Firefox.
- Modify the configuration as usual.
- Close Firefox. The configuration is saved to the file only
when Firefox is completely closed.
- See the Path value in %APPDATA\Mozilla\Firefox\profile.ini.
For example, the value may be Profiles/sx4fgjw2.default.
- Copy prefs.js in the folder pointed to by the Path value
(relative to the path of profile.ini) to:
- XULRunner??_?\defaults\pref. The preferences are considered
to be set by the software developer. For example, copy
C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\sx4fgjw2.default\prefs.js
to XULRunner??_?\defaults\pref.
- some place outside of XULRunner??_? and set the file path
(including the file name) to the GeckoPrefFile registry value.
The preferences are considered to be set by the end user. See
below for the differences between preferences set by the end user
and those set by the software developer.
- Do not delete or change the first line in prefs.js.
You need only the lines relevant for your configuration change.
You can delete other irrelevant lines.
Preferences set by the end user are in the JavaScript file whose
path is assigned to the GeckoPrefFile
registry value. (Registry values can alternatively be specified in web.config or app.config.)
The file is loaded after all JavaScript files in "XULRunner??_?\defaults\pref",
so user-set preferences take precedence. Some preferences
are in effect only when set by the end user. Here is an
incomplete list of such preferences:
| Preference in effect only if it is set by the end user |
Default Value |
Description |
| intl.accept_languages |
"en-US, en" |
The order of languages of the fonts to search when
the specified font does not support a character. The Gecko
engine appends to the list the ones that are missing in the
following in order ja, ko, zh-CN, zh-HK, zh-TW. For example,
without specifying this preference, a piece of simplified
Chinese text (in a Latin font) may be imported
in multiple fonts because some characters are supported by
Japanese fonts and some are not. |
Additional supported settings:
| Preference |
Default Value |
| print.print_shrink_to_fit |
true |
| print.print_scaling |
"1" |
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Each HTML engine supports a different subset of HtmlOptions methods and properties.
You can use one of the filter objects: ForMSHtml
and ForGecko,
to filter the supported options in your IDE. |
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