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Gecko:Overview: Difference between revisions
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The loading of CSS style sheets from the network is managed by the | The loading of CSS style sheets from the network is managed by the | ||
[https:// | [https://dxr.mozilla.org/mozilla-central/source/layout/style/Loader.h CSS loader]; | ||
they are then tokenized by the | they are then tokenized by the | ||
[https:// | [https://dxr.mozilla.org/mozilla-central/source/layout/style/nsCSSScanner.h CSS scanner] | ||
and parsed by the | and parsed by the | ||
[https:// | [https://dxr.mozilla.org/mozilla-central/source/layout/style/nsCSSParser.h CSS parser]. | ||
Those that are attached to the document also expose APIs to | Those that are attached to the document also expose APIs to | ||
script that are known as the CSS Object Model, or CSSOM. | script that are known as the CSS Object Model, or CSSOM. | ||
The style sheets that apply to a document are managed by a class called | The style sheets that apply to a document are managed by a class called | ||
the [https:// | the [https://dxr.mozilla.org/mozilla-central/source/layout/style/nsStyleSet.h style set]. | ||
The style set interacts with the different types of | The style set interacts with the different types of | ||
style sheets (representing CSS style sheets, presentational | style sheets (representing CSS style sheets, presentational | ||
attributes, and 'style' attributes) through two interfaces: | attributes, and 'style' attributes) through two interfaces: | ||
[http:// | [http://dxr.mozilla.org/mozilla-central/source/layout/style/nsIStyleSheet.h nsIStyleSheet] for basic management of style sheets and | ||
[http:// | [http://dxr.mozilla.org/mozilla-central/source/layout/style/nsIStyleRuleProcessor.h nsIStyleRuleProcessor] for getting the style data out of them. Usually | ||
the same object implements both interfaces, except in the most important | the same object implements both interfaces, except in the most important | ||
case, CSS style sheets, where there is a single rule processor for all | case, CSS style sheets, where there is a single rule processor for all | ||
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The process of turning the style sheets into computed style data goes | The process of turning the style sheets into computed style data goes | ||
through three main steps, the first two of which closely relate to the | through three main steps, the first two of which closely relate to the | ||
[http:// | [http://dxr.mozilla.org/mozilla-central/source/layout/style/nsIStyleRule.h nsIStyleRule] interface, which represents an immutable source of style | ||
data, conceptually representing (and for CSS style rules, directly | data, conceptually representing (and for CSS style rules, directly | ||
storing) a set of property:value pairs. (It is similar to the idea of a | storing) a set of property:value pairs. (It is similar to the idea of a | ||
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with a simple mark and sweep collector (which often never needs to run). | with a simple mark and sweep collector (which often never needs to run). | ||
* code: [http:// | * code: [http://dxr.mozilla.org/mozilla-central/source/layout/style/ layout/style/], where most files have useful one line descriptions at the top that show up in DXR | ||
* Bugzilla: Style System (CSS) | * Bugzilla: Style System (CSS) | ||
* specifications | * specifications | ||
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TODO: link to documentation of XUL frame classes | TODO: link to documentation of XUL frame classes | ||
Code (note that most files in base and generic have useful one line descriptions at the top that show up in | Code (note that most files in base and generic have useful one line descriptions at the top that show up in DXR): | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/layout/base/ layout/base/] contains objects that coordinate everything and a bunch of other miscellaneous things | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/layout/generic/ layout/generic/] contains the basic frame classes as well as support code for their reflow methods (nsHTMLReflowState, nsHTMLReflowMetrics) | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/layout/forms/ layout/forms/] contains frame classes for HTML form controls | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/layout/tables/ layout/tables/] contains frame classes for CSS/HTML tables | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/layout/mathml/ layout/mathml/] contains frame classes for MathML | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/layout/svg/ layout/svg/] contains frame classes for SVG | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/layout/xul/ layout/xul/] contains frame classes for the XUL box model and for various XUL widgets | ||
Bugzilla: | Bugzilla: | ||
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* Code to create frames from frame construction items. | * Code to create frames from frame construction items. | ||
Code: [http:// | Code: [http://dxr.mozilla.org/mozilla-central/source/layout/base/nsCSSFrameConstructor.h layout/base/nsCSSFrameConstructor.h] and [http://dxr.mozilla.org/mozilla-central/source/layout/base/nsCSSFrameConstructor.cpp layout/base/nsCSSFrameConstructor.cpp] | ||
==== Reflow ==== | ==== Reflow ==== | ||
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It is worth reading the inline code documentation in the following files: | It is worth reading the inline code documentation in the following files: | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/gfx/layers/Compositor.h gfx/layers/Compositor.h] | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/gfx/layers/ShadowLayers.h gfx/layers/ShadowLayers.h] | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/gfx/layers/Layers.h gfx/layers/Layers.h] | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/gfx/layers/host/TextureHost.h gfx/layers/host/TextureHost.h] | ||
* [http:// | * [http://dxr.mozilla.org/mozilla-central/source/gfx/layers/client/CompositableClient.h gfx/layers/client/CompositableClient.h] | ||
To visualize how a web page is layered, turn on the pref "layers.draw-borders" in about:config. When this pref is on, the borders of layers and tiles are displayed on top of the content. This only works when using the new Compositor API, that is when off-main-thread compositing is activated. OMTC is activated by default on all mobile platforms, and will progressively get activated on desktop platforms (not yet, though). On platforms where OMTC is not used, this pref has no effect. | To visualize how a web page is layered, turn on the pref "layers.draw-borders" in about:config. When this pref is on, the borders of layers and tiles are displayed on top of the content. This only works when using the new Compositor API, that is when off-main-thread compositing is activated. OMTC is activated by default on all mobile platforms, and will progressively get activated on desktop platforms (not yet, though). On platforms where OMTC is not used, this pref has no effect. | ||