Aggregation relationship in html and css jon

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aggregation relationship in html and css jon

Could be as simple as one object is calling a method of another object. Aggregation. Objects being made of other objects. Known as the "Has-A" relationship. Jonathan Marsh, Microsoft Corporation Relationship to HTML and CSS The association of elements in the source tree to flow objects is. Join jon snow on Treehouse today to learn web design, web development, and iOS development. CSS. 0 pts. Achievements. 0 pts. Forum. •. 0. HTML. 0 pts. Achievements. 0 pts. Forum. Points are earned whenever you take an important action on Treehouse. Table Relationships Aggregate and Numeric Functions .

This example applies to a para element that has a appendix ancestor, and also has a changed descendant. In this case, these elements match exactly one element in the source element hierarchy. The following pattern matches elements that have a grandparent of type data-samples, regardless of the type of the target element or the parent element. Attributes Attributes on the source element or any of its ancestor or descendant elements can also be used to determine whether a particular construction rule applies.

The attribute element is included in an element or target-element element to test the value of a source attribute. The following example matches an item element that has for its parent a list element whose liststyle attribute has the value enum: When the has-value attribute has the value yes, a source element matches the pattern when the attribute in question has been given a value in the source either by an explicit assignment or by receiving a default value.

aggregation relationship in html and css jon

When the has-value attribute has the value no, a source element matches the pattern when the default value of the source attribute is IMPLIED and the source attribute has no explicit assignment.

If the value attribute has been assigned, the has-value attribute is ignored. The following example matches an item element that has for its parent a list element whose compact attribute has some value as opposed to being left unassigned and implied: This is done using an id element, with an attribute attribute specifying the name of the attribute that should be in the id category. The following would put a name attribute on any element in the id category.

This will match a source element that has an attribute in the id category with the same value. In a stylesheet a class element is used to declare the name of an attribute that should be in the class category. For example, the following would put a family attribute on any element in the class category: This will match a source element that has an attribute in the class category with the same value.

Qualifiers There are two qualifiers, position and only, each expressed as an attribute on the element and target-element elements. The position qualifier specifies the position of an element among its siblings.

The values of the position qualifier are: The element must be the first sibling of its type.

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The element must be the last sibling of its type. The element must be the first sibling of any type. The element must be the last sibling of any type. The only qualifier specifies whether the source element has any siblings or not. The element must have no element siblings of the same type. The element must have no element siblings at all. The following pattern matches the first item in a list: Conflicts It is possible for a source element to match patterns in several different rules.

XSL has an algorithm for determining which rules should be invoked in this situation. It also allows the stylesheet to override this by specifying importance and priority attributes on the rule and style-rule elements. When an element matches more than one pattern, then the most specific pattern will be used. The precedence order for establishing the most specific pattern is: For construction rules, it is an error if, for any source element, there is not a unique matching pattern that is more specific than all other matching patterns.

Overview When the rule that is to be applied to the source element has been identified, the action part of the rule is invoked. The structure of the elements comprising the action represents the structure of flow objects to create. Flow object elements may be combined with literal text which generates character flow objects and programmatically generated text eval element to create a flow object sub-tree.

Characteristics as Attributes The characteristics of the flow objects are applied as attributes of the element representing the flow object. All attributes of flow object elements are of type string. Selection within an Action Selection within an action controls which source elements are processed after a rule fires. There are two elements used, the children element and the select element. The children element processes the immediate children of the source element while the select element processes either the children or the descendants of the source element, and provides powerful filtering through the use of patterns.

This example creates a display-group for a chapter element and then processes its immediate children. The above example could also be written using the select element with the from attribute set to children. The values of the from attribute are: The children of the element are processed, the default. The descendants of the element are processed.

The select element, by default, processes the immediate children of the source element. To process all of the descendants of the source element the from attribute can be set to descendants. This example processes all of the heading elements contained in the book element.

Filters can be added to the select element to further control which elements are processed. Only elements that match the filter pattern are processed. The filter pattern uses the same syntax as the pattern part of the rule. In this example, after creating a paragraph for the employee element, the exempt children are selected for processing.

Multiple children or select elements can be used within a single action to do simple reordering. Getting Started Before we start throwing ems around a stylesheet, we need to know what the default font size is in the browser. All popular browsers have a default font size of 16px.

aggregation relationship in html and css jon

So, before a single CSS selector is written, the browser has a 16px deafult font size. We can now specify any element size we need to using ems! Both have merit, but it seems more logical to me to leave it at the browser default and change it for child elements if necessary.

So, we know that the body font size will be 16px by default. We also know that if a person has changed their settings, our elastic interface will not break, but adjust. Perfect, so we can set: So another selector is needed to get IE to behave: IE will now behave and resize text gracefully, rather than in mighty leaps of stupefying grandeur. Our initial CSS ends up like this: Keep a calculator handy.

aggregation relationship in html and css jon

I am no maths wizard, so I needed a simple formula to remember. I calculate what 1px is in ems and multiple by the pixel size I need. That gives me the equivalent em value. We know that 1em is always equal to the font size of the parent element, therefore: Pixel to ems conversion table for font sizes.

aggregation relationship in html and css jon

Building an Elastic Container: What is px in ems? Set a px width in ems for our layer: So we can calculate what 1px is in ems: Ems allow only three decimal places. More is fine in calculations but before writing CSS, round it up to three. Then multiply by to get ems: Find 1px is in ems for that element.

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Multiple that by the pixel value you require to get the em equivalent. Apply the width in ems, center the layer in the viewport using the auto left and right margins, give it a 1px gray border with a white background and align the text left: While we're here, we might as well add some typographic goodness by selecting a basic leading and adding some vertical rhythmwith everything expressed in ems. It is expressed in CSS as line-height but instead of adding space below, it increases the space above and below each line of text.

The heading font size will be 18px. The paragraph font size will be 12px with an 18px line height. Everything else will be proportional to that. A note on CSS inheritance: Set a 12px font size with 18px line height and margin for paragraphs: From our previous calculation, we already know that 1px is 0. We simply multiple that by 12 to get the em value for 12px: To calculate the desired line height and margin of 18px for our basic leading we do the following: In this example, the line height is 1 and a half times the font size: Add line height and margin properties to the CSS: