April 2025
Intermediate to advanced
1128 pages
32h 5m
Portuguese (Portugal, Brazil)
Content preview from CSS: O Guia Definitivo, 5ª Edição
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Capítulo 21. CSS At-Rules
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Durante 20 capítulos, explorámos as propriedades, valores e selectores que podem ser combinados para criar regras CSS. Estas são o que podemos chamar de regras normais ou regras regulares, e são poderosas, mas por vezes é necessário mais. Por vezes, é necessária uma forma de encapsular determinados estilos em blocos condicionais, de modo a que os estilos possam ser aplicados a determinadas larguras de página ou apenas se uma determinada caraterística CSS for reconhecida pelo browser que processa a folha de estilos.
Estas estão quase invariavelmente incluídas em regras at, assim chamadas porque começam com um símbolo at (@). Já viste algumas destas regras em capítulos anteriores, como @font-face e @counter-style, mas ainda há mais que não estão tão delimitadas a especificidades de estilo. Este capítulo explora as três poderosas regras at @media, @container, e @supports.
Consultas multimédia
Graças aos mecanismos definidos em HTML e CSS, denominados media queries, é possível restringir qualquer conjunto de estilos (incluindo folhas de estilo inteiras) a um meio específico, como o ecrã ou a impressão, e a um conjunto específico de condições de meios. Estes mecanismos permitem-te definir uma combinação de tipos de meios e condições, como o tamanho do ecrã ou a profundidade da cor, para dar dois exemplos. Abordaremos a forma básica antes ...
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