The `@font-face` rule allows developers to introduce custom fonts, breaking free from browser defaults and enhancing design flexibility. Its basic syntax includes defining font names, file paths, weight, style, and loading behavior. Modern web pages commonly use WOFF2 and WOFF formats to balance compression and compatibility. Multiple font weights require separate definitions for different variants, while variable fonts enable diverse style control with a single file. Optimization strategies involve the `font-display` property and preloading critical fonts. Practical applications include multilingual support and icon font implementation. Common issues include font flickering and local-first solutions. Performance monitoring can be achieved via JavaScript. Advanced features involve OpenType functionality. When using fonts, special attention must be paid to copyright licensing, with recommended resources like Google Fonts for compliant usage.
Read more
CSS font properties control various aspects of text visual presentation, including font family, size, weight, and style. Proper settings can enhance aesthetics and readability. The font family is defined via `font-family`, allowing multiple fallback options to ensure cross-device compatibility. Font size is recommended to use relative units like `rem`, combined with media queries for responsive adjustments. Font weight and style are controlled by `font-weight` and `font-style`, while line height and spacing impact layout. The shorthand property `font` can set multiple parameters at once. Variable fonts enable multiple variations from a single file. Font loading optimization strategies like `font-display` and preloading improve performance. Multilingual support requires consideration of dedicated fonts. Establishing vertical rhythm involves coordinating font size and line height. Font rendering optimization enhances display across platforms. Responsive typography uses viewport units for smooth scaling. Color selection must meet accessibility contrast requirements. Decorative effects should maintain readability. Performance optimization includes font subsetting and system font stack usage.
Read more
CSS centering layout methods comprehensively cover various scenarios: - **Inline elements horizontal centering**: Achieved by setting `text-align: center` on the parent element. - **Block-level elements**: Require a defined width and `margin: 0 auto`. - **Flexbox layout**: Use `justify-content: center` for more flexibility. - **Vertical centering**: - Single-line text: Use `line-height` equal to the container height. - Absolute positioning with negative margins: Requires known dimensions. - Flexbox: Use `align-items: center`. - **Absolute centering**: Recommended `transform` method, no need to know element dimensions. - **Grid layout**: `place-items: center` for the simplest solution. - **Special scenarios**: - Floating elements require relative positioning. - Table cells use `vertical-align`. - **Responsive design**: Can use viewport units and CSS variables. - **Multiple element alignment**: Flexbox and Grid each have advantages. - **Browser compatibility**: Traditional solutions like `transform` fallbacks for IE should be considered.
Read more
The stacking context is a key concept in CSS that controls the Z-axis stacking order of elements, determining the layering relationship between elements and their children. Various CSS properties can create a stacking context, including `position` with `z-index`, `opacity` less than 1, `transform` with a value other than `none`, `filter` with a value other than `none`, `will-change` specifying relevant properties, `mix-blend-mode` with a value other than `normal`, and `isolation: isolate`. These properties establish an independent stacking environment, confining the stacking scope of child elements. In practical development, stacking contexts are often used to resolve `z-index` conflicts between components, such as controlling the layering of modal dialogs and dropdown menus. However, excessive use may impact performance. Stacking contexts have a nested nature—the stacking order of child elements is only valid within the parent context. During debugging, developer tools can help inspect stacking relationships. Proper use of stacking contexts effectively manages the visual hierarchy of page elements.
Read more
The CSS stacking order determines the display priority of overlapping elements. When z-index is not set, elements are rendered according to the DOM flow, with later elements covering earlier ones. Conditions for creating a stacking context include positioning properties, opacity, transforms, filters, etc. The standard stacking order ranges from backgrounds and borders to elements with positive z-index, arranged sequentially. z-index only takes effect within the same stacking context, and z-index values from different contexts do not affect each other. Special properties like blend modes and isolation can influence stacking behavior. In practice, modal dialogs require proper z-index settings. During rendering, the browser parses the DOM tree and composites layers according to the stacking order. Debugging can be done using developer tools to inspect stacking contexts. Excessive use of z-index can impact performance, so it's advisable to minimize stacking levels and avoid excessively high z-index values.
Read more
The stacking context is a key concept in CSS that controls the display hierarchy of elements. Its formation conditions include the root element, positioning properties combined with z-index, flex children combined with z-index, opacity less than 1, transform properties other than none, etc. The stacking order follows rules ranging from backgrounds to positive z-index values and features nesting, where a child element's z-index is only effective within its parent stacking context. Common issues include z-index failure and opacity unintentionally creating a stacking context. Debugging can be done using browser tools. Performance-wise, excessive stacking contexts can impact rendering efficiency. It interacts with other features like blend modes and filters, and mobile devices may exhibit special behaviors requiring targeted optimization.
Read more
The z-index is a key property in CSS that controls the stacking order of elements, using integer values to determine their display priority. The default value is auto, equivalent to 0, and it only takes effect under specific conditions, such as when the position is not static or when certain CSS properties create a stacking context. The stacking order follows a bottom-to-top rule, including the root element, elements with negative z-index, elements in normal flow, etc. z-index is not inherited, and child elements are only compared within their parent's stacking context. Common issues include z-index not working and unexpected stacking order, with solutions such as checking the position property and adjusting the stacking context. Advanced techniques involve CSS variable management and negative z-index applications. Browser compatibility requires attention to issues like IE6's select element. Performance optimization suggests reducing stacking contexts. Practical examples include navigation menus and image galleries, while debugging can utilize developer tools and temporary borders for visual assistance.
Read more
CSS sticky positioning (`position: sticky`) combines the characteristics of relative and fixed positioning. Before scrolling reaches a specific threshold, the element behaves like a relative position, and then it becomes fixed at that location. This feature is particularly suitable for dynamic fixing scenarios like navigation bars and table of contents. The basic syntax requires specifying a threshold and positioning relative to the nearest scrolling ancestor. Practical applications include fixed top navigation bars and table header fixation. Advanced techniques involve multi-level sticky positioning and dynamic thresholds. Common issues include failure due to parent container overflow (`overflow: hidden`) and performance optimization considerations. In terms of browser compatibility, modern browsers generally support it, but older versions may require prefixes. It can also interact with JavaScript to enable state detection and class name toggling. Creative uses include progressive fixing and parallax effects. For responsive design, different screen sizes must be considered. Accessibility requires ensuring content isn’t obscured and providing skip options.
Read more
Fixed positioning is an important method in CSS that positions elements relative to the viewport, keeping them in place while scrolling. Elements with fixed positioning are removed from the document flow and do not affect the layout of other elements. When an ancestor element has properties like `transform` applied, the positioning reference becomes that ancestor. On mobile browsers, fixed positioning may behave differently due to virtual keyboard pop-ups. Fixed positioning creates a new stacking context, where `z-index` values are effective within that context. Overusing fixed positioning can impact page performance, especially on low-end devices. When fixed elements are inside scrollable containers, their behavior may not match expectations. In print stylesheets, fixed elements behave similarly to absolutely positioned ones. Dynamic content changes require consideration of potential overlaps with fixed elements. In modern front-end frameworks like React, special handling (e.g., portals) may be needed for fixed positioning. CSS variables can be combined with fixed positioning to create flexible layouts. In responsive design, fixed elements may need adjustments based on screen size. Fixed positioning is often used for scroll-based interactions, such as hide/show effects. Complex layouts with multiple fixed elements may lead to stacking conflicts. Combining fixed positioning with CSS animations can create visual effects but requires performance awareness. Accessibility must be considered to ensure keyboard users can access all content. Fixed positioning is commonly paired with viewport units for full-screen effects or scroll-driven animations like parallax. Despite being out of the document flow, fixed elements can still interact with Grid and Flexbox layouts. Forms with fixed positioning require special attention to mobile keyboard behavior. Browser support for fixed positioning varies, requiring testing and fallback solutions.
Read more
Absolute positioning is a layout method in CSS achieved through `position: absolute`, which removes the element from the document flow and positions it relative to the nearest positioned ancestor. If no positioned ancestor exists, it is positioned relative to the initial containing block (typically the viewport). The positioning reference is determined by the nearest ancestor with `relative`, `absolute`, `fixed`, or `sticky` positioning. The `transform` property can also create a new positioning reference. Absolute positioning is commonly used for overlays, tooltips, etc. In responsive design, careful consideration is needed when selecting the positioning reference, and `z-index` is often used to control stacking order. Overuse of absolute positioning may impact performance, especially in scenarios involving animations or frequent reflows, as the browser must continuously recalculate the element's position.
Read more
