CSS clip-path button with stepped shape: how to offset drop-shadow only at bottom-right (not full width)?

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Summary

The problem at hand is creating a custom “stepped” button shape using CSS clip-path and adding a localized offset shadow only at the bottom-right corner of the shape, without using wrapper elements and regardless of the background color. The current implementation using filter: drop-shadow() creates a shadow that follows the entire bottom edge of the clipped shape, rather than just the desired corner.

Root Cause

The root cause of this issue is that drop-shadow() is applied to the entire element, and there is no built-in way to selectively apply it to only a part of the element. The clip-path property only affects the visible area of the element, but does not affect the shadow.

Why This Happens in Real Systems

This issue occurs in real systems because:

  • CSS clip-path is used to create complex shapes, but it does not provide a way to control the shadow independently.
  • filter: drop-shadow() is a global property that affects the entire element, making it difficult to achieve localized shadows.
  • The lack of support for wrapper elements and background color limitations add to the complexity of the problem.

Real-World Impact

The real-world impact of this issue is:

  • Limited design flexibility: The inability to create localized shadows limits the design possibilities for custom button shapes.
  • Increased complexity: The need to use alternative solutions, such as additional HTML elements or JavaScript, can add complexity to the code and make it harder to maintain.
  • Compatibility issues: Different browsers may handle clip-path and drop-shadow() differently, leading to compatibility issues.

Example or Code

.button {
  clip-path: polygon(0 20px, 20px 0, 100% 0, 100% 100%, 80px 100%, 60px 80px);
  filter: drop-shadow(10px 10px 0 yellow);
}

This code creates a basic stepped shape using clip-path and applies a drop-shadow() to the entire element.

How Senior Engineers Fix It

Senior engineers can fix this issue by:

  • Using SVG elements to create the custom shape and shadow, allowing for more precise control over the shadow.
  • Utilizing CSS pseudo-elements to create a separate element for the shadow, which can be positioned and styled independently.
  • Employing JavaScript to dynamically create and position the shadow element based on the button’s shape and size.

Why Juniors Miss It

Juniors may miss this issue because:

  • They may not be familiar with the limitations of CSS clip-path and drop-shadow().
  • They may not consider the implications of using filter: drop-shadow() on a clipped element.
  • They may not have experience with alternative solutions, such as SVG or CSS pseudo-elements, and may not know how to apply them to this problem.