Input / button elements not shrinking in a flex container

Default form elements behavior in Flexbox

The preloaded width of input elements is influenced by browser stylesheets, prescribing an immutable minimum width. When seated in a flex container, their behaviour becomes counterintuitive due to min-width: auto which automatically sets the minimum content size as the default width of these items.

How to override default width behaviors

To effect a better measure of elasticity in your layout, override these settings:

• Assign each input a min-width: 0 property so they don't respect their default size.
• Deploy width: 100% to fill all available width, or width: 0 combined with flex-grow to enable proportional scaling.

Voila! The application:

input {
  min-width: 0; /* Like when you ignore your daily calorie limit */
  width: 100%; /* "This is a stick-up. Now, hands off all available space!" */
}
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Fine-tuning flex properties

Dictate precise control over your elements' sizing with the glorious trio of flex-grow, flex-shrink, and flex-basis:

• flex-grow: "I ain't small, just tiny till more space comes along."
• flex-shrink: "I am not fat. I am just easy to see."
• flex-basis: Default size, or as elements call it, their "feel-good size."

input {
  flex-grow: 1; /* The Hulk in element form */
  flex-shrink: 2; /* Ant-man, is that you? */
  flex-basis: 0; /* Starts from nothing, open to all possibilities */
}
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Wrapper styling: The tactical cover-up

For all intents and purposes, wrapping input and button elements in divs can be a lifesaver:

• Wrapping works like the older, responsible sibling: takes on all the flex properties leaving the younger ones (input, buttons) shielded.
• It offers consistent styling while the inner input remains oblivious.
• Lets you craft more responsive form fields without creating a DOM battle.

Example of the wrap life:

<div class="input-wrapper">
  <input type="text" />
</div>
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.input-wrapper {
  flex: 1; /* Flex shorthand. Because typing out three properties is just too mainstream */
}
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Addressing browser differences: The diplomatic stance

Despite best efforts, you will encounter browser-specific variations. Some ignore your carefully crafted min-width: 0 or width: 0 rules, while others demand vendor prefixes or more styles for compatibility.

Act diplomatically: use graceful degradation or progressive enhancement to ensure maximum compatibility.

Expanding horizons with the calc() function

In situations that demand more finesse than fixed values offer, CSS's calc() function shines:

• Use calc(100% - Xpx) to craft inputs that liase with sibling elements featuring fixed sizes.
• calc() lets you perform complex calculations, blending percentages, and fixed units for a perfect fit.

input {
  width: calc(100% - 20px); /* "I am 100% - already-occupied-space. Room for all!" */
}
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Wrapping up: flex properties and form elements

Remember these points when dealing with input and button elements in flex containers:

• Apply min-width: 0 or width: 0 to handle non-shrinking issues, like haughty high-borns refusing to look at the ground.
• Tune flex-grow, flex-shrink, and flex-basis properties to your advantage.
• When in doubt, wrap those elements. A little cover-up never hurt anybody.
• Browsers are like people, they don't always agree. Baby steps and diplomacy are your allies.
• Use calc() for complex layouts that require varying widths. It's like a Swiss knife.