Why does CSS not support negative padding

Question

I have seen this many a times that the prospect of a negative padding might help the development of CSS of certain page elements become better and easier  Yet  there is no provision for a negative padding in the W3C CSS  What is the reason behind this  Is there any obstruction to the property that prevents it s use as such  Thanks for your answers   UPDATE As I see  for example  in case you are using a font that has something  say  a 20px of vertical spacing  and you wish to apply a dashed border to the bottom of the font  say when a hyperlink appears  In such cases you ll find the style to be way too shabby  as the dashed border will appear 20px below the specified word  if you use negative margin  it s not going to work  as margin alters the area outside borders  Negative padding might help in such situations

User · Answer

This could help  by the way   The box-sizing CSS property is used to alter the default CSS box model used to calculate widths and heights of elements   http   www w3 org TR css3-ui  box-sizing  https   developer mozilla org En CSS Box-sizing

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You asked WHY  not how to cheat it   Usually because of laziness of programmers of the initial implementation  because they HAVE already put way more effort in other features  delivering more odd side-effects like floats  because they were more requested by designers back then and yet they haven t taken the time to allow this so we can use the FOUR properties to push pull an element against its neighbors  now we only have four to push  and only 2 to pull    When html was designed  magazines loved text reflown around images back then  now hated because today we have touch trends  and love squary things with lots of space and nothing to read  That s why they put more pressure on floats than on centering  or they could have designed something like margin-top  fill  or margin  average 0  to simply align the content to the bottom  or distribute its extra space around   In this case I think it hasn t been implemented because of the same reason that makes CSS to lack of a  parent pseudo-selector  To prevent looping evaluations   Without being an engineer  I can see that CSS right now is made to paint elements once  remember some properties for future elements to be painted  but NEVER going back to already-painted elements   That s why  I guess  padding is calculated on the width  because that s the value that was available at the time of starting to paint it   If you had a negative value for padding  it would affect the outer limits  which has ALREADY been defined when the margin has already been set  I know  nothing has been painted yet  but when you read how the painting process goes  created by geniuses with 90 s technology  I feel like I am asking dumb questions and just say  thanks  hehe   One of the requirements of web pages is that they are quickly available  unlike an app that can take its time and eat the computer resources to get everything correct before displaying it  web pages need to use little resources  so they are fit in every device possible  and be scrolled in a breeze   If you see applications with complex reflowing and positioning  like InDesign  you can t scroll that fast  It takes a big effort both from processors and graphic card to jump to next pages   So painting and calculating forward and forgetting about an element once drawn  for now it seems to be a MUST

User · Answer

Padding by definition is a positive integer  including 0    Negative padding would cause the border to collapse into the content  see the box-model page on w3  - this would make the content area smaller than the content  which doesn t make sense

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Because the designers of CSS didn t have the foresight to imagine the flexibility this would bring  There are plenty of reasons to expand the content area of a box without affecting its relationship to neighbouring elements  If you think it s not possible  put some long nowrap d text in a box  set a width on the box  and watch how the overflowed content does nothing to the layout   Yes  this is still relevant with CSS3 in 2019  case in point  flexbox layouts  Flexbox items  margins do not collapse  so in order to space them evenly and align them with the visual edge of the container  one must subtract the items  margins from their container s padding  If any result is  lt  0  you must use a negative margin on the container  or sum that negative with the existing margin  I e  the content of the element effects how one defines the margins for it  which is backwards  Summing doesn t work cleanly when flex elements  content have margins defined in different units or are affected by a different font-size  etc   The example below should  ideally have aligned and evenly spaced grey boxes but  sadly they aren t    x000D   x000D  body   x000D    font-family  sans-serif  x000D    margin  2rem  x000D    x000D  body  gt      x000D    margin  2rem 0 0  x000D    x000D  body  gt   first-child   x000D    margin-top  0  x000D    x000D  h1  x000D  li  x000D  p   x000D    padding  10px  x000D    background  lightgray  x000D    x000D  ul   x000D    list-style  none  x000D    display  flex  x000D    flex-wrap  wrap  x000D    padding  0    just to reset    x000D    padding  -5px    would allow correct alignment    x000D    x000D  li   x000D    flex  1 1 auto  x000D    margin  5px  x000D    x000D   lt h1 gt Cras facilisis orci ligula lt  h1 gt  x000D   x000D   lt ul gt  x000D     lt li gt a lacinia purus porttitor eget lt  li gt  x000D     lt li gt donec ut nunc lorem lt  li gt  x000D     lt li gt duis in est dictum lt  li gt  x000D     lt li gt tempor metus non lt  li gt  x000D     lt li gt dapibus sapien lt  li gt  x000D     lt li gt phasellus bibendum tincidunt lt  li gt  x000D     lt li gt quam vitae accumsan lt  li gt  x000D     lt li gt ut interdum eget nisl in eleifend lt  li gt  x000D     lt li gt maecenas sodales interdum quam sed accumsan lt  li gt  x000D   lt  ul gt  x000D   x000D   lt p gt Fusce convallis  arcu vel elementum pulvinar  diam arcu tempus dolor  nec venenatis sapien diam non dui  Nulla mollis velit dapibus magna pellentesque  at tempor sapien blandit  Sed consectetur nec orci ac lobortis  lt  p gt  x000D   x000D   lt p gt Integer nibh purus  convallis eget tincidunt id  eleifend id lectus  Vivamus tristique orci finibus  feugiat eros id  semper augue  lt  p gt  x000D   x000D   x000D    I have encountered enough of these little issues over the years where a little negative padding would have gone a long way  but instead I m forced to add non-semantic markup  use calc    or CSS preprocessors which only work when the units are the same  etc

User · Answer

I would like to describe a very good example of why negative padding would be useful and awesome   As all of us CSS developers know  vertically aligning a dynamically sizing div within another is a hassle  and for the most part  viewed as being impossible only using CSS  The incorporation of negative padding could change this   Please review the following HTML    lt div style  height 600px  width 100    gt       lt div class  vertical-align  style  width 100  height auto    gt          This DIV s height will change based the width of the screen       lt  div gt   lt  div gt    With the following CSS  we would be able to vertically center the content of the inner div within the outer div    vertical-align       position  absolute      top 50       padding-top -50       overflow  visible      Allow me to explain     Absolutely positioning the inner div s top at 50  places the top edge of the inner div at the center of the outer div  Pretty simple  This is because percentage based positioning is relative to the inner dimensions of the parent element   Percentage based padding  on the other hand  is based on the inner dimensions of the targeted element  So  by applying the property of padding-top  -50   we have shifted the content of the inner div upward by a distance of 50  of the height of the inner div s content  therefore centering the inner div s content within the outer div and still allowing the height dimension of the inner div to be dynamic   If you ask me OP  this would be the best use-case  and I think it should be implemented just so I can do this hack  lol  Or  they should just fix the functionality of vertical-align and give us a version of vertical-align that works on all elements

User · Answer

Fitting an Iframe inside containers will not match the size of the container   It adds about 20px of padding   Currently there is no easy way to fix this   You need javascript  http   css-tricks com snippets jquery fit-iframe-to-content    Negative margins would be an easy solution

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I recently answered a different question where I discussed why the box model is the way it is   There are specific reasons for each part of the box model  Padding is meant to extend the background beyond its contents  If you need to shrink the background of the container  you should make the parent container the correct size and give the child element some negative margins  In this case the content is not being padded  it s overflowing

[html] Why does CSS not support negative padding?

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