Configure compass browser support (Compass 1.x syntax)

Question

With 0.12.x version of Compass, I was defining support for oldies that way:

@import "compass/support"

$legacy-support-for-ie6: false;
$legacy-support-for-ie7: true;
$legacy-support-for-ie8: true;
$legacy-support-for-mozilla: false;

@if ($legacy-support-for-ie7) {
  // specific declaration if ie7 is supported
}

I'm wonder how I should define browser support following Compass 1.x system. Maybe something like that:

// Add support for a specific browser
$browser-minimum-versions: (
  'ie': "7",
  'ie': "8"
);

// Reject browsers
$supported-browsers: reject(browser-versions("ie"), "6", "7", "8");

But it returns that error (running on Compass 1.0.1):

(Line 206 of /Library/Ruby/Gems/2.0.0/gems/compass-core-1.0.1/stylesheets/compass/_support.scss: 5.5 is not known browser.)

Answer 1

Excluding browsers is done by modifying the $graceful-usage-threshold variable. If Browser X only has 4.99% of the market share, you want to set it to 5.

$debug-browser-support: true;
$browser-minimum-versions: (
  "ie": "9"
);
$graceful-usage-threshold: 4.46163;

@import "compass";

.foo {
  @include opacity(.5);
  @include border-radius(10px);
}

Output:

.foo {
  /* Content for ie 8 omitted.
     Minimum support is 9. */
  opacity: 0.5;
  /* Capability border-radius is not prefixed with -moz because 0.25036% of users are affected which is less than the threshold of 4.46163. */
  /* Capability border-radius is not prefixed with -ms because 0% of users are affected which is less than the threshold of 4.46163. */
  /* Capability border-radius is not prefixed with -o because 0% of users are affected which is less than the threshold of 4.46163. */
  /* Capability border-radius is not prefixed with -webkit because 0.1583% of users are affected which is less than the threshold of 4.46163. */
  border-radius: 10px;
}

Note that this causes other minority browsers to be excluded that you may want to support. That's when the $browser-minimum-versions comes into play.

$browser-minimum-versions: (
  "ie": "9",
  "safari": "4"
);

Output:

.foo {
  /* Content for ie 8 omitted.
     Minimum support is 9. */
  opacity: 0.5;
  /* Capability border-radius is not prefixed with -moz because 0.25036% of users are affected which is less than the threshold of 4.46163. */
  /* Capability border-radius is not prefixed with -ms because 0% of users are affected which is less than the threshold of 4.46163. */
  /* Capability border-radius is not prefixed with -o because 0% of users are affected which is less than the threshold of 4.46163. */
  /* Capability border-radius is prefixed with -webkit because safari "4" is required. */
  /* Creating new -webkit context. */
  -webkit-border-radius: 10px;
  border-radius: 10px;
}

There are changes in the works to make it easier to exclude old browsers. You can follow them here: https://github.com/Compass/compass/issues/1762

If you want to make rules for a specific browser, then the $critical-usage-threshold variable comes into play:

$debug-browser-support: true;
$browser-minimum-versions: (
  "ie": "9"
);
$critical-usage-threshold: 4.46163;
$graceful-usage-threshold: 4.46163;

@import "compass";

.foo {
  @include for-legacy-browser('ie', '8') {
    color: green;
    // this is based on $critical-usage-threshold by default
    // if $critical-usage-threshold is lower than the version's usage
    // then this content will be generated
  }
  @if support-legacy-browser('ie', '8') {
    color: red;
  }
}