Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1317 insertions, 0 deletions

diff --git a/layout/style/test/flexbox_layout_testcases.js b/layout/style/test/flexbox_layout_testcases.js
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+++ b/layout/style/test/flexbox_layout_testcases.js
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+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 sw=2 sts=2 et: */
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * For the purposes of this test, flex items are specified as a hash with a
+ * hash-entry for each CSS property that is to be set.  In these per-property
+ * entries, the key is the property-name, and the value can be either of the
+ * following:
+ *  (a) the property's specified value (which indicates that we don't need to
+ *      bother checking the computed value of this particular property)
+ *  ...OR...
+ *  (b) an array with 2-3 entries...
+ *        [specifiedValue, expectedComputedValue (, epsilon) ]
+ *      ...which indicates that the property's computed value should be
+ *      checked.  The array's first entry (for the specified value) may be
+ *      null; this means that no value should be explicitly specified for this
+ *      property. The second entry is the property's expected computed
+ *      value. The third (optional) entry is an epsilon value, which allows for
+ *      fuzzy equality when testing the computed value.
+ *
+ * To allow these testcases to be re-used in both horizontal and vertical
+ * flex containers, we specify "width"/"min-width"/etc. using the aliases
+ * "_main-size", "_min-main-size", etc.  The test code can map these
+ * placeholder names to their corresponding property-names using the maps
+ * defined below -- gRowPropertyMapping, gColumnPropertyMapping, etc.
+ *
+ * If the testcase needs to customize its flex container at all (e.g. by
+ * specifying a custom container-size), it can do so by including a hash
+ * called "container_properties", with propertyName:propertyValue mappings.
+ * (This hash can use aliased property-names like "_main-size" as well.)
+ */
+
+// The standard main-size we'll use for our flex container when setting up
+// the testcases defined below:
+var gDefaultFlexContainerSize = "200px";
+
+// Left-to-right versions of placeholder property-names used in
+// testcases below:
+var gRowPropertyMapping = {
+  "_main-size": "width",
+  "_min-main-size": "min-width",
+  "_max-main-size": "max-width",
+  "_border-main-start-width": "border-left-width",
+  "_border-main-end-width": "border-right-width",
+  "_padding-main-start": "padding-left",
+  "_padding-main-end": "padding-right",
+  "_margin-main-start": "margin-left",
+  "_margin-main-end": "margin-right",
+};
+
+// Right-to-left versions of placeholder property-names used in
+// testcases below:
+var gRowReversePropertyMapping = {
+  "_main-size": "width",
+  "_min-main-size": "min-width",
+  "_max-main-size": "max-width",
+  "_border-main-start-width": "border-right-width",
+  "_border-main-end-width": "border-left-width",
+  "_padding-main-start": "padding-right",
+  "_padding-main-end": "padding-left",
+  "_margin-main-start": "margin-right",
+  "_margin-main-end": "margin-left",
+};
+
+// Top-to-bottom versions of placeholder property-names used in
+// testcases below:
+var gColumnPropertyMapping = {
+  "_main-size": "height",
+  "_min-main-size": "min-height",
+  "_max-main-size": "max-height",
+  "_border-main-start-width": "border-top-width",
+  "_border-main-end-width": "border-bottom-width",
+  "_padding-main-start": "padding-top",
+  "_padding-main-end": "padding-bottom",
+  "_margin-main-start": "margin-top",
+  "_margin-main-end": "margin-bottom",
+};
+
+// Bottom-to-top versions of placeholder property-names used in
+// testcases below:
+var gColumnReversePropertyMapping = {
+  "_main-size": "height",
+  "_min-main-size": "min-height",
+  "_max-main-size": "max-height",
+  "_border-main-start-width": "border-bottom-width",
+  "_border-main-end-width": "border-top-width",
+  "_padding-main-start": "padding-bottom",
+  "_padding-main-end": "padding-top",
+  "_margin-main-start": "margin-bottom",
+  "_margin-main-end": "margin-top",
+};
+
+// The list of actual testcase definitions:
+var gFlexboxTestcases = [
+  // No flex properties specified --> should just use 'width' for sizing
+  {
+    items: [
+      { "_main-size": ["40px", "40px"] },
+      { "_main-size": ["65px", "65px"] },
+    ],
+  },
+  // flex-basis is specified:
+  {
+    items: [
+      { "flex-basis": "50px", "_main-size": [null, "50px"] },
+      {
+        "flex-basis": "20px",
+        "_main-size": [null, "20px"],
+      },
+    ],
+  },
+  // flex-basis is *large* -- sum of flex-basis values is > flex container size:
+  // (w/ 0 flex-shrink so we don't shrink):
+  {
+    items: [
+      {
+        flex: "0 0 150px",
+        "_main-size": [null, "150px"],
+      },
+      {
+        flex: "0 0 90px",
+        "_main-size": [null, "90px"],
+      },
+    ],
+  },
+  // flex-basis is *large* -- each flex-basis value is > flex container size:
+  // (w/ 0 flex-shrink so we don't shrink):
+  {
+    items: [
+      {
+        flex: "0 0 250px",
+        "_main-size": [null, "250px"],
+      },
+      {
+        flex: "0 0 400px",
+        "_main-size": [null, "400px"],
+      },
+    ],
+  },
+  // flex-basis has percentage value:
+  {
+    items: [
+      {
+        "flex-basis": "30%",
+        "_main-size": [null, "60px"],
+      },
+      {
+        "flex-basis": "45%",
+        "_main-size": [null, "90px"],
+      },
+    ],
+  },
+  // flex-basis has calc(percentage) value:
+  {
+    items: [
+      {
+        "flex-basis": "calc(20%)",
+        "_main-size": [null, "40px"],
+      },
+      {
+        "flex-basis": "calc(80%)",
+        "_main-size": [null, "160px"],
+      },
+    ],
+  },
+  // flex-basis has calc(percentage +/- length) value:
+  {
+    items: [
+      {
+        "flex-basis": "calc(10px + 20%)",
+        "_main-size": [null, "50px"],
+      },
+      {
+        "flex-basis": "calc(60% - 1px)",
+        "_main-size": [null, "119px"],
+      },
+    ],
+  },
+  // flex-grow is specified:
+  {
+    items: [
+      {
+        flex: "1",
+        "_main-size": [null, "60px"],
+      },
+      {
+        flex: "2",
+        "_main-size": [null, "120px"],
+      },
+      {
+        flex: "0 20px",
+        "_main-size": [null, "20px"],
+      },
+    ],
+  },
+  // Same ratio as prev. testcase; making sure we handle float inaccuracy
+  {
+    items: [
+      {
+        flex: "100000",
+        "_main-size": [null, "60px"],
+      },
+      {
+        flex: "200000",
+        "_main-size": [null, "120px"],
+      },
+      {
+        flex: "0.000001 20px",
+        "_main-size": [null, "20px"],
+      },
+    ],
+  },
+  // Same ratio as prev. testcase, but with items cycled and w/
+  // "flex: none" & explicit size instead of "flex: 0 20px"
+  {
+    items: [
+      {
+        flex: "none",
+        "_main-size": ["20px", "20px"],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "60px"],
+      },
+      {
+        flex: "2",
+        "_main-size": [null, "120px"],
+      },
+    ],
+  },
+
+  // ...and now with flex-grow:[huge] to be sure we handle infinite float values
+  // gracefully.
+  {
+    items: [
+      {
+        flex: "9999999999999999999999999999999999999999999999999999999",
+        "_main-size": [null, "200px"],
+      },
+    ],
+  },
+  {
+    items: [
+      {
+        flex: "9999999999999999999999999999999999999999999999999999999",
+        "_main-size": [null, "50px"],
+      },
+      {
+        flex: "9999999999999999999999999999999999999999999999999999999",
+        "_main-size": [null, "50px"],
+      },
+      {
+        flex: "9999999999999999999999999999999999999999999999999999999",
+        "_main-size": [null, "50px"],
+      },
+      {
+        flex: "9999999999999999999999999999999999999999999999999999999",
+        "_main-size": [null, "50px"],
+      },
+    ],
+  },
+  {
+    items: [
+      {
+        flex: "99999999999999999999999999999999999",
+        "_main-size": [null, "50px"],
+      },
+      {
+        flex: "99999999999999999999999999999999999",
+        "_main-size": [null, "50px"],
+      },
+      {
+        flex: "99999999999999999999999999999999999",
+        "_main-size": [null, "50px"],
+      },
+      {
+        flex: "99999999999999999999999999999999999",
+        "_main-size": [null, "50px"],
+      },
+    ],
+  },
+
+  // And now, some testcases to check that we handle float accumulation error
+  // gracefully.
+
+  // First, a testcase with just a custom-sized huge container, to be sure we'll
+  // be able to handle content on that scale, in the subsequent more-complex
+  // testcases:
+  {
+    container_properties: {
+      "_main-size": "9000000px",
+    },
+    items: [
+      {
+        flex: "1",
+        "_main-size": [null, "9000000px"],
+      },
+    ],
+  },
+  // ...and now with two flex items dividing up that container's huge size:
+  {
+    container_properties: {
+      "_main-size": "9000000px",
+    },
+    items: [
+      {
+        flex: "2",
+        "_main-size": [null, "6000000px"],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "3000000px"],
+      },
+    ],
+  },
+
+  // OK, now to actually test accumulation error. Below, we have six flex items
+  // splitting up the container's size, with huge differences between flex
+  // weights.  For simplicity, I've set up the weights so that they sum exactly
+  // to the container's size in px. So 1 unit of flex *should* get you 1px.
+  //
+  // NOTE: The expected computed "_main-size" values for the flex items below
+  // appear to add up to more than their container's size, which would suggest
+  // that they overflow their container unnecessarily. But they don't actually
+  // overflow -- this discrepancy is simply because Gecko's code for reporting
+  // computed-sizes rounds to 6 significant figures (in particular, the method
+  // (nsTSubstring_CharT::AppendFloat() does this).  Internally, in app-units,
+  // the child frames' main-sizes add up exactly to the container's main-size,
+  // as you'd hope & expect.
+  {
+    container_properties: {
+      "_main-size": "9000000px",
+    },
+    items: [
+      {
+        flex: "3000000",
+        "_main-size": [null, "3000000px"],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "1px"],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "1px"],
+      },
+      {
+        flex: "2999999",
+        // NOTE: Expected value is off slightly, from float error when
+        // resolving flexible lengths & when generating computed value string:
+        "_main-size": [null, "3000000px"],
+      },
+      {
+        flex: "2999998",
+        // NOTE: Expected value is off slightly, from float error when
+        // resolving flexible lengths & when generating computed value string:
+        "_main-size": [null, "3000000px"],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "1px", 0.2],
+      },
+    ],
+  },
+  // Same flex items as previous testcase, but now reordered such that the items
+  // with tiny flex weights are all listed last:
+  {
+    container_properties: {
+      "_main-size": "9000000px",
+    },
+    items: [
+      {
+        flex: "3000000",
+        "_main-size": [null, "3000000px"],
+      },
+      {
+        flex: "2999999",
+        // NOTE: Expected value is off slightly, from float error when
+        // resolving flexible lengths & when generating computed value string:
+        "_main-size": [null, "3000000px"],
+      },
+      {
+        flex: "2999998",
+        // NOTE: Expected value is off slightly, from float error when
+        // resolving flexible lengths & when generating computed value string:
+        "_main-size": [null, "3000000px"],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "1px", 0.2],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "1px", 0.2],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "1px", 0.2],
+      },
+    ],
+  },
+  // Same flex items as previous testcase, but now reordered such that the items
+  // with tiny flex weights are all listed first:
+  {
+    container_properties: {
+      "_main-size": "9000000px",
+    },
+    items: [
+      {
+        flex: "1",
+        // NOTE: Expected value is off slightly, from float error when
+        // resolving flexible lengths:
+        "_main-size": [null, "1px", 0.2],
+      },
+      {
+        flex: "1",
+        // NOTE: Expected value is off slightly, from float error when
+        // resolving flexible lengths:
+        "_main-size": [null, "1px", 0.2],
+      },
+      {
+        flex: "1",
+        // NOTE: Expected value is off slightly, from float error when
+        // resolving flexible lengths:
+        "_main-size": [null, "1px", 0.2],
+      },
+      {
+        flex: "3000000",
+        "_main-size": [null, "3000000px"],
+      },
+      {
+        flex: "2999999",
+        // NOTE: Expected value is off slightly, from float error when
+        // resolving flexible lengths & when generating computed value string:
+        "_main-size": [null, "3000000px"],
+      },
+      {
+        flex: "2999998",
+        // NOTE: Expected value is off slightly, from float error when
+        // resolving flexible lengths & when generating computed value string:
+        "_main-size": [null, "3000000px"],
+      },
+    ],
+  },
+
+  // Trying "flex: auto" (== "1 1 auto") w/ a mix of flex-grow/flex-basis values
+  {
+    items: [
+      {
+        flex: "auto",
+        "_main-size": [null, "45px"],
+      },
+      {
+        flex: "2",
+        "_main-size": [null, "90px"],
+      },
+      {
+        flex: "20px 1 0",
+        "_main-size": [null, "65px"],
+      },
+    ],
+  },
+  // Same as previous, but with items cycled & different syntax
+  {
+    items: [
+      {
+        flex: "20px",
+        "_main-size": [null, "65px"],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "45px"],
+      },
+      {
+        flex: "2",
+        "_main-size": [null, "90px"],
+      },
+    ],
+  },
+  {
+    items: [
+      {
+        flex: "2",
+        "_main-size": [null, "100px"],
+        border: "0px dashed",
+        "_border-main-start-width": ["5px", "5px"],
+        "_border-main-end-width": ["15px", "15px"],
+        "_margin-main-start": ["22px", "22px"],
+        "_margin-main-end": ["8px", "8px"],
+      },
+      {
+        flex: "1",
+        "_main-size": [null, "50px"],
+        "_margin-main-start": ["auto", "0px"],
+        "_padding-main-end": ["auto", "0px"],
+      },
+    ],
+  },
+  // Test negative flexibility:
+
+  // Basic testcase: just 1 item (relying on initial "flex-shrink: 1") --
+  // should shrink to container size.
+  {
+    items: [{ "_main-size": ["400px", "200px"] }],
+  },
+  // ...and now with a "flex" specification and a different flex-shrink value:
+  {
+    items: [
+      {
+        flex: "4 2 250px",
+        "_main-size": [null, "200px"],
+      },
+    ],
+  },
+  // ...and now with multiple items, which all shrink proportionally (by 50%)
+  // to fit to the container, since they have the same (initial) flex-shrink val
+  {
+    items: [
+      { "_main-size": ["80px", "40px"] },
+      { "_main-size": ["40px", "20px"] },
+      { "_main-size": ["30px", "15px"] },
+      { "_main-size": ["250px", "125px"] },
+    ],
+  },
+  // ...and now with positive flexibility specified. (should have no effect, so
+  // everything still shrinks by the same proportion, since the flex-shrink
+  // values are all the same).
+  {
+    items: [
+      {
+        flex: "4 3 100px",
+        "_main-size": [null, "80px"],
+      },
+      {
+        flex: "5 3 50px",
+        "_main-size": [null, "40px"],
+      },
+      {
+        flex: "0 3 100px",
+        "_main-size": [null, "80px"],
+      },
+    ],
+  },
+  // ...and now with *different* flex-shrink values:
+  {
+    items: [
+      {
+        flex: "4 2 50px",
+        "_main-size": [null, "30px"],
+      },
+      {
+        flex: "5 3 50px",
+        "_main-size": [null, "20px"],
+      },
+      {
+        flex: "0 0 150px",
+        "_main-size": [null, "150px"],
+      },
+    ],
+  },
+  // Same ratio as prev. testcase; making sure we handle float inaccuracy
+  {
+    items: [
+      {
+        flex: "4 20000000 50px",
+        "_main-size": [null, "30px"],
+      },
+      {
+        flex: "5 30000000 50px",
+        "_main-size": [null, "20px"],
+      },
+      {
+        flex: "0 0.0000001 150px",
+        "_main-size": [null, "150px"],
+      },
+    ],
+  },
+  // Another "different flex-shrink values" testcase:
+  {
+    items: [
+      {
+        flex: "4 2 115px",
+        "_main-size": [null, "69px"],
+      },
+      {
+        flex: "5 1 150px",
+        "_main-size": [null, "120px"],
+      },
+      {
+        flex: "1 4 30px",
+        "_main-size": [null, "6px"],
+      },
+      {
+        flex: "1 0 5px",
+        "_main-size": [null, "5px"],
+      },
+    ],
+  },
+
+  // ...and now with min-size (clamping the effects of flex-shrink on one item):
+  {
+    items: [
+      {
+        flex: "4 5 75px",
+        "_min-main-size": "50px",
+        "_main-size": [null, "50px"],
+      },
+      {
+        flex: "5 5 100px",
+        "_main-size": [null, "62.5px"],
+      },
+      {
+        flex: "0 4 125px",
+        "_main-size": [null, "87.5px"],
+      },
+    ],
+  },
+
+  // Test a min-size that's much larger than initial preferred size, but small
+  // enough that our flexed size pushes us over it:
+  {
+    items: [
+      {
+        flex: "auto",
+        "_min-main-size": "110px",
+        "_main-size": ["50px", "125px"],
+      },
+      {
+        flex: "auto",
+        "_main-size": [null, "75px"],
+      },
+    ],
+  },
+
+  // Test a min-size that's much larger than initial preferred size, and is
+  // even larger than our positively-flexed size, so that we have to increase it
+  // (as a 'min violation') after we've flexed.
+  {
+    items: [
+      {
+        flex: "auto",
+        "_min-main-size": "150px",
+        "_main-size": ["50px", "150px"],
+      },
+      {
+        flex: "auto",
+        "_main-size": [null, "50px"],
+      },
+    ],
+  },
+
+  // Test min-size on multiple items simultaneously:
+  {
+    items: [
+      {
+        flex: "auto",
+        "_min-main-size": "20px",
+        "_main-size": [null, "20px"],
+      },
+      {
+        flex: "9 auto",
+        "_min-main-size": "150px",
+        "_main-size": ["50px", "180px"],
+      },
+    ],
+  },
+  {
+    items: [
+      {
+        flex: "1 1 0px",
+        "_min-main-size": "90px",
+        "_main-size": [null, "90px"],
+      },
+      {
+        flex: "1 1 0px",
+        "_min-main-size": "80px",
+        "_main-size": [null, "80px"],
+      },
+      {
+        flex: "1 1 40px",
+        "_main-size": [null, "30px"],
+      },
+    ],
+  },
+
+  // Test a case where _min-main-size will be violated on different items in
+  // successive iterations of the "resolve the flexible lengths" loop
+  {
+    items: [
+      {
+        flex: "1 2 100px",
+        "_min-main-size": "90px",
+        "_main-size": [null, "90px"],
+      },
+      {
+        flex: "1 1 100px",
+        "_min-main-size": "70px",
+        "_main-size": [null, "70px"],
+      },
+      {
+        flex: "1 1 100px",
+        "_main-size": [null, "40px"],
+      },
+    ],
+  },
+
+  // Test some cases that have a min-size violation on one item and a
+  // max-size violation on another:
+
+  // Here, both items initially grow to 100px. That violates both
+  // items' sizing constraints (it's smaller than the min-size and larger than
+  // the max-size), so we clamp both of them and sum the clamping-differences:
+  //
+  //   (130px - 100px) + (50px - 100px) = (30px) + (-50px) = -20px
+  //
+  // This sum is negative, so (per spec) we freeze the item that had its
+  // max-size violated (the second one) and restart the algorithm.  This time,
+  // all the available space (200px - 50px = 150px) goes to the not-yet-frozen
+  // first item, and that puts it above its min-size, so all is well.
+  {
+    items: [
+      {
+        flex: "auto",
+        "_min-main-size": "130px",
+        "_main-size": [null, "150px"],
+      },
+      {
+        flex: "auto",
+        "_max-main-size": "50px",
+        "_main-size": [null, "50px"],
+      },
+    ],
+  },
+
+  // As above, both items initially grow to 100px, and that violates both items'
+  // constraints. However, now the sum of the clamping differences is:
+  //
+  //   (130px - 100px) + (80px - 100px) = (30px) + (-20px) = 10px
+  //
+  // This sum is positive, so (per spec) we freeze the item that had its
+  // min-size violated (the first one) and restart the algorithm. This time,
+  // all the available space (200px - 130px = 70px) goes to the not-yet-frozen
+  // second item, and that puts it below its max-size, so all is well.
+  {
+    items: [
+      {
+        flex: "auto",
+        "_min-main-size": "130px",
+        "_main-size": [null, "130px"],
+      },
+      {
+        flex: "auto",
+        "_max-main-size": "80px",
+        "_main-size": [null, "70px"],
+      },
+    ],
+  },
+
+  // As above, both items initially grow to 100px, and that violates both items'
+  // constraints. So we clamp both items and sum the clamping differences to
+  // see what to do next.  The sum is:
+  //
+  //   (80px - 100px) + (120px - 100px) = (-20px) + (20px) = 0px
+  //
+  // Per spec, if the sum is 0, we're done -- we leave both items at their
+  // clamped sizes.
+  {
+    items: [
+      {
+        flex: "auto",
+        "_max-main-size": "80px",
+        "_main-size": [null, "80px"],
+      },
+      {
+        flex: "auto",
+        "_min-main-size": "120px",
+        "_main-size": [null, "120px"],
+      },
+    ],
+  },
+
+  // Test cases where flex-grow sums to less than 1:
+  // ===============================================
+  // This makes us treat the flexibilities like "fraction of free space"
+  // instead of weights, so that e.g. a single item with "flex-grow: 0.1"
+  // will only get 10% of the free space instead of all of the free space.
+
+  // Basic cases where flex-grow sum is less than 1:
+  {
+    items: [
+      {
+        flex: "0.1 100px",
+        "_main-size": [null, "110px"], // +10% of free space
+      },
+    ],
+  },
+  {
+    items: [
+      {
+        flex: "0.8 0px",
+        "_main-size": [null, "160px"], // +80% of free space
+      },
+    ],
+  },
+
+  // ... and now with two flex items:
+  {
+    items: [
+      {
+        flex: "0.4 70px",
+        "_main-size": [null, "110px"], // +40% of free space
+      },
+      {
+        flex: "0.2 30px",
+        "_main-size": [null, "50px"], // +20% of free space
+      },
+    ],
+  },
+
+  // ...and now with max-size modifying how much free space one item can take:
+  {
+    items: [
+      {
+        flex: "0.4 70px",
+        "_main-size": [null, "110px"], // +40% of free space
+      },
+      {
+        flex: "0.2 30px",
+        "_max-main-size": "35px",
+        "_main-size": [null, "35px"], // +20% free space, then clamped
+      },
+    ],
+  },
+  // ...and now with a max-size smaller than our flex-basis:
+  // (This makes us freeze the second item right away, before we compute
+  // the initial free space.)
+  {
+    items: [
+      {
+        flex: "0.4 70px",
+        "_main-size": [null, "118px"], // +40% of 200px-70px-10px
+      },
+      {
+        flex: "0.2 30px",
+        "_max-main-size": "10px",
+        "_main-size": [null, "10px"], // immediately frozen
+      },
+    ],
+  },
+  // ...and now with a max-size and a huge flex-basis, such that we initially
+  // have negative free space, which makes the "% of [original] free space"
+  // calculations a bit more subtle. We set the "original free space" after
+  // we've clamped the second item (the first time the free space is positive).
+  {
+    items: [
+      {
+        flex: "0.4 70px",
+        "_main-size": [null, "118px"], // +40% of free space _after freezing
+        // the other item_
+      },
+      {
+        flex: "0.2 150px",
+        "_max-main-size": "10px",
+        "_main-size": [null, "10px"], // clamped immediately
+      },
+    ],
+  },
+
+  // Now with min-size modifying how much free space our items take:
+  {
+    items: [
+      {
+        flex: "0.4 70px",
+        "_main-size": [null, "110px"], // +40% of free space
+      },
+      {
+        flex: "0.2 30px",
+        "_min-main-size": "70px",
+        "_main-size": [null, "70px"], // +20% free space, then clamped
+      },
+    ],
+  },
+
+  // ...and now with a large enough min-size that it prevents the other flex
+  // item from taking its full desired portion of the original free space:
+  {
+    items: [
+      {
+        flex: "0.4 70px",
+        "_main-size": [null, "80px"], // (Can't take my full +40% of
+        // free space due to other item's
+        // large min-size.)
+      },
+      {
+        flex: "0.2 30px",
+        "_min-main-size": "120px",
+        "_main-size": [null, "120px"], // +20% free space, then clamped
+      },
+    ],
+  },
+  // ...and now with a large-enough min-size that it pushes the other flex item
+  // to actually shrink a bit (with default "flex-shrink:1"):
+  {
+    items: [
+      {
+        flex: "0.3 30px",
+        "_main-size": [null, "20px"], // -10px, instead of desired +45px
+      },
+      {
+        flex: "0.2 20px",
+        "_min-main-size": "180px",
+        "_main-size": [null, "180px"], // +160px, instead of desired +30px
+      },
+    ],
+  },
+
+  // In this case, the items' flexibilities don't initially sum to < 1, but they
+  // do after we freeze the third item for violating its max-size.
+  {
+    items: [
+      {
+        flex: "0.3 30px",
+        "_main-size": [null, "75px"],
+        // 1st loop: desires (0.3 / 5) * 150px = 9px. Tentatively granted.
+        // 2nd loop: desires 0.3 * 150px = 45px. Tentatively granted.
+        // 3rd loop: desires 0.3 * 150px = 45px. Granted +45px.
+      },
+      {
+        flex: "0.2 20px",
+        "_max-main-size": "30px",
+        "_main-size": [null, "30px"],
+        // First loop: desires (0.2 / 5) * 150px = 6px. Tentatively granted.
+        // Second loop: desires 0.2 * 150px = 30px. Frozen at +10px.
+      },
+      {
+        flex: "4.5 0px",
+        "_max-main-size": "20px",
+        "_main-size": [null, "20px"],
+        // First loop: desires (4.5 / 5) * 150px = 135px. Frozen at +20px.
+      },
+    ],
+  },
+
+  // Make sure we calculate "original free space" correctly when one of our
+  // flex items will be clamped right away, due to max-size preventing it from
+  // growing at all:
+  {
+    // Here, the second flex item is effectively inflexible; it's
+    // immediately frozen at 40px since we're growing & this item's max size
+    // trivially prevents it from growing. This leaves us with an "original
+    // free space" of 60px. The first flex item takes half of that, due to
+    // its flex-grow value of 0.5.
+    items: [
+      {
+        flex: "0.5 100px",
+        "_main-size": [null, "130px"],
+      },
+      {
+        flex: "1 98px",
+        "_max-main-size": "40px",
+        "_main-size": [null, "40px"],
+      },
+    ],
+  },
+  {
+    // Same as previous example, but with a larger flex-basis on the second
+    // element (which shouldn't ultimately matter, because its max size clamps
+    // its size immediately anyway).
+    items: [
+      {
+        flex: "0.5 100px",
+        "_main-size": [null, "130px"],
+      },
+      {
+        flex: "1 101px",
+        "_max-main-size": "40px",
+        "_main-size": [null, "40px"],
+      },
+    ],
+  },
+
+  {
+    // Here, the third flex item is effectively inflexible; it's immediately
+    // frozen at 0px since we're growing & this item's max size trivially
+    // prevents it from growing. This leaves us with an "original free space" of
+    // 100px. The first flex item takes 40px, and the third takes 50px, due to
+    // their flex values of 0.4 and 0.5.
+    items: [
+      {
+        flex: "0.4 50px",
+        "_main-size": [null, "90px"],
+      },
+      {
+        flex: "0.5 50px",
+        "_main-size": [null, "100px"],
+      },
+      {
+        flex: "0 90px",
+        "_max-main-size": "0px",
+        "_main-size": [null, "0px"],
+      },
+    ],
+  },
+  {
+    // Same as previous example, but with slightly larger flex-grow values on
+    // the first and second items, which sum to 1.0 and produce slightly larger
+    // main sizes. This demonstrates that there's no discontinuity between the
+    // "< 1.0 sum" to ">= 1.0 sum" behavior, in this situation at least.
+    items: [
+      {
+        flex: "0.45 50px",
+        "_main-size": [null, "95px"],
+      },
+      {
+        flex: "0.55 50px",
+        "_main-size": [null, "105px"],
+      },
+      {
+        flex: "0 90px",
+        "_max-main-size": "0px",
+        "_main-size": [null, "0px"],
+      },
+    ],
+  },
+
+  // Test cases where flex-shrink sums to less than 1:
+  // =================================================
+  // This makes us treat the flexibilities more like "fraction of (negative)
+  // free space" instead of weights, so that e.g. a single item with
+  // "flex-shrink: 0.1" will only shrink by 10% of amount that it overflows
+  // its container by.
+  //
+  // It gets a bit more complex when there are multiple flex items, because
+  // flex-shrink is scaled by the flex-basis before it's used as a weight. But
+  // even with that scaling, the general principal is that e.g. if the
+  // flex-shrink values *sum* to 0.6, then the items will collectively only
+  // shrink by 60% (and hence will still overflow).
+
+  // Basic cases where flex-grow sum is less than 1:
+  {
+    items: [
+      {
+        flex: "0 0.1 300px",
+        "_main-size": [null, "290px"], // +10% of (negative) free space
+      },
+    ],
+  },
+  {
+    items: [
+      {
+        flex: "0 0.8 400px",
+        "_main-size": [null, "240px"], // +80% of (negative) free space
+      },
+    ],
+  },
+
+  // ...now with two flex items, with the same flex-basis value:
+  {
+    items: [
+      {
+        flex: "0 0.4 150px",
+        "_main-size": [null, "110px"], // +40% of (negative) free space
+      },
+      {
+        flex: "0 0.2 150px",
+        "_main-size": [null, "130px"], // +20% of (negative) free space
+      },
+    ],
+  },
+
+  // ...now with two flex items, with different flex-basis values (and hence
+  // differently-scaled flex factors):
+  {
+    items: [
+      {
+        flex: "0 0.3 100px",
+        "_main-size": [null, "76px"],
+      },
+      {
+        flex: "0 0.1 200px",
+        "_main-size": [null, "184px"],
+      },
+    ],
+    // Notes:
+    //  - Free space: -100px
+    //  - Sum of flex-shrink factors: 0.3 + 0.1 = 0.4
+    //  - Since that sum ^ is < 1, we'll only distribute that fraction of
+    //    the free space. We'll distribute: -100px * 0.4 = -40px
+    //
+    //  - 1st item's scaled flex factor:  0.3 * 100px = 30
+    //  - 2nd item's scaled flex factor:  0.1 * 200px = 20
+    //  - 1st item's share of distributed free space: 30/(30+20) = 60%
+    //  - 2nd item's share of distributed free space: 20/(30+20) = 40%
+    //
+    // SO:
+    //  - 1st item gets 60% * -40px = -24px.  100px-24px = 76px
+    //  - 2nd item gets 40% * -40px = -16px.  200px-16px = 184px
+  },
+
+  // ...now with min-size modifying how much one item can shrink:
+  {
+    items: [
+      {
+        flex: "0 0.3 100px",
+        "_main-size": [null, "70px"],
+      },
+      {
+        flex: "0 0.1 200px",
+        "_min-main-size": "190px",
+        "_main-size": [null, "190px"],
+      },
+    ],
+    // Notes:
+    //  - We proceed as in previous testcase, but clamp the second flex item
+    //    at its min main size.
+    //  - After that point, we have a total flex-shrink of = 0.3, so we
+    //    distribute 0.3 * -100px = -30px to the remaining unfrozen flex
+    //    items. Since there's only one unfrozen item left, it gets all of it.
+  },
+
+  // ...now with min-size larger than our flex-basis:
+  // (This makes us freeze the second item right away, before we compute
+  // the initial free space.)
+  {
+    items: [
+      {
+        flex: "0 0.3 100px",
+        "_main-size": [null, "55px"], // +30% of 200px-100px-250px
+      },
+      {
+        flex: "0 0.1 200px",
+        "_min-main-size": "250px",
+        "_main-size": [null, "250px"], // immediately frozen
+      },
+    ],
+    // (Same as previous example, except the min-main-size prevents the
+    // second item from shrinking at all)
+  },
+
+  // ...and now with a min-size and a small flex-basis, such that we initially
+  // have positive free space, which makes the "% of [original] free space"
+  // calculations a bit more subtle. We set the "original free space" after
+  // we've clamped the second item (the first time the free space is negative).
+  {
+    items: [
+      {
+        flex: "0 0.3 100px",
+        "_main-size": [null, "70px"],
+      },
+      {
+        flex: "0 0.1 50px",
+        "_min-main-size": "200px",
+        "_main-size": [null, "200px"],
+      },
+    ],
+  },
+
+  // Now with max-size making an item shrink more than its flex-shrink value
+  // calls for:
+  {
+    items: [
+      {
+        flex: "0 0.3 100px",
+        "_main-size": [null, "70px"],
+      },
+      {
+        flex: "0 0.1 200px",
+        "_max-main-size": "150px",
+        "_main-size": [null, "150px"],
+      },
+    ],
+    // Notes:
+    //  - We proceed as in an earlier testcase, but clamp the second flex item
+    //    at its max main size.
+    //  - After that point, we have a total flex-shrink of = 0.3, so we
+    //    distribute 0.3 * -100px = -30px to the remaining unfrozen flex
+    //    items. Since there's only one unfrozen item left, it gets all of it.
+  },
+
+  // ...and now with a small enough max-size that it prevents the other flex
+  // item from taking its full desired portion of the (negative) original free
+  // space:
+  {
+    items: [
+      {
+        flex: "0 0.3 100px",
+        "_main-size": [null, "90px"],
+      },
+      {
+        flex: "0 0.1 200px",
+        "_max-main-size": "110px",
+        "_main-size": [null, "110px"],
+      },
+    ],
+    // Notes:
+    //  - We proceed as in an earlier testcase, but clamp the second flex item
+    //    at its max main size.
+    //  - After that point, we have a total flex-shrink of 0.3, which would
+    //    have us distribute 0.3 * -100px = -30px to the (one) remaining
+    //    unfrozen flex item. But our remaining free space is only -10px at
+    //    that point, so we distribute that instead.
+  },
+
+  // ...and now with a small enough max-size that it pushes the other flex item
+  // to actually grow a bit (with custom "flex-grow: 1" for this testcase):
+  {
+    items: [
+      {
+        flex: "1 0.3 100px",
+        "_main-size": [null, "120px"],
+      },
+      {
+        flex: "1 0.1 200px",
+        "_max-main-size": "80px",
+        "_main-size": [null, "80px"],
+      },
+    ],
+  },
+
+  // In this case, the items' flexibilities don't initially sum to < 1, but they
+  // do after we freeze the third item for violating its min-size.
+  {
+    items: [
+      {
+        flex: "0 0.3 100px",
+        "_main-size": [null, "76px"],
+      },
+      {
+        flex: "0 0.1 150px",
+        "_main-size": [null, "138px"],
+      },
+      {
+        flex: "0 0.8 10px",
+        "_min-main-size": "40px",
+        "_main-size": [null, "40px"],
+      },
+    ],
+    // Notes:
+    //  - We immediately freeze the 3rd item, since we're shrinking and its
+    //    min size obviously prevents it from shrinking at all.  This leaves
+    //    200px - 100px - 150px - 40px = -90px of "initial free space".
+    //
+    //  - Our remaining flexible items have a total flex-shrink of 0.4,
+    //    so we can distribute a total of 0.4 * -90px = -36px
+    //
+    //  - We distribute that space using *scaled* flex factors:
+    //    * 1st item's scaled flex factor:  0.3 * 100px = 30
+    //    * 2nd item's scaled flex factor:  0.1 * 150px = 15
+    //   ...which means...
+    //    * 1st item's share of distributed free space: 30/(30+15) = 2/3
+    //    * 2nd item's share of distributed free space: 15/(30+15) = 1/3
+    //
+    // SO:
+    //  - 1st item gets 2/3 * -36px = -24px. 100px - 24px = 76px
+    //  - 2nd item gets 1/3 * -36px = -12px. 150px - 12px = 138px
+  },
+
+  // In this case, the items' flexibilities sum to > 1, in part due to an item
+  // that *can't actually shrink* due to its 0 flex-basis (which gives it a
+  // "scaled flex factor" of 0). This prevents us from triggering the special
+  // behavior for flexibilities that sum to less than 1, and as a result, the
+  // first item ends up absorbing all of the free space.
+  {
+    items: [
+      {
+        flex: "0 .5 300px",
+        "_main-size": [null, "200px"],
+      },
+      {
+        flex: "0 5 0px",
+        "_main-size": [null, "0px"],
+      },
+    ],
+  },
+
+  // This case is similar to the one above, but with a *barely* nonzero base
+  // size for the second item. This should produce a result similar to the case
+  // above. (In particular, we should first distribute a very small amount of
+  // negative free space to the second item, getting it to approximately zero,
+  // and distribute the bulk of the negative free space to the first item,
+  // getting it to approximately 200px.)
+  {
+    items: [
+      {
+        flex: "0 .5 300px",
+        "_main-size": [null, "200px"],
+      },
+      {
+        flex: "0 1 0.01px",
+        "_main-size": [null, "0px"],
+      },
+    ],
+  },
+  // This case is similar to the ones above, but now we've increased the
+  // flex-shrink value on the second-item so that it claims enough of the
+  // negative free space to go below its min-size (0px). So, it triggers a min
+  // violation & is frozen. For the loop *after* the min violation, the sum of
+  // the remaining flex items' flex-shrink values is less than 1, so we trigger
+  // the special <1 behavior and only distribute half of the remaining
+  // (negative) free space to the first item (instead of all of it).
+  {
+    items: [
+      {
+        flex: "0 .5 300px",
+        "_main-size": [null, "250px"],
+      },
+      {
+        flex: "0 5 0.01px",
+        "_main-size": [null, "0px"],
+      },
+    ],
+  },
+];