LibWeb: Don't touch flex items after they we've been frozen

awesomekling · awesomekling · commit f3556f239e47 · 2023-03-11T11:52:19.000+01:00
When using the flex shrink factor, the flexible length resolution
algorithm was incorrectly ignoring the `frozen` flag on items and would
update the same items again, causing overconsumption of the remaining
free space on the flex line.
diff --git a/Tests/LibWeb/Layout/expected/flex-frozen-items-should-be-respected.txt b/Tests/LibWeb/Layout/expected/flex-frozen-items-should-be-respected.txt
@@ -0,0 +1,29 @@
+Viewport <#document> at (0,0) content-size 800x600 children: not-inline
+  BlockContainer <html> at (1,1) content-size 798x70 children: not-inline
+    BlockContainer <body> at (10,10) content-size 780x52 children: not-inline
+      Box <div.flexbox> at (11,11) content-size 778x50 flex-container(row) children: not-inline
+        BlockContainer <div> at (12,12) content-size 136.3125x48 flex-item children: inline
+          line 0 width: 136.3125, height: 17.46875, bottom: 17.46875, baseline: 13.53125
+            frag 0 from TextNode start: 0, length: 15, rect: [12,12 136.3125x17.46875]
+              "LongPieceOfText"
+          TextNode <#text>
+        BlockContainer <div> at (150.3125,12) content-size 136.3125x48 flex-item children: inline
+          line 0 width: 136.3125, height: 17.46875, bottom: 17.46875, baseline: 13.53125
+            frag 0 from TextNode start: 0, length: 15, rect: [150.3125,12 136.3125x17.46875]
+              "LongPieceOfText"
+          TextNode <#text>
+        BlockContainer <div> at (288.625,12) content-size 136.3125x48 flex-item children: inline
+          line 0 width: 136.3125, height: 17.46875, bottom: 17.46875, baseline: 13.53125
+            frag 0 from TextNode start: 0, length: 15, rect: [288.625,12 136.3125x17.46875]
+              "LongPieceOfText"
+          TextNode <#text>
+        BlockContainer <div> at (426.9375,12) content-size 136.3125x48 flex-item children: inline
+          line 0 width: 136.3125, height: 17.46875, bottom: 17.46875, baseline: 13.53125
+            frag 0 from TextNode start: 0, length: 15, rect: [426.9375,12 136.3125x17.46875]
+              "LongPieceOfText"
+          TextNode <#text>
+        BlockContainer <div.last.item> at (565.25,12) content-size 222.75x48 flex-item children: inline
+          line 0 width: 136.3125, height: 17.46875, bottom: 17.46875, baseline: 13.53125
+            frag 0 from TextNode start: 0, length: 15, rect: [565.25,12 136.3125x17.46875]
+              "LongPieceOfText"
+          TextNode <#text>
diff --git a/Tests/LibWeb/Layout/input/flex-frozen-items-should-be-respected.html b/Tests/LibWeb/Layout/input/flex-frozen-items-should-be-respected.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html><html><head><style>
+      * {
+        border: 1px solid black;
+        font-family: 'SerenitySans';
+      }
+      .flexbox {
+        display: flex;
+        height: 50px;
+      }
+      .last {
+        width: 500px;
+      }
+</style></head><body><div class="flexbox"><div>LongPieceOfText</div><div>LongPieceOfText</div><div>LongPieceOfText</div><div>LongPieceOfText</div><div class="last item">LongPieceOfText</div></div></div></body></html>
diff --git a/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp b/Userland/Libraries/LibWeb/Layout/FlexFormattingContext.cpp
@@ -972,10 +972,14 @@ void FlexFormattingContext::resolve_flexible_lengths_for_line(FlexLine& line)
             else if (used_flex_factor == FlexFactor::FlexShrinkFactor) {
                 // For every unfrozen item on the line, multiply its flex shrink factor by its inner flex base size, and note this as its scaled flex shrink factor.
                 for (auto& item : line.items) {
+                    if (item.frozen)
+                        continue;
                     item.scaled_flex_shrink_factor = item.flex_factor.value() * item.flex_base_size.value();
                 }
                 auto sum_of_scaled_flex_shrink_factors_of_all_unfrozen_items_on_line = line.sum_of_scaled_flex_shrink_factor_of_unfrozen_items();
                 for (auto& item : line.items) {
+                    if (item.frozen)
+                        continue;
                     // Find the ratio of the item’s scaled flex shrink factor to the sum of the scaled flex shrink factors of all unfrozen items on the line.
                     float ratio = 1.0f;
                     if (sum_of_scaled_flex_shrink_factors_of_all_unfrozen_items_on_line != 0)
