ClipBox too small with transformed reused shape (circus tent emoji example)

Simplifying the circus tent emoji, in the Skia rendering, the second yellow patch of the vertical tent wall goes missing. This path seems to be a mirrored version of the left side left patch of the vertical wall.

Whether it gets shifted out of the viewport or whether something goes wrong with the color line coordinates, similar to issue #334 needs investigation.

Simplified SVG

<svg enable-background="new 0 0 128 128" viewBox="0 0 128 128"
	xmlns="http://www.w3.org/2000/svg">
	<linearGradient id="g" x1="32.5" x2="32.5" y1="64.167" y2="125.94" gradientUnits="userSpaceOnUse">
		<stop stop-color="#FDD835" offset="0"/>
		<stop stop-color="#F9A825" offset="1"/>
	</linearGradient>
	<path d="m20 64s12 24 8 60h16s4-44-4-60h-20z" fill="url(#g)"/>
	<linearGradient id="f" x1="95.5" x2="95.5" y1="64.167" y2="125.94" gradientUnits="userSpaceOnUse">
		<stop stop-color="#FDD835" offset="0"/>
		<stop stop-color="#F9A825" offset="1"/>
	</linearGradient>
	<path d="m108 64s-12 24-8 60h-16s-4-44 4-60h20z" fill="url(#f)"/>
</svg>

COLR

 <COLR>
    <Version value="1"/>
    <!-- BaseGlyphRecordCount=0 -->
    <!-- LayerRecordCount=0 -->
    <BaseGlyphList>
      <!-- BaseGlyphCount=1 -->
      <BaseGlyphPaintRecord index="0">
        <BaseGlyph value="u1F3AA"/>
        <Paint Format="1"><!-- PaintColrLayers -->
          <NumLayers value="2"/>
          <FirstLayerIndex value="0"/>
        </Paint>
      </BaseGlyphPaintRecord>
    </BaseGlyphList>
    <LayerList>
      <!-- LayerCount=2 -->
      <Paint index="0" Format="10"><!-- PaintGlyph -->
        <Paint Format="4"><!-- PaintLinearGradient -->
          <ColorLine>
            <Extend value="pad"/>
            <!-- StopCount=2 -->
            <ColorStop index="0">
              <StopOffset value="0.0"/>
              <PaletteIndex value="1"/>
              <Alpha value="1.0"/>
            </ColorStop>
            <ColorStop index="1">
              <StopOffset value="1.0"/>
              <PaletteIndex value="0"/>
              <Alpha value="1.0"/>
            </ColorStop>
          </ColorLine>
          <x0 value="342"/>
          <y0 value="348"/>
          <x1 value="342"/>
          <y1 value="-231"/>
          <x2 value="-237"/>
          <y2 value="348"/>
        </Paint>
        <Glyph value="glyph00003"/>
      </Paint>
      <Paint index="1" Format="12"><!-- PaintTransform -->
        <Paint Format="10"><!-- PaintGlyph -->
          <Paint Format="4"><!-- PaintLinearGradient -->
            <ColorLine>
              <Extend value="pad"/>
              <!-- StopCount=2 -->
              <ColorStop index="0">
                <StopOffset value="0.0"/>
                <PaletteIndex value="1"/>
                <Alpha value="1.0"/>
              </ColorStop>
              <ColorStop index="1">
                <StopOffset value="1.0"/>
                <PaletteIndex value="0"/>
                <Alpha value="1.0"/>
              </ColorStop>
            </ColorLine>
            <x0 value="933"/>
            <y0 value="348"/>
            <x1 value="933"/>
            <y1 value="-231"/>
            <x2 value="354"/>
            <y2 value="348"/>
          </Paint>
          <Glyph value="glyph00003"/>
        </Paint>
        <Transform>
          <xx value="-1.0"/>
          <yx value="0.0"/>
          <xy value="0.0"/>
          <yy value="1.0"/>
          <dx value="1275.0"/>
          <dy value="0.0"/>
        </Transform>
      </Paint>
    </LayerList>
    <ClipList Format="1">
      <Clip>
        <Glyph value="u1F3AA"/>
        <ClipBox Format="1">
          <xMin value="220"/>
          <yMin value="-220"/>
          <xMax value="800"/>
          <yMax value="360"/>
        </ClipBox>
      </Clip>
    </ClipList>
  </COLR>

[anthrotype]

I can repro now

[anthrotype]

ok, I found where the issue is. When traversing the paint graph and unioning the bounding boxes of the various PaintGlyphs, when a reflection is found (e.g. negtive xx or yy whereby coordinates get flipped along the axes), the code was not normalizing the transformed bounding rectangle by turning it the right way up i.e. such that xMin <= xMax and yMin <= yMax FontTools arrayTools module has a normRect function that does just that. After using it, I get correct bounding boxes and no more unwanted clipping. I’ll make a PR now