1692807 - Investigate how we generate malformed hit testing tree and stop doing it

Status: NEW

(Core :: Panning and Zooming, task)

Description

[Hiroyuki Ikezoe (:hiro)]

In bug 1691997, we saw malformed hit testing trees both on https://pdf.wondershare.com/buy/pdfelement-windows.html and https://www.lecho.be/entreprises/general/les-hommes-de-pouvoir-portent-un-brocelet/10168713.html.

In the case of pdfelement-windows case, the tree looks like;

HitTestingTreeNode (0x7f53bec7cd40) APZC (0x7f53bb73a000) g=({ l=0x100000001, p=1, v=3 }) r=({ }) t=([ I ]) c=([0,0,1276,1145])
  HitTestingTreeNode (0x7f53acd2fa60) APZC ((nil)) g=(l=0x100000001) r=({ }) t=([ 1 0; 0 1; 0 74; ]) c=(none)
    HitTestingTreeNode (0x7f53acd2f2e0) APZC ((nil)) g=(l=0x10000000b) r=({ }) t=([ I ]) c=(none)
      HitTestingTreeNode (0x7f53af5435c0) APZC ((nil)) g=(l=0x10000000b) r=({ }) t=([ I ]) c=(none) scrollbar
        HitTestingTreeNode (0x7f53a9ff9200) APZC ((nil)) g=(l=0x10000000b) r=({ }) t=([ I ]) c=(none) scrollbar scrollthumb
      HitTestingTreeNode (0x7f53af2e4a60) APZC (0x7f53acc81000) g=({ l=0x10000000b, p=2, v=3 }) r=({ }) t=([ I ]) c=([0,0,1264,1071])
      HitTestingTreeNode (0x7f53af2e4e20) APZC ((nil)) g=(l=0x10000000b) fixed=3 r=({ }) t=([ I ]) c=(none)
      HitTestingTreeNode (0x7f53a9fd5100) APZC (0x7f53acc81000) g=({ l=0x10000000b, p=2, v=3 }) r=({ }) t=([ I ]) c=([0,0,1264,1071])
      HitTestingTreeNode (0x7f53a9ff9020) APZC ((nil)) g=(l=0x10000000b) fixed=3 r=({ }) t=([ I ]) c=(none)
      HitTestingTreeNode (0x7f53acd2fe20) APZC ((nil)) g=(l=0x10000000b) fixed=3 r=({ }) t=([ I ]) c=(none)
        HitTestingTreeNode (0x7f53aa069200) APZC ((nil)) g=(l=0x10000000b) r=({ }) t=([ 1 0; 0 1; 0 1071; ]) c=(none)
          HitTestingTreeNode (0x7f53af2e4880) APZC (0x7f53acc81000) g=({ l=0x10000000b, p=2, v=3 }) r=({ }) t=([ I ]) c=([0,0,1264,1071])
            HitTestingTreeNode (0x7f53aa069020) APZC ((nil)) g=(l=0x10000000b) r=({ }) t=([ I ]) c=(none)
      HitTestingTreeNode (0x7f53acd2f6a0) APZC ((nil)) g=(l=0x10000000b) fixed=3 r=({ }) t=([ I ]) c=(none)
      HitTestingTreeNode (0x7f53acd2e200) APZC ((nil)) g=(l=0x10000000b) fixed=3 r=({ }) t=([ I ]) c=(none)

In the case of lecho.de, it looks like;

HitTestingTreeNode (0x7f3fdbd5ea60) APZC (0x7f3fdbdd8000) g=({ l=0x100000001, p=1, v=3 }) r=({ }) t=([ I ]) c=([0,0,1280,1609])
  HitTestingTreeNode (0x7f3fca514a60) APZC (0x7f3fca4b0000) g=({ l=0x100000001, p=1, v=5 }) r=({ }) t=([ I ]) c=([284,39,921,67])
  HitTestingTreeNode (0x7f3fcd7e4980) APZC ((nil)) g=(l=0x100000001) r=({ }) t=([ I ]) c=(none)
  HitTestingTreeNode (0x7f3fcbd6df20) APZC ((nil)) g=(l=0x100000001) r=({ }) t=([ 1 0; 0 1; 0 74; ]) c=(none)
    HitTestingTreeNode (0x7f3fcf9c3d40) APZC ((nil)) g=(l=0x10000000d) r=({ }) t=([ I ]) c=(none)
      HitTestingTreeNode (0x7f3fc82974c0) APZC ((nil)) g=(l=0x10000000d) r=({ }) t=([ I ]) c=(none) scrollbar
        HitTestingTreeNode (0x7f3fcd7bcb60) APZC ((nil)) g=(l=0x10000000d) r=({ }) t=([ I ]) c=(none) scrollbar scrollthumb
      HitTestingTreeNode (0x7f3fcf9c37a0) APZC ((nil)) g=(l=0x10000000d) r=({ }) t=([ I ]) c=(none)
        HitTestingTreeNode (0x7f3fcf9c46a0) APZC (0x7f3fcd4e4000) g=({ l=0x10000000d, p=2, v=3 }) r=({ }) t=([ I ]) c=(none)
        HitTestingTreeNode (0x7f3fca53a200) APZC ((nil)) g=(l=0x10000000d) fixed=3 r=({ }) t=([ I ]) c=(none)
          HitTestingTreeNode (0x7f3fca9f5b60) APZC ((nil)) g=(l=0x10000000d) r=({ }) t=([ 1 0; 0 1; 214 -166; ]) c=(none)
            HitTestingTreeNode (0x7f3fca9f55c0) APZC ((nil)) g=(l=0x10000000f) r=({ }) t=([ I ]) c=(none)
              HitTestingTreeNode (0x7f3fc8297880) APZC (0x7f3fc93fe000) g=({ l=0x10000000f, p=3, v=3 }) r=({ }) t=([ I ]) c=([0,0,840,150])
        HitTestingTreeNode (0x7f3fca52f020) APZC (0x7f3fcd4e4000) g=({ l=0x10000000d, p=2, v=3 }) r=({ }) t=([ I ]) c=(none)
        HitTestingTreeNode (0x7f3fca9da020) APZC ((nil)) g=(l=0x10000000d) fixed=3 r=({ }) t=([ I ]) c=(none)
          HitTestingTreeNode (0x7f3fca530880) APZC (0x7f3fcd4e4000) g=({ l=0x10000000d, p=2, v=3 }) r=({ }) t=([ I ]) c=(none)
            HitTestingTreeNode (0x7f3fca52ea60) APZC ((nil)) g=(l=0x10000000d) r=({ }) t=([ I ]) c=(none)
        HitTestingTreeNode (0x7f3fce71a880) APZC ((nil)) g=(l=0x10000000d) fixed=3 r=({ }) t=([ I ]) c=(none)

Both have fixed tree nodes having descendant nodes which have the same scroll id for the fixed target. Botond said it shouldn't happen.

I tried to generate reduced test cases, but the malformed tree doesn't happen on downloaded versions of the sites, and unfortunately it doesn't happen with rr recording.