Bug 199770 – Blur Filter causes element to get cut off over multiple screens

• Status: NEW
• Component: CSS

[Thomas]

Created attachment 374056 [details]
Test script displays the bug, uses javascript to generate text

Overview:
When using the blur filter on an element, it cuts off the element around what I estimate to be ~4000px. When you try to measure it using development tools, it suddenly comes correct.

Steps to reproduce:
1) Stretch out a browser using webkit to span multiple screens
2) Load a file containing a blur filter on an element (see attached one provided)

Actual Results:
The element gets cropped at ~4000px across and no content from the element can be seen anymore past this point, The blur also completes but leaves a hard edge on the edge where it gets cropped

Expected Results: 
The full element, with all contained text should be displayed across the page

Build Date & Hardware:
13 July 2019 on Manjaro Linux 

Additional Builds and Platforms:
 The following both have the problem:
   - lightdm-webkit2-greeter (v2.2.5)
   - Midori (v8.0)
 On Firefox (v67.0 x64) this does not occur

[Thomas]

Created attachment 374063 [details]
What happens with the blur enabled

[Thomas]

Created attachment 374064 [details]
What happens with the blur disabled

[Thomas]

Created attachment 374065 [details]
What should happen with blur enabled (from firefox)