Changes between Initial Version and Version 1 of 2014 Meeting Subpixel Layout


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Timestamp:
Apr 22, 2014 10:27:22 AM (5 years ago)
Author:
Bem Jones-Bey
Comment:

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  • 2014 Meeting Subpixel Layout

    v1 v1  
     1== Subpixel Layout ==
     2
     3Started by Google 2 years ago
     4
     5 * to do better space distribution in the short term
     6   * sub pixel layout
     7
     8 * support hiDPI displays by painting on odd device pixels in the long term
     9   * sub pixel painting
     10
     11Subpixel Layout works right now
     12has some directional rounding errors for non-horizontal-tb flows
     13Subpixel painting/rendering
     14work in progress
     15
     16=== how does it work? ===
     17
     18==== what is a layout unit ====
     19
     20 * made integer based to support fractional values without the burden of float arithmetic
     21 * 1 layout unit == 1/64 CSS pixels
     22
     23 * Layout units are not rounded/etc during layout except in some cases, like in RenderLayer
     24
     25 * value is snapped during painting time
     26
     27==== how does snapping work? ====
     28
     29 * float value gets snapped to device pixel boundary, still a float after being snapped
     30 * this mostly happens in paint() in RenderObject classes
     31 * can't do in GraphicsContext since sometimes you need to do floor or ceil instead of rounding
     32    * border types like groove, ridge, double require floor/ceil to keep the spacing
     33
     34==== Testing ====
     35
     36  * prefix test case with 'hidpi-'
     37      * that will cause the test framework to switch to hidpi mode
     38
     39