[WebGL Conformance] clipping work incorrectly on y-axis

Submitted by xinghua

Assigned to Intel 3D Bugs Mailing List

Link to original bug (#111247)

Description

The issue exists on mesa master, and is a regression on mesa, it does not exist on mesa-19.1.2. Steps:

1. Use mesa master libraries.
2. Download latest chrome, and open https://www.khronos.org/registry/webgl/sdk/tests/deqp/functional/gles3/clipping.html?webglVersion=2&quiet=0&quick=1
3. One case fail.

Case details:

1. Drawing window size (128, 128), set viewport (38, 25, 76, 64), viewport size(76, 64)
2. Draw lines(line_width = 5)
3. On x-axis, lines, {(-1+1/76, -0.17218), (1+1/76, -0.17218)} // This line width is 76 {(-1-1/76, 0.2028), (1-1/76, 0.2028)} // This line width is 75, one lack at the line end. {(-1+1/76, 0.5153), (1-1/76, 0.5153)} // This line width is 75, one lack at the line end. The behaviors are the same on mesa and reference.
4. on y-axis, lines, {(-0.1976, -1+1/64), (-0.1976, 1+1/64)} // On mesa line height is 63, one lack at the line begin; but line height is 64 on reference. {(0.2234, -1-1/64), (0.2234, 1-1/64)} // On mesa line height is 64; but line height is 63 on reference, one lack at the line end. {(0.5128, -1+1/64),(0.5128, 1-1/64)} // line heights are all 63, but one lack is at the line begin on mesa, and the other is at the line end on reference. The x-axis and y-axis behaviors are different on mesa.

Version: git