From 216bb7f96014a140a0659db6c7bbaddc6b8335db Mon Sep 17 00:00:00 2001 From: Daniel van Vugt Date: Thu, 20 May 2021 17:39:44 +0800 Subject: [PATCH] cogl/clip-stack-gl: Set glStencilMask correctly for clip regions Previously we were using a mask of 0x1 for the lifetime of the stencil. This was wrong for two reasons: * The intersection algorithm needs to count up to a maximum 2, so a mask of 1 would clamp to 1 instead. Then decrementing all pixels resulted in all pixels being zero even though we want some to be 1. So the stencil then blocked some color buffer pixels being rendered. * The lifetime of the mask was too long. By leaving it non-zero at the end of the function we could accidentally end up modifying the stencil contents during our later color buffer paints. This fixes faulty rendering of some actors seen in gnome-shell with test case: `env COGL_DEBUG=stencilling` Part-of: --- cogl/cogl/driver/gl/cogl-clip-stack-gl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/cogl/cogl/driver/gl/cogl-clip-stack-gl.c b/cogl/cogl/driver/gl/cogl-clip-stack-gl.c index c2cccf0ee..a693903b3 100644 --- a/cogl/cogl/driver/gl/cogl-clip-stack-gl.c +++ b/cogl/cogl/driver/gl/cogl-clip-stack-gl.c @@ -158,6 +158,7 @@ add_stencil_clip_region (CoglFramebuffer *framebuffer, GE( ctx, glColorMask (FALSE, FALSE, FALSE, FALSE) ); GE( ctx, glDepthMask (FALSE) ); + GE( ctx, glStencilMask (0x3) ); if (merge) { @@ -167,7 +168,6 @@ add_stencil_clip_region (CoglFramebuffer *framebuffer, else { GE( ctx, glEnable (GL_STENCIL_TEST) ); - GE( ctx, glStencilMask (0x1) ); /* Initially disallow everything */ GE( ctx, glClearStencil (0) ); @@ -240,6 +240,7 @@ add_stencil_clip_region (CoglFramebuffer *framebuffer, /* Restore the stencil mode */ GE (ctx, glDepthMask (TRUE)); GE (ctx, glColorMask (TRUE, TRUE, TRUE, TRUE)); + GE( ctx, glStencilMask (0x0) ); GE( ctx, glStencilFunc (GL_EQUAL, 0x1, 0x1) ); GE( ctx, glStencilOp (GL_KEEP, GL_KEEP, GL_KEEP) ); }