Clamping texture coordinates prevents OpenGL from blending the left and
right edge (or top and bottom edge) when scaling textures with GL_LINEAR
filtering. This prevents visual artifacts like swaywm/sway#5809.
Per discussion on IRC, this behaviour is made default. Compositors that want
the wrapping behaviour (e.g. for tiled patterns) can override this by doing:
struct wlr_gles2_texture_attribs attribs;
wlr_gles2_texture_get_attribs(texture, &attribs);
glBindTexture(attribs.target, attribs.tex);
glTexParameteri(attribs.target, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(attribs.target, GL_TEXTURE_WRAP_T, GL_REPEAT);
glBindTexture(attribs.target, 0);
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