push graphic-context
viewbox 0 0 100 100
affine 1 0 0 1 -0 -0
push defs
push gradient 'diagonal' linear 0,0 100,100
stop-color 'rgb(255,255,0)' 0%
stop-color 'rgb(255,0,0)' 100%
pop gradient
pop defs
push graphic-context
fill 'url(#diagonal)'
rectangle 10,10 90,90
pop graphic-context
pop graphic-context