Locus of the time evolution of 1 − 10 TeV emission in surface brightness and angular size, for our three typical SNR-PWN systems. The top panel results from a calculation without particle escape, and PWN is the only emission component. The bottom panel results from a calculation with particle escape across the system, and gamma-ray emission is contributed by the PWN, SNR, and CSM components altogether. The extent of the CSM component was computed under the assumption of suppressed spatial diffusion, by a factor of 1000 with respect to the average Galactic value. Smaller suppression factors would push the set of red curves down and to the right. The model predictions correspond to a distance of 1 kpc to the system. Larger distances would lead to smaller angular sizes while surface brightnesses would be preserved, shrinking all curves towards the ordinate axis. Model-predicted emission is compared to data from the HGPS and LHAASO catalogues.