Your adjusted cost base is determined on the day you landed in canada and your gain or loss will be calculated based on that.
e.g. bought shares in 2008 $100,000
landed May 1, 2022 Fmv-closing price of these stock on he last trading day before you landed $300,000
Sold Dec 1, 2022 $350,000
Total gain $350,000- $100,000 = $250,000
Gain for Canada T1 = $350,000-$300,000 = $50,000
Taxable capital gain = $50,000 X 50% = $25,000
Tax - based on your marginal rate.
If sell price is $150,000 then
Total gain $150,000-$100,000= $50,000
Canada- $300,000-$150,000= $150,000 capital loss
taxable capital loss is $150,000 X50% = $75,000