Note 15 - Stock-based Compensation - Summary of Stock Options Outstanding and Exercisable (Details) - $ / shares	12 Months Ended
	Jul. 31, 2022	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2019
Options Outstanding Outstanding (in shares)	8,880,527	10,404,333	15,514,750	15,738,350
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.58	$ 1.21	$ 1.13	$ 1.30
Options Outstanding Weighted Average Remaining Contractual Term (Year)	6 years 11 months 23 days
Options Exercisable (in shares)	6,694,373
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.14
Options Exercisable Weighted Average Remaining Contractual Term (Year)	6 years 3 months
Exercise Price Range 1 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 0.80
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 0.99
Options Outstanding Outstanding (in shares)	3,968,499
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 0.92
Options Outstanding Weighted Average Remaining Contractual Term (Year)	7 years 6 months 18 days
Options Exercisable (in shares)	3,968,499
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 0.92
Options Exercisable Weighted Average Remaining Contractual Term (Year)	7 years 6 months 18 days
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 0.80
Range of Exercise Prices, Upper Limit (in dollars per share)	0.99
Exercise Price Range 2 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	1.00
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 1.99
Options Outstanding Outstanding (in shares)	2,738,875
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 1.29
Options Outstanding Weighted Average Remaining Contractual Term (Year)	4 years 2 months 23 days
Options Exercisable (in shares)	2,297,207
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 1.32
Options Exercisable Weighted Average Remaining Contractual Term (Year)	3 years 6 months 7 days
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 1.00
Range of Exercise Prices, Upper Limit (in dollars per share)	1.99
Exercise Price Range 3 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	2.00
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 2.99
Options Outstanding Outstanding (in shares)	903,461
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 2.22
Options Outstanding Weighted Average Remaining Contractual Term (Year)	8 years 11 months 12 days
Options Exercisable (in shares)	416,167
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 2.22
Options Exercisable Weighted Average Remaining Contractual Term (Year)	8 years 11 months 8 days
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 2.00
Range of Exercise Prices, Upper Limit (in dollars per share)	2.99
Exercise Price Range 4 [Member]
Range of Exercise Prices, Lower Limit (in dollars per share)	3.00
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 3.98
Options Outstanding Outstanding (in shares)	1,269,692
Options Outstanding Weighted Average Exercise Price (in dollars per share)	$ 3.80
Options Outstanding Weighted Average Remaining Contractual Term (Year)	9 years 9 months
Options Exercisable (in shares)	12,500
Options Exercisable Weighted Average Exercise Price (in dollars per share)	$ 3.18
Options Exercisable Weighted Average Remaining Contractual Term (Year)	4 years 10 months 28 days
Range of Exercise Prices, Lower Limit (in dollars per share)	$ 3.00
Range of Exercise Prices, Upper Limit (in dollars per share)	$ 3.98