Minmax #866
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Minmax #866
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Contributor
UrielCh
commented
Mar 9, 2023
UrielCh
commented
- add cv.min
- add cv.max
- integrate native-node-utils code inside cc/native-node-utils
- add comments in native-node-utils
Matrix constructor from rows, cols, Buffer, step
Update highguiConstants.cc
In some scenarios the JS files of the library may be reloaded, such as when loaded by Jest. It seems that the underlying node extension is not reloaded in this case. This causes an exception to be thrown when rebuilding the exported API object: > TypeError: Cannot read properties of undefined (reading 'constructor') This happens in the `isAsyncFn` function inside `promisify.js` because `fn.prototype` is undefined. This code works fine the first time, so why does it fail when run again? The reason is that the functions attached to the `cv` namespace are all defined in C++ and are thus essentially the equivalent of a `FunctionExpression`, which have a `prototype.constructor.name`. Calling `loadOpenCV` calls `getOpenCV` which loads the node extension, then calls `promisify` on that namespace, and finally calls `extendWithJsSources`. This is where we run into problems. These are the functions that get added to the `cv` namespace from JS: ``` drawTextBox drawDetection toMatTypeName getScoreMax dropOverlappingZone ``` Almost all of these are defined as `ArrowFunctionExpression`s which DO NOT have a `prototype`. So after the JS files get cleared from `require.cache` by Jest or some other means, loading this library again REUSES the `cv` namespace because the node extension is not cleared from memory. But this time it has those extra functions attached, causing the exception mentioned above in `isAsyncFn`. I changed two things to fix this: 1. make `promisify.ts` not assume that all functions have prototypes; they don't. 2. define the extra from-JS functions as `FunctionExpression`s so they will have prototypes (and names).
fix exception thrown on reload
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