Unable to build pxt-scrollbit against v3.1.17 / v6.4.13

[Gadgetoid]

Attempting to do a cloud build of pxt-scrollbit, I was running into an obtuse error:

TypeError: Cannot read property 'length' of null
    at compressHex (/home/phil/Development/pxt/pxt-scrollbit/node_modules/pxt-core/built/pxt.js:103646:37)
    at /home/phil/Development/pxt/pxt-scrollbit/node_modules/pxt-core/built/pxt.js:103575:36
    at tryCatcher (/home/phil/Development/pxt/pxt-scrollbit/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/home/phil/Development/pxt/pxt-scrollbit/node_modules/bluebird/js/release/promise.js:512:31)
    at Promise._settlePromise (/home/phil/Development/pxt/pxt-scrollbit/node_modules/bluebird/js/release/promise.js:569:18)
    at Promise._settlePromise0 (/home/phil/Development/pxt/pxt-scrollbit/node_modules/bluebird/js/release/promise.js:614:10)
    at Promise._settlePromises (/home/phil/Development/pxt/pxt-scrollbit/node_modules/bluebird/js/release/promise.js:693:18)
    at Async._drainQueue (/home/phil/Development/pxt/pxt-scrollbit/node_modules/bluebird/js/release/async.js:133:16)
    at Async._drainQueues (/home/phil/Development/pxt/pxt-scrollbit/node_modules/bluebird/js/release/async.js:143:10)
    at Immediate.Async.drainQueues [as _onImmediate] (/home/phil/Development/pxt/pxt-scrollbit/node_modules/bluebird/js/release/async.js:17:14)
    at runCallback (timers.js:705:18)
    at tryOnImmediate (timers.js:676:5)
    at processImmediate (timers.js:658:5)
{ sha:
   '08eb6b80026aa7260db0e25151435634e6b06694713c52895a397cce23c9d9df' }
test.ts(1,1): error TS9200: Cannot read property 'hex' of null

Scrolling up the backlog suggests this is probably because font.cpp is failing to compile. This file has not changed since the micro:bit V1.x, but the underlying DAL/Codal/PXT appears to have removed or omitted MicroBitFont.

/home/build/prjclone/pxtapp/scrollbit/font.cpp: In function 'int scrollbit::getFontDataByte(int)':
/home/build/prjclone/pxtapp/scrollbit/font.cpp:15:9: error: 'MicroBitFont' was not declared in this scope
         MicroBitFont font = MicroBitFont::getSystemFont();
         ^~~~~~~~~~~~
/home/build/prjclone/pxtapp/scrollbit/font.cpp:16:24: error: 'font' was not declared in this scope
         return (char)*(font.characters + index);
                        ^~~~
/home/build/prjclone/pxtapp/scrollbit/font.cpp: In function 'int scrollbit::getCharWidth(int)':
/home/build/prjclone/pxtapp/scrollbit/font.cpp:23:9: error: 'MicroBitFont' was not declared in this scope
         MicroBitFont font = MicroBitFont::getSystemFont();
         ^~~~~~~~~~~~
/home/build/prjclone/pxtapp/scrollbit/font.cpp:25:36: error: 'font' was not declared in this scope
         uint8_t width = (uint8_t)*(font.characters + offset)
                                    ^~~~
/home/build/prjclone/pxtapp/scrollbit/font.cpp: In function 'pxt::BoxedBuffer* scrollbit::getFontData(int)':
/home/build/prjclone/pxtapp/scrollbit/font.cpp:41:9: error: 'MicroBitFont' was not declared in this scope
         MicroBitFont font = MicroBitFont::getSystemFont();
         ^~~~~~~~~~~~
In file included from /home/build/prjclone/pxtapp/pxt.h:8:0,
                 from /home/build/prjclone/pxtapp/scrollbit/font.cpp:1:
/home/build/prjclone/pxtapp/scrollbit/font.cpp:44:46: error: 'font' was not declared in this scope
         return PXT_CREATE_BUFFER((uint8_t *)(font.characters + offset), 5);
                                              ^
/home/build/prjclone/pxtapp/pxtbase.h:797:52: note: in definition of macro 'PXT_CREATE_BUFFER'
 #define PXT_CREATE_BUFFER(data, len) pxt::mkBuffer(data, len)
                                                    ^~~~

I can't see any evidence that I was doing anything wrong by using MicroBitFont in the past, so I guess this should probably work?

Or- is there an alternative approach here?

Finally- is there any specific version of pxt-core and pxt-microbit I should be building against, currently? I assumed the latest for targeting V2.

[pelikhan]

Your library is using C++ so you need to make it compatible with the micro:bit v1 stack (nrf51, microbit-dal) and v2 stack (nrf52, codal) stack.

In this case, the font class has moved and is now at https://github.com/lancaster-university/codal-core/blob/master/inc/types/BitmapFont.h -- in particular https://github.com/lancaster-university/codal-core/blob/9643ee76d2af1eb501f70d5d8cbc405ab7a42291/inc/types/BitmapFont.h#L96

In C++, use this preprocessor test to determine if you are building against CODAL (v2) or not (v1)

#if MICROBIT_CODAL
// v2 code
#else
// v1 code
#endif

[Gadgetoid]

Thank you- this stack is so deep and dizzying that I didn't get close to finding where I was going wrong. Looks like ScrollBit is now working!

[pelikhan]

A sandwich is only as good as how many layers its got squiched together.

[Gadgetoid]

Having just thrown together a burger with more fillings than a Subway counter, I tend to agree. Though it doesn't lend itself well to peeling apart the layers of the sandwich and trying to figure out what's what 😆

With ^3.1.17 and ^6.0.0 am I targeting approximately the right pxt-microbit and pxt-core versions?

[pelikhan]

The branch that will go live is stable3.0 https://github.com/microsoft/pxt-microbit/commits/stable3.0

The best is to look into the package.json in that branch to figure out precisely the branch of pxt-common-packages and pxt-core: https://github.com/microsoft/pxt-microbit/blob/stable3.0/package.json#L47

• pxt-core: stable6.0
• pxt-common-packages: stable7.0

[pelikhan]

we are integrating the relevant fixes from pxt-microbit#master (v3.1) to v3.0

[pelikhan]

I'm going to close this one since it seems that you've been unlocked.