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52 lines
1.6 KiB
Markdown
52 lines
1.6 KiB
Markdown
Hacking
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=======
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## How to Debug
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We have a helper function called `logger.dbg` to help with debugging. You can use that function to print string and tables:
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```lua
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local logger = require("logger")
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a = {"1", "2", "3"}
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logger.dbg("table a: ", a)
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```
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Anything printed by `logger.dbg` starts with `DEBUG`.
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On most target platforms, log output is saved to `crash.log` in the `koreader` directory.
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```
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04/06/17-21:44:53 DEBUG foo
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```
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In production code, remember that arguments are *always* evaluated in Lua, so,
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don't inline complex computations in logger functions' arguments.
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If you *really* have to, hide the whole thing behind a `dbg.is_on` branch,
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like in [frontend/device/input.lua](https://github.com/koreader/koreader/blob/ba6fef4d7ba217ca558072f090849000e72ba142/frontend/device/input.lua#L1131-L1134).
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## Bug hunting in KPV (KOReader's predecessor)
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A real example of bug hunting in KPV's cache system: <https://github.com/koreader/kindlepdfviewer/pull/475>
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## Developing UI widgets ##
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`tools/wbuilder.lua` is your friend, if you need to create new UI widgets. It
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sets up a minimal environment to bootstrap KOReader's UI framework to avoid
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starting the whole reader. This gives you quick feedback loop while iterating
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through your widget changes. It's also a handy tool for debugging widget
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issues.
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To get a taste of how it works, try running this command at the root of
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KOReader's source tree:
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```
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./kodev wbuilder
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```
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It will spawn up an emulator window with a grid and simple timer widget for
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demonstration.
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You can add more `UIManager:show` call at the end of `tools/wbuilder.lua` to
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test your new widgets.
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