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73 lines
3.9 KiB
Markdown
73 lines
3.9 KiB
Markdown
Coding Style
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============
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The coding style for EmulationStation-DE is mostly a combination of the Linux Kernel and Google C++ coding guidelines. \
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Please refer to these documents here: \
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https://www.kernel.org/doc/html/v4.10/process/coding-style.html \
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https://google.github.io/styleguide/cppguide.html \
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There are some deviations though, mostly due to historical reasons as the original code did not use this coding style.
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Some key points:
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* Column width (line length) is 100 characters
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* Indentation is 4 spaces, don't use tabs as they can be interpreted differently!
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* Line break is Unix-style (line feed only, no carriage return)
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* Do not leave trailing whitespaces at the end of the lines (a good source code editor should have a setting to automatically trim these for you)
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* When breaking up long lines into multiple lines, consider what could be useful data to grep for so you don't break in the middle of such a string
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* Comments always in C++ style, i.e. // instead of /* */
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* Comments should be proper sentences, starting with a capital letter and ending with a dot
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* Use K&R placements of braces, read the Linux Kernel coding style document for clarifications
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* Always use spaces between keywords and opening brackets, i.e. `if ()`, `for ()`, `while ()` etc.
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* Use `std::string` instead of `char *` or `char []` unless there is a specific reason requiring the latter
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* If the arguments (and initializer list) for a function or class exceeds 4 items, arrange them vertically to make the code easier to read
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* Always declare one variable per line, never combine multiple declarations of the same type
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* Name local variables with the first word in small letters and the proceeding words starting with capital letters, e.g. myExampleVariable
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* Name member variables starting with a small 'm', e.g. mMyMemberVariable
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* Use the same naming convention for functions as for local variables, e.g. someFunction()
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* Inline functions makes perfect sense to use, but don't overdo it by using them for functions that won't be called very frequently
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* Never put more than one statement on a single line, except for lambda expressions
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* Avoid overoptimizations, especially if it sacrifices readability, makes the code hard to expand on or is error prone
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* For the rest, check the code and have fun! :)
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Development Environment
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=======================
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EmulationStation-DE is developed and compiled using GCC and GDB. Any code editor can be used of course, I use [VSCodium](https://vscodium.com). \
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For debugging purposes, starting the application like this could make sense:
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`emulationstation --windowed --debug --resolution 1280 720`
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Creating a new GuiComponent
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===========================
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You probably want to override:
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`bool input(InputConfig* config, Input input);`
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Check if some input is mapped to some action with `config->isMappedTo("a", input);`.
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Check if an input is "pressed" with `input.value != 0` (input.value *can* be negative in the case of axes).
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`void update(int deltaTime);`
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`deltaTime` is in milliseconds.
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`void render(const Transform4x4f& parentTrans);`
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You probably want to do `Transform4x4f trans = parentTrans * getTransform();` to get your final "modelview" matrix.
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Apply the modelview matrix with `Renderer::setMatrix(const Transform4x4f&)`.
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Render any children the component may have with `renderChildren(parentTrans);`.
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Creating a new GameListView Class
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=================================
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1. Don't allow the user to navigate to the root node's parent. If you use a stack of some sort to keep track of past cursor states this will be a natural side effect.
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Creating a new Component
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========================
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If your component is not made up of other components, and you draw something to the screen with OpenGL, make sure:
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* Your vertex positions are rounded before you render (you can use round(float) in Util.h to do this).
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* Your transform matrix's translation is rounded (you can use roundMatrix(affine3f) in Util.h to do this).
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