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Many widget classes need to run substantial initialization code after they have been setup from GML. With this change, an initialize_fallibles() function is called if available, allowing the initialization to be invoked from the GML setup automatically. This means that the GML-generated creation function can now be used directly for many more cases, and reduces code duplication.
65 lines
2.4 KiB
Markdown
65 lines
2.4 KiB
Markdown
## Name
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GML Usage
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## Description
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How to use GML in SerenityOS C++ applications
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## Note
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This manpage describes the new method of loading GML files via generated C++ code. There also is the runtime `load_from_gml` function which has the same behavior. The runtime method should not be used except for specific use cases such as [GMLPlayground](help://man/1/Applications/GMLPlayground).
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## CMake
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Include `compile_gml()` your application's CMake file. The generated source file name is not fixed, but should follow this convention.
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```cmake
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compile_gml(MyApp.gml MyAppGML.cpp)
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```
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Include the name of the source file that will be compiled from your GML file in your `SOURCES`.
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```cmake
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set(SOURCES
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MyAppGML.cpp
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)
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```
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## C++
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The C++ source file that is generated will provide an implementation for the `ErrorOr<NonnullRefPtr<MyApp::Widget>> MyApp::Widget::try_create()` function, given that the root widget of the GML file is `MyApp::Widget`. For this to work, you have to add a declaration for this function in the header of the `MyApp::Widget` class. (The function will not collide with functions provided by `Core::Object`, do not worry.) Additionally, there must be a no-argument constructor in `MyApp::Widget`, which is used by the `try_create` implementation.
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Calling the `try_create` function directly or indirectly (e.g. `Window::try_set_main_widget`) will now automatically load the structure defined in GML.
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From there, you can use `find_descendant_of_type_named` to select widgets from your GML by their `name` property.
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```gml
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@MyApp::Widget {
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@GUI::Button {
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name: "mem_add_button"
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text: "M+"
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fixed_width: 35
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fixed_height: 28
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foreground_color: "red"
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}
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}
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```
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```cpp
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// MyApp::Widget::foo_bar
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m_mem_add_button = *find_descendant_of_type_named<GUI::Button>("mem_add_button");
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```
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### `initialize` Pattern
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Initialization, like adding models, attaching callbacks, etc., should be done in a member function with the signature:
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```cpp
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// MyApp::Widget
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ErrorOr<void> initialize();
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```
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This initializer function, if it exists, will automatically be called after the structure of your widget was set up by the auto-generated GML code.
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The only case where this function cannot be used is when your initialization requires additional parameters, like a GUI window. You may still consider moving as much initialization to the canonical function as possible.
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