81 lines
2.6 KiB
Go
81 lines
2.6 KiB
Go
package stone
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import "image"
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import "errors"
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// Backend represents a backend for stone. Backends can be registered for use
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// with the RegisterBackend() function. All of the below methods MUST be thread
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// safe!
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type Backend interface {
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// Run is the backend's event loop. It must cleanly exit when the user
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// closes the window, but not before calling the OnQuit event. Run
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// must call event handlers within its own event loop in a
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// non-concurrent fashion.
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//
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// The OnStart event handler must run after the backend has been fully
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// initialized, and right before updates are first pushed to the screen.
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// Whatever the application draws from within this event handler must be
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// the first thing that appears on-screen.
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//
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// The OnResize event handler must run whenever the window is resized.
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// The backend must push updates to the screen after OnResize has been
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// run.
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//
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// The backend must not push updates to the screen in any other case,
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// except when its Draw() method is specifically called.
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//
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// The OnPress, OnRelease, OnMouseMove, and OnMouseScroll events are to
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// be called when such events happen. It is reccommended to compress
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// resize, mouse move, and mouse scroll events whenever possible to
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// reduce the likelihood of event buildup.
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Run ()
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// SetTitle sets the application title. This will most often be the
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// window title. This method may not always produce an effect, depending
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// on the backend.
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SetTitle (title string) (err error)
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// SetIcon takes in a set of images of different sizes and sets the
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// window's icon to them. This method may not always produce an effect,
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// depending on the backend.
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SetIcon (icons []image.Image) (err error)
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// Draw pushes all updates made to the application's buffer to the
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// screen.
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Draw ()
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}
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// BackendFactory must completely initialize a backend, and return it. If
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// anything goes wrong, it must stop, clean up any resources and return an
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// error so another backend can be chosen.
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type BackendFactory func (
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application *Application,
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callbackManager *CallbackManager,
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) (
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backend Backend,
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err error,
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)
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var factories []BackendFactory
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// RegisterBackend registers a backend factory.
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func RegisterBackend (factory BackendFactory) {
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factories = append(factories, factory)
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}
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func instantiateBackend (application *Application) (backend Backend, err error) {
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// find a suitable backend
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for _, factory := range factories {
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backend, err = factory(application, &application.callbackManager)
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if err == nil && backend != nil { return }
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}
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// if none were found, but there was no error produced, produce an
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// error
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if err == nil {
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err = errors.New("no available backends")
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}
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return
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}
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