flutter_windows.h

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_PUBLIC_FLUTTER_WINDOWS_H_
#define FLUTTER_SHELL_PLATFORM_WINDOWS_PUBLIC_FLUTTER_WINDOWS_H_
 
#include <dxgi.h>
#include <stddef.h>
#include <stdint.h>
#include <windows.h>
 
#include "flutter_export.h"
#include "flutter_messenger.h"
#include "flutter_plugin_registrar.h"
 
#if defined(__cplusplus)
extern "C" {
#endif
 
typedef void (*VoidCallback)(void* /* user data */);
 
// Opaque reference to a Flutter view controller.
struct FlutterDesktopViewController;
typedef struct FlutterDesktopViewController* FlutterDesktopViewControllerRef;
 
// Opaque reference to a Flutter window.
struct FlutterDesktopView;
typedef struct FlutterDesktopView* FlutterDesktopViewRef;
 
// Opaque reference to a Flutter engine instance.
struct FlutterDesktopEngine;
typedef struct FlutterDesktopEngine* FlutterDesktopEngineRef;
 
// The unique identifier for a view.
typedef int64_t FlutterDesktopViewId;
 
// Configures how the Flutter engine selects a GPU.
typedef enum {
  // No preference.
  NoPreference,
  // Prefer energy efficiency over performance, such as an integrated GPU.
  // This falls back to a high performance GPU if no low power GPU is
  // available.
  LowPowerPreference,
} FlutterDesktopGpuPreference;
 
// Configures the thread policy for running the UI isolate.
typedef enum {
  // Default value. Currently will run the UI isolate on separate thread,
  // later will be changed to running the UI isolate on platform thread.
  Default,
  // Run the UI isolate on platform thread.
  RunOnPlatformThread,
  // Run the UI isolate on a separate thread.
  RunOnSeparateThread,
} FlutterDesktopUIThreadPolicy;
 
// Properties for configuring a Flutter engine instance.
typedef struct {
  // The path to the flutter_assets folder for the application to be run.
  // This can either be an absolute path or a path relative to the directory
  // containing the executable.
  const wchar_t* assets_path;
 
  // The path to the icudtl.dat file for the version of Flutter you are using.
  // This can either be an absolute path or a path relative to the directory
  // containing the executable.
  const wchar_t* icu_data_path;
 
  // The path to the AOT library file for your application, if any.
  // This can either be an absolute path or a path relative to the directory
  // containing the executable. This can be nullptr for a non-AOT build, as
  // it will be ignored in that case.
  const wchar_t* aot_library_path;
 
  // The name of the top-level Dart entrypoint function. If null or the empty
  // string, 'main' is assumed. If a custom entrypoint is used, this parameter
  // must specifiy the name of a top-level function in the same Dart library as
  // the app's main() function. Custom entrypoint functions must be decorated
  // with `@pragma('vm:entry-point')` to ensure the method is not tree-shaken
  // by the Dart compiler.
  const char* dart_entrypoint;
 
  // Number of elements in the array passed in as dart_entrypoint_argv.
  int dart_entrypoint_argc;
 
  // Array of Dart entrypoint arguments. This is deep copied during the call
  // to FlutterDesktopEngineCreate.
  const char** dart_entrypoint_argv;
 
  // GPU choice preference
  FlutterDesktopGpuPreference gpu_preference;
 
  // Policy for the thread that runs UI isolate.
  FlutterDesktopUIThreadPolicy ui_thread_policy;
} FlutterDesktopEngineProperties;
 
// ========== View Controller ==========
 
// Creates a view that hosts and displays the given engine instance.
//
// This takes ownership of |engine|, so FlutterDesktopEngineDestroy should no
// longer be called on it, as it will be called internally when the view
// controller is destroyed. If creating the view controller fails, the engine
// will be destroyed immediately.
//
// If |engine| is not already running, the view controller will start running
// it automatically before displaying the window.
//
// The caller owns the returned reference, and is responsible for calling
// FlutterDesktopViewControllerDestroy. Returns a null pointer in the event of
// an error.
//
// The Win32 implementation accepts width, height with view hookup explicitly
// performed using the caller using HWND parenting.
FLUTTER_EXPORT FlutterDesktopViewControllerRef
FlutterDesktopViewControllerCreate(int width,
                                   int height,
                                   FlutterDesktopEngineRef engine);
 
// Shuts down the engine instance associated with |controller|, and cleans up
// associated state.
//
// |controller| is no longer valid after this call.
FLUTTER_EXPORT void FlutterDesktopViewControllerDestroy(
    FlutterDesktopViewControllerRef controller);
 
// Returns the view controller's view ID.
FLUTTER_EXPORT FlutterDesktopViewId FlutterDesktopViewControllerGetViewId(
    FlutterDesktopViewControllerRef view_controller);
 
// Returns the handle for the engine running in FlutterDesktopViewControllerRef.
//
// Its lifetime is the same as the |controller|'s.
FLUTTER_EXPORT FlutterDesktopEngineRef FlutterDesktopViewControllerGetEngine(
    FlutterDesktopViewControllerRef controller);
 
// Returns the view managed by the given controller.
FLUTTER_EXPORT FlutterDesktopViewRef FlutterDesktopViewControllerGetView(
    FlutterDesktopViewControllerRef controller);
 
// Requests new frame from the engine and repaints the view.
FLUTTER_EXPORT void FlutterDesktopViewControllerForceRedraw(
    FlutterDesktopViewControllerRef controller);
 
// Allows the Flutter engine and any interested plugins an opportunity to
// handle the given message.
//
// If the WindowProc was handled and further handling should stop, this returns
// true and |result| will be populated. |result| is not set if returning false.
FLUTTER_EXPORT bool FlutterDesktopViewControllerHandleTopLevelWindowProc(
    FlutterDesktopViewControllerRef controller,
    HWND hwnd,
    UINT message,
    WPARAM wparam,
    LPARAM lparam,
    LRESULT* result);
 
// ========== Engine ==========
 
// Creates a Flutter engine with the given properties.
//
// The caller owns the returned reference, and is responsible for calling
// FlutterDesktopEngineDestroy. The lifetime of |engine_properties| is required
// to extend only until the end of this call.
FLUTTER_EXPORT FlutterDesktopEngineRef FlutterDesktopEngineCreate(
    const FlutterDesktopEngineProperties* engine_properties);
 
// Shuts down and destroys the given engine instance. Returns true if the
// shutdown was successful, or if the engine was not running.
//
// |engine| is no longer valid after this call.
FLUTTER_EXPORT bool FlutterDesktopEngineDestroy(FlutterDesktopEngineRef engine);
 
// Starts running the given engine instance.
//
// The entry_point parameter is deprecated but preserved for
// backward-compatibility. If desired, a custom Dart entrypoint function can be
// set in the dart_entrypoint field of the FlutterDesktopEngineProperties
// struct passed to FlutterDesktopEngineCreate.
//
// If specified, entry_point must be the name of a top-level function from the
// same Dart library that contains the app's main() function, and must be
// decorated with `@pragma(vm:entry-point)` to ensure the method is not
// tree-shaken by the Dart compiler. If conflicting non-null values are passed
// to this function and via the FlutterDesktopEngineProperties struct, the run
// will fail.
//
// Returns false if running the engine failed.
FLUTTER_EXPORT bool FlutterDesktopEngineRun(FlutterDesktopEngineRef engine,
                                            const char* entry_point);
 
// DEPRECATED: This is no longer necessary to call, Flutter will take care of
// processing engine messages transparently through DispatchMessage.
//
// Processes any pending events in the Flutter engine, and returns the
// number of nanoseconds until the next scheduled event (or max, if none).
//
// This should be called on every run of the application-level runloop, and
// a wait for native events in the runloop should never be longer than the
// last return value from this function.
FLUTTER_EXPORT uint64_t FlutterDesktopEngineProcessMessages(
    FlutterDesktopEngineRef engine);
 
FLUTTER_EXPORT void FlutterDesktopEngineReloadSystemFonts(
    FlutterDesktopEngineRef engine);
 
// Returns the plugin registrar handle for the plugin with the given name.
//
// The name must be unique across the application.
FLUTTER_EXPORT FlutterDesktopPluginRegistrarRef
FlutterDesktopEngineGetPluginRegistrar(FlutterDesktopEngineRef engine,
                                       const char* plugin_name);
 
// Returns the messenger associated with the engine.
//
// This does not provide an owning reference, so should *not* be balanced with a
// call to |FlutterDesktopMessengerRelease|.
//
// Callers should use |FlutterDesktopMessengerAddRef| if the returned pointer
// will potentially outlive 'engine', such as when passing it to another thread.
FLUTTER_EXPORT FlutterDesktopMessengerRef FlutterDesktopEngineGetMessenger(
    FlutterDesktopEngineRef engine);
 
// Returns the texture registrar associated with the engine.
FLUTTER_EXPORT FlutterDesktopTextureRegistrarRef
FlutterDesktopEngineGetTextureRegistrar(FlutterDesktopEngineRef engine);
 
// Schedule a callback to be called after the next frame is drawn.
//
// This must be called from the platform thread. The callback is executed only
// once on the platform thread.
FLUTTER_EXPORT void FlutterDesktopEngineSetNextFrameCallback(
    FlutterDesktopEngineRef engine,
    VoidCallback callback,
    void* user_data);
 
// ========== View ==========
 
// Returns the backing HWND for manipulation in host application.
FLUTTER_EXPORT HWND FlutterDesktopViewGetHWND(FlutterDesktopViewRef view);
 
// Returns the DXGI adapter used for rendering or nullptr in case of error.
FLUTTER_EXPORT IDXGIAdapter* FlutterDesktopViewGetGraphicsAdapter(
    FlutterDesktopViewRef view);
 
// Called to pass an external window message to the engine for lifecycle
// state updates. Non-Flutter windows must call this method in their WndProc
// in order to be included in the logic for application lifecycle state
// updates. Returns a result if the message should be consumed.
FLUTTER_EXPORT bool FlutterDesktopEngineProcessExternalWindowMessage(
    FlutterDesktopEngineRef engine,
    HWND hwnd,
    UINT message,
    WPARAM wparam,
    LPARAM lparam,
    LRESULT* result);
 
// ========== Plugin Registrar (extensions) ==========
// These are Windows-specific extensions to flutter_plugin_registrar.h
 
// Function pointer type for top level WindowProc delegate registration.
//
// The user data will be whatever was passed to
// FlutterDesktopRegisterTopLevelWindowProcHandler.
//
// Implementations should populate |result| and return true if the WindowProc
// was handled and further handling should stop. |result| is ignored if the
// function returns false.
typedef bool (*FlutterDesktopWindowProcCallback)(HWND /* hwnd */,
                                                 UINT /* uMsg */,
                                                 WPARAM /*wParam*/,
                                                 LPARAM /* lParam*/,
                                                 void* /* user data */,
                                                 LRESULT* result);
 
// Returns the implicit view associated with this registrar's engine instance,
// or null if there is no implicit view.
//
// See:
// https://api.flutter.dev/flutter/dart-ui/PlatformDispatcher/implicitView.html
//
// DEPRECATED: Use |FlutterDesktopPluginRegistrarGetViewById| instead.
FLUTTER_EXPORT FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetView(
    FlutterDesktopPluginRegistrarRef registrar);
 
// Returns the view associated with the registrar's engine instance, or null if
// the view does not exist.
FLUTTER_EXPORT FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetViewById(
    FlutterDesktopPluginRegistrarRef registrar,
    FlutterDesktopViewId view_id);
 
FLUTTER_EXPORT void
FlutterDesktopPluginRegistrarRegisterTopLevelWindowProcDelegate(
    FlutterDesktopPluginRegistrarRef registrar,
    FlutterDesktopWindowProcCallback delegate,
    void* user_data);
 
FLUTTER_EXPORT void
FlutterDesktopPluginRegistrarUnregisterTopLevelWindowProcDelegate(
    FlutterDesktopPluginRegistrarRef registrar,
    FlutterDesktopWindowProcCallback delegate);
 
// ========== Freestanding Utilities ==========
 
// Gets the DPI for a given |hwnd|, depending on the supported APIs per
// windows version and DPI awareness mode. If nullptr is passed, returns the DPI
// of the primary monitor.
//
// This uses the same logic and fallback for older Windows versions that is used
// internally by Flutter to determine the DPI to use for displaying Flutter
// content, so should be used by any code (e.g., in plugins) that translates
// between Windows and Dart sizes/offsets.
FLUTTER_EXPORT UINT FlutterDesktopGetDpiForHWND(HWND hwnd);
 
// Gets the DPI for a given |monitor|. If the API is not available, a default
// DPI of 96 is returned.
//
// See FlutterDesktopGetDpiForHWND for more information.
FLUTTER_EXPORT UINT FlutterDesktopGetDpiForMonitor(HMONITOR monitor);
 
// Reopens stdout and stderr and resysncs the standard library output streams.
// Should be called if output is being directed somewhere in the runner process
// (e.g., after an AllocConsole call).
FLUTTER_EXPORT void FlutterDesktopResyncOutputStreams();
 
#if defined(__cplusplus)
}  // extern "C"
#endif
 
#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_PUBLIC_FLUTTER_WINDOWS_H_