Add package event (#930)

Package event is a package that models events that occur during
the execution of a program. The current implementation is mock
and we plan to add implementation later.

Updates #926

event/event.go

@@ -0,0 +1,238 @@
+// Copyright 2019 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package event is a package that models events that occur during
+// the execution of a program.
+package event
+
+// Event is an interface that custom events should implement.
+// It is empty for now because there are no general methods
+// required of events yet.
+type Event interface {
+}
+
+// KeyCharacter is an event that occurs when a character is actually typed on
+// the keyboard. This may be provided by an input method.
+type KeyCharacter struct {
+	// Code is the key code of the key typed.
+	// TODO: this should change later from an int to an enumeration type.
+	Code int
+	// Modifiers are the modifiers pressed together with the key.
+	// TODO: this should change later from an int to an enumeration type.
+	Modifiers int
+	// Character is the character that was typed.
+	Character rune
+}
+
+// KeyDown is an event that occurs when a key is pressed on the keyboard.
+type KeyDown struct {
+	// Code is the key code of the key pressed or released.
+	// TODO: this should change later from an int to an enumeration type.
+	Code int
+	// Modifiers are the modifiers pressed together with the key.
+	// TODO: this should change later from an int to an enumeration type.
+	Modifiers int
+}
+
+// KeyUp is an event that occurs when a key is released on the keyboard.
+// The data is the same as for a KeyDown event.
+type KeyUp KeyDown
+
+// GamepadAxis is for event where an axis on a gamepad changes.
+type GamepadAxis struct {
+	// ID represents which gamepad caused the event.
+	ID int
+	// Axis is the axis of the game pad that changed position.
+	Axis int
+	// Position is the psoition of the axis after the change.
+	// It varies between -1.0 and 1.0.
+	Position float32
+}
+
+// GamepadButtonDown is a gamepad button press event.
+type GamepadButtonDown struct {
+	// ID represents which gamepad caused the event.
+	ID int
+	// Button is the button that was pressed on the game pad.
+	Button int
+	// Pressure is the pressure that is applied to the gamepad button.
+	// It varies between 0.0 for not pressed, and 1.0 for completely pressed.
+	Pressure float32
+}
+
+// GamepadButtonDown is a gamepad button release event.
+// The data is identical to a GamePadButtonDown event.
+type GamepadButtonUp GamepadButtonDown
+
+// GamepadAttach happens when a new gamepad is attached.
+type GamepadAttach struct {
+	// ID represents which gamepad caused the event.
+	ID int
+	// Axes represents the amount of axes the gamepad has.
+	Axes int
+	// Buttons represents the amount of buttons the gamepad has.
+	Buttons int
+}
+
+// GamepadDetach happens when a gamepad is detached.
+type GamepadDetach struct {
+	// ID represents which gamepad caused the event.
+	ID int
+}
+
+// MouseMove is a mouse movement event.
+type MouseMove struct {
+	// X is the X position of the mouse pointer.
+	// This value is expressed in device independent pixels.
+	X float32
+	// Y is the Y position of the mouse pointer.
+	// This value is expressed in device independent pixels.
+	Y float32
+	// DeltaX is the change in X since the last MouseMove event.
+	// This value is expressed in device independent pixels.
+	DeltaX float32
+	// DeltaY is the change in Y since the last MouseMove event.
+	// This value is expressed in device independent pixels.
+	DeltaY float32
+}
+
+// MouseWheel is a mouse wheel event.
+type MouseWheel struct {
+	// X is the X position of the mouse wheel.
+	// This value is expressed in arbitrary units.
+	// It increases when the mouse wheel is scrolled downwards,
+	// and decreases when the mouse is scrolled upwards.
+	X float32
+	// Y is the Y position of the mouse wheel.
+	// This value is expressed in arbitrary units.
+	// It increases when the mouse wheel is scrolled to the right,
+	// and decreases when the mouse is scrolled to the left.
+	Y float32
+	// DeltaX is the change in X since the last MouseWheel event.
+	// This value is expressed in arbitrary units.
+	// It is positive when the mouse wheel is scrolled downwards,
+	// and negative when the mouse is scrolled upwards.
+	DeltaX float32
+	// DeltaY is the change in Y since the last MouseWheel event.
+	// This value is expressed in arbitrary units.
+	// It is positive when the mouse wheel is scrolled to the right,
+	// and negative when the mouse is scrolled to the left.
+	DeltaY float32
+}
+
+// MouseButtonDown is a mouse button press event.
+type MouseButtonDown struct {
+	// X is the X position of the mouse pointer.
+	// This value is expressed in device independent pixels.
+	X float32
+	// Y is the Y position of the mouse pointer.
+	// This value is expressed in device independent pixels.
+	Y float32
+	// Button is the button on the mouse that was pressed.
+	// TODO: this should change later from an int to an enumeration type.
+	Button int
+	// Pressure is the pressure applied on the mouse button.
+	// It varies between 0.0 for not pressed, and 1.0 for completely pressed.
+	Pressure float32
+}
+
+// MouseButtonDown is a mouse button Release event.
+// The data is identical to a MouseButtonDown event.
+type MouseButtonUp MouseButtonDown
+
+// MouseEnter occurs when the mouse enters the view window.
+type MouseEnter struct {
+	// X is the X position of the mouse pointer.
+	// This value is expressed in device independent pixels.
+	X float32
+	// Y is the Y position of the mouse pointer.
+	// This value is expressed in device independent pixels.
+	Y float32
+}
+
+// MouseLeave occurs when the mouse leaves the view window.
+// The data is identical to MouseEnter.
+type MouseLeave MouseEnter
+
+// ViewUpdate occurs when the application is ready to update
+// the next frame on the view port.
+type ViewUpdate struct {
+	// No data neccesary, for now.
+}
+
+// ViewSize occurs when the size of the application's view port changes.
+type ViewSize struct {
+	// Width is the width of the view.
+	// This value is expressed in device independent pixels.
+	Width int
+	// Height is the height of the view.
+	// This value is expressed in device independent pixels.
+	Height int
+}
+
+// TouchBegin occurs when a touch begins.
+type TouchBegin struct {
+	// ID identifies the touch that caused the touch event.
+	ID int
+	// X is the X position of the touch.
+	// This value is expressed in device independent pixels.
+	X float32
+	// Y is the Y position of the touch.
+	// This value is expressed in device independent pixels.
+	Y float32
+	// Pressure is the pressure applied to the touch.
+	// It varies between 0.0 for not pressed, and 1.0 for completely pressed.
+	Pressure float32
+	// Primary represents whether the touch event is the primary touch or not.
+	// If it is true, then it is a primary touch.
+	// Otherwise it is false.
+	Primary bool
+}
+
+// TouchMove occurs when a touch moved, or in other words, is dragged.
+type TouchMove struct {
+	// ID identifies the touch that caused the touch event.
+	ID int
+	// X is the X position of the touch.
+	// This value is expressed in device independent pixels.
+	X float32
+	// Y is the Y position of the touch.
+	// This value is expressed in device independent pixels.
+	Y float32
+	// DeltaX is the change in X since last touch event.
+	// This value is expressed in device independent pixels.
+	DeltaX float32
+	// Deltay is the change in Y since last touch event.
+	// This value is expressed in device independent pixels.
+	DeltaY float32
+	// Pressure of applied touch.
+	// It varies between 0.0 for not pressed, and 1.0 for completely pressed.
+	Pressure float32
+	// Primary represents whether the touch event is the primary touch or not.
+	// If it is true, then it is a primary touch.
+	// If it is false then it is not.
+	Primary bool
+}
+
+// TouchEnd occurs when a touch ends.
+// The data is the same as for a TouchMove event.
+type TouchEnd TouchMove
+
+// TouchCancel occurs when a touch is canceled.
+// This can happen in various situations, depending on the underlying platform,
+// for example when the aplication loses focus.
+type TouchCancel struct {
+	// ID identifies the touch that caused the touch event.
+	ID int
+}