From 04d2ea4767cecaaad49ee12248eae9c48074ca9a Mon Sep 17 00:00:00 2001
From: Sasha Koshka <sashakoshka@tebibyte.media>
Date: Thu, 2 Feb 2023 01:47:01 -0500
Subject: [PATCH] Atomized the functionality of the base tomo package

---
 backend.go          |   8 ++-
 canvas/canvas.go    |  90 +++++++++++++++++++++++++
 data/data.go        |  20 ++++++
 elements/element.go | 159 ++++++++++++++++++++++++++++++++++++++++++++
 elements/window.go  |  39 +++++++++++
 input/input.go      | 131 ++++++++++++++++++++++++++++++++++++
 layouts/layout.go   |  37 +++++++++++
 tomo.go             |   8 ++-
 8 files changed, 486 insertions(+), 6 deletions(-)
 create mode 100644 canvas/canvas.go
 create mode 100644 data/data.go
 create mode 100644 elements/element.go
 create mode 100644 elements/window.go
 create mode 100644 input/input.go
 create mode 100644 layouts/layout.go

diff --git a/backend.go b/backend.go
index 6ad3f70..3b1ff31 100644
--- a/backend.go
+++ b/backend.go
@@ -1,6 +1,8 @@
 package tomo
 
 import "errors"
+import "git.tebibyte.media/sashakoshka/tomo/data"
+import "git.tebibyte.media/sashakoshka/tomo/elements"
 
 // Backend represents a connection to a display server, or something similar.
 // It is capable of managing an event loop, and creating windows.
@@ -19,13 +21,13 @@ type Backend interface {
 	// NewWindow creates a new window with the specified width and height,
 	// and returns a struct representing it that fulfills the Window
 	// interface.
-	NewWindow (width, height int) (window Window, err error)
+	NewWindow (width, height int) (window elements.Window, err error)
 
 	// Copy puts data into the clipboard.
-	Copy (Data)
+	Copy (data.Data)
 
 	// Paste returns the data currently in the clipboard.
-	Paste (accept []Mime) (Data)
+	Paste (accept []data.Mime) (data.Data)
 }
 
 // BackendFactory represents a function capable of constructing a backend
diff --git a/canvas/canvas.go b/canvas/canvas.go
new file mode 100644
index 0000000..cb2da2a
--- /dev/null
+++ b/canvas/canvas.go
@@ -0,0 +1,90 @@
+package canvas
+
+import "image"
+import "image/draw"
+import "image/color"
+
+// Canvas is like draw.Image but is also able to return a raw pixel buffer for
+// more efficient drawing. This interface can be easily satisfied using a
+// BasicCanvas struct.
+type Canvas interface {
+	draw.Image
+	Buffer () (data []color.RGBA, stride int)
+}
+
+// BasicCanvas is a general purpose implementation of tomo.Canvas.
+type BasicCanvas struct {
+	pix    []color.RGBA
+	stride int
+	rect   image.Rectangle
+}
+
+// NewBasicCanvas creates a new basic canvas with the specified width and
+// height, allocating a buffer for it.
+func NewBasicCanvas (width, height int) (canvas BasicCanvas) {
+	canvas.pix    = make([]color.RGBA, height * width)
+	canvas.stride = width
+	canvas.rect = image.Rect(0, 0, width, height)
+	return
+}
+
+// you know what it do
+func (canvas BasicCanvas) Bounds () (bounds image.Rectangle) {
+	return canvas.rect
+}
+
+// you know what it do
+func (canvas BasicCanvas) At (x, y int) (color.Color) {
+	if !image.Pt(x, y).In(canvas.rect) { return nil }
+	return canvas.pix[x + y * canvas.stride]
+}
+
+// you know what it do
+func (canvas BasicCanvas) ColorModel () (model color.Model) {
+	return color.RGBAModel
+}
+
+// you know what it do
+func (canvas BasicCanvas) Set (x, y int, c color.Color) {
+	if !image.Pt(x, y).In(canvas.rect) { return }
+	r, g, b, a := c.RGBA()
+	canvas.pix[x + y * canvas.stride] = color.RGBA {
+		R: uint8(r >> 8),
+		G: uint8(g >> 8),
+		B: uint8(b >> 8),
+		A: uint8(a >> 8),
+	}
+}
+
+// you know what it do
+func (canvas BasicCanvas) Buffer () (data []color.RGBA, stride int) {
+	return canvas.pix, canvas.stride
+}
+
+// Reallocate efficiently reallocates the canvas. The data within will be
+// garbage. This method will do nothing if this is a cut image.
+func (canvas *BasicCanvas) Reallocate (width, height int) {
+	if canvas.rect.Min != (image.Point { }) { return }
+
+	previousLen := len(canvas.pix)
+	newLen := width * height
+	bigger  := newLen > previousLen
+	smaller := newLen < previousLen / 2
+	if bigger || smaller {
+		canvas.pix = make (
+			[]color.RGBA,
+			((height * width) / 4096) * 4096 + 4096)
+	}
+	canvas.stride = width
+	canvas.rect = image.Rect(0, 0, width, height)
+}
+
+// Cut returns a sub-canvas of a given canvas.
+func Cut (canvas Canvas, bounds image.Rectangle) (reduced BasicCanvas) {
+	// println(canvas.Bounds().String(), bounds.String())
+	bounds = bounds.Intersect(canvas.Bounds())
+	if bounds.Empty() { return }
+	reduced.rect = bounds
+	reduced.pix, reduced.stride = canvas.Buffer()
+	return
+}
diff --git a/data/data.go b/data/data.go
new file mode 100644
index 0000000..8055711
--- /dev/null
+++ b/data/data.go
@@ -0,0 +1,20 @@
+package data
+
+import "io"
+
+// Data represents arbitrary polymorphic data that can be used for data transfer
+// between applications.
+type Data map[Mime] io.ReadCloser
+
+// Mime represents a MIME type.
+type Mime struct {
+	// Type is the first half of the MIME type, and Subtype is the second
+	// half. The separating slash is not included in either. For example,
+	// text/html becomes:
+	// Mime { Type: "text", Subtype: "html" }
+	Type, Subtype string
+}
+
+var MimePlain = Mime { "text", "plain" }
+
+var MimeFile = Mime { "text", "uri-list" }
diff --git a/elements/element.go b/elements/element.go
new file mode 100644
index 0000000..f97a48c
--- /dev/null
+++ b/elements/element.go
@@ -0,0 +1,159 @@
+package elements
+
+import "image"
+import "git.tebibyte.media/sashakoshka/tomo/input"
+import "git.tebibyte.media/sashakoshka/tomo/canvas"
+
+// Element represents a basic on-screen object.
+type Element interface {
+	// Element must implement the Canvas interface. Elements should start
+	// out with a completely blank buffer, and only allocate memory and draw
+	// on it for the first time when sent an EventResize event.
+	canvas.Canvas
+
+	// MinimumSize specifies the minimum amount of pixels this element's
+	// width and height may be set to. If the element is given a resize
+	// event with dimensions smaller than this, it will use its minimum
+	// instead of the offending dimension(s).
+	MinimumSize () (width, height int)
+
+	// DrawTo sets this element's canvas. This should only be called by the
+	// parent element. This is typically a region of the parent element's
+	// canvas.
+	DrawTo (canvas canvas.Canvas)
+
+	// OnDamage sets a function to be called when an area of the element is
+	// drawn on and should be pushed to the screen.
+	OnDamage (callback func (region canvas.Canvas))
+
+	// OnMinimumSizeChange sets a function to be called when the element's
+	// minimum size is changed.
+	OnMinimumSizeChange (callback func ())
+}
+
+// Focusable represents an element that has keyboard navigation support. This
+// includes inputs, buttons, sliders, etc. as well as any elements that have
+// children (so keyboard navigation events can be propagated downward).
+type Focusable interface {
+	Element
+
+	// Focused returns whether or not this element is currently focused.
+	Focused () (selected bool)
+
+	// Focus focuses this element, if its parent element grants the
+	// request.
+	Focus ()
+
+	// HandleFocus causes this element to mark itself as focused. If the
+	// element does not have children, it is disabled, or there are no more
+	// selectable children in the given direction, it should return false
+	// and do nothing. Otherwise, it should select itself and any children
+	// (if applicable) and return true.
+	HandleFocus (direction input.KeynavDirection) (accepted bool)
+
+	// HandleDeselection causes this element to mark itself and all of its
+	// children as unfocused.
+	HandleUnfocus ()
+
+	// OnFocusRequest sets a function to be called when this element wants
+	// its parent element to focus it. Parent elements should return true if
+	// the request was granted, and false if it was not.
+	OnFocusRequest (func () (granted bool))
+
+	// OnFocusMotionRequest sets a function to be called when this
+	// element wants its parent element to focus the element behind or in
+	// front of it, depending on the specified direction. Parent elements
+	// should return true if the request was granted, and false if it was
+	// not.
+	OnFocusMotionRequest (func (direction input.KeynavDirection) (granted bool))
+}
+
+// KeyboardTarget represents an element that can receive keyboard input.
+type KeyboardTarget interface {
+	Element
+
+	// HandleKeyDown is called when a key is pressed down or repeated while
+	// this element has keyboard focus. It is important to note that not
+	// every key down event is guaranteed to be paired with exactly one key
+	// up event. This is the reason a list of modifier keys held down at the
+	// time of the key press is given.
+	HandleKeyDown (key input.Key, modifiers input.Modifiers)
+
+	// HandleKeyUp is called when a key is released while this element has
+	// keyboard focus.
+	HandleKeyUp (key input.Key, modifiers input.Modifiers)
+}
+
+// MouseTarget represents an element that can receive mouse events.
+type MouseTarget interface {
+	Element
+
+	// Each of these handler methods is passed the position of the mouse
+	// cursor at the time of the event as x, y.
+
+	// HandleMouseDown is called when a mouse button is pressed down on this
+	// element.
+	HandleMouseDown (x, y int, button input.Button)
+
+	// HandleMouseUp is called when a mouse button is released that was
+	// originally pressed down on this element.
+	HandleMouseUp (x, y int, button input.Button)
+
+	// HandleMouseMove is called when the mouse is moved over this element,
+	// or the mouse is moving while being held down and originally pressed
+	// down on this element.
+	HandleMouseMove (x, y int)
+
+	// HandleScroll is called when the mouse is scrolled. The X and Y
+	// direction of the scroll event are passed as deltaX and deltaY.
+	HandleMouseScroll (x, y int, deltaX, deltaY float64)
+}
+
+// Flexible represents an element who's preferred minimum height can change in
+// response to its width.
+type Flexible interface {
+	Element
+
+	// FlexibleHeightFor returns what the element's minimum height would be
+	// if resized to a specified width. This does not actually alter the
+	// state of the element in any way, but it may perform significant work,
+	// so it should be called sparingly.
+	//
+	// It is reccomended that parent containers check for this interface and
+	// take this method's value into account in order to support things like
+	// flow layouts and text wrapping, but it is not absolutely necessary.
+	// The element's MinimumSize method will still return the absolute
+	// minimum size that the element may be resized to.
+	//
+	// It is important to note that if a parent container checks for
+	// flexible chilren, it itself will likely need to be flexible.
+	FlexibleHeightFor (width int) (height int)
+
+	// OnFlexibleHeightChange sets a function to be called when the
+	// parameters affecting this element's flexible height are changed.
+	OnFlexibleHeightChange (callback func ())
+}
+
+// Scrollable represents an element that can be scrolled. It acts as a viewport
+// through which its contents can be observed.
+type Scrollable interface {
+	Element
+
+	// ScrollContentBounds returns the full content size of the element.
+	ScrollContentBounds () (bounds image.Rectangle)
+
+	// ScrollViewportBounds returns the size and position of the element's
+	// viewport relative to ScrollBounds.
+	ScrollViewportBounds () (bounds image.Rectangle)
+
+	// ScrollTo scrolls the viewport to the specified point relative to
+	// ScrollBounds.
+	ScrollTo (position image.Point)
+
+	// ScrollAxes returns the supported axes for scrolling.
+	ScrollAxes () (horizontal, vertical bool)
+
+	// OnScrollBoundsChange sets a function to be called when the element's
+	// ScrollContentBounds, ScrollViewportBounds, or ScrollAxes are changed.
+	OnScrollBoundsChange (callback func ())
+}
diff --git a/elements/window.go b/elements/window.go
new file mode 100644
index 0000000..618d795
--- /dev/null
+++ b/elements/window.go
@@ -0,0 +1,39 @@
+package elements
+
+import "image"
+
+// Window represents a top-level container generated by the currently running
+// backend. It can contain a single element. It is hidden by default, and must
+// be explicitly shown with the Show() method. If it contains no element, it
+// displays a black (or transprent) background.
+type Window interface {
+	// Adopt sets the root element of the window. There can only be one of
+	// these at one time.
+	Adopt (child Element)
+
+	// Child returns the root element of the window.
+	Child () (child Element)
+
+	// SetTitle sets the title that appears on the window's title bar. This
+	// method might have no effect with some backends.
+	SetTitle (title string)
+
+	// SetIcon taks in a list different sizes of the same icon and selects
+	// the best one to display on the window title bar, dock, or whatever is
+	// applicable for the given backend. This method might have no effect
+	// for some backends.
+	SetIcon (sizes []image.Image)
+
+	// Show shows the window. The window starts off hidden, so this must be
+	// called after initial setup to make sure it is visible.
+	Show ()
+
+	// Hide hides the window.
+	Hide ()
+
+	// Close closes the window.
+	Close ()
+
+	// OnClose specifies a function to be called when the window is closed.
+	OnClose (func ())
+}
diff --git a/input/input.go b/input/input.go
new file mode 100644
index 0000000..b523829
--- /dev/null
+++ b/input/input.go
@@ -0,0 +1,131 @@
+package input
+
+import "unicode"
+
+// Key represents a keyboard key.
+type Key int
+
+const (
+	KeyNone Key = 0
+	
+	KeyInsert      Key = 1
+	KeyMenu        Key = 2
+	KeyPrintScreen Key = 3
+	KeyPause       Key = 4
+	KeyCapsLock    Key = 5
+	KeyScrollLock  Key = 6
+	KeyNumLock     Key = 7
+	KeyBackspace   Key = 8
+	KeyTab         Key = 9
+	KeyEnter       Key = 10
+	KeyEscape      Key = 11
+	
+	KeyUp       Key = 12
+	KeyDown     Key = 13
+	KeyLeft     Key = 14
+	KeyRight    Key = 15
+	KeyPageUp   Key = 16
+	KeyPageDown Key = 17
+	KeyHome     Key = 18
+	KeyEnd      Key = 19
+	
+	KeyLeftShift    Key = 20
+	KeyRightShift   Key = 21
+	KeyLeftControl  Key = 22
+	KeyRightControl Key = 23
+	KeyLeftAlt      Key = 24
+	KeyRightAlt     Key = 25
+	KeyLeftMeta     Key = 26
+	KeyRightMeta    Key = 27	
+	KeyLeftSuper    Key = 28
+	KeyRightSuper   Key = 29
+	KeyLeftHyper    Key = 30
+	KeyRightHyper   Key = 31
+	
+	KeyDelete Key = 127
+	
+	KeyDead Key = 128
+	
+	KeyF1  Key = 129
+	KeyF2  Key = 130
+	KeyF3  Key = 131
+	KeyF4  Key = 132
+	KeyF5  Key = 133
+	KeyF6  Key = 134
+	KeyF7  Key = 135
+	KeyF8  Key = 136
+	KeyF9  Key = 137
+	KeyF10 Key = 138
+	KeyF11 Key = 139
+	KeyF12 Key = 140
+)
+
+// Button represents a mouse button.
+type Button int
+
+const (
+	ButtonNone Button = iota
+	
+	Button1
+	Button2
+	Button3
+	Button4
+	Button5
+	Button6
+	Button7
+	Button8
+	Button9
+	
+	ButtonLeft    Button = Button1
+	ButtonMiddle  Button = Button2
+	ButtonRight   Button = Button3
+	ButtonBack    Button = Button8
+	ButtonForward Button = Button9
+)
+
+// Printable returns whether or not the key's character could show up on screen.
+// If this function returns true, the key can be cast to a rune and used as
+// such.
+func (key Key) Printable () (printable bool) {
+	printable = unicode.IsPrint(rune(key))
+	return
+}
+
+// Modifiers lists what modifier keys are being pressed. This is used in
+// conjunction with a Key code in a Key press event. These should be used
+// instead of attempting to track the state of the modifier keys, because there
+// is no guarantee that one press event will be coupled with one release event.
+type Modifiers struct {
+	Shift   bool
+	Control bool
+	Alt     bool
+	Meta    bool
+	Super   bool
+	Hyper   bool
+
+	// NumberPad does not represent a key, but it behaves like one. If it is
+	// set to true, the Key was pressed on the number pad. It is treated
+	// as a modifier key because if you don't care whether a key was pressed
+	// on the number pad or not, you can just ignore this value.
+	NumberPad bool
+}
+
+// KeynavDirection represents a keyboard navigation direction.
+type KeynavDirection int
+
+const (
+	KeynavDirectionNeutral  KeynavDirection =  0
+	KeynavDirectionBackward KeynavDirection = -1
+	KeynavDirectionForward  KeynavDirection =  1
+)
+
+// Canon returns a well-formed direction.
+func (direction KeynavDirection) Canon () (canon KeynavDirection) {
+	if direction > 0 {
+		return KeynavDirectionForward
+	} else if direction == 0 {
+		return KeynavDirectionNeutral
+	} else {
+		return KeynavDirectionBackward
+	}
+}
diff --git a/layouts/layout.go b/layouts/layout.go
new file mode 100644
index 0000000..1e44f9b
--- /dev/null
+++ b/layouts/layout.go
@@ -0,0 +1,37 @@
+package layouts
+
+import "image"
+import "git.tebibyte.media/sashakoshka/tomo/elements"
+
+// LayoutEntry associates an element with layout and positioning information so
+// it can be arranged by a Layout.
+type LayoutEntry struct {
+	elements.Element
+	Bounds image.Rectangle
+	Expand bool
+}
+
+// Layout is capable of arranging elements within a container. It is also able
+// to determine the minimum amount of room it needs to do so.
+type Layout interface {
+	// Arrange takes in a slice of entries and a bounding width and height,
+	// and changes the position of the entiries in the slice so that they
+	// are properly laid out. The given width and height should not be less
+	// than what is returned by MinimumSize.
+	Arrange (entries []LayoutEntry, margin int, bounds image.Rectangle)
+
+	// MinimumSize returns the minimum width and height that the layout
+	// needs to properly arrange the given slice of layout entries.
+	MinimumSize (entries []LayoutEntry, margin int) (width, height int)
+
+	// FlexibleHeightFor Returns the minimum height the layout needs to lay
+	// out the specified elements at the given width, taking into account
+	// flexible elements.
+	FlexibleHeightFor (
+		entries []LayoutEntry,
+		margin int,
+		squeeze int,
+	) (
+		height int,
+	)
+}
diff --git a/tomo.go b/tomo.go
index 5dc4dde..b1416b0 100644
--- a/tomo.go
+++ b/tomo.go
@@ -1,6 +1,8 @@
 package tomo
 
 import "errors"
+import "git.tebibyte.media/sashakoshka/tomo/data"
+import "git.tebibyte.media/sashakoshka/tomo/elements"
 
 var backend Backend
 
@@ -32,7 +34,7 @@ func Do (callback func ()) {
 // Window. If the window could not be created, an error is returned explaining
 // why. If this function is called without a running backend, an error is
 // returned as well.
-func NewWindow (width, height int) (window Window, err error) {
+func NewWindow (width, height int) (window elements.Window, err error) {
 	if backend == nil {
 		err = errors.New("no backend is running.")
 		return
@@ -41,14 +43,14 @@ func NewWindow (width, height int) (window Window, err error) {
 }
 
 // Copy puts data into the clipboard.
-func Copy (data Data) {
+func Copy (data data.Data) {
 	if backend == nil { panic("no backend is running") }
 	backend.Copy(data)
 }
 
 // Paste returns the data currently in the clipboard. This method may
 // return nil.
-func Paste (accept []Mime) (Data) {
+func Paste (accept []data.Mime) (data.Data) {
 	if backend == nil { panic("no backend is running") }
 	return backend.Paste(accept)
 }